tirefryin_s10

iTrader: (3)

So for a little history .... This is a 1979th400 that I rebuilt for my car using the following parts:



Generic cheap rebuild kit

TCI Reverse pattern manual valve body

otherwise all stock internals minus the mods neccesary for the valve body.



car was a roughly 550 rwhp turbocharged ls1 in a 3100 lb mustang. drove nice for roughly 1500 km and 25-30 track passes all in the 130+ mph range and NEVER once felt it slip. Always did my burnouts 1-2-3 I now know this is wrong but at the time did not know any better. one day after doing a large 1-2-3 burnout on the street the trans started to "whine" a little bit and shortly there after roughly 50kms or so it lost 2nd and 3rd gear and reverse was kinda hit and miss but first gear worked fine to limp it home. I dis-assembled the trans expecting to find a blown up stock 16 element ramp style sprag but instead I found some other broken bits ....





Broken retaining plate:









Fried Clutches including hot spots on all the steels:











If anyone can tell me something I did wrong in the build or something that could have caused this and what I should check out on re-assembly I would GREATLY appreciate it - thanks neil

Gilbert@Ace Racing

Well, it'll be hard from the pics.... but... do you have an idea of where your line pressure was / is?

What was the clearance on those clutch packs?

What was the overall total end play of the stack?

What condition are the planets in?

g

tirefryin_s10

iTrader: (3)

Dont remember any of the end plays but they were all within spec ... didnt test line pressure ... the planets apear to be in good shape.

tirefryin_s10

iTrader: (3)

anymore input from the pros?

Gilbert@Ace Racing

Well ordinarilly when a reaction plate fractures like that one did it is related to abusive shifts (blocked accumulators / high line pressure) or an improperly set up clutch pack.

Also, if the plate was replaced during the build, it could have been an inferior part to begin with... brittle steel.

Give us a call if you would like to discuss the build in detail!

g

team39763

iTrader: (3)

QUOTE:Always did my burnouts 1-2-3 I now know this is wrong but at the time did not know any better.

How are supposed to do them? I have TH350 in mine, and I've heard that you're supposed to start in first and once you get the wheels spinning good, quickly get to third and roll out in third.

tirefryin_s10

iTrader: (3)

A th350 is alot different then a th400 and also a full manual valvebody th400 ..... I thin kthis failure can be blamed on high line pressure and possibly an inferior plate ... as far as line pressure goes I just did the mods that were laid out in the instructions for the TCI RMVB so if they are set up too high whats the best way to lower line pressure some?

Gilbert@Ace Racing

Well keep in mind I am not saying that is what caused the failure. It is simply a suggested reason for the failure. The unit would need to be rebuilt and then have a pressure gauge installed to find out where the line pressure is actually at, and then adjust accordingly.

There are simply too many possibilities for the failure to be able to pin it down in a discussion on the phone or on the web.

g

tirefryin_s10

iTrader: (3)

Ok so if I put it all back together wiht a new drum better sprag new clutches etc and a pressure gauge is hooked up how does a guy go about adjusting line pressure if need be?

Gilbert@Ace Racing

The only way to modify Line Pressure in a TH400 is to do one of a few things related to the Pressure Regulator valve in the Pump. Change the Spring, shim the Spring or replace the valve with an aftermarket valve (not likely). Also, it could have a stuck or sticking PR valve.

If you did not modify the pump then chances are that is not the issue.

TCI has you essentially remove Accumuation (cushions the shift). If the clutch packs are not set up properly and an old / blistered Reaction Plate was used then that itself could be the cause of that plate grenading.

g

tirefryin_s10

iTrader: (3)

TCI also has you change the spring in the pump as well ... Not sure if that could have something to do with it?

Gilbert@Ace Racing

Sometimes the answers to problems inside Automatics are not straight forward. Sometimes we make minor changes to setups and get coarse results. And vice versa.

There is a direct correlation to the hydraulic and clutch pack setup. If we have a very harsh hydraulic setup and a sloppy clutch setup bad things can happen. And conversely, if we have a weak hydraulic setup with a tight clutch pack then we can get into trouble just as easily.

The key is understanding the balance.

g

LS1curious

Did you shift to nuetral at high speeds ? Looks like the drum cracked. Any pistures of the drum ?

meandmyls1

I'd clean it out and rebuild it, then take some pressure readings.
I built a RMVB TH400 with a Turbo Action VB. Used a vacuum mod plug, stock pressure spring.
I always did my burnouts starting in second, then to third.
When I sold the car five years later it had been behind three big blocks, never been opened up, been up to 8500 rpm. Fluid was still bright red.

I've dropped at least one of those pressure plates and didn't see the crack it left right away.
I think if that was missed it may have failed similiar to yours.

Rock-On

iTrader: (-2)

Inferior plate replace and set up stack, put it back toget and look at line pressure...you got a boost spring with your valve body, use it , look at your pressure when you've got it together 300 psi is,nt un common for performance build while your there dump the cast rings, they don't like high pressure...hope this helps..Dave

tirefryin_s10

iTrader: (3)

drum appears ok , but I will have to inspect it better ... the trans was never shifted to neutral at speed (I know better then that) only problem is this trans is going to be sold to a buddy and it wont be super easy to get a pressure reading on it anytime soon.

Rock-On

iTrader: (-2)

theres nothing in your pics that indicate high pressure, These parts are pushing over thirty years use, build up the unit and reinstall, this plate breaking is common. Don't get confused with cast iron parts vs. alum parts. These units will handle 300 psi where the 60e's won't. Thats what makes for a good hard launch, but i really doubt you have a hi pressue problem. Hope this helps Dave

tirefryin_s10

iTrader: (3)

Ya thanks alot ... Next thing is in a 450 hp application if the burnout is always done 2-3 how will a ramp style 16 element sprag hold up ? Im looking to get this back together without spending a pile of cash on another drum / sprag etc ... the car its going in now doesnt make near the power of mine and mine didnt hurt the sprag even with doing burnouts the wrong way.

FLT

iTrader: (1)

I don't care what unit your running. 300psi is way to much pressure. For a 400 175-225psi is more than sufficient. To the original OP. As mentioned a pressure test is not a bad idea. Might want to check your boost valve sleeve in the pump. Make sure that it is not worn. I know in a 4l80e pressure spikes from a worn boost valve have been known to break pistons, drums and pressure plates in the direct circuit. Might be something to consider.

tirefryin_s10

iTrader: (3)

I checked it out pretty good when replacing the spring but maybe ill check it out again while its aprart , thanks again for all the input guys it really helps !