Hello everyone!!

I'm having an issue with my transmission. I was traveling at highway speeds and heard a "clunk" as I was passing another car, then I lost overdrive. I am still able to use gears 1-3 and reverse. If I try to run the car in D it whines a little, but goes away when I shift it to 3. Also, when the transmission worked normally, I have noticed at highway speeds (55-75mph) that the car downshifts from 4-3 often, even just to overtake other cars. Is this normal? Can these shift points be changed to keep the car in 4th longer so the transmission isn't hunting around all the time?

History: I had the original transmission rebuilt @72,000 miles at a ASE certified transmission shop in AZ. I had the fluid checked regularly at 20k intervals, and flushed once at around 120k. I now have about 150k on it. About 1 month prior to the "clunk" I had it flushed once more as it was overheating and shifting poorly. I have not pulled the pan to look for debris. I have checked the level and it is normal, but I have a small amount of leakage from the pan. I have also noticed the car overheating regularly...probably due to the transmission, right?

So... What should I do?
1- Does it sound like another full or partial rebuild is in my future?
2- Rebuild or replace? I've replaced many parts myself (latest was the steering rack and all 4 struts) but I'm rather scared by the idea of replacing a transmission on my own...
3- The Pressure Control Solenoid - I have more problems than just this part, right? Should I have this replaced first? Or should it be replaced as part of a rebuild?
4- I read about the hardened splines for the '03 - Can this shaft be built into my transmission to prevent this from happening again?
5- What about a shift kit? I read this: https://www.gmforum.com/showthread.p...t=transmission Should I have this done or buy different accumulators while the transmission is being rebuilt?
6- Any other major issues to address while I undertake this AGAIN? Any possibility of replacing my transmission with another model that'* better suited? Or a newer year?

I really enjoy the car and use it mainly commuting to work...And I love not having a car payment, so a repair bill now and again is OK. Thanks for the help in advance!!!

Sounds like your 4th gear clutch hub splines probably sheered off. This is common if the 2003 hardened shaft hasn't been put into the trans yet.

Being in Phoenix, there'* a local GP guy that rebuilds them in your area. He'* in Chandler to be exact. User name is PDXGTP, I'd probably toss him an email/pm and see what he says.

I had the same clunk while passing when my 4th gear clutch hub splines went...replaced with a post 2003 hardened shaft to fix the problem. The post 2003 splines had 50k miles on them and looked brand new.