After everything warms up for a while of driving, when i'm in 3rd gear and give it some gas the RPM's go up but it doesn't accelerate the car.....1st and 2nd gear are strong and the fluid is full still.....The tranny has about 50k on it and never had anything done. It feels like it just can't hold itself in gear in 3rd after the oil is good and warm. Thanks
TH 400 3nd gear slip Check main line pressure. Drive range-second gear ,forward clutch-on,direct clutch -off,intermediate clutch-on.In Drive range-third gear direct clutch is on,check for worn direct clutches.
ok, as I know basically nothing of automatics when I get done with my 19 days of work I am just going to take it into one of the transmission shops that's been around for years. I don't know how to check any of that stuff myself (if it's even possible myself) Thanks for the info.
As mentioned, the direct clutch is the problem. When warm, does your reverse work ok? This clutch is used in both 3rd and reverse. One other problem happens with 71 on up trannys that have not been rebuilt. Starting in 71 (maybe some very late 70) TH400's, metal sealing rings were replaced with teflon ones. As they age, they tend to leak and the pressure to the direct clutch may drop. The main problem are the seals on the center support that feed the direct clutch. Reverse may be slow, but sometimes not as the apply pressure is greater than in 3rd. The only solution at this point is to have the trans rebuilt using ONLY metal rings and no teflon. The center support and direct clutch should be checked for wear. It doesn't happen often on a TH400, but is possible. With only 50K miles on it, a rebuild with quality clutches and rings should solve the problem. It wouldn't hurt to make a few mods to shift firmness. I don't usually recommend a shift kit as just leaving a couple of springs out and 1 check ball will do this. If the trans shop doesn't know how to make the mods, then a shift kit is a simple solution. Good Luck, Mark
Last week I pulled the tranny out and took it apart to put the shift kit in it I bought from JEG's. I have never really done anything with a automatic trans before so it was all new to me and it is crazy how much crap is in a auto trans....anyway, I got it all back together and man does it shift great, it's like a brand new transmission through all the gears, I ran it up from a stop at full throttle to 95mph and now it actually goes to redline before 3rd gear. Thanks for everyone that helped me out with advice also.
Is there a link you can point me to regarding the "home brew" shift kit? I was going to put one in but this seems to have grabbed my attention. By springs I'm assuming you mean in the valvebody. Would this mod be equal to the street option or the race option that most kits let you choose between. TIA :3gears: :beer
the springs I replaced were 1 in the governor, 1 in the valve body 2-3 shift piston (i think that 's what it's called) and one in the front pump housing. The kit also came with 6 new ball bearings and gaskets and a new 2-3 piston.
Glenn, This information on shift kits has been posted a couple of times in the juicebox section. Look for the posts on Switch Pitch valve bodys and the Official rebuild. Am pretty sure I covered what you need in the later post. You can also do a search and find some pics of valve body plates and what holes need to be drilled and what sizes. If you need more info, you can PM me here or send an email to me direct. Mark
