1994 Silverado Transmission Issue

[pumprmn3]

I have a 94 Z71 with a 350 engine. I have been having issues with the transmission shifting really hard from park to drive and from 1st to 2nd. This evening, I was coming back from a trip and stopped at a traffic light. When I went to take off the transmission did not shift down to 1st gear. Two more stops resulted in the same issue. Any advise on what could be causing this?

[Blue Bowtie]

Can you manually select each range and get proper engagement?

[j cAT]

Originally Posted by pumprmn3

I have a 94 Z71 with a 350 engine. I have been having issues with the transmission shifting really hard from park to drive and from 1st to 2nd. This evening, I was coming back from a trip and stopped at a traffic light. When I went to take off the transmission did not shift down to 1st gear. Two more stops resulted in the same issue. Any advise on what could be causing this?

when the tranny slips the tranny pressures are commanded to max then the slamming into gears.

drop pan see whats up. replace filter and the fluid use the dexron VI.

old damaged dexron III can cause these problems. also old dexron III eats at the a/b valve bodies. then pressures drop which causes harsh upshifting because of the slippage. also this increases the tranny fluid temps and with non synthetic dexron III this type fluid turns into acid much faster..

very possible you will need a compete re build ...it all depends on how you did your tranny maintenance..

engine idle RPM is 600..if higher fix that first.

[pumprmn3]

Hey, thanks for the reply. I have changed the fluid twice, at 75000 mile intervals. I replaced fluid with Dexron III. I don't believe the transmission is slipping, it don't slam into all gears, just from drive to 1st and from 1st to 2nd. It doesn't matter if it is hot or cold. Other gears shift smoothly. Idle is correct. I will try the VI and a new filter and see what happens.
Thanks again.

[pumprmn3]

Hey BB, not sure if it will shift manually. Don't know if this is electronically shifted or vacuum. Thought I would get under it this morning and see what it looks like.

Thanks.

[j cAT]

Originally Posted by pumprmn3

Hey, thanks for the reply. I have changed the fluid twice, at 75000 mile intervals. I replaced fluid with Dexron III. I don't believe the transmission is slipping, it don't slam into all gears, just from drive to 1st and from 1st to 2nd. It doesn't matter if it is hot or cold. Other gears shift smoothly. Idle is correct. I will try the VI and a new filter and see what happens.
Thanks again.

the 3/4 shifts will not be harsh due to the speed but 1/2 shifts will be if the pressure is high.

GM messed up with this dexron III 20K miles is about all it is good for. 75K is too long for a truck. filter replacing and the pan clean is very important.

trucks should have this fluid dexron VI replaced at 40K miles.plus filter and pan clean.. never do a flush on these type trannys. it will kill them.

[Blue Bowtie]

Originally Posted by pumprmn3

Hey BB, not sure if it will shift manually. Don't know if this is electronically shifted or vacuum. Thought I would get under it this morning and see what it looks like.

Thanks.

It is shifted by solenoid, but operating the sector through the range manually still operates a spool valve that will force a manual shift. See if it engages correctly in all ranges.

[pumprmn3]

Hey Bowtie,
It will only shift between 2nd and 3rd, both up and down. Will not shift all the way down to first. Yesterday it shifted fine through all the gears both up and down, other than the hard shifts. Today, it started not shifting down again and I think I have lost od too. I am thinking replacement or rebuild!!

[kdadeo]

I had the sporadic same issue on my 96, high idle at times, hard 1-2, 2-3, or sometimes too soft of a 2-3, it just finally threw a code for TPS and became a constant issue, changed the throttle position switch and cured the problem, otherwise it was real erratic when it would happen, I suppose that part of the TPS also signals the trannie how hard of a throttle is being applied.