Hey gang - 88 GTA TPI 350 Auto Trans. Car's in amazing shape and drives really well. Just one small nuisance that's been happening for years. Not getting worse. Just not getting better either. Hoping you can help!

When driving uphill (generally at speeds of 30MPH or higher), the car can't decide which gear it wants. I could hold the gas pedal completely still and it'll constantly shift between (I THINK) 3rd and fourth gears....or fourth and overdrive. It never does this otherwise. Shifting seems completely normal on flat roads or downhill.

I've never really done anything to the tranny...and who knows what the previous owners did. I can't tell if its the original or not. The tranny fluid was drained (not completely...just maintenance) earlier this year. No difference afterwards. But the problem like I said has been going on since i got the car in 2010.

It's not something that has gotten worse over time. It's just annoying and I figured I'd see if anyone had some suggestions on what i can look at. Thanks everyone!

 

hey just went through this with my 700r4. doing exact same thing. one of my valves were bad. he fixed it and its much better. it would bog the car down very bad going uphill. hope this may help ya

 

Thanks for the possible cause. When you say 'Valves', what do you mean exactly? How did they determine which valve was bad? Can you give me an idea of how much work is involved in fixing this? Or how much the labor was to have someone else do it? I know it's not an exact science. Just trying to figure out if I should pursue this aggressively or not. Thanks much!

 

Fourth gear is overdrive.

If you're in OD range, try D range and see if it stops doing what you describe. It might be normal behavior. IIRC, around 40MPH or so the trans may start to drop in and out of overdrive.

 

I always use "D" around town and only "OD" at 40mph or higher like jumping on the freeway. "D" or even "2nd" up steep hills/slopes and that's with 3.42 ratio. That's what the lower trans gears are for.

 

Awesome suggestion. I will give it a try to see if the symptoms go away. THANK YOU!