jfg455

iTrader: (5)

We have an issue with a TH400 that we put a trans brake in. It is behind a 5.3 with a T70 . Issue is the trans runs about 300 miles, shifts perfectly, brake works perfectly, and then it tears all of the lugs out of the center of the case. We are on case # 4 now and it still does the same thing. We have double and triple checked everything and haven't come up with anything. We thought on #3 that we found it as we found the pressure relief valve in the front pump was in backwards. Fixed that, new converter #3 and it blew up 100 miles later same way. Any ideas fellas? Thanks.

performabuilt

iTrader: (25)

Excessivly high line presure Have you had a guage on it ?

jakeshoe

iTrader: (14)

Too much line pressure is one problem, if you have over 200 psi line you will blow out the case lugs on a TH400. 180 psi will support over 1000 HP if it's properly assembled.

160 psi (stock new PR spring) will support 800 easily.

You need to install a heavy duty snap ring on top of the intermediate pressure plate and also a support. Several vendors have the supports, Rossler is one (and a supporting vendor IIRC).

That will fix your woes,
you can fix the cases with the blown out lugs...

Vortech Converters

if it has you putting a spring and ball in the reverse passage of the case, get rid of that trans brake and get another one.

use a wave steel in the intermediate pack (will probably get flamed for this one)

use a .088 or .106 torqueflight 727 front clutch snap ring for the th400 Intermediate clutch. (which ever one gets you the correct clearance)

To use 4 clutches in the intermediate>> 1 th400 wave steel, 3 4l80-e intermediate steels, 4 4l80-e high energy frictions, and a stock 400 intermediate pressure plate. ='s no more problems. will more than likely use the .088 tf727 snap ring.

jfg455

iTrader: (5)

We were going to put a gauge on it this time around after replacing the T converter (broke the stator) but we only made it a mile after putting it in and the lugs let go again. When we had it out to put the converter in we tore it down and inspected it to see if there was any damage starting. Didn't see any.
The brake is from rednecks off of ebay. I will have to check and see if they use the spring ball set up in the reverse passage as I don't remeber. Thanks for the info.

Vortech Converters

knock off of the tci brake which will work ok. That brake doesn't use the check ball in the case by the center support. Your going to have to get a pressure gauge on it, no two ways about it. You don't want to keep scrapping the expensive chevy cases.

jfg455

iTrader: (5)

LOL! Yea we are down to our last 2 cases. We will have to get it right this time.

WE TODD DID

iTrader: (2)

How much clearance do you have in the intermediates? Too much clearance will do that as well.

ForcedInduction

iTrader: (2)

which snap ring does where? there is a larger one and a smaller one (and the fretting one)

Ive seen them in both locations

I just took a rebuilt th400 apart today and the smaller of the two (the one without the taper) was retaining the intermediate clutches. While the larger one was above the center support.

But have see it the other way around.

Which goes where?

WE TODD DID

iTrader: (2)

The way you said is the correct way.

jfg455

iTrader: (5)

Ok, We checked line pressure before tearing it back out and it was at 190psi@idle in park neutral or drive. It dropped in reverse but that could be because it has an issue. We are pulling it apart now and will see what the clearance is. We are going to assemble it in a new case and check clearance and use a stock spring before rechecking line pressure. We did not have a wave plate in the intermedietes.

Ah! here we go. no broken lugs this time but it did blow the seal clean out of the center support. When we checked the intermediete clearance it was about 3/16"! I would say it is way to much! Ok so it might be more like .150" or so. We will reassemble with new seals and reset the clearance to what it is supposed to be.

jfg455

iTrader: (5)

Put it all back together and it looks like it has .035" clearance (from rest to applied) in the intermediete clutches. It seems there was no steel in the bottom of the pack (WTF big D?). We will see how this one runs.

WE TODD DID

iTrader: (2)

When you check the line pressure, you need to "spike" it and see how high it gets.

jfg455

iTrader: (5)

We ran it to 6k rpm in 1st gear and it never went over 190psi. Same on the brake. It is at 175psi at idle hot and drops to 125psi in reverse.

WE TODD DID

iTrader: (2)

Sounds like you found your problem. You shouldn't have anymore case failures if all is in order.