I have no idea what's going on.... 401 Nailhead, 10" torque converter, ST400. This is the second time it's been rebuilt. The first time my close friend Jimmy TuTone and I went through and rebuilt it. New, quality kit that was built to stock specs. Second time I had a well known racecar transmission rebuilder go through it. Both times the same problem surfaced. Once it shifts into 3rd it feels like I put the brakes on and stays on as I'm slowing down until it reaches idle then it lets loose. Go through 1st and 2nd fine and hits 3rd and on goes a brake feel. Jacked up the rear and cycled through the gears this way. When it goes into 3rd it seems like it locks and unlocks. Clunk, Clunk, Clunk.... It also has no engine braking in 1st. I've also disconnected the electricals with no difference. Any thoughts??? BloodyKnuckles
I am going to start with the no engine braking in first; Was the rear band apply piston rings replaced and if so with what, I prefer the cast iron rings, was the rear band pin length checked for the proper length with the Kent Moore band apply tool ? Hits 3rd brake feel Does the center support have a shim under it ? later ones do. The center support can rock in the case when this happens you will see wear marks in the case and also on the center support; a lot of the times the center support bolt will be broke. If the case and the center support look good; how was the center support bushing installed ? I prefer to coat the outside of the bushing with 518 locktite before pressing it in the center support this will seal It; as you can have leaks when applying this clutch "direct drum" (This is applied in third and also in reverse) was there ring wear in the drum? If you have witness marks much wider than the rings you have to much end play. I like to lightly hone these drums "direct clutch" with a ball hone before assembly. I would also recommend new bushings in the pump as the oil has to change directions (apply and release) for the switch pitch to work. I would also apply power to the switch pitch solenoid and blow air into it while doing so, so you know the solenoid is working properly. There has to be two component's applied for each gear in Auto D (first gear) the forward drum is applied in first along with the sprag or roller clutch behind the center support. Auto D (second gear) the forward drum is applied the roller clutch attached to the direct drum is in play. Auto D (third gear) the forward drum is applied and the direct drum is applied. D1 the forward drum is applied in first along with the rear band (if the rear band is not applied you will feel no braking) the sprag or roller clutch behind the center support will take over. D2 (second gear manual) the forward drum is applied the front band is applied ( if the front band was missing or would not apply the roller clutch attached to the direct drum would take over however you will feel no braking. I think if you have a switch pitch you are probably running sprags instead of roller clutches a sprag can be flipped and lock in the wrong direction also there is a ribbon that pulls the cams around this can be damaged. Have you put a pressure gauge on the line tap? If you need to replace the center support the new one with the shim is thinner to accommodate the shim. Sorry I was so long winded but their are a lot of things involved. I would recommend checking pressure first and then If you have to tear it down look real hard at the center support. if you change center supports you will need a front planet for a roller clutch
There is a sprag unit used in the first couple of years for this trans that is easily assembled wrong when rebuilding. Get the correct manual and there will be a photo of the correct installation. The Buick unit has a few differences. Your symptoms sound like this could be your problem.
Guys, I can't thank you enough for all the help and info. We tore it down and found the sprag was installed incorrectly. My transmission rebuilder was embarrassed. I explained to him that all professionals make mistakes and we're all human. All I cared about was that it was fixed. The car runs great now!! I am very, very pleased. Thanks. BloodyKnuckles
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