QuestionI own a '02 Buick Rendevouse Cx with all-wheel and 30k miles on the vehicle and tranny. As soon as I purchased the vehicle, I noticed the transmission was not shifting out of third or into overdrive. I am actually a shop supervisor for Kargo Repair of Indianapolis, And a A.S.E. certified mechanic. I have been in charge of my shop for ten years and recently lost my transmission diagnostic specialist To small cell lung cancer. Anyway Roland, through the years I've lost track of modern technology, and I never enjoyed paying people who weren't experts for such thing as the complexities of transmissions.
I'm trying to say I don't kwon WWHAT the problem could be, External, or the dreaded internal! I'm trying desperately not to sound ignorant so I apologize Roland, for taking such a small question and creating a monster. PLEASE let me know your opinion on this. I greatly appreciate your valuable time. You're doing a wocerful job here. Thanks again. I will follow up with you as soon as I figure this out(and as long as you don't object)
CHRIS LOWE, BDACAMEL@YAHOO.COM
AnswerP.S. The title of your question, relating to overdrive "fluid" might imply a separate overdrive unit. I notice that the 'overdrive' term is applied to the fourth gear of many automatic transmissions if the final drive ratio is less than 1.0, so in that respect they have no separate overdrive unit, like in the good old manual trans with overdrive units on the end of them (and whose fluid I have seen).
Hi Chris,
I am totally unfamiliar with the GM transmission, but if it is an electronically controlled one like the contemporary Chrysler corp. one then the failure to upshift into overdrive may be due to too low an engine coolant temperature, too low hydraulic pressure internally from a clogged filter; or it could be due to a valve body malfunction or leakage which also can be serviced without removing the trans.
The trans also, if electronic, would have a fault code readout capability that might specify why the 'no upshift' is occuring but that requires a code reader.
The last reasons given are internal damage: reaction shaft support seal rings broken or warn or faulty overdrive clutch. I am not an expert in these beasts, just some book "larning". It is not a small question!
I would try to determine if you can get a fault code readout done and if so, see what that reveals. Changing the filter and transfluid also sometimes can cure these sorts of problems, but it is a chance phenomenon.
Good luck, and let me know what you learn.
Roland
