[Blobby]

I’m working on a firm letter to accompany my TC replacement request. Where on the TSB is it written that the dealer need not reproduce the problem? Or is it just NOT written that they NEED to reproduce it.

[arpad_m]

Originally Posted by Blobby

I’m working on a firm letter to accompany my TC replacement request. Where on the TSB is it written that the dealer need not reproduce the problem? Or is it just NOT written that they NEED to reproduce it.

Here is the TSB, and it specifically states the following:

"Diagnosis beyond the customer compliant is not required if vehicle was built prior to production dates indicated above"

...the covered date range being from SOP (start of production, I believe) to Feb 1, 2019.

Yes, it does say customer compliant, hope this isn't some massive Freudian on their part .

[Blobby]

Ok i see. Thought that could be interpreters as further investigation beyond the TC problem didn’t need to be done.

[joekd]

Originally Posted by wwiiavfan

Now put an AFM delete on it to help keep the boogie man away.

Have had the range AFM since day 1

[SomeGeoffGuy]

Originally Posted by Blobby

I’m working on a firm letter to accompany my TC replacement request. Where on the TSB is it written that the dealer need not reproduce the problem? Or is it just NOT written that they NEED to reproduce it.

My guess is that the "Complaint only" requirement would lead them to do a fluid swap, not a TC replacement. They are probably going to have to duplicate the TC issue after a fluid swap in order to do a full replacement. I would offer to take them for a ride and demonstrate it. I was all ready to do it on mine - I found a spot on I696 right down the street from my dealer where I could duplicate it every time with a major shudder at 64 mph. I did a few practice runs too.

-Geoff

[Blobby]

Originally Posted by SomeGeoffGuy

My guess is that the "Complaint only" requirement would lead them to do a fluid swap, not a TC replacement. They are probably going to have to duplicate the TC issue after a fluid swap in order to do a full replacement. I would offer to take them for a ride and demonstrate it. I was all ready to do it on mine - I found a spot on I696 right down the street from my dealer where I could duplicate it every time with a major shudder at 64 mph. I did a few practice runs too.

-Geoff

Didn’t even consider that as an option. I’ll do the same. I’m trying to pinpoint reliably where it shudders. It seems that this is the most reliable method:
1- go down hill at constant speed in 5th+ gear so engine is idle or close to it and TC is unlocked
2- transition to up hill so Engine applies power. Tranny will stay in current gear or down shift. Tc will shudder in this transition when trying to lock. Shudder lasts for a brief moment to a couple seconds. Doesn’t do it every time tho.

General question too. The old 4 speeds would shift thru the gears then the TC lock would be OD. Does this tranny lock in every gear? That’s how it feels.

[SomeGeoffGuy]

Originally Posted by Blobby

General question too. The old 4 speeds would shift thru the gears then the TC lock would be OD. Does this tranny lock in every gear? That’s how it feels.

I don't know what the locking algorithm is. I do know that it is not like old school transmissions like 2004R with just the lock/unlock though. It is PWM now so that the calibrator can vary the lead in and lead out. You can really here it in the 8-speed on my Silverado where it flares then catches as you tip the throttle - that is all TC lockup.

-Geoff

[SomeGeoffGuy]

Got my car back - smooth as silk in about 10 miles on the highway. I got to the same spot and speed where it would shudder at 64 mph and nothing happened. Very happy with the fix so far!

-Geoff

[Blobby]

I just talked to the head mechanic at the dealer. He said the TC should be fine and another flush is probably all it needs. Have it scheduled for a few weeks. Need to make sure it’ll be a warranty thing.

[Blobby]

I got a second flush and put 600 miles on it. It’s a good deal better, but not gone. I still get a bit at certain times and still suspect damaged TC.

[Kramer1986]

I am bringing it into my dealer tomorrow morning, hopefully it is a free repair as per:
https://static.nhtsa.gov/odi/tsbs/20...54635-9999.pdf

On Wednesday July 28th Addison Chev in Mississauga, Ontario did the TSB #18-NA-355 and they used 20 liters of that Mobil 1 Synthetic LV ATF HP (with the Blue Label). Thankfully GM covered the cost.
The car only has 17,700 k/m (approximately 11,000 miles) on it. Seems OK now on my highway return trip home. Hopefully that did the trick.

[Blobby]

I’ll give an update for my car. I had the first flush (current TSB) around 25 or 30k. Improved 80% but still shuddered. Got another flush around 40k and saw minor improvement. Now at 44k it goes in next week to be looked over and the tech on the phone sounded like it would be approved for a warranty TC replacement.

It looks like everything will be done before warranty is up. What happens if I still have trouble after a TC replacement and my warranty is out? Will they still service it on their dime since it’s the same problem that manifested while under warranty?

[arpad_m]

Originally Posted by Blobby

I’ll give an update for my car. I had the first flush (current TSB) around 25 or 30k. Improved 80% but still shuddered. Got another flush around 40k and saw minor improvement. Now at 44k it goes in next week to be looked over and the tech on the phone sounded like it would be approved for a warranty TC replacement.

It looks like everything will be done before warranty is up. What happens if I still have trouble after a TC replacement and my warranty is out? Will they still service it on their dime since it’s the same problem that manifested while under warranty?

I don't think so, but TC replacement with the new fluid is likely sufficient to resolve the issue. Tuning the transmission to get rid of or at least reduce the configured slip will also help extend the lifespan of TC clutches.

There was a class action against GM about the 8L90, since the same problem occurs in their other cars and trucks, not sure if it got anywhere.

[Blobby]

Originally Posted by arpad_m

I don't think so, but TC replacement with the new fluid is likely sufficient to resolve the issue. Tuning the transmission to get rid of or at least reduce the configured slip will also help extend the lifespan of TC clutches.

There was a class action against GM about the 8L90, since the same problem occurs in their other cars and trucks, not sure if it got anywhere.

I’m not sure how many 8 speeds GM has (Camaro is 8L45?), but it seems that every GM vehicle with an 8 speed has this problem. Last I read is the suit will be unsuccessful. Something about design defects not covered under warranty.

I was reading about stall speeds somewhere on here, and that particular forum was debating whether or not to go aftermarket TC or GM. They seemed to think the OEM TC was defective. Is this strictly a fluid issue or does the TC also have problems?