[chuckies76ta]

Hi Folks: Could use some advice. Need to know what it take to build a TH400 to live at 800-1000 H/P. No Trans break.
What has to be done? Need a list of hard parts. I don't know alot about transmissions.

I already have the 4L80E drum, 34 element sprag, and spiral locking ring. Will this support 800-1000H/P?
I have the heavy duty snap ring. It also has rollerized bearings.
I'm installing a JW Bellhousing on the Case. I have the early BOP tranny case with the metal vent tube.
I also have a Hughes Reverse Manual valve body, that we been using for couple years now.




Thanks
Charles

[steve25]

S A designs has a great book on rebuilding the TB400!

It's worth every one of the 28 bucks you will spend on it and more, I would get it and digest it front to back a few times!

[chuckies76ta]

Thanks for the info. I have Cliff Ruggles book somewhere here but can't find it. After my new garage build it has to be in a box somewhere or I lent it out. I'll have to order a new one.

Charles

[Formulas]

One easy upgrade is the forward clutch hub its cast iron in a stock TH400 and cast steel in a 4L80 plus there is a billet option I would at least go steel

[ErikW]

800 - 1000HP is about the split point before you need a good input shaft and possibly upgrading to a 36 element (pro mod) sprag and drum. If not, at least upgrade your center support to a modified one with a support ring. It's a good idea to have the front surface of the pump "faced" or trued up in a lathe where the bellhousing will bolt on. Also spend the couple of bucks on the case saver to help support the intermediate snap ring. There are so many mods and opinions out there. Do your research. Good luck.

[taff2]

We would use at a minimum- a Vasco input shaft, billet steel fwd hub(or 4L80E steel hub), alloy case lug protector for the HD case snap ring, ATI bushed center support , a roller bearing rear case conversion, alloy pistons in all clutch packs . We also use a Borg Warner high carbon smooth low/rev band and Borg Warner intermediate sprag and low roller 'sprag'.

[chuckies76ta]

Thank you Steve25, Formulas, ErikW, and Taff2. for the info. I ordered Cliff's book yesterday. Time to get reading. I will talk to my builder about the info posted. Thanks again guys.

Charles

[Cliff R]

TH400's can take a lot of power without spending a lot of money on aftermarket upgrades. Most of the ones that come in here that failed in high HP applications pushed the snap ring (tac welded) off the drum or rolled the 34 element sprag over, or both. I've not to date observed a twisted input shaft like we see in TH350's, but it's still a very good move in that direction when you get into the power level you are going to be at.

A little trick I do here to help save the sprag is to use the factory style "waved" intermediate frictions instead of the waffled or aftermarket "flat" variety. This softens the "hit" just a tad and with less shock load the sprag has a better chance of survival. When not using a manual valve body I'm also more conservative with separator plate hole sizing. There is NEVER a need for a lot of line pressure and "window shattering" shifts even for racing applications, it's just hard on everything in the driveline.

It's all about the torque and how hard the trans get "hit" with big power that kills them. High winding high HP engines are not nearly as hard on them. These big CID high torque Pontiac engines are trying to "kill" EVERYTHING behind them and do a pretty good job of it from what I've seen.

The converter is another pretty big player here and the more efficient it is the harder it will shock the trans on the launch and on upshifts......Cliff

[chuckies76ta]

Thanks Cliff. The TH400 that is in the car now has been flawless for a least 6 years. fluid is still nice and pink. I will be removing is fairly soon and have it checked out by my builder. This will tell us what and where to go from here. Were going to add a JW bell housing on the case. I've already have 3 of these BOP cases to work with. The TH400 has been behind our 468 which made 600 hp and 600 torque.
The new engine should make somewhere around 700 to 750 hp and not sure on torque. Just want to have a built tranny that will last the season. Will remove and go throw it to see how it's doing after a season. Maybe shouting for 800 to 1000 is too high for what were doing. I always like to be overkill.

Thanks for the help.
Charles

[Cliff R]

I'm sure it will be just fine at that power level.

I have a TH350 out there surviving coming up on 20 years now behind Pontiac engine at that power level. It's a 505 with 14 to 1 compression, high port heads, well over 700hp pushing a 3400 pound car to high 9's over 135mph. The TH350 has all the goodies, bolt in center support, input shaft, drums machined for additional clutches, 4L60 low sprag, 36 element intermediate sprag/drum, etc. A well prepared TH400 will do all of that without much trouble with just a couple of upgrades in a few places........Cliff

[chuckies76ta]

Thanks Cliff

Charles

[chuckies76ta]

I have another question. I do have a call into Hughes about the booster valve.
So were using Hughes Reverse pattern Manual valve body HP2211R. In the first set of instructions from 5 years ago, it says, Remove boost valve from sleeve, grind two large flats on large land of the valve.
In their latest instructions is does not talk about this mod.
Why do we cut the booster valve large lands down?
And, If that mod is done do we plug the hole in the case?

Anyone!

Thanks
Charles

[Skip Fix]

After fighting getting bellhousing bolts in with a shield I'd look at the SFI certified case at that HP unless you have floorboard/firewall that pulls off easy.
http://www.atiracing.com/products/tr.../supercase.htm

[chuckies76ta]

Thanks Skip: Yes I have been looking at the Reed case, ATI Case. Do you actually own one of these case, and if so what is your opinion on them or which one do you like? I'll check out the link.

Thanks
Charles

[Half-Inch Stud]

HP from BOOST can make too much TQ into the TH400; so steel input Hub, tough Shaft are wise.

Otherwise Stock TH400 Hard parts can handle Ported N/A HP with RPM just fine.

[chuckies76ta]

Yes I have a new upgraded input shaft and forward drum. Also have the Steel hub. It's been a real learning curb, but I'm really enjoying it.

Thanks

[taff2]

The reverse boost valve mod is done to vent the very high line pressure increase to reverse gear that you get when you have a fixed (non vacuum modulated) line pressure, and yes the hole in the case has to be plugged. Some RMVB's have it done internally.
We've used both the Reid and ATI cases, both pretty good, the ATI has machined case passages whereas the Reid has them cast in like a factory case. We preferred the ATI, however, check the case carefully before you use it, we've recently had 2 x ATI cases that had some serious core shift/machining shift that took a bit of time to sort out.

[chuckies76ta]

Well, Thank you very much for the info.. I did manage to talk with a rep at Hughes and said the samething. But I do appreciate your time and info. It's always nice to have backup confirmation..

Charles

Thanks Cliff for the book and your help also..

[70 bird]

I haven't seen this one mentioned. I used a 4l80e intermediate pressure plate. Its thinner than the th400 and allows a 4 friction stack. I bought one new about 10 years ago, it was only about 15 bucks.

[chuckies76ta]

Thank you. I'll talk with builder about it. Good to know

Charles