04 Monte Carlo

[GM Guy]

04 Monte Carlo 3400 eng. 70k mi. No CEL present in the info center. I do not have a scanner to watch real data.
While highway driving this week, I noticed that while at cruising speed, the engine rpm's would jump about 2-300 rpm according to the tach. After seeing that I began to listen more carefully and indeed the engine rpm was erratic and not steady. Under load the rpm is steady.
My first thought is to change F & F in the trans thinking the TC was slipping.
My question to the experts is : Does this sound like a familiar (minor I hope) problem?

 

[JackC]

Hopefully some trans expert will jump in here, because I am not one.

But I like the idea of the TC slipping. Or maybe even disengaging. Perhaps the brake switch or ?? is causing it to disengage. You might try temporarily disengaging the TCC by unplugging it for a test. If you still have the problem with the TCC disconnected, then you know it is not the TCC.

 

[GM Guy]

Another symptom is a firmer-than-normal shift that is present only when the car is up to operating temp. After reading other posts about 4L60E and 4T60E trans on this forum, the problem may lie in the plastic valve in the valve body. I'm going to change the F & F today and add some Lucas trans additive and see if that cures it. I will disconnect the TCC plug and see if that makes a difference too.

 

[billr]

Does the CEL operate normally, i.e. come on at key-on, before engine starts? My '97 4L60E has sensors in the trans to detect slippage and set codes, it's hard to believe an '04 doesn't have similar, or more...

 

[GM Guy]

On this car, there's an "Information Center" where trouble codes are displayed. It works normally.
What I was referring to is my handheld code reader. It is an Actron CL9125. I don't think it has the capability to read codes above P0999, that is according to the literature that came with it. Very simple and basic.
I did a F&F change on the car and it had some normal fines in the pan plus a single, rather large metal chip like I've never seen in a trans before. The fluid was not burned, though it was 9 yrs old and in need of a change. The car has a warranty until the middle of June so I will watch it closely and if the F&F change doesn't make a difference then I'll have to take it to a trans shop.

 

[jasonn20]

In certain years, which I can not find the information now, there was a bad programming on the PCM that could cause something like this.

If the pan is cleanish/normal and everything checks out on scanner with no codes then the PCM may need a reflash..

 

[bp042665]

it sounds like it could be a tcc slip and the hash shift could be from long shift addapt you really need to get this checked out soon i have seen this and it is valve body and or channel plate but with more miles on it

 

[GM Guy]

Sorry so late to update.
The F & F change along with Lucas a/t additive took care of all the symptoms. I also had the ecm scanned for codes that my reader could not read and there were none.
Concerning the cel operation, it works fine. I hadn't paid attention to it and had previously just looked at the message center, which simply informs the driver when he's got a door ajar, etc.