NEED HELP TB EXT dropping out of gear, overheating

[Charles Austin Miller]

2005 Trailblazer EXT 4.2 straight 6, 4WD

About a month ago, I noticed that the transmission was starting to drop out of 4th during normal highway driving. Immediately took it to my transmission guy. He checked it out and said it had a slow fluid leak. He disassembled and cleaned the transfer case, put in a new seal kit and filled it with fluid (over $450). Thirty minutes after I picked up the TB from the shop, I was back out on the road when the transmission dropped out of 4th again. Immediately took it back to the shop and left it for them to road test it. EIGHT DAYS LATER, he called me and said they couldn't duplicate the problem, and the diagnostic showed no transmission errors (no charge, but a shitload of inconvenience). Since then, I can only drive short distances before the transmission starts dropping out of 4th, and now the engine is overheating badly (bubbling hot for 15 to 20 minutes after I stop). I hate to do it, but might have to go back to the transmission guy again, because he's the only one with a "good reputation" in the area. Before I do, I just want to ask who else in here has been through this (with these symptoms), and what did you find out at what cost?

 

[Mounce]

Sounds like two separate issues to me.

 

[Charles Austin Miller]

No, actually, an overheating transmission can affect the engine's cooling system. Likewise, an overheating engine can affect transmission performance. In my case, the TB drops out of 4th gear, and the temperature gauge immediately starts climbing above normal. Definitely related.

 

[Mooseman]

Although the early years had issues with the fan clutch and transmission shifting (which was fixed by a PCM update), this might be what is going on with yours, especially if it overheats only while idling or moving slowly. Test the fan as per this thread:
How to test the electro-viscous fan clutch

 

[Charles Austin Miller]

That's a good idea, thank you for that suggestion, it could be a fan clutch issue. I'll test it in the morning. The fan clutch alone looks pretty expensive, and I know how much labor is these days. So, you think it might be a $600+ bill at the shop?

 

[Mooseman]

Hard to say since we do mostly our own work but it's about an hour's worth of work. If you do need one, encourage your mechanic to get a Hayden brand. It is the best cost vs. quality. Dorman is junk and parts store house brands are made by ???.

 

[shovenose]

When my Crown Vic had a dead cooling fan, it ran fine even with the temp gauge pegged above H and three check engine light codes for overheating, but it stopped moving because the tranny got too hot, and far before it stopped moving at all it was shifting really poorly, so an overheating transmission can definitely cause temporary issues is all I'm trying to say.

I'd say solve your overheating problem first and then worry about the tranny.

 

[Charles Austin Miller]

Exactly. I tested the thermal fan this morning, let it run and come up to temperature for about 20 minutes. Then I popped the hood and watched for 20 more minutes. The fan never switched on even once. I then tried spinning the fan, and it wouldn't spin. I checked the fusebox, and the fan fuse tested fine. So, I ordered the Hayden thermal fan clutch and will replace it myself, saving several hundreds of dollars.

 

[Mooseman]

You do know you'll need a tune to turn off the fan codes, right? Otherwise you'll be staring at the CEL constantly.

 

[Charles Austin Miller]

You do know you'll need a tune to turn off the fan codes, right? Otherwise you'll be staring at the CEL constantly.

I realize it, but not sure how to go about it. From what I've read, some people just let it go and the fan syncs up after a few days. What kind of tune is required? Completely re-flashing the PCM or something? Or can I do it myself?

 

[Mooseman]

You send in your PCM to a tuner and he turns the codes off, as well as give you a little performance boost and better shifts. @limequat does them for $99 shipped.
http://www.lime-swap.com/

And also tune out your SAIS (Secondary Air Injection System) so when it dies, and it will, you get a CEL for it. All it does is heat up the cat faster during warmup.

Only thing though is your truck is undrivable while the PCM is out for a few days unless you get a loaner from him.

 

[Charles Austin Miller]

You send in your PCM to a tuner and he turns the codes off, as well as give you a little performance boost and better shifts. @limequat does them for $99 shipped.
http://www.lime-swap.com/

And also tune out your SAIS (Secondary Air Injection System) so when it dies, and it will, you get a CEL for it. All it does is heat up the cat faster during warmup.

Only thing though is your truck is undrivable while the PCM is out for a few days unless you get a loaner from him.

Thanks for the link. I live out in the Smoky Mountains, where it's difficult to find anybody who can re-flash BCM and PCM... In fact, NOBODY does it. I do most of my own work on the Trailblazer except for transmission and onboard computer programming. Thanks again, and I'll give an update in a few days.

 

[Charles Austin Miller]

BTW, the reason I don't do my own transmission work is because my older brother once had a transmission drop and hit him hard in the chest, fracturing a vertebra in his back. Several surgeries later, he was pretty much paralyzed in both arms and was on timed-drip pain medication, which led to his early death five years ago. So, I promised my wife I'd never work on transmissions after that.

 

[Wooluf1952]

I checked the fusebox, and the fan fuse tested fine.

I may have missed it, but, did you check the fan relay? (#45 under the hood fusebox)

 

[Charles Austin Miller]

I may have missed it, but, did you check the fan relay? (#45 under the hood fusebox)

I meant relay

 

[Charles Austin Miller]

Are you acquainted with PCM of NC (pcmofnc)? They're in North Carolina and they do what Lime-Swap does. PCM of NC says that they hang out here at GMTNation, also. So, I'm wondering if you know them and how do they compare to Lime-Swap?

 

[Mooseman]

Sure I know them, they did my first tune (PCM4less at the time). Great service. Nothing bad to say about them.

Also got a tune from lime-swap.com. Great service as well and actually hangs out here more then PCM of NC. And much cheaper. $99 including shipping.

And a tune is a tune. You get what you ask for no matter who does it (as far as mail order tunes go). Not much difference except cost.

 

[Charles Austin Miller]

I mean, I looked at Lime-Swap, and I'm seeing a mail-in $149 price (unless they've got the $99 hidden elsewhere on the site). PCMOFNC lists their mail-in at $159, but they don't calibrate the speedometer for some reason. For $20 difference, I'm thinking of getting it done here in North Carolina (they're only 50 miles away).

 

[Charles Austin Miller]

At Lime-Swap, I'm seeing "all reflashes $99, and then I'm seeing $149 also for what looks like the same description. Maybe they went up on price, haven't completely updated the site?

 

[christo829]

Look at the Atlas tune Lime Swap offers. That's for all the inline Atlas motors like the 4.2 in most of our vehicles (unless you're lucky enough to have a V8!). That service is $99.

Cheers-

Chris

 

[Charles Austin Miller]

Look at the Atlas tune Lime Swap offers. That's for all the inline Atlas motors like the 4.2 in most of our vehicles (unless you're lucky enough to have a V8!). That service is $99.

Cheers-

Chris

Thanks!

 

[Mooseman]

He actually charges the same $99 for the V8 too on our platform.

However, if PCMofNC is local to you, might make it worthwhile to use them to avoid the down time or doing the loaner thing.

 

[Charles Austin Miller]

He actually charges the same $99 for the V8 too on our platform.

However, if PCMofNC is local to you, might make it worthwhile to use them to avoid the down time or doing the loaner thing.

Thanks again. As you point out, I could be looking at over a week downtime with shipping to and from Michigan. PCMofNC is just 50 miles from here, so the increased cost might be worth shorter shipping delays.

 

[Matt]

If it's only 50 miles, I'd drive there and have it done in situ.

 

[Charles Austin Miller]

If it's only 50 miles, I'd drive there and have it done in situ.

Yeah, I'll call ahead and see what they can do.

 

[Wooluf1952]

I meant relay

OK. Then kind of the same question, did you check the fuse? (#20 Cooling Fan under the hood fuse box)

 

[Charles Austin Miller]

I checked everything. I also went ahead and pulled the fan clutch, at which time I made an important discovery. Apparently, the last time I took my car into the shop for an emergency water pump replacement (about 4 years ago), they replaced the fan clutch...with the wrong fan clutch. And they didn't tell me. This fan clutch I removed yesterday is about an inch and a quarter deeper (shaft) than it should be. And I know this because the fan was worn away on the edges from striking the inside edge of the fan shroud. That must have made a hell of a noise when they first installed it, but they must have kept it running until the fan wore away. I compared the old fan clutch to the new Hayden fan clutch (for the 2005 TB EXT), and the Hayden is a full 1-1/4" smaller in depth. All I can figure is that the shop picked up the wrong GM fan clutch for a larger truck and jammed it in there. Hell of a thing. And the old fan clutch nut looked like it had been hammered off with a chisel.

 

[Mooseman]

AKAIK, our platform is the only one that uses the electro-viscous fan clutch. I even checked the Colorado that has the Atlas L5 and L4 engines and they use thermal. I even checked between the V8 and L6 and they both use the same clutch. It should have been very evident to them that it was the wrong one.

As for the chisel marks, that's one trick for getting them off when they are stuck by using an air hammer with a chisel to get them off.

If you could post pics of both side by side, would be interesting to see.

 

[Charles Austin Miller]

First pic shows the new Hayden (on the left) compared to the old Behr fan clutch, showing that the body of the Behr is deeper than the body of the Hayden...

 

[Charles Austin Miller]

First pic shows the new Hayden (on the left) compared to the old Behr fan clutch, showing that the body of the Behr is deeper than the body of the Hayden...

Sorry, photo came out upside down. Hayden is on the right now.

 

[Charles Austin Miller]

Second pic shows that the Behr shaft is a half-inch longer than the Hayden, meaning the fan is a half-inch further away from the pulley...

 

[Charles Austin Miller]

Last shot shows the fan itself, with a hole worn through the edge of all blades from where it impacted the inner edge of the fan shroud (because the old Behr fan shaft was too long)...

 

[jsheahawk]

I wouldn't take it back to that shop!

Did you get the new one installed? Did it fix your issue?

 

[Charles Austin Miller]

I wouldn't take it back to that shop!

Did you get the new one installed? Did it fix your issue?

New Hayden fan clutch installed, no problem, now getting the PCM re-flashed.

 

[Tiggerr]

Second pic shows that the Behr shaft is a half-inch longer than the Hayden, meaning the fan is a half-inch further away from the pulley...

Not to be disagreeable but they look the same depth to me....IMHO

Take into account the difference in the aluminum "finned" part...
the shaft shows more on the old one, but when you look at the new one, there's a part of the aluminum sticking out further than on the other one hiding the shaft itself...

They're definitely two different mfg...

I think the problem with the fan itself may predate the last clutch....could've been caused by a former faulty/wobbly clutch or water pump...

 

[Charles Austin Miller]

Not to be disagreeable but they look the same depth to me....IMHO

Take into account the difference in the aluminum "finned" part...
the shaft shows more on the old one, but when you look at the new one, there's a part of the aluminum sticking out further than on the other one hiding the shaft itself...

They're definitely two different mfg...

I think the problem with the fan itself may predate the last clutch....could've been caused by a former faulty/wobbly....

You have to measure the distance from where the fan attaches to the clutch to the end of the shaft. It's a half-inch longer, so the fan blades were a half-inch deeper inside the shroud.

 

[Tiggerr]

You have to measure the distance from where the fan attaches to the clutch to the end of the shaft. It's a half-inch longer, so the fan blades were a half-inch deeper inside the shroud.

I see what you're saying now... that's the area I was referring to as being different on the new one... wonder if there was a spacer that was missing or something... that's a totally different mounting....odd

 

[jsheahawk]

New Hayden fan clutch installed, no problem, now getting the PCM re-flashed.

So it did fix your overheating issue? Did that fix the dropped gear issue as well?

 

[Charles Austin Miller]

So it did fix your overheating issue? Did that fix the dropped gear issue as well?

I believe the PCM tune will address the shifting issue. PCMofNC said they were aware of the issue in other Trailblazers, so they'll re-flash it with an updated operating system, with a few other tweaks. I'm not driving it anywhere until I get the PCM back and reinstalled.

But, yeah, so far, it's not overheating.

[ Mod edit: Please do not successively. Use the edit button to add more info to your post. Thanks]

 

[Mounce]

Sounds like two separate issues to me.

Glad you found the bad clutch. Hopefully new flash fixes the other trans issue, if not hello rebuild.