Trans running too cool?

Spong

Original poster
Member
Dec 12, 2011
59
I installed a PCMforLess trans cooler kit this summer. Today I drove my TB from Iowa to Michigan. I pulled out of my 60 degree garage into -2 temps early this morning. I watched my DashHawk and the trans temp didn't make it above 90 degrees until I stopped for lunch and it had time to heat soak. Temps outside got warmer and when I stopped for lunch the ext temp was 24 and the trans temp got up to 122 after sitting. When I got going again, the temps dropped to 114.

Is it possible the trans is running too cool?

Thanks,
Steve
 

djthumper

Administrator
Nov 20, 2011
14,956
North Las Vegas
Did you happen to install it after the built-in cooler? There have been discussions of putting an after market cooler before it enters the radiator area to warm it back up for the winter months like this.
 

Spong

Original poster
Member
Dec 12, 2011
59
I don't know if it's in line before or after the stock cooler but they are in series.
 

HARDTRAILZ

Moderator
Nov 18, 2011
49,665
Certainly seems to cool. There has been discussion of needing to hit 160 to get the water out of fluid and for proper viscosity
 

Spong

Original poster
Member
Dec 12, 2011
59
Well I hope being cool doesn't damage something!

Drove back home from Michigan through all the wonderful snow and mess. Was upper teens in MI and -3 at home. Temps for the last 60 or so miles were only in the upper 80s! :eek:

I'm heading down to Mississippi next week. Hopefully it will be warm enough there to get the temp over 160.
 

Mark20

Member
Dec 6, 2011
1,630
Except when towing with my Silverado my tranny temps there are around 135F and it has an external cooler. It can take a while to get to that temperature.
 

Spong

Original poster
Member
Dec 12, 2011
59
I would *think* that temps in the 80-90 degree range the fluid should flow properly. I can understand not getting hot enough to burn off the moisture. I would be very worried about that if I parked outside in these cold temps because I could see something possibly freezing up.
 

lint

Member
Dec 4, 2011
155
I know ,I have said this before somewhere . but I use a bypass, works well, Still takes sometime coming up to temp in winter ,But then i took it off ,And on short trips in winter ,Stock cooler took the same time so I know its working. and opening full at 180. 185. I was to lazy to put cardboard out there every winter.

transmissioncoolers.us: Tru-Cool Remote External bypass
 

Bartonmd

Member
Nov 20, 2011
545
Spong said:
I would *think* that temps in the 80-90 degree range the fluid should flow properly. I can understand not getting hot enough to burn off the moisture. I would be very worried about that if I parked outside in these cold temps because I could see something possibly freezing up.

Eh, it's made to physically work down to -40F, but the design temperature for "warmed up" is between 160F and 220F. Running it colder works fine, but the thicker fluid just hits valveing and pistons harder and such. It's not optimum, but it's not a "going to blow up tomorrow" thing, either. Just a little extra wear.

I have had the moisture problem, where it does freeze stuff up. I would just run my Caprice hard in town until it was warmed up, and it would be fine for another month or so.

Mike
 

canadianbacon

Member
Jan 23, 2012
15
I have not installed my PCM4Less kit yet but I am thinking that if you really want to warm it up why not just cover it ? couldn't you just wrap the aux cooler in foil ?
 

RayVoy

Member
Nov 20, 2011
939
Auto transmissions should operate around 200 deg f, a range of 175 to 225 deg f.

Under normal operating conditions, winter, or summer, the cooler in the engine radiator should maintain the correct operating range with out the aid of a cooler.

It is my opinion, that any tranny cooler should be installed between the tranny and the radiator, on the transmission out line (hot side).

Installing on this side, does 2 things:
- it lets the radiator "adjust" the temp of the oil as it returns to the tranny;
- if towing, or very hot conditions, the cooler can reduce the oil temp before it gets to the radiator, letting the radiator (and thus, the engine and transmission) operate within it's correct temp range.
 

Spong

Original poster
Member
Dec 12, 2011
59
Thanks for all the info. I'm down in MS this week. Yesterday temps were in upper 50s and I saw trans temps in the 130s while driving. It should get warmer as I head south so we'll see what the trans temps are. I'm hoping to warm it up enough to burn off any moisture.

Lint- How hard was the bypass to hook up?

RayVoy- How would I know which side is the Hot side?

Bartonmd- I'm hoping to warm it up enough to burn off any moisture this week while driving!
 

RayVoy

Member
Nov 20, 2011
939
Spong said:
RayVoy- How would I know which side is the Hot side?
Spong, a tranny mechanic probably knows by looking, I don't.
but, there are two ways for us backyard guys.
- Start the engine and crawl under, the line that gets hot first is the out (hot) side.
- You can open/disconnect one line and have someone bump the starter (if engine starts, quickly turn it off), if the fluid is pumped out of the line going to the tranny, you have the hot side open; if the fluid is pumped out of the line going to the radiator, you have opened the cold side.

There actually a third way for you (because you have a cooler installed), the tranny line going to the new cooler is probably the cold side line.
I say this, because most shops put the new cooler after the radiator cooler, in the return (cold) side.

Note, in my thread, I said IMO. That is the way I think it should be installed, most installers differ.
 

Spong

Original poster
Member
Dec 12, 2011
59
Thanks for all the info guys. I did get the temp up over 160 a couple days last week in southern MS when the OAT was in the 70s.

I have to run to Michigan again next week. I'm thinking about going ghetto and putting cardboard behind the grill, in front of the cooler as a test to see if it makes a big difference.
 

Iahawkeye

Member
Jan 24, 2012
52
Spong said:
Thanks for all the info guys. I did get the temp up over 160 a couple days last week in southern MS when the OAT was in the 70s.

I have to run to Michigan again next week. I'm thinking about going ghetto and putting cardboard behind the grill, in front of the cooler as a test to see if it makes a big difference.

That is what i always do for my truck in the winter. I would rather have a colder running transmission in the summer for mountains ad hard pulling and slide a piece of cardboard in the winter.

I overheated the transmission, once coming out of a steep grade. Once i hit the flats, it would not shift into OD. Scared me to death. An oil change and a transmission cooler and i never had a problem again.
 
Dec 4, 2011
520
This has been a very interesting discussion on Tranny coolers.

I subscribe to the theory of putting the cooler on the return line back to the tranny. By the way on my 5.3 the line on the left (sitting in the drivers seat) is the return line. I don't know if the 4.2's are the same or not. As suggested the easiest way to test is to remove one line and turn over the engine, depending which line you remove and where the fluid exits from, will determine which line is which. My guess would be that a 4L60E is a 4L60E so it wouldn't matter which vehicle it is in.

Now to my question. I have a Tru-Cool in my truck with a cold temp bypass built into the cooler. Has anyone taken Air temps and Tranny temps using an internal bypass in a Tru-Cool Cooler? I would really be interested in some numbers. For additional information I live where winter temps sometimes get to -40 (at that temp it doesn't matter whether is F or C). I have not had this cooler covered and I have not had any tranny problems in the last half dozen vehicles I have had using this method.

I know that heat kills transmissions but I am not sure that you can chill out a tranny. On a cold start at -40 everything is cold for at least a little while. Even if it ran a little cool for awhile, because tranny's generate their own heat eventually they will warm up and evaporate any moisture. Water will evaporate at 160 degrees it just takes a little longer than when it is at 200.
 

canadianbacon

Member
Jan 23, 2012
15
RedEnvoyDenal said:
This has been a very interesting discussion on Tranny coolers.

I subscribe to the theory of putting the cooler on the return line back to the tranny. By the way on my 5.3 the line on the left (sitting in the drivers seat) is the return line. I don't know if the 4.2's are the same or not. As suggested the easiest way to test is to remove one line and turn over the engine, depending which line you remove and where the fluid exits from, will determine which line is which. My guess would be that a 4L60E is a 4L60E so it wouldn't matter which vehicle it is in.

Now to my question. I have a Tru-Cool in my truck with a cold temp bypass built into the cooler. Has anyone taken Air temps and Tranny temps using an internal bypass in a Tru-Cool Cooler? I would really be interested in some numbers. For additional information I live where winter temps sometimes get to -40 (at that temp it doesn't matter whether is F or C). I have not had this cooler covered and I have not had any tranny problems in the last half dozen vehicles I have had using this method.

I know that heat kills transmissions but I am not sure that you can chill out a tranny. On a cold start at -40 everything is cold for at least a little while. Even if it ran a little cool for awhile, because tranny's generate their own heat eventually they will warm up and evaporate any moisture. Water will evaporate at 160 degrees it just takes a little longer than when it is at 200.



I have a ScanGuage connected to my truck and have been monitoring TFT for the past 12 to 14 months. I have NOT installed my PCM4Less unit yet but will do it this spring. This is what I found in general:

+20 to +30c in general the trans temp will run approx 190f to 200f on the highway (and up to 210f - 215f sitting in bumper to bumper) with 2 people in the truck.
- in the same temps When towing my trailer with 3 bikes and 3 people and loaded with gear, it is about 200f-210f freeway and generally 220f'ish in bumper to bumper. On long grades in the mountains I have seen it hit a high of 225-230f, when it goes above 220f I usually slow it down. And I am climbing it in 3rd (not OD)

in the +10 to +19c range the are in the 180fto 190f range with 2 people in the truck and 20f warmer in bumper to bumper
- when towing it is still in the 200-210f, doesn't seem to change

in the 0 to +9c range the temps are now at 150-160f with 2 people and I have NEVER seen it above 170f even in bumper to bumper
- when towing at this temp it is still in the 190-210f range

from approx -10 to 0 the trans temps are in the 150-160f range but it takes a really long time to get there (approx 15km of highway driving). bumper to bumper traffic no longer has affect on trans temp
- towing at this temp is in the neighborhood of 180-200f.

from -20 to -10c temps still make it to 150-160f but takes even longer. My commute used to be approx 120km for 1 way and it would take about half the drive before it got to those temps, so approx 60km.
- never towed at this temp

from -30c to -20c temps would make only 140-150f and would take my ENTIRE 120km commute to get there. It does get to about 100f VERY EASILY but from 100f up to 140f/150f it takes forever.

I never drove at -40c so cannot tell you what it would take.
 
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Dec 4, 2011
520
canadianbacon said:
I have a ScanGuage connected to my truck and have been monitoring TFT for the past 12 to 14 months. I have NOT installed my PCM4Less unit yet but will do it this spring. This is what I found in general:

+20 to +30c in general the trans temp will run approx 190f to 200f on the highway (and up to 210f - 215f sitting in bumper to bumper) with 2 people in the truck.
- in the same temps When towing my trailer with 3 bikes and 3 people and loaded with gear, it is about 200f-210f freeway and generally 220f'ish in bumper to bumper. On long grades in the mountains I have seen it hit a high of 225-230f, when it goes above 220f I usually slow it down. And I am climbing it in 3rd (not OD)

in the +10 to +19c range the are in the 180fto 190f range with 2 people in the truck and 20f warmer in bumper to bumper
- when towing it is still in the 200-210f, doesn't seem to change

in the 0 to +9c range the temps are now at 150-160f with 2 people and I have NEVER seen it above 170f even in bumper to bumper
- when towing at this temp it is still in the 190-210f range

from approx -10 to 0 the trans temps are in the 150-160f range but it takes a really long time to get there (approx 15km of highway driving). bumper to bumper traffic no longer has affect on trans temp
- towing at this temp is in the neighborhood of 180-200f.

from -20 to -10c temps still make it to 150-160f but takes even longer. My commute used to be approx 120km for 1 way and it would take about half the drive before it got to those temps, so approx 60km.
- never towed at this temp

from -30c to -20c temps would make only 140-150f and would take my ENTIRE 120km commute to get there. It does get to about 100f VERY EASILY but from 100f up to 140f/150f it takes forever.

I never drove at -40c so cannot tell you what it would take.

:thumbsup:Thank you very much for this very detailed report, it is exactly what I was looking for.:thumbsup: What tranny cooler do you have in your truck and what size is it? have you ever gotten stuck in the snow and seen how fast the temps go up trying to get unstuck?
 

canadianbacon

Member
Jan 23, 2012
15
RedEnvoyDenal said:
:thumbsup:Thank you very much for this very detailed report, it is exactly what I was looking for.:thumbsup: What tranny cooler do you have in your truck and what size is it? have you ever gotten stuck in the snow and seen how fast the temps go up trying to get unstuck?

I haven't installed the tranny cooler yet, but it is the TruCool unit (I believe M7B was stamped on the box ?) It is the kit from PCM4Less and I have a 5.3L V8 in mine

I have never really been stuck in the snow, I always use winter tires so I've always pushed thru anything I'm in.
 

neelskit

Member
Dec 7, 2011
69
RayVoy said:
Auto transmissions should operate around 200 deg f, a range of 175 to 225 deg f.

Under normal operating conditions, winter, or summer, the cooler in the engine radiator should maintain the correct operating range with out the aid of a cooler.

It is my opinion, that any tranny cooler should be installed between the tranny and the radiator, on the transmission out line (hot side).

Installing on this side, does 2 things:
- it lets the radiator "adjust" the temp of the oil as it returns to the tranny;
- if towing, or very hot conditions, the cooler can reduce the oil temp before it gets to the radiator, letting the radiator (and thus, the engine and transmission) operate within it's correct temp range.

FYI, I pulled a 12,000lb trailer with a 2011 GMC Sierra (3500 Dually w/Duramax/Allison) from Orlando, FL to Indianapolis, IN last week and the warmest the trans temp ever got to was 130*F. Ambient temps were only slightly below freezing in northern TN, other than that, ambient temps were 50-60*F. The truck is completely stock, came standard with an AUX trans cooler. The only time I've ever seen the trans temp above 160*F was pulling the same rig through the Mojave Desert last summer where it maybe reached 170*F in the mountains SE of Bakersfield, CA.
 

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