Tranny Slipping

19stang66 said:

So I finally got to drive my Stang for the first time this year. I fixed a couple of tranny leaks and replaced the rear axle seals and put new rear end fluid in the differential.

Now my problem. When I shift into reverse or drive I have to rev the engine before the Tranny will engage into whatever gear i'm in. But once I'm up to speed it doesn't slip at all and runs just fine. I never had this problem last year before I stored her. So I'm thinking it has to be something I just did recently.

Could the new rear end fluid make it slip? I used the Royal Purple Synthetic stuff. Could have I screwed something up when I removed the axles and cracked the differential to drain the fluid? I really don't know whats wrong.

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did you check your fluid at hot idle to see if it's low or not?

anything you did to the rear end shouldnt effect slippage when shiftign the transmission, the rear end is pretty much a completely mechanically driven unit whereas the tranny uses a pump and fluid pressure to get into drive reverse etc
hook up a guage to the test port on your c4 its on the right side of the tranny i believe. wait for it to warm up and check the fluid pressure. use an oil pressure test guage that can read up to a couple hundred psi the test port is a plug right in front of the shift lever on the c4 i beleive. start the car and let it heat up to op temp have a buddy watch the guage and write down the pressures in each gear. hold the brake and shift from park to revers neutral drive 2 and 1 in reverse you should have somewhere between 150 to 180 psi 90-110 in 2 or 1 60-90 in drive and 50-90 in neutral. check each gear while holdign the brake and give it at least 10 seconds in each gear then change gears.
since revers requires such a large amount of pressure to engage correctly if your pump isnt opperating right, normally you will find slippage in reverse before any other gear.

Tom