[n20ta2]

I getting ready to order parts to build My original 69 gto th400 and I was going to get a 97 and up 4l80e direct drum and 34 element sprag. I discovered if I'm not mistaken that 69 th400 might have a drum that will accept a 34 element sprag?

[70 bird]

It should have a smooth drum and a 16 element sprag. IF no one has been in it.

[n20ta2]

Is that drum upgradeable?

[Kenth]

Yes, your drum will take the 34 element sprag.

[n20ta2]

Originally Posted by Kenth

Yes, your drum will take the 34 element sprag.

Ok great! I had a rebuild kit ready to ship from ptc with a drum and sprag but I may piece together one of my own if I don't need the drum. I think it was 435.00 bucks with the drum.

[Cliff R]

Pay very close attention to the smooth surface on the drum where the sprag rides. It is NOT uncommon to see "chatter" or "witness" marks indicating that the sprag had been slipping some on the drum. I made the mistake of installing one once that had noticeable marks on that surface and ended up with a delay on the 1-2 upshift that required drum replacement. Not fun at all but thankfully it was one of my own units and not a TH400 I shipped clear across the country!..........

[n20ta2]

Originally Posted by Cliff R

Pay very close attention to the smooth surface on the drum where the sprag rides. It is NOT uncommon to see "chatter" or "witness" marks indicating that the sprag had been slipping some on the drum. I made the mistake of installing one once that had noticeable marks on that surface and ended up with a delay on the 1-2 upshift that required drum replacement. Not fun at all but thankfully it was one of my own units and not a TH400 I shipped clear across the country!..........

I will for sure, I was wanting to order parts before I took it apart but maybe I should disassemble it first. I'm thinking someone has been in there at aome point as the fluid looks and smeels great. Guess I will know when I get into it. Where would you go for parts?

[Scott Thelander]

https://www.youtube.com/watch?v=pGOfyFLWYUw&t=1249s

[n20ta2]

Originally Posted by Scott Thelander

https://www.youtube.com/watch?v=pGOfyFLWYUw&t=1249s

I watched that last week, that guy is very knowledgeable. I wish he would do a build series on the 400. I have some experience building transmissions but my knowledge is limited and I haven't done a 400 yet. I built a 4l60e a few years back using as many Sonax parts as I could find and it worked out great. I think if you can build that a th400 would be easy? Im mostly concerned with my clutch pack clearances and stacks and wich parts I should use to get a good trans that will last behind 700 hp

[AG]

They are easy to build especially with a good set of instructions. I've built about 10 of them all mostly stock, including the trans in my race car which got a 34 element sprag and a full manual valve body otherwise it was just replacement steels/friction discs and bushings. It has held up well going 10.0.

[chuckies76ta]

This guy has alot of video on TH400 building and upgrading parts . Mountain Garage. https://www.youtube.com/channel/UCgh...1mIJM6Q/videos. Also get Cliff's TH400 book. Very nice to have, lots of pics also. The 4L80E drum is the one that is most commonly used with an BorgWarner 34 element sprag. Make sure to use the GM spiral locking ring. Do the dual feed on the drum/tranny. Sonnax makes a nice bushing and bearing upgrade for the tailhousing area in case. Get yourself the case saver. Heavy duty case snap ring. I used after market pistons in the forward and direct. Allows more clutch/steel combo. I upgraded the input shaft/forward drum. I also replaced the forward clutch hub and comes with bearings. Cut the housing off and go with a JW bellhousing. find yourself the BOPC case as it the best TH400 case. (strength wise.) deep pan. Brass high flow fliter. on and on. Lots of options.

[Cliff R]

I've haven't been doing a lot of transmissions in recent years. The last one I did was a 200-4R for a local guy for his 1984 Hurst Olds. That trans survived the 350 that replaced the weak 307, then a 425 at 425hp, and now getting abused by a 455 at the 460 hp mark.

I also built a new TH400 for the Ventura after it developed a very slight "slide-bump" on the 1-2 upshift at WOT.

I purchased complete rebuild kits on Ebay and sourced out the 4L80E smooth drum, 34 element sprag, molded apply piston, spiral lock ring and high energy direct frictions from Jake. He also sent me the lower torrington bearing upgrade and a couple other recommended items.

I used to buy from Trasnstar, then Aceomatic Recon in PA, but I quit doing enough per month to stay on their good side so they kicked me to the curb. The Ebay kits are less expensive anyhow, and I don't know how they do it, plus free shipping.

I would "over-buy" on the kit, get EVERYTHING to do the job, bushings, thrust washers (torrington bearings), selectives, bands, steels, frictions, modulator, gaskets/;small parts, but no need to buy fancy steels or friction material. Probably OK if you do but I've never had the first issue once with stock Raybestos, Borg Warner and Alto stuff......Cliff

[Cliff R]

PS: I love watching Richard go thru transmissions, one cool guy right there. He doesn't "bash" to make himself look better or steer work in his direction, which is just plain cool in my book. If you are good at what you do you don't have to resort to all that crap anyhow.......IMHO......

[chuckies76ta]

Originally Posted by Cliff R

PS: I love watching Richard go thru transmissions, one cool guy right there. He doesn't "bash" to make himself look better or steer work in his direction, which is just plain cool in my book. If you are good at what you do you don't have to resort to all that crap anyhow.......IMHO......

Yes he comes across as a very nice guy.
Big Thank you to you also Cliff for all the help over the years to me personally. Just got done building two Th400's
The book sure helps. Nice to see you back.

[Cliff R]

You are most welcome.

Richard is easy going, sounds like a self-taught "country boy" to me. Not sure where he's from or where the shop is at, mid-west maybe?.....

[n20ta2]

I think he is out of Texas.