Technical Need help on a Th400

Hey guys,
I'm going to be rebuilding my Th400. I've never rebuilt a trans before. Can anyone point me to some good books or videos on how to do this. I can use all the help I can get. Oh and a good place to buy the parts would be helpful to. Thanks

 

Google search....there are several great books on rebuilding and modifying T400's....also several good places to get parts and upgraded pieces.

Sent from my Venue 8 3830 using Tapatalk

 

Automatic transmissions like astro tuff are a communist plot.

 

Kiman Transmission & Parts
Hesperia, CA
(760) 935-7020

Close to you. If you have a half price book store near you look for the Motors Automatic Trans Manual. I have one from around 1975 that has great coverage on all A/T.

 

I know the guy who wrote this book, he tried to make it as simple as possible with basic tools.
https://www.amazon.com/Rebuild-Modify-Turbo-Transmissions-Workbench/dp/1934709204

 

Thanks for the info guys. Anyone else have any input. The more info the better. This will be my first rebuild of a trans.

 

Buy the book that was suggested and prepare to get real dirty. With some luck the drums and planetary stuff will be okay to use again, it is available but not cheap. Still you'll spend way less than what a shop would want. Back around 1999 I had a TH350 done as a carry-in and that ran me $300 at the time. I used to do Powerglides (front jobs..) and C4s all the time.

 

Get and keep all parts sparkling clean!

 

I just received an email from Car Tech Auto Books & More, the How To Rebuild and Modify GM Turbo 400 book is on sale at a 20% discount thru Sunday.
Add book to your cart and click “Apply Coupon” with this code-DOW. They charge shipping so I imagine the coupon at least saves that.

 

That is sitting on the bench, right next to me. Good book.

 

I have the Ron Sessions book on the 400, it might be out of print now?

But I still rely on a GM factory shop manual for a 60s or 70s car, for most of my work like that. I have quite a few manuals I've collected over the years.

And I also started playing with them young, when I was in high school....not being afraid of automatic transmissions, goes a long ways towards being able to fix them.

Be sure to ask questions when you get into it, lots of guys here can help

 

Have a big, clean work surface. Place all of your components in the same orientation. I put them in the direction that they face the engine.

I use two milk crates, with the bottoms cut out, so I can put the housing tail-down in them. It makes a nice stand, on the cheap.

Before I had dedicated bushing and seal drivers, I used a revertible multitude of sockets, and a cheap extension.

If you get stuck, stop, take a picture, and ask here.

 

Thank you all so much for all the information. A Chevy th400 and a Pontiac th400 are the same trans but have a different bell housing right? Just asking because I do have Firebird Shop manual I need to check it out and see if it has the trans break down in it. Again Thank you everyone for your input keep it coming.

 

So I just called Kiman Transmission and parts. They'll rebuild it for 800 and they wouldn't give me the price for hard parts. Its better to replace all the hard parts with new right? If your in there and have it apart shouldn't you replace everything with new?

 

Yes, and no. If they are within tolerable specifications, then you would be effectively be replacing like with like.

 

Yes. There are a few variances beyond that, in some bushings. A bunch of new 4L80E stuff fits, too.

 

General you can get buy with a master rebuild kit.
It is always best to disassemble the transmission first, then make a parts list.

 

Agree. "at some point, all of us had parents that stopped tying our shoes, so we learned how"...(or went with sandals)

I did my first and only TH400 in 1983. The only tool I did not have during disassembly , was a 12 point thinwall deep socket needed inside the trans. Back then I had a HS friend working as GM parts guy and he sourced an off brand kit for cheap, as he said that is what his GM dealership used in that shop. I know it had clutch soft & hard plates and every seal & O-ring, but I just don't recall if it had much else in the kit.

I ran it in a 4wd pulling trailers and hauling a pickup camper through deep sand at ocean beach camping, then in 1995, I swapped all the drivetrain into my current 66 Chev camper special. I lost track of miles on that rebuild, maybe 150k max, but it still works perfectly to the present. I suppose I might have installed another TC seal in 95 when it was out.

 

If you have worn out hard parts (pump, drums, shafts, geartrain, etc) then you would probably be better off finding another core transmission to get the parts from, or to rebuild. Usually these parts are in good condition. There were some changes from year to year, but for the most part TH400 is one of the most interchangeable transmissions there is, internally. And they were produced from the mid 60s to the early 90s, used in big cars up to the mid 70s, then in Chevy and GMC trucks for a long time. They are not that hard to find.

 

A few tips:
Yes, BOPC and Chevy are pretty much the same in the shop manuals.
Some models have a different amount of clutches.
Keep everything you take out until you're done, so you can match things up. This includes valve body gaskets. You need to match up them up with the correct ones.
Most kits will have more than you need for yours. Don't worry about it . Just match up the pieces you have in yours.

Buy some Trans-jel and a small brush , and don't be afraid to use it.

Somebody mentioned to keep your sub-assemblies separated and then clean and build them , one at a time, until you get familiar with this stuff.

Use your phone camera often.

Have a rubber tip blow gun handy, and air check your clutch packs as you go along, and then after full assembly.

Don't force anything. You shouldn't have to, if the assembly is correct.

Jump in.. We'll bail you out if we have to. LOL

 

Ok Thanks for all the info and encouragement. So this might be a stupid thing to ask but How will I know what hard parts are good and what's bad?

 

you have to look for wear. Common places are in the pump, the ends of the inner gear teeth will wear against the crescent. The surface inside the drum, where the sealing rings contact it, will wear grooves in it. The bushings can wear down the shafts they ride on. The drums can wear where the band rides on them. usually, you can feel the wear with your fingertip, as well as see it. If you have specific questions, post close up, in focus pictures of the parts, so we can help you evaluate the wear.

 

Look at the planetary gears and ring real close. Also check end play and thrust washers on same.

 

Regarding automatic transmissions
I forgot everything from trade school except one tip from my instructors.
"Keep those red shop rags away from an automatic transmission".