Direct drum explosion

[Matt69olds]

Anyone who spends a little time on this area of the forum have probably read about my rantings of not shutting off the engine at high speeds, putting the shifter in neutral at speeds, high engine RPM with a cast iron direct drum, proper burnout procedure at the track, etc. This is why it’s so important. Before anyone starts in with “junk Mopar” comments, the exact same thing happens to th350 and 400 transmissions. I have seen the carnage many times, I consider myself very fortunate that I don’t personally know anyone who has been injured by this.


https://bangshift.com/general-news/...res/kaboom-this-cudas-transmission-explosion/

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[Vbb199]

I don't really know ****, but I thought it to be wise to setup a scattershield in the floor to keep someone from getting hurt when it grenades?

 

[Matt69olds]

After a certain elapsed time a blanket or shield is required. Unfortunately, some cars have really tight transmission tunnels and a shield won’t fit without extensive floorboard surgery. Which is much preferred to foot surgery!!

Some of the aftermarket transmission cases are S.F.I. approved and don’t require a shield, or have an internal liner to contain the shrapnel.

 

[Keith Seymore]

Re: Video #2 - nice oiling down the middle of the track, Mr Mopar guy.

K

 

[Matt69olds]

I noticed that as well. Common courtesy to get as close to the edge of the track as possible in the event of oil down.

 

[Vbb199]

After a certain elapsed time a blanket or shield is required. Unfortunately, some cars have really tight transmission tunnels and a shield won’t fit without extensive floorboard surgery. Which is much preferred to foot surgery!!

Some of the aftermarket transmission cases are S.F.I. approved and don’t require a shield, or have an internal liner to contain the shrapnel.

I've seen those before while browsing for transmissions

 

[jeff406cid]

It's always amazed me that the Turbo 400 direct drum is turning at 2.5 x speed of the input shaft in the opposite direction. That means at 5000 RPMs in a shift from 1st to 2nd that drum is turning 12,500 RPM, and has to be stopped dead to complete the 1 to 2 Shift!!!

 

[Matt69olds]

And then accelerated back up to engine speed for the 2-3 shift. When you think about it it’s amazing they hold up as well as they do.

I try and steer people towards the aluminum drum when they start talking about 7k-plus shift points. Those 14 pound steel drums were never designed to spin that fast, and considering they are 40 plus years old, it’s just smart.


If your lucky and it just rolls the sprag, all you have lost is 2nd gear. If you can even find the desirable sprag style 400 drum, just the34 element sprag is a 90 bucks. The 4l80 drum cost about 100 bucks and doesn’t work as well for transbrake applications. At the minimum, your looking at 300 bucks in parts to fix a rolled sprag. Your halfway there to a good aftermarket aluminum drum.

 

[Keith Seymore]

Matt - do you happen to know if a trans brake valve body is available for a standard forward shift pattern?

Seems like they are only out there commercially for a reverse pattern.

K

 

[Matt69olds]

CK performance offers one, I installed one years ago for a buddy. It worked ok, it wasn’t super fast release, but he wanted a brake and to keep his factory shifter.


Jakes performance offers a automatic shift transbrake (forward pattern). I don’t think he sells the valve body separately anymore.

There was also article in ATRA on building a homemade transbrake, I’ll see if I can find the article. I actually built one, I need to machine a valve to be able to actually try it

 

[Matt69olds]

Well, I found the article discussing it on yellowbullet. But for whatever reason I can’t view it.

https://www.yellowbullet.com/threads/do-it-yourself-th400-transbrake.1024042/