Drum explosion...

-
LXguy

LXguy

Well-Known Member
Joined
Jul 23, 2008
Messages
2,302
Reaction score
109
Location
Champaign IL
Hey All:

Seems like all the transmission builders have all kinds of horror stories about drum explosions in mopar transmissions.

Does this happen a lot or what? Why doesn't this happen to Ford or Chevy transmissions? (or at least I've messed with both of those and nobody's got all the skulls and crossbones about the stock Ford/GM stuff).

Do you guys run these upgraded drums in your trannies?

Steve
 
LXguy said:
Hmm:

I wonder how hard it is to put a th350 in a Dart?
Click to expand...

Not hard at all if you trade it for a Nova. :snakeman:

How often are you going to see 9000 RPM? If the answer is not at all or very seldom, don't worry about it. If it will make you feel any better, I have never had, seen, or heard from anyone I know, of a Torqueflite exploding. I have seen 2 TH350s explode behind a warmed over 350. The stoutest engine I ever knew of being hooked to a Torqueflite was a tunnel rammed Hemi.
Remember, tranny builders are not giving out information for free unless they can make a dollar off it.
 
True that there on money and hints for anything.

Torqueflights are known to be the baddest ***' in the biz.
 
i had a 727 in my 66 charger with a mildly worked 440
and trust me they can take a beating :-D

oh we need to get the dancing banana emote like they have on astro empires
it rocks
 
ive never heard of a tf drum exslosion....try rick at A@A TRANS 317 831 3066 all he dose is tfs....good luck
 
as long as you have as low band apply valve body , bolt in sprag , a trans blanket , or shield ... no worries.

dont forget to always start your burnout in 2nd gear.

Ive never seen a TF explode personally
 
Very good points, 496dart. However, a bolt-in sprag won't prevent an explosion. We like to upgrade to the 16 element bolt in sprag for better holding power/sprag protection over the 12 element sprag.

Along with the low band apply valve body, I'd highly recommend a billet from drum that is capable of freewheeling 15,000+ rpm. It's the drum that over-revs and explodes (stock drum explodes around 9000 rpm) when the sprag fails. Keep in mind that's transmission gear-train RPM (engine rpm x gear ratio).

Like was mentioned, it's a tough transmission and works very well with good components/build techniques.

:thumbrig:
 
Do I have to Drill/Beat this into your Heads? The "Explosions" your hear about in Mopar tranny's come from "running the car" AFTER the "sprag" gets damaged with an improper burnout or mechanical failure. Most don't recognize the failure, And Upon the 2 nd run you'll have tranny parts Scattering all about. The sprag usually fails in 1st gear where all over a sudden you hook on dry ground. Easy way out, Just get em spinning n go to 2nd gear as quick as possible. You'll never have a problem
Now, Here's where it gets tricky... If you run a 904 stock n fresh ...Say 750 HP (Which it will handle) you gotta redo it every round of racing. Say 500 hp into a 904 redo it every year, 400HP and it will last say 5 years.

Anything more than 700 Hp and you'll want the 727 for sure. But Same Rules Apply... RACE it Hard (aka 1000hp +), redo every round .... Race it say 800 HP and your good for a "Season".

Someone add to this I know I left a bunch out but it late here

Eric
 
A stock 904 will handle 750 HP?? Then that means my 727 will handle my 380HP for life!! Hot damn!

I think the 727 & the powerglide are at the top of the list as far as trannies go. Im not a GM person, but I will admit, powerglides are some bad ****'s.
 
The sprag's outer diameter is splined and so is the case. In stock form it is held in place by a set screw and the splines. If splines/setscrew/elements fail, the front drum will spin twice the engine rpm. The stock drum is pressed powdered metal. It will explode at 9000 rpm (4500 engine rpm). The bolt-in sprag with the additional elements (rollers) will help prevent this and the billet drum won't explode.

Chris is right and knows his stuff, that's why I recomended him to you. Chris was kind enough to supply parts and knowledge to me on my 4x4 727 build and I couldn't happier with his service. Like I said before, I've seen his trans's make pass after pass after pass here at Bandimere raceway on a 10.4 second car. BTW, that car and driver won ET class last time I saw it.

Chris, thanks for all your help! The trans works great and shifts good and tight.
 
Joe, Thanks for the kind words, and thanks so much for your business. I'm glad to hear the trans. is working great! :thumbrig:
 
The onlu way to permanently fix that possiblility is a billet front clutch retainer. That's the part that fails when somethign else does. Never seen it in person, but there's a lot of guys that are new to driving these cars that have no clue how to do it without hurting them. A&A sells a drum in steel or aluminum, as do I think about 3 others. It also lets you run the Hemi band and extra clutch disks, so it's not just safety, but gives you more holding power too.
 
I've only seen one 727 explode, it was in a wheelstander called Chevy Rebellion. Blown big block chevy with a 727 behind it. Damn thing didn't even have a shield on it. It had one the next time it came around though.

Everyone is right that sprag failure causes the front clutch drum to overspeed and explode. That drum is big and heavy in a 727. I've never heard of a 904 drum exploding. And Eric my friend I've run my 904 at 600 horsepower, with 4000 rpm tranny brake launches in a 3100 pound car for years without the need to rebuild. They are a lot tougher than many people think. The Super Stock racers were using 904 guts in a 727 case many years ago and they lived up to around 850 HP. Now ProTrans out in California and Marv Ripe's A1 trans make all billet pieces for the 904 and ProTrans adapts it all into a 727 case for the Stock and Super Stock guys that have to run the original type trans case.

My personal opinion is you don't need a rear band apply valve body if you take certain precautions. Start your burnout in 2nd gear, or shift to 2nd right away. Don't race the car after a driveline failure that occured in 1st gear until you take the trans apart and inspect the over running clutch and drum. If the trans doesn't seem to be working right when taking off from a stop, don't race it, fix it first. And most importantly, do use an SFI approved shield or blanket.
 
You must log in or register to reply here.
-

Back
Top