Ive been wondering, as with everything ive done in my car, i want to learn first hand how to do every single thing, so far everything ive done from rebuilding rear ends, to engine builds ive done successfully. cant stop there, so im asking has anyone ever rebuild a th400 tranny? i know its a trial error thing so i would not be too mad if i were to waste that money in learning, im still getting my th400 rebuilt by a pro though, but would love to learn the hardway i guess. any input would be great. thanks
Ideally you would want to find a professional transmission guy to help you with it so you can learn the little things that aren't in books. I am also a do-it-yourselfer who has never been afraid to dive into something new. About 30 years ago I had a K5 Blazer and was off road one day and ended up breaking both ends of the case in the trans. The cause, of course, was stupidity, but I knew the trans was good other than it as no longer connected to the engine or transfer case and I had another th350 trans out of a `69 Impala that I knew nothing about. This was my opportnity to learn so I bought a rebuild kit from GM and pulled the Blazer trans all apart and laid it all out on a sheet as I took it apart. I then installed all the components from the good trans into the Impala case I had torn down, replacing the parts as I went with the new parts that came in the kit, then put it all back together. I was pretty proud that it actually worked great........for about 5 miles, at which point I lost 3rd gear. By the time I got back home all I had was 1st. Feeling defeated I went to the junkyard traded it in as a core for a good used one. Some time later I was talking to a transmission guy and he said to bring it in and he'd take a look. Unfortunately I didn't have it anymore but he told me it could have been something very simple, like I may have nicked a seal when I put it together, which was a definite possibility because I didn't have the proper tools, I just lined stuff up and dropped it in. That was my 1st and last experience with automatic transmissions other than changing them and installing shift kits. I'd love to try it again someday if time permits it, only with the proper tools next time. I have a book by Ron Sessions marketed by Motorbooks International called 'How to work with and Modify the Turbo Hydra-Matic 400 Transmission". I think purchasing a copy of it or a similar book would be a good starting point and a excellent reference while you're working on the your transmission.
I did "sort of" The bus mechanic at school has his own shop he and I rebuilt my trans. There are a ton of parts but they can only go together in a certain way. I imagine after you did a few it would be real easy. In closing GO FOR IT. Seems like you have the right attitude for it.
I bought me a book Walter, and have a tranny sitting in the floor. I'll get there some day soon. Go for it.
Get the manual from ATSG; It covers most of the mods needed and updates. Hardeest part is the special tools needed; Some can be made using angle iron, flat bar stock, steel tubing, and a welder. Will definitely need a press. I made seal install guides using 0.002 thick flat brass shim stock and a pair of shears, and lip seal tool using piano wire and a small piece of aluminum tubing. (No; I'm not Mcguiver) This was on a 200-4R with 'original' Art Carr (now CPT) super rebuild kitfor my turbo Limited Regal. Held up for over ten years,and I was NOT gentle with that car.
Just last week I finished my first TH400 rebuild (not just the steels and plates, but every single seal and bushing).... a good manual and taking lots of time did the trick. The second TH400 I already disassembled... now a rebuild is fun to do (and faster)
Yea, i learned few tricks a while back when i replaced 3 front pumps from a th350 th400 and a th700 r4. i will look forward to finding the book. hopefully i can get on that pretty soon. So far ive been lucky enough to get every DO-it-Yourself thing good enough to hold on. So if this does work ill be proud of myself. i figured there are guys in my area doing hi performance builds for about 400-600 for the th400 and i imagine, after a couple of trannies and having the right tools, it should be pretty straight forward. We'll see what happens. Dont be amazed if i start a thread later on about putting it back together.o No: So whats the first thing that goes wrong when, the tranny slips a bit from parking to gear. You have to tap the gas a bit for the tranny to engage, maybe its just the front pump or something like that. happens all the time as if it has low fluid, but its good. works great after its that. only at take off. figured it be the front pump again.
A worn front pump can result in low line pressure which means less clutch pack compression, but internal leakage past old rubber piston seals can do this too. If you want, you can plumb an external pressure gage and perform the pressure tests mentioned in the Sessions book to get a better idea of what's going on. I did my frst TH400 in the '80's with that book plus the chassis manual, but had to rely on a neighbor who had some of the other tools mentioned; he answered a lot of questions for me too. I made sure I had plenty of open, clean space to keep everything in order as it came apart. You'll need lots of clean mineral spirits and compressed air for parts cleaning. No shop rags allowed. Devon
Yep, ive heard allot of stories behind shop rags, ive heard of a story when someone rebuilt a tranny and used nothing but shop towels and the tranny went bad, they opened it apart and found a furrball inside. So i know for sure not to use that. my main question is where and how the clutches go, also how many clutches can i include for harder and stronger shifts. ill be getting a manual and a dvd so we'll c what happens.
Disclaimer: I have not yet rebuilt an automatic transmission, but plan to this summer. However, I HIGHLY recommend getting one of the DVD's (I got mine on ebay for $25 or $30). That way you can see exactly how things come apart AND go back together, in color, with the guy explaining exactly how you do it. I think that the manuals can be helpful, but that the DVD just gives that much more. Every step by step is shown, not every third or fourth like most of the manuals have. I have at least 4 manuals by the way and figure between those and the DVD I should be set. I also purchased the correct specialty tool for clutch pack compression and something else(?). It was a KD tool from summit racing, and it was around $120 if I remember right. I think it will work for both TH400 and TH350 so eventually it should pay for itself.
I have rebuild about a dozen TH400 thus far. I highly recommend the book "How to work with and modify the Turbo Hydra-matic 400 Transmission" by Ron Sessions. Shows how to rebuild the thing and any special tools you may need, or other tools you can get by with. Great book and I have had some transmissions in 11 second cars with no problems. Good luck. http://www.amazon.com/Modify-Hydra-Matic-Transmission-Motorbooks-Workshop/dp/0879382678/ref=sr_1_1?ie=UTF8&s=books&qid=1263783433&sr=8-1
