Opinions Wanted: Bypass OEM Transmission Cooler?

Blckshdw

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Nov 20, 2011
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Tampa Bay Area, FL
As I wait on a new radiator to arrive, the thought of bypassing the OEM tranny cooler, and running the aux cooler with built in thermal bypass by itself, crossed my mind. Since I'm in FL, we rarely see super cold temps. The few times we get near the freezing mark, is overnight during our short 'winters', and the truck is garage parked. So I don't think I'm gonna see the scenarios where the tranny fluid needs to get warmed up by the engine coolant.

For the most part, my drives aren't very long (distance, or time wise) usually under an hour. The transmission temp tends to read 20-30 degrees below the coolant temp. On the rare occasions I do longer trips out of town, I'll see the tranny temp climb after being on the highway for a couple of hours, then hit heavy traffic with a lot of idling, so not much air flow. One time I remember it getting up past 210, which I'm sure is still acceptable, but it's considerably higher than what I'm used to seeing, so that made me nervous. :ugh:

Anyone know of any cons to this idea, that I'm missing? The return line is already connected to the aux cooler, so moving the other hose to the feed line wouldn't be too hard. Can't remember from when I did the filter and fluid change, how much dripped out when the lines were disconnected, so I'll have to make sure I have some extra fluid on hand just in case.
 

TollKeeper

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I personally dont see an issue with it. All the bypass will do is mean that the trans stays cooler longer doing 1st start ups. With the thermal bypass, I personally think you will be fine.
 

Mooseman

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Dec 4, 2011
25,257
Ottawa, ON
Some speculate that the radiator cooler actually puts heat into the fluid until it reaches the same temp as the coolant, then the cooling starts, kinda.

You could do the experiment. Try it bypassed and see what it does. If your aux cooler is oversized, it might be enough. The fan does pull more air if you're stopped in traffic and things start heating up.
 

Mounce

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Mar 29, 2014
13,667
Tuscaloosa, AL
Have ours bypassed with a 11x11 cooler, seen temps run steady around 160 on a 400 mile trip, not sure around town, been a while since I watched it.


BARELY fits with everything going on in front of the rad, header panel is pretty obstructive and I actually had to cut it to pass the fittings past it.
 

Blckshdw

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Nov 20, 2011
10,665
Tampa Bay Area, FL
Some speculate that the radiator cooler actually puts heat into the fluid until it reaches the same temp as the coolant, then the cooling starts, kinda.

I've actually thought that on a few occasions, which sort of prompted the idea.

You could do the experiment. Try it bypassed and see what it does. If your aux cooler is oversized, it might be enough. The fan does pull more air if you're stopped in traffic and things start heating up.

Have ours bypassed with a 11x11 cooler, seen temps run steady around 160 on a 400 mile trip, not sure around town, been a while since I watched it.

BARELY fits with everything going on in front of the rad, header panel is pretty obstructive and I actually had to cut it to pass the fittings past it.

The majority of the time, my temps stay right at 195, sometimes getting up to 200. I remember from looking at the commanded fan speed vs temp table from HP Tuners, that the fan won't really kick on until things get a bit warmer than what I've seen on my truck.

I didn't get one of the biggest ones available, aimed for one that would fit in the open spot behind the grille. I had to trim a little bit near the hood latch, have the fittings pointed upwards.

90666


Laid under the truck this evening, I may need to get another length of hose, as the one that's on there doesn't look like it has enough slack to reach over to the passenger side. :undecided:
 
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Reprise

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I'll give you two answers... if you tow, or if you don't

If you don't... put in a 10K BTU unit, and you'll run 160-180 all day long (180 when it gets about +95F out)

If you do tow... maybe get something a little larger, but you can still run it in bypass.
I had 4500lb on the bumper, @ 6800ft, in 95F temps last year with the Envoy (in Montana), with a Derale 10K stacked plate - and the highest it got was mid-230s. Truck was shifting between 2nd-3rd gear up the mountain (no tow mode in the Envoy, so I keep it in '3' when towing), so the truck was being stressed, no doubt.

A year later, the fluid still looks / smells new, and I have no issues with the trans (it was rebuilt about a year before I took that trip). I have admittedly retired it from tow duty, now that I have the Sierra HD.

As far as 'max temp' on Dex 6 - I've seen it listed (in more than one place) at 275F. If you look at a temp gauge from a HD pickup, the 'overheat' marks don't start until after 250F...
90667

Granted, I had a 'full synthetic' Dex-specific fluid (Valvoline). But regular Dexron VI is supposed to be fully synthetic as well (they just don't list it as such).

The old adage was "under 200F, or you shorten the life". Per my experience above, I wouldn't worry about an occasional 210F at all on Dex 6, especially if it's really hot out, and / or you're towing.

Finally... Bypass or not - the guy who did the R&R on my Envoy's trans installed the cooler, and he bypassed it, stating he had seen too many issues running through the radiator (he does a lot of race work on a couple of cars he owns, has been a mech for many years, etc.) When I expressed concern about my 10K cooler being too small, running in bypass, he said I'd never need another cooler in that truck. If I were still towing with the Voy, I'd most likely jump to the next size cooler, just to be safe. But, technically, he's been right so far. And when I'm not towing, I'm at 160-165F about 90% of the time.

Looking at the pic of your cooler that you posted just now... mine is fully half the size of yours. You should be just fine, IMO.
 

Blckshdw

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Nov 20, 2011
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Tampa Bay Area, FL
Nah I don't tow. Part of the reason I installed my first back up camera in the trailer hitch receiver, was to deter friends from getting the bright idea to ask me to tow moving trailers for them :satan:

I checked the amazon ad for this model, doesn't list the BTU rating, but compared to the size of yours, I guess that point is moot. I put the cooler in 11/2016, and the fluid was in good shape then, but I ended up losing it back in April. Metal in the pan, lost all the clutches. Man I was mad!! :hissyfit:

Speaking of issues running through the radiator, one of the reviews I read, the guy said the radiator started leaking internally with the tranny cooler, and the coolant caused transmission failure. I hadn't heard of such a thing before, that's gotta be an ultra rare occurrence (unless that's what your guy has seen that happen a lot?) but that's the last thing I'd want to deal with right now.
 

Mooseman

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Dec 4, 2011
25,257
Ottawa, ON
I remember hearing about it here a couple of times IIRC. Doesn't happen a lot but it does happen. Maybe the quality of this particular radiator is in question (China). I had a cheap Chinese radiator in the old TB for a number of years without any issues.
 
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Blckshdw

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Tampa Bay Area, FL
I've been checking the reservoir when I get home from work, and I'm not losing a ton each day, but it is weeping from that crack, and continues to after shut down. Luckily it's on the top, would be a different story if it was the bottom tank. Replacement won't get here until Tuesday, so I'll probably need to top it off this weekend.
 

Reprise

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Speaking of issues running through the radiator, one of the reviews I read, the guy said the radiator started leaking internally with the tranny cooler, and the coolant caused transmission failure. I hadn't heard of such a thing before, that's gotta be an ultra rare occurrence (unless that's what your guy has seen that happen a lot?) but that's the last thing I'd want to deal with right now.

I don't recall him specifically saying that, but I can't think of any other reason why it would be a problem. He didn't say it was GM-specific (he works on all makes, but his 'toys' & DDs are GM.)

It might be rare, but I've heard mention of the 'strawberry milkshake' 30yrs ago, so it's nothing new.

I suppose that if one believes the fluid will run just as cool in bypass, that it makes sense to bypass - one less risk factor.

Just make sure your connections are flared (or put two clamps on instead of one per line)

On edit: Apparently, Hayden doesn't list BTU ratings on their site, but the one you got is listed as sufficient for 'up to a Class A motorhome' @ '22,000 GVWR'. That should be adequate (barely.... LMAO) :wink:
 
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Blckshdw

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Nov 20, 2011
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Tampa Bay Area, FL
Welp, that experiment didn't quite go as planned :hissyfit: Last night after I got the new hose line put in, I topped off the fluid and checked for leaks, since all was well, called it a night instead of going for a test drive like I should have.

Got up this morning to hit the beach, traffic was understandably very light and free flowing for the most part. Of course, torque wanted to act up and not read my transmission fluid temp accurately, as it's prone to do every once in a while, but the Scangauge was hooked up and always works fine. 10 minutes into the drive, the temp was around 150, coolant was at 195, pretty normal. Few minutes later once I was on the highway, transmission was at 174. OK, that's cool, and also normal. Then I realize I forgot my damn beach chair, and had to go back :duh:

This is when things got interesting. Flipped a U turn and started heading back. Got off the highway, and temp was up to 180. It doesn't even get that high in my stop and go evening commute traffic. It continued to creep up until it reached the engine coolant temp and seemed to stay there the last 5-10 minutes until I got home.

20190831_093237.jpg



So I guess forgetting my chair was a blessing, cuz I wasn't even halfway through my trip, and I know traffic is always a mess out there. Currently have my garage fan cooling down the engine bay, and once that's safe to handle, I'll reconnect the stock cooler. :frown:
 

Mooseman

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Dec 4, 2011
25,257
Ottawa, ON
Well at least now we know.
 

Blckshdw

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Nov 20, 2011
10,665
Tampa Bay Area, FL
Got the old hose put back in on the return side, and feed line reconnected to the OEM cooler. Went for the same drive, to see the difference. Outdoor temps were almost 10 degrees warmer, with a bit more traffic, and take off transmission temp was 147. Had nearly the same results, not quite as hot, but did get up to 194 as I turned into my neighborhood.

Not sure what the deal is. Maybe some air getting into the system with having the lines disconnected, but it would end up in the aux cooler, which has both ports pointed upwards, so I would think it would push the air into the pan rather quickly into a drive wouldn't it? Would being low on fluid cause higher temps? Wondering if maybe my garage floor isn't as level as I think it is, and that threw off my reading?
 

Mounce

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Mar 29, 2014
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Tuscaloosa, AL
Hey.. Um.. Reading your unfortunate post I went through my mind trying to figure out why you had issues and.. I just realized that I didn't bypass the stock cooler. Complete memory lapse. I put my additional cooler inline after the factory cooler. Sorry for that misinformation... :dunce:
 

Blckshdw

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Nov 20, 2011
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Tampa Bay Area, FL
That's the same way I had mine hooked up as well. Bigger concern is why it continued to run hot, after running both coolers in series again.

Parked the truck backed in like I usually have it, let it idle for a few minutes, and checked the fluid level again. Same reading I got when it was facing the other way, so unless I'm reading the stick wrong, fluid level isn't the issue either... :confused:


20190831_143256.jpg
 

Blckshdw

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Nov 20, 2011
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Tampa Bay Area, FL
Since my radiator showed up early, I broke everything down, and went back to the bypass. Rerouted the outbound hose to come up the passenger side of the radiator and over to the aux cooler. Checked the hoses for tight bends, and looped them out a bit for better flow, in case that was the issue. Fluid level read the same as before, even though I lost some during the swap, so I added a little bit more. Not even a quarter of a quart.

Left the grille off, and went for a drive for about an hour total. Stayed on surface streets for the first 30 minutes, temps steadily climbed and plateaued around 174. Then I got on the highway for about 5 minutes, and temps started climbing again to 185 when I got back onto side streets, and then it got up to 190 and stopped there.

For kicks, turned on the AC to see if forcing the fan to come on would do anything. Well the temps didn't go any higher... Stayed right at 190 through a couple red light stops, and just before getting to my neighborhood, dipped to 188 until I got home. The shifts are smooth, no slipping or anything. I'll go for another test drive in the morning, and run the AC for the whole trip, see how it behaves then.
 

Blckshdw

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Nov 20, 2011
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Tampa Bay Area, FL
Disconnected and drained the aux cooler, flushed 4 quarts through the system out of the vacant cooler hose, dropped the pan and filter. Fluid doesn't look bad (to me) considering I hit 203 towards the end of the drive home from the beach yesterday. :ugh: Little bit of metal shavings on both magnets, but nothing sizable.

I can't seem to get the filter seal out of the transmission, anyone have any tips on pulling that sucker out of there? Kinda at a standstill for now.

20190902_112712.jpg


20190902_112815.jpg
 

littleblazer

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Jul 6, 2014
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Bend a screwdriver into the shape of an L and pull down on the seal lip. I honestly wouldn't bother replacing it though.

As for bypassing the stock cooler, my uncle tried that on the 67... It runs through the radiator now... My Colorado only has an air to fluid for the transmission, no radiator hookup but the cooler on it is roughly the size of our radiator... It runs 130-140 even in 100+ and the hottest I ever got was 165 towing the boat. I know I couldn't fit that in the TB.
 
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mrrsm

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Regarding the R&R of the 4L60E Transmission Filter Metal Cup-Rubber Seal... Please review this Excellent "How-To" Video covering ALL aspects of this Transmission Fluid-Filter R&R. At around 6:50 Minutes in... The Instructor shows an alternative technique that may NOT be as easy as the suggestion first made by @littleblazer on how to extract that recalcitrant Filter Seal.

He also demonstrates his practical method for properly hammering in a Brand New One. I'm recommending watching the entire instructional, as the VOP Eric "O" has a few Extra Tips and Tricks worth watching that might make your life a bit easier:

 
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Blckshdw

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Tampa Bay Area, FL
Thanks for the tips guys, I ended up leaving it there. Figured it's only 4 months old, and if the flush and fill doesn't resolve my issue, I'm gonna have to take it to a dealer anyway. Got everything buttoned up, and put 5 quarts in to fill the pan. Ran the engine for about a minute to fill the lines and cooler, then added another quart. Dip stick was at the top of the cold range, so went for a test drive.

Pretty much the same result. Slow increase in temperature for the 45 minutes I was out there. Topped out at 195 when I was close to home. Pulled the dip stick, it was low, so added about half a quart. Temp dropped to 185. Drove around the neighborhood for about 10 more minutes, temp fluctuated between 183 and 185.

At this point, I'm all out of ideas. May go for another drive in the morning since I'll be off, to see if there's any glimmer of hope because this last drive was low on fluid, but I'm not holding my breath that things will be any better. :frown:
 

littleblazer

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Jul 6, 2014
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Thanks for the tips guys, I ended up leaving it there. Figured it's only 4 months old, and if the flush and fill doesn't resolve my issue, I'm gonna have to take it to a dealer anyway. Got everything buttoned up, and put 5 quarts in to fill the pan. Ran the engine for about a minute to fill the lines and cooler, then added another quart. Dip stick was at the top of the cold range, so went for a test drive.

Pretty much the same result. Slow increase in temperature for the 45 minutes I was out there. Topped out at 195 when I was close to home. Pulled the dip stick, it was low, so added about half a quart. Temp dropped to 185. Drove around the neighborhood for about 10 more minutes, temp fluctuated between 183 and 185.

At this point, I'm all out of ideas. May go for another drive in the morning since I'll be off, to see if there's any glimmer of hope because this last drive was low on fluid, but I'm not holding my breath that things will be any better. :frown:
190 isn't horrible... you sure the air cooler is hooked up after and not before... those temps seem in line with that imo.
 

Blckshdw

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Tampa Bay Area, FL
you sure the air cooler is hooked up after and not before... those temps seem in line with that imo.

Prior to this weekend, the aux cooler was after the radiator. Friday night, I bypassed the radiator, and ran the aux cooler standalone, that's when my issues started. I put it back to the way it was, but it's like something got damaged, cuz the problem continued. I was looking at some aux coolers online, and one review said his had some internal restriction from the start, caused him to overheat.
:lightbulb:
I JUST finished disconnecting the aux cooler completely, and hooked up the hard lines to the radiator. Last ditch effort here. The hope is, possibly that internal thermal bypass has failed and stuck closed, not allowing proper use of all the cooling surfaces. Only other thing I can think of, is something was inside that new length of hose I bought, and when fluid rain through it, passed through getting lodged inside the cooler? Seems unlikely

190 isn't horrible...

You're right, when I checked GMSI, they said to get a proper fluid level reading, the tranny temp should be between 180-200, so it's acceptable, but way above the norm of what I usually see. I had been running in the 160s most of the time I paid attention to it.
 

littleblazer

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Jul 6, 2014
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Prior to this weekend, the aux cooler was after the radiator. Friday night, I bypassed the radiator, and ran the aux cooler standalone, that's when my issues started. I put it back to the way it was, but it's like something got damaged, cuz the problem continued. I was looking at some aux coolers online, and one review said his had some internal restriction from the start, caused him to overheat.
:lightbulb:
I JUST finished disconnecting the aux cooler completely, and hooked up the hard lines to the radiator. Last ditch effort here. The hope is, possibly that internal thermal bypass has failed and stuck closed, not allowing proper use of all the cooling surfaces. Only other thing I can think of, is something was inside that new length of hose I bought, and when fluid rain through it, passed through getting lodged inside the cooler? Seems unlikely



You're right, when I checked GMSI, they said to get a proper fluid level reading, the tranny temp should be between 180-200, so it's acceptable, but way above the norm of what I usually see. I had been running in the 160s most of the time I paid attention to it.
Good. IDK what the thermal bypass on yours looks like but mine was just an orifice, once the fluid warmed up it could direct to the rest of the cooler. Sounds like you may have something!
 
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Blckshdw

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Tampa Bay Area, FL
Fingers crossed man. I'll let the truck sit and cool down for a few hours, then later on tonight, go drive the same route, see what happens. All this random driving around for no reason, reminds me of back in the day when we used to go cruising. :biggrin:
 

Blckshdw

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Nov 20, 2011
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Tampa Bay Area, FL
Don't you hate it, when you're your own worst enemy? Apparently I didn't have the return line fully clipped into the radiator. Although it didn't leak when idling in the garage yesterday, today was a different story. The passenger side put up a fight, so extra attention was put on that one to get it snapped in. That should have been a clue that the driver's side should have been checked again, with a more forceful tug.

I went to a local shop to discard the 4 gallons of spent fluids that were starting to fumigate the garage, and proceeded to cruise around town. Got stopped by a train crossing for about 5 minutes. Noticed the temps climbing slightly faster than before, so cut the trip short. Ended up topping out at 223* by the time I got back, I knew something else was wrong, because the engine temp was fluctuating between 190 and 195 depending on traffic flow. I could smell the tranny fluid as I went, so I tried to baby it. Got home to see this, I never had a chance, of course it was gonna overheat! :hopeless:

This was from me leaving...

20190903_105256.jpg


And this is what I had been doing the whole way home...

20190903_105309.jpg


I've got a gallon jug left, so I can top things off. There's tranny fluid all over the undercarriage, so going to roll it out onto the driveway, jack up one side, and give it a Simple Green bath and rinse.

20190903_105642.jpg
 

TollKeeper

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Could have been worse, you coulda just ignored the smell, and then when the tranny ran out of fluid.... Well you know where it goes from here.

Its what most people do today. "oh the check engine lights been on for a long time" "oh the oil lights been on for days" "You mean the tire isnt suppose to look like that?"
 
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Blckshdw

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Tampa Bay Area, FL
Well it may still get worse... Called the closest dealership, asked if I had them take a look at it, would it be covered under warranty if there's something wrong with the tranny. She kept saying, it's a parts only warranty, but if they diagnosed a problem with it, it would be covered. Well duh, it's a big expensive part, that's why I'm asking!

Since I live alone and that's my only vehicle, I asked if they had a loaner or rental program, since I know it would take some time to work on, and I'd have no way to get home or to work. She said I'd have to wait until they diagnose the problem, and THEN they would arrange transportation with me. So I'm bringing it in on Thursday morning.
 

TollKeeper

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Dealers are such a pain in the ass..

I am almost willing to bet they find nothing wrong, and say its operating normal. Or if they do find a problem, they will blame it on your transmission cooler.

When my 2nd gear started slipping, I took it to the dealer almost immediately. "No problems found" was the response. 1 year later, tranny went out completely.
 
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Mooseman

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Dec 4, 2011
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Ottawa, ON
That's the rub. If it works and shifts fine, temp notwithstanding, they'll say it's fine. "Normal" people don't monitor tranny temps and doesn't affect it's performance unless it actually overheats" is what they'll say.

That being said, this all started when you tried bypassing the rad cooler. Check to see if the flow in and out of each cooler is good. I once had a freshly rebuilt tranny burn up on me because of something wrong with the flow from the cooler lines, and they had even installed an aux cooler. They wound up having to rebuild it again. They never told me what happened.
 

Blckshdw

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Tampa Bay Area, FL
I'm starting to wonder if this issue has been around for a while, and I just never noticed it because my drives are always pretty short distances. Work is only 6 miles away, the beach is 25. It's been a couple of months since I've taken any decent length drives longer than maybe 10 miles at a time, and not many multiple stops all over the place that involve a lot of road time.

Think there's any chance there's a problem with the pump, and it's not moving enough fluid at speed like it should? When I flushed the system, fluid seemed to come out at a pretty good rate, but no way to tell at 1500 rpm compared to 650... Maybe that's something the dealer can test for?
 

Reprise

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Question for you, since you had this rebuilt - did you stick with the stock stall on the converter, or did you happen to have a higher one put in (you might need to check with your builder, but since high stall converters cost $$$, I doubt he put one in on his own unless he "just had one laying around gathering dust" (e.g.; doubtful...but figured I'd ask). It'll run hotter if you have one.

In my experience (granted, about +20 degrees north latitude, compared to you), it takes about 30min to get the fluid up to 150F or so, depending on driving conditions. With the 4L80 in my Sierra, the gage reads about 150F almost all the time at temp, puttering around town with its factory cooler (in series.) If you're short-tripping like you say, I'm wondering if the fluid is really getting that hot - ?

Was looking at a GM station wagon forum (big Roadmasters / Caprices), and found some useful (?) info there from 3-4 years back - talking about a possible faulty sensor, and how to diagnose. There's a service port on the side of the trans - you could (have someone) hook up a known good gauge and see if it jives with what your ECU is reporting (it does take its reading from the sensor, of course)


Re: pump. Normally, they'll start making a whining noise when they're on the way out or being overworked (like with a clogged filter, which you don't have.) I'm not 'feeling' pump, TBH. Given that you probably didn't get a new one when the trans was rebuilt... how many 'total' miles are on the pump? Unless you're north of 300-400K, which I doubt you are, I don't think the pump is at fault, given how I know you take care of / maintain your truck (you'd have reported the whine, if you had it.) Just a hunch on my part.

If you have the DIC, I believe it'll chime / display a message if the trans temp gets too hot. Of course, if you ever see it, it's probably 'too late'. I don't know the upper boundary temp that will trigger the notification, but it's probably listed... somewhere... if it exists. <on edit - strike this - I didn't get any notification on my DIC when I burned mine up a couple of years ago>
 
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mrrsm

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FWIW ...You could try preparing a temporary Pair of Short, 3/8" Fuel-Proof Hoses between the line juncture of the Transmission Line-Out and the In-Flow Adapter to the Transmission Cooler with a Brass 3/8" "T" in between. Likewise... with the use of another long length of the similar tubing to reach an Analog Oil Pressure Gauge and then you'd be able to see the changes and Proof of Oil Pressure... Dynamically.

IIANM ... There are Kits made with all of the Brass or Nylon Adapters, Bits & Baubles as well as the necessary S/S Hose Clamps that will suit the situation nicely. No APPs... No Electronics to sift through...No Guesswork and NO Worries ...Just REAL pressure your eyes can appreciate... and believe. :>)
 
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Mooseman

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Come to think about it, when I was towing the trailer with the Saab long distance in 28c (82f) it never went higher than 196f and that would be after it would downshift to 2nd on a long incline. In 3rd and TC locked, it would hang around 190f. It has a thermal fan clutch and the aux cooler is zip tied to the condenser so it may be getting more air through it. It's also in series with the rad cooler.

How's the flow out of the coolers? How's your fan clutch?
 

Blckshdw

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Tampa Bay Area, FL
The dealership said they replaced the whole transmission, so not a rebuild. I assume they put in a stock stall.

My morning commutes, usually run 35-40 minutes, and I am usually in the 160's when I get to the office. Interesting point with the converter maybe not locking up in O/D. I'm in 45 mph zones the whole way to work, and much of it is light to light traffic, so I may never need it there. The times I ran the hottest, I got on a long stretch of highway where I could stretch its legs. But at the same time, I would think cruising on surface streets in the lower gears, should lower the temp some. That's the thing that bothers me, the temp almost NEVER goes down. It may dip a degree or 2 for a couple seconds, then go right to where it was, or higher. I'll pay attention to the shift points on the way home from work today, maybe add the Torque PID so I can check it at a glance. Was considering bailing on the dealer, since the more I think about it, the more I figured they won't find anything wrong based on me saying "My transmission runs warmer than it usually does, but as long as I don't drive more than 30 miles in a trip, it stays within acceptable ranges"

Was looking at a GM station wagon forum (big Roadmasters / Caprices), and found some useful (?) info there from 3-4 years back - talking about a possible faulty sensor, and how to diagnose. There's a service port on the side of the trans - you could (have someone) hook up a known good gauge and see if it jives with what your ECU is reporting (it does take its reading from the sensor, of course)


That thread says lockup is being prevented cuz the engine is too hot. So if I'm not locking up, that's not gonna be the cause. I'll usually sit right at 195, sometimes dip below that depending on stops and starts.

How's the flow out of the coolers? How's your fan clutch?

Flow from the OEM cooler is fine, plus it's brand new. I'll pull the return hose off the aux cooler and test that after work. Fan clutch seems normal to me. Actually this morning when I backed out of the garage, noticed a wet spot, think my pan may have a slight leak. I got out to go take a look, and while the truck was idling in the driveway behind me, the fan kicked on for about 10 seconds.

Think I'll be stopping at HF on the way home for some ramps (have gotten pretty annoyed with lugging out the jack and stands so much lately) small torque wrench (cuz I guesstimated on the pan bolts) and a laser thermometer.
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
If you still have the EV clutch, you should check it with a rag to be sure it's not just freewheeling after it's warmed up. It might seem to run while the silicone moves around on startup but the electronics may be dead.
 
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TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,045
Brighton, CO
The TC lockup is a really easy test to see if its working. Get it up to a cruising speed with light throttle, using your left foot, press on the brake pedal just enough to get the brake lights to turn on, while still pressing on the gas pedal. You should see a 250-400 jump in RPM.
 
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Blckshdw

Original poster
Moderator
Nov 20, 2011
10,665
Tampa Bay Area, FL
TC does lock up, tapped the brakes while doing 50, and saw the RPM needle do a quick hop. Got home and got under it, the trans pan was leaking from the drain plug. Tightened that down, and wiped it off. Not sure the seal is good enough, is it OK to use teflon tape on the threads?

Also found out the new radiator leaks. :hissyfit: From the filler neck, just under the overflow tube, and both transmission cooler ports are wet underneath. Considered putting some teflon tape on the port threads too, until I saw the filler neck leak. So much for cutting a cost corner on that fix. Gonna try and get a refund, and order an OEM one later in the week.

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After that, figured I'd skip testing the cooler outflow. When I have to put in the new radiator, all that will get disconnected, so I can do it then. Tried testing the fan clutch. Turned on the AC, and hit the side of it with a rag. There was some initial resistance, but it stopped pretty quickly. Let it go a few times, and was able to stop it again with ease. No tugging at all. Safe to assume that's dead then?
 
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