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1996 chevy Z71 pickup transmission

Transmission works fine cold. After driving for about 30 minutes, it skips 3rd gear on the up shift and down shift. Has been recently rebuilt. No problems before except noisy in 1st gear. There are no codes on the scanner. Works fine if you shift manually.

This sounds like a mechanical failure of a pump (One of the pumps) which probably wont show up on a computer diagnosis because it is purely a mechanical problem. when you down shift manually you are forcing fluid to circulate: forcing the pump to work. Thus tricking the computer.
I’m being perfectly honest with you when I give the advice to get rid of your GM product while the getting out is good. I predicted the trouble GM is in now many many months ago and people payed little regard to it and called me crazy. Ford has not been hit very hard with the current struggle because they have always stood up to the unions and they have several investments in the European car markets, not just the asian markets. You’ll notice I didn’t mention Chrysler…they’ve been on the ropes since Iacoca schemed a temporary bail out. Please take my advice before you get screwed. Get rid of the GM product while the GM dealerships are still open and parts are available and mechanics are employed. Also consider that GM has patent protection on most of their parts which means nobody else sells certain parts that are critical.

One of the pumps??? There’s only one pump in this transmission. Very doubtful you are looking at a pump issue. In order to even make a guess at this thread we need to know some other thngs. First of all, how many miles has it been since the overhaul?? Has it been acting up since the overhaul?? When you say it is skipping 3rd gear, what exactly is it doing instead of hitting 3rd gear?? I’m thinking in the area of a leak in the input drum somewhere. Possibly a sealing ring or piston seal.

transman

It has been about 2000 miles since overhaul. We have taken it back 2 times and they still can’t fix it. It has been acting up since the overhaul. When it skips 3rd it goes from 2nd to 4th instead of 3rd. On the downshift it goes from 4th to 2nd. It has to be warm before it does this. When I go to pass someone, I have to shift manually into 3rd. After it does get hot the 1st to 2nd shift is very harsh. The fluid is clear and no odor. There is no slippage. Thanks for your help!!

Ok, now that you have explained it more detailed to me, it sounds like a problem in the 2-4 band. Either there is some sticking going on in the servo somewhere or maybe even some cross leaks keeping the band applied. Heres why I think so. In 2nd gear the 2-4 band is applied, to achieve 3rd gear the 2-4 band releases and the 3-4 clutches apply, to achieve 4th gear, the 2-4 band reapplies so what that means is if you are not hitting 3rd, the band is not releasing for 3rd. It is staying applied causing 4th gear. If I were working on this trans, I would first scan the computer and monitor the computer commands to see if the computer is commanding all gears. Also, with my scanner I can bypass the computer and shift the transmission just by pressing buttons on the scanner. This makes it much easier to diagnose mechanical issues. From what you describe, it sure sounds like the band is causing the problem. Take it back again and again until they fix it. I think they are trying to do everything they can to not pull the trans again…

Let me know what you find out…

transman

since Iacocca schemed a temporary bail out.
Really? How did they pay that off early, then? It was a loan, paid off square and early. Once he LEFT they mismanaged themselves back into the hole. Every car maker has their good and crappy cars. No one line is all perfect nor all crap. Get off your soapbox, this is not the place for it.

I asked for help with my transmission, not a speach about GM. I have had GM cars for 50 years and have been pleased. I’m just having a transmission problem. GM will probably be around long after you’re gone. I don’t believe I will ever have a problem getting parts. My next vehicle will also be a GM product.

Thanks!! I will print this out and take it back to the transmission shop with me. I really appreciate your help.