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just rebuilt my turbo 400 ,installed steels clutches springs ,manual valve body,also spring in pump!! Set clutch packs @ low .036. Inter .048 forward .060. End play rear .014. Front .018. Shifts great in 1. 2nd 3rd but I have no reverse!!! Line pressure is about 190-200 but reverse is 310. Any help would be appreciated Thx Dan
almost forgot install ATI MANUAL VALVEBODY THAT I FOUND OUT DOSNT WORK WITH 1987 AND NEWER 400 NOT SURE WHAT MINE IS COULD THIS BE THE PROBLEM
Last edited by Danlennox; Apr 17, 2021 at 01:13 PM.
Since you have 3rd, the direct clutch is ok. I’m not familiar with the ATI manual valve body, does it use gaskets? If so, could you have switched them,
Remove the valve body, apply air to the rear servo apply feed hole. Make sure you can hear and see the band apply. If the wheels are off the ground, you can make the output shaft “walk” each time the servo apply and releases.
Most manual valve body’s use fixed line pressure, that means line pressure doesn’t change with engine load or gear position. If your valve body kit uses a modulator plug in place of the vacuum modulator, no detent solenoid, and omits the governor tubes, it’s fixed line pressure. Depending on what regulator spring you installed line pressure will probably be around 180 (stock spring with 2 horseshoe shims) to a max of 220 (most aftermarket regulator springs). The fact that you have over 300 suggests something is still feeding reverse oil to the reverse boost valve (once again, incorrect gaskets?). Line pressure in reverse maxes out stock around 260 (I think) line pressure as high as yours could have broken the band or cracked the servo piston.
What’s the part number of the valve body you installed?
BTW, the 87 and up case added a 7th check ball and restriction to the rear servo feed, all to soften the reverse gear. To the best of my knowledge, every manufacturer designs a plate to work with every model year case.
Since you have 3rd, the direct clutch is ok. I’m not familiar with the ATI manual valve body, does it use gaskets? If so, could you have switched them,
Remove the valve body, apply air to the rear servo apply feed hole. Make sure you can hear and see the band apply. If the wheels are off the ground, you can make the output shaft “walk” each time the servo apply and releases.
Most manual valve body’s use fixed line pressure, that means line pressure doesn’t change with engine load or gear position. If your valve body kit uses a modulator plug in place of the vacuum modulator, no detent solenoid, and omits the governor tubes, it’s fixed line pressure. Depending on what regulator spring you installed line pressure will probably be around 180 (stock spring with 2 horseshoe shims) to a max of 220 (most aftermarket regulator springs). The fact that you have over 300 suggests something is still feeding reverse oil to the reverse boost valve (once again, incorrect gaskets?). Line pressure in reverse maxes out stock around 260 (I think) line pressure as high as yours could have broken the band or cracked the servo piston.
What’s the part number of the valve body you installed?
part # 403300 pressure checked drums both working , can you tell me how I can air check applied reverse piston servo to see if band is applying
I just looked up that part number valve body, that’s a forward pattern full manual. That changes some things. If this is a Oldsmobile transmission, you don’t need to worry about compatibility issues with a late model case and the 7th check ball. GM didn’t use the 400 trans behind anything but Chevy in 1987 (that I’m aware of).
i found a pic of a case with the 7th ball to help identify what you have.
Last edited by matt69olds; Apr 19, 2021 at 06:23 AM.
I just looked up that part number valve body, that’s a forward pattern full manual. That changes some things. If this is a Oldsmobile transmission, you don’t need to worry about compatibility issues with a late model case and the 7th check ball. GM didn’t use the 400 trans behind anything but Chevy in 1987 (that I’m aware of).
i found a pic of a case with the 7th ball to help identify what you have.
Matt thx for your help,found out it was the Gear vendor od!!! Everyone says if you have forward gears then reverse has to work well thars bull I went through the trans 5 times because of that and sure enough it was the GV took it off and no more problems. Thx again. DAN
Matt just to let people know the GV uses a sprag for forward but clutches for reverse so if it fails you can still drive but YOU CAN LOOSE REVERSE. that came from the manufacturer I spoke with today thx again
I know the gear vender uses a cone style clutch to apply the overdrive, I didn’t know about a sprag inside. So are they saying the sprag is locked all the time? I assume it locks in forward, but need to freewheel in reverse? Now I’m going to have to look up the theory of operation!!!
