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Need some help-Jerky Transmission

I have a 2004 Buick Rendezvous and, about a month ago, I noticed that my automatic transmission is changing gears roughly, causing the car to jerk. I checked the transmission fluid and it is fine. I’ve had the transmission serviced (fluid changed, filter changed, etc), but it was last year.

It doesn’t happen all of the time, just from time to time.

Is it possible that it could be bad gas or could it be something worse?

Thanks for the help!

Might be time for plugs and wires

Thanks!

Before you run off and start buying parts and spending money, try accelerating at full throttle from a dead stop to 70 mph a couple of times… This little test will usually pin=point any problems. Have someone who knows about cars go with you…

OK. I’ve got some automotive knowledge, but not a tremendous amount involving transmissions. I figured it was a transmission problem because it happens when it shifts into gear. But, what stumped me is that it doesn’t happen all of the time.

What will the full throttle test show me or what should I look for?

Thanks!!

“it happens when it shifts into gear.”

Into which gear?

Does the symptom differ, depending on whether the engine is cold or at operating temperature?

really it can happen in any gear. I notice it more going from 1st to 2nd, but can also happen going into higher gears.

The symptoms don’t really differ dependent on the engine temp. The first time I noticed it, I had just filled it up with gas and was on the interstate. At that time, it was happening at each gear. About 30 minutes later when I got to where I was going, I stopped off and checked the transmission fluid. It was normal. At that time, I thought maybe I just got some bad gas. But now it happens off an on. Sometimes, it happens when I’m at a dead stop and start out kinda fast.

How many miles are on it and what was its service history other than last year?

You may want to do some searches for problems with the “EPC Solenoid” (Electronic Pressure Control) in GM transmissions of this vintage.

I’m not saying that is it, but you may have the kind of transmission that has had these issues. Apparently they can act up for no apparent reason, though dirty fluid (at any time during its life) may make a difference.

We bought it used about 3 years ago. Not sure if the transmission had been serviced before I got it. However, since that time, the oil is changed every 3K-6K miles and the transmission has been serviced once. Right now, there are 88K miles.

thanks for the advice!!

You need to have it scanned for codes. If for some reason the computer picks up a fault, it is designed to command full line pressure in the transmission to keep it from destroying itself. This, in its own will cause the harsh shifting. The best time to have it checked is when it starts acting up. When it starts acting up, drive it directly, and without shutting the ignition off, to one of your local auto parts stores and have them scan the computer for codes. Remember, DO NOT shut the engine off until the scanner has been hooked up and the codes have been read. Post back here with the code/s they pull from it and we can go from there.

transman

Katie, Transman has a scanner which can scan the engine computer and the transmission computer; but, the auto parts stores scanner will only scan the engine computer. So, they might not be able to help you; though, you can ask them.
Does the check engine light ever come on? Does the D at the shifter, or on the dash, ever flash? Your car might have some other indication that there is a transmission trouble code set in the transmission computer. I lack that knowledge. If you have the Driver’s Handbook, check it for transmission trouble lights.

Thanks! I will definitely do that.

Katie

I have a similar problem. My transmission clunks hard sometimes when taking off from a stop. When I first got the car it did that and the transmission died then and there. It was replaced under warranty. Now it is doing it again so I am worried that this is a precursor to transmission failure. Good luck.