I have a 98 chev 4x4 with a trans that has delayed reverse engagement.
I installed a line pressure gauge and found the following
cold fluid 80 degrees
PNRD321- 65psi @idle no change in any gear
hot fluid
PND321- 65-psi @idle 220@wot
reverse-75 psi@ idle 270@wot
Also when I hit the throttle in park and the rpm come down the pressure spikes and almost stalls the engine. All the forward gears work fine and theres no slippage I can feel in forward, but can feel some when pressure is down in reverse. Can this be fixed in the vehicle? Any help would be appreciated.
pressures fine 4L60e have slow reverse if its slipping it probley has burnt clutch plates couple mods u can do is change the seperator plate the trans go replacement seperator plate has the reverse feed hole enlarged if u rebuild it set clutch clearances to the min side add a .500 boost valve
Try changing the boost valve, preferably using the .050 valve.This can be done by dropping the pan.How many miles on the transmission?Common problem with the 4L60E.
EDIT: This should have been .500.Not .050.
I would change boost valve 1st to see if the problem is gone.If not,then go from there.At 1 time in the early years of the 4L60E,it was recommended to be changed out every 60,000 miles.
The guy said it was a rebuild with 60kms. It feels strong in forward gears and only slips in reverse when the pressure doesn't come up, but when pressure is at 120 or higher it won't slip at all in reverse so I think clutch pack is OK so far and fluid looks ok.
Can I just enlarge the required hole in plate? I was hoping it could be fixed by pulling pan and not the valvebody.
This is just a stock unit and not looking for performance just a quicker engagement in reverse.
Could the boost valve be sticking? I just wonder why it won't work right with the factory parts?
Crosley would the pressure be as high during WOT test if the reverse circuit was bleeding pressure off somewhere? I will try another used boost valve and see if there is a change.
Also if there was leak wouldn't pressure be higher with cold fluid instead of lower like it is when cold?
If reverse is slipping, likely it is burned as mentioned.
GM made running changes in reverse feed holes, to soften apply.
Drums for reverse input clutch pack with a small feed hole, created a probelm with trans age. Slippage was a result.
larger feed hole in separator plate, does not do much to help small feed hole in drum. Bleed hole in piston must be reduced in size.
Your pressure readings seem wrong at cold. That needs to be diagnosed, repaired. Unless you are in extreme cold , below freezing, the pressure should be higher
It will smoke the tires in reverse so I don't think its slipping, it seems to be a pressure issue, either losing it or not making enough. Yesterday when truck was operating temp the reverse pressure was 120psi and only 75psi when trans was cold or about 70 degrees.
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