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High Milage and Transmission Fluid Change

I have a 2004 Buick Rendezvous with 214,000 miles. It has been a great vehicle and I really have not done anything to it except the ususal scheduled mainenance.

I changed the transmission fluid every 30,000 miles with no problems until the 150,000 change. As you have probably guessed by now, when I changed the trans fluid this time it started shifting rather roughly at times.

I spoke to a mechanic who explained that that essentially, the gunk in the trans fluid was actually helping the shifting (clutch) and when I changed the fluid I lost this extra grit and thus it started shifting roughly. He put in a transmission fluid additive and that did the trick.

My problem now is that I have not changed the fliud now since the 150,000 and I have 214,000 miles on the vehicle. As you can immagine the fluid is getting a little dark and I don’t know what I should do.

Do I change it again and add the aditive again? Is there any way to change the fluid and save the Gunk? Am I at eh end of the line and looking at a new tansmission. It really runs fine right now with gunk and dark fluid.


I disagree with your mechanic - you were doing exactly the right thing for your tranny changing it every 30k, and there is no reason to think changing it caused a problem. You were preventing ‘gunk’ from collecting in the first place! You’ve now gone 64k, if it was me I’d change it. But the fact you’ve been having rough shifting points to a transmission problem completely unrelated to your changing the fluid. And the problem may get worse, again not related to your changing the fluid.

What exactly was the additive that fixed it last time?

My gut tells me to change the fluid and add the same additive, but I’d want to know what the additive is first.

I agree 100% with texases. I would like to add that automatic transmissions can fail even if you take good care of them, as you did up until the 150,000 mile mark. I don’t think your automatic transmission exhibited problems because you changed the fluid every 30,000 miles. I think it is simply worn out, and based on your great maintenance habits, I don’t think anything could have prevented it.

I totally disagree with the mechanic. If you changed the fluid and filter every 30k there wont be any “gunk” in there to be holding anything together. Change the fluid and filter again and put a bottle of Lube-Gard in the RED bottle in the trans. No need to be looking for a new transmission just yet.


I also agree with Texases and Transman.