Posted By: A_Roldan
904 Transmission Slips into Third Gear - 05/09/11 05:37 PM
I have a 1973 Plymouth Satellite w/ a 2BBL/318 and a 904 automatic transmission (the engine does not appear to be original - date stamped 1984 on the block). I've had it for almost 2 years now. Ever since I bought it, it has had a slip in the transmission shift from 2nd to 3rd. I'll try and describe the slip and hopefully someone can give me some tips on diagnosing it.
Under normal/light acceleration, the slip is there but not significant. Under moderate acceleration, the slip is obvious and feels like a trans that is low on fluid and "SLIPS". Under hard acceleration, the slip is severe and the engine will rev high for a second or two then the trans will "slam" into 3rd.
When manually shifting, the slip will still be there under moderate or hard acceleration; it's non-existent under light acceleration or if I take my foot completely off the accelerator pedal, shift into 3rd manually, and then accelerate.
Before I just start throwing parts at it or I pull the trans out of the car, does anyone have any tips on diagnosing this problem?
The fluid levels are normal. The fluid does not smell burnt and it is not dark. I see no debris, shavings or any contamination in the fluid.
Could this be a pressure problem related to a botched shift kit installation? Is it possible that someone has drilled a hole in the valve body separator plate that is too large and it is causing a pressure problem? Maybe swapped some springs and messed up? Could there be check balls in the valve body missing or misplaced? I used to re-build transmissions (almost 20 years ago now...wow!) and I remember installing some shift kits that required specific sized holes being enlarged in the plates, springs being swapped in the valve body and/or check balls being removed. How would I diagnose this without another separator plate and valve body to compare it with?
Is the governor valve something I should be looking into as well? How do I test that or check that it functions properly?
I'd like to eliminate things that can be fixed, changed and accessed from the outside of the trans while it is still in the car before I decide to remove it.
I've rebuilt dozens and dozens of these, but I have never actually had to diagnose one... ironic, isn't it?
Thanks for any help in advance. I appreciate it!
~Angel
Under normal/light acceleration, the slip is there but not significant. Under moderate acceleration, the slip is obvious and feels like a trans that is low on fluid and "SLIPS". Under hard acceleration, the slip is severe and the engine will rev high for a second or two then the trans will "slam" into 3rd.
When manually shifting, the slip will still be there under moderate or hard acceleration; it's non-existent under light acceleration or if I take my foot completely off the accelerator pedal, shift into 3rd manually, and then accelerate.
Before I just start throwing parts at it or I pull the trans out of the car, does anyone have any tips on diagnosing this problem?
The fluid levels are normal. The fluid does not smell burnt and it is not dark. I see no debris, shavings or any contamination in the fluid.
Could this be a pressure problem related to a botched shift kit installation? Is it possible that someone has drilled a hole in the valve body separator plate that is too large and it is causing a pressure problem? Maybe swapped some springs and messed up? Could there be check balls in the valve body missing or misplaced? I used to re-build transmissions (almost 20 years ago now...wow!) and I remember installing some shift kits that required specific sized holes being enlarged in the plates, springs being swapped in the valve body and/or check balls being removed. How would I diagnose this without another separator plate and valve body to compare it with?
Is the governor valve something I should be looking into as well? How do I test that or check that it functions properly?
I'd like to eliminate things that can be fixed, changed and accessed from the outside of the trans while it is still in the car before I decide to remove it.
I've rebuilt dozens and dozens of these, but I have never actually had to diagnose one... ironic, isn't it?
Thanks for any help in advance. I appreciate it!
~Angel