I have a 2000 silverado z71, and recently while getting on the onramp the truck shifted 1-2 no problem, when it shifted 2-3, 3rd just free revved up the rpms. I slowed down to a stop and manually shifted it up 1-2, then 2-3, then 3-4 and the truck went into overdrive when i manually shifted. Coming to a stop, the truck downshifted on its own. We pulled the pan, and not much residue or clutch debris-pretty normal. Replaced the 1-2, 3-4 and tcc solenoids, refilled with fluid and went for a test drive-now the truck would slip even in 3rd and 4th when giving throttle. Fast forward to yesterday, buddy goes to pick the truck up and says he can manually shift it again, holds 3rd and 4th even when flooring it-no slippage detected. At first we thought it was electronic, but now thinking it might be something simple. I'm going to go ahead and have the trans rebuilt because it has 10+ years and 250,000 miles on it from the first rebuild, but kinda scratching my head on what it could be. If it was the clutches it wouldn't hold at 3rd or 4th at all in the throttle, and the pan would reveal a lot of debris I would think. In any case, thought I would post up here to see if anyone has come across this. Thanks in advance.

Ws6Luvr.

 

I was having the same problem in a 2001 and it was the pump.

 

Mine did the same thing. I just blew it up so hopefully I will get a chance to open it up and see what's going on in side.

I did not have gauges to put on it to check the pressures.

I have been told if the 3-4 clutch packs are loose it can hang up and not engauge like that.

Also I was told it is possible the valve in the valve body is hanging up. Either the bore is damaged or there is debris causing it to hang up.

I tend to believe it must have a pressure leak or a weak pump as it seems to lose pressure when it attempts to shift from 2-3. Possibly the spring is weak. I know in the Shift kits and they typically give you a stiffer spring for the pump.

I noticed that in my case it would only do it under about 1/2 to full throttle and it was not always consistent when it would happen.

 

Failed input sprag.

 

How would that cause an interment no 3rd condition?

I am curious now

 

Trans will be at the trans builders shop by the end of the week, will let you guys know exactly what he said failed as soon as I know

 

update:

Trans builder got it all torn down, said "got it torn down, cleaned and converter cut. Converter Lock up is almost gone but not burnt...just worn. Transmission 3-4 is shot like we thought...but the OD planetary gear is loose so I'm working on that as we speak"