what would make a 94 suburban with a 350 auto not go into gear after it is warmed up? works fine when cold?

Answer 1

one of two things
either your filter is picking up too much debris. the longer it runs and gets plugged (you need a rebuild)
or
you have an internal hydraulic leak .works ok cold( thicker fluid)
and when it gets hot( thinner fluid )too much of a leak in the hydraulic circuit .not enough pressure to apply the clutches
and /or bands(you need a rebuild)
if it didnt work cold but ok hot i would say low fluid level
i have been in the transmission business for 23 yrs.just bought my own shop 2 yrs ago its been great so far
P.S. i know thats probably not what you wanted to hear but its the truth .good luck!

Answer 2

It does sound like the transmission pump has some wear and tear and when the fluid thins out when it wamrs up the pump can't keep up the pressure that circulates fluid in and out of the torque convertor and other parts inside the tranny.

Also, if you are even one quart low on fluid, many tranny's will slip and or not move at all. This is because there isn't enough fluid in the torque convertor to move the whole process along.

Make sure your tranny is at the full mark on the dipstick with the motor running and engine hot. You might get lucky and just need to put a quart or two or three of fluid in it. The typical TH350 might slip with only one quart low since it only holds about four or five quarts total if you got every drop out. Mine only takes 3 1/2 quarts of fluid when I service the tranny and it will not move if it's one quart low.

Good Luck!

Answer 3

Your transmission operates by hydraulic pressure. If your car stops shifting when your vehicle heats up, this means that your fluid has lost its viscosity and cannot keep the requisite pressure to operate the transmission.

You can try changing the fluid, but if you've driven your car to the point that the fluid is this fried, it's also lost its ability to lubricate a long time ago, and therefore the hundreds of tiny, sensitive parts inside your trans have probably been damaged. If you got 13 years out of that trans, that's actually pretty good!