Need help troubleshooting a 4R70W
I know this is my first post, but I've searched everywhere and this seems to be a pretty active place for questions on these trannys.
Ok, short background. I transplanted a 4.6 and a 4R70W from a '93 Lincoln Mark VIII into a hot rod. I am using the PCM and tranny harness to operate the tranny only. The engine fuel and spark are on a stand alone system. I fed the PCM a TPS signal, a brake signal and the required grounds and power inputs and connected the tranny harness. The transmission WAS working, but there seemed to be a 2-3 slippage. After a short time I lost 3 & 4 all together, it would just rev up like neutral.
I just completed a tranny swap from another Mark VIII ('95). I have all four gears, but again, there is slppage going to 3rd. It catches if I back off the throttle.
I have a couple of specific questions that might help me.
1. How is line pressure controlled? What effect does the TPS have on it? Right now the TPS is shared with the EFI system and maybe that's causing a problem.
2. Are there any other inputs needed for the PCM to properly shift?
3. Is too low an RPM a problem? I'm running 2.79 gears and that make the engine RPMs very low for cruising. The car only weighs about 1,600#'s so I wouldn't think that it impose that great a load compared to a 4,000# car.
I know the first instict is I have two bad transmissions, but I don't want to put a good one in and ruin it too. I know the optimum setup would be an aftermarlet controller, but again, I'm not totally conviced that would solve the problem.
Any info would be appreciated.