I just rebuilt the transmission in my 95 Jimmy, installed great. The transmission had no 3/4 gear and no reverse; both of those problems now fixed. Truck now always reverses instantly and strongly with no problems whatsoever; vehicle also does fine in OD and D at highway speeds.

My problem is acceleration from 0. At operating temperature, a whole lot of engine power is required to get the thing rolling; almost like the clutches are slipping. At roughly 10mph or so, I can feel a noticeable "grab" and after this the vehicle accelerates normally; I can't tell though if this is a shift from 1st to 2nd or not. It does not feel like a typical transmission shift. The start from 0 is slightly better when the car is cold, and the problem worsens when the engine/trans warms up.


There are no acceleration problems in 2nd; although it takes a while for the transmission to shift to third (sometimes after spending a long time accelerating up to speed in 2nd, the transmission shifts to 3rd and then immediately to 4th if the speed is appropriate.

All clutches are new; all planets and shells and spragues and so forth were in perfect shape. I'm suspecting some torque converter trouble, but don't know for sure.

Any suggestions?

 

How about manually in 1st? not a
tranny guy but it does sound like tourqe converter. did you fill the converter with fluid during install?

 

Did you use the old torque converter?

 

internal components of valve body installed improperly.Actuator piston isnt working properly.Drank too much beer while overhauling the trans.

 

I did use the original torque converter. After spending a day and night draining it I did not pre-fill it; I let the pump do that, and it's been on and running for a good month at least so it should be filled by now.

In 1st gear manually - same problem. In 2nd, a bit more pick-up, but the "grab" moment still comes and is hard under load, spinning the wheels for a second.

I can accept that I may have put a valve body component back incorrectly. It means some complicated work and by now I'll probably need a new set of gaskets right? And does anybody have a diagram handy so I can double-check the valve body components?

 

Read these it may help
FYI 4L60E common problems / failures | GM Truck Headquarters

 

Thank you; however, I did check that already and my symptoms don't appear there (which is another thing that causes me to suspect 1st may be right about me putting a valve body component in backwards or something).