Tranny explosion

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gm1236

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I saw this on Classracer, a tranny explosion at Numidia today. This is why, as much as a pain in the a$$ they are, you need to run a blanket or shield. I don’t know if this car had one, but I doubt it. I have no idea how fast this car is, my guess it’s just above the 10.99 e.t. that requires one. Most likely a 727. I could be wrong, but I don’t think 904’s explode like that.
 
View attachment 1715534530 View attachment 1715534531 View attachment 1715534532 I saw this on Classracer, a tranny explosion at Numidia today. This is why, as much as a pain in the a$$ they are, you need to run a blanket or shield. I don’t know if this car had one, but I doubt it. I have no idea how fast this car is, my guess it’s just above the 10.99 e.t. that requires one. Most likely a 727. I could be wrong, but I don’t think 904’s explode like that.
Don’t need to be doing low gear hi rev burn outs. Get the rear tires spinning go to second gear. Been running 727 for over twenty years. Never once exploded one! Most of those years with a trans brake !!
 
See above. Shift into second before getting out of the burn out. A bolt in sprag with extra rollers and a valve body with low band apply are good upgrades.
I recently had a sprag let go while lightly accelerating through a light. It locked the back wheels up very violently. It destroyed the sprag but luckily the case was still intact. Numbers matching 340 car so I was very concerned the case was going to be toast.
Hope that driver didnt loose any toes!
Yeah a 904 can do this too. It might be less common since the drum is much smaller.
 
I've seen one 727 let go, it was in a mid 10 second B body. They had a blanket on it but it still bent up the floor board. The transmission looked like a bomb went off in it.

I run a LBA valve body and a steel front drum in mine. It would be great if some one made a SFI approved 727 case.
 
Lighter weight, smaller diameter. Not sure how fast it would have to spin to disintegrate one of those. Never heard of it happening.

IIRC, You'd need roughly 8000-8500 rpm input shaft speed to hit the 904 critical mass RPM point. Yeah, there are a lot of those mopars spinning that level running around!

Even with the shifter in second on a auto VB, you are still in low gear. If you have that situation, as soon as it's up on the tire, get to second gear. I used to get the tire turning with less than full throttle and click to second and lay into the pedal, click to 3rd and let it begin to roll out. If you mash the gas right out the gate in low gear, that's when bad things may occur when something breaks.

With a manual VB, absolutely, start in second with a 727.

Blankets might slow things down. I've seen blankets shredded and shrapnel all over the place inside a car from a 727 bomb going off. Sometimes you are lucky, other times you aren't.
 
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Curious why 2nd gear for burnout ?

To protect the roller clutch from being damaged.

The only thing applied in low, besides the forward clutch, is the roller clutch and the low band if it's a LBA valve body. The band helps hold the reverse drum. The roller clutch is not good at surviving being shocked or going violently from being locked to overrun and smashing the springs.

In 2nd, the front band is on, there is no load on the roller clutch, little chance of damaging it and no way of spinning the front drum to burst speed.

You need to keep from damaging the roller clutch in the water and then having it fly to pieces when you hit it on the starting line, which is the usual scenario. Blowing one up in the water takes some special skillz.
 
I do my burnouts in 2nd gear (high) in my powerglide builds. 5800 stall so you can’t baby it.
 
I rolled the sprag last year. Just barely cracked the case. The problem is people that say “never do a burnout in first” and we have a large range of levels of experience on here. So I’m pretty new and go into the box with my auto shift 727 sitting in 2nd and think I’m ok because I’m in manual 2nd. No, the car is in first. There are just too many variables to make blanket statements about how to run a 727. Here’s what you do, run a 727 you run a shield or blanket. You also run a billet drum. Then you ask a good trans builder what you should do with the exact equipment you have!
 
So I’m pretty new and go into the box with my auto shift 727 sitting in 2nd and think I’m ok because I’m in manual 2nd. No, the car is in first. There are just too many variables to make blanket statements about how to run a 727. have!

Manual low on a auto shift valve body applies the rear band. 2nd or D does not.

A billet drum is good advice regardless what else has been done.
 
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The reason I posted this was to educate the newer mopar racers who have never seen what can happen when one of these bombs lets go. Follow the advice of these experienced racers and never, I mean never make a pass after breaking a rear end without taking the tranny out and checking the overrun clutch. Especially if you are running a Turbo Action cheeta valve body. You can hammer it in second but never let off in first, even in the pits.
Be careful and have fun!
 
See above. Shift into second before getting out of the burn out. A bolt in sprag with extra rollers and a valve body with low band apply are good upgrades.
I recently had a sprag let go while lightly accelerating through a light. It locked the back wheels up very violently. It destroyed the sprag but luckily the case was still intact. Numbers matching 340 car so I was very concerned the case was going to be toast.
Hope that driver didnt loose any toes!
Yeah a 904 can do this too. It might be less common since the drum is much smaller.
You can bevel the edge of the rollers top and bottom!! Then you can double spring every roller ! Install a harden bolt in outer race !! This will help with making the rear sprag as strong as it can be ! I tore up my forward planetary. When I tore the transmission down I found that my bolt in sprag outer race had a crack in it !! So anytime you go into your transmission you need to check that sprag and all the pieces to it !!
 
The way I was showed (right or wrong) by S.Hauser who ran the ex Rossi Challenger here was, 1st gear, lay into the throttle and shift 2nd>3rd almost instantly, my revs would settle at 5000, let the smoke develop and roll out....727 std.pattern MVB. 530hp 440, 4.88's 14x32's, 4800 stall 8". Did 1st gear starts with the 340 car 727MVB, 10x28's 4.30's 4200stall only 370hp, shift to 2nd same way. Never an issue...perhaps I was lucky?...total of 10yrs racing with both.
 
View attachment 1715534530 View attachment 1715534531 View attachment 1715534532 I saw this on Classracer, a tranny explosion at Numidia today. This is why, as much as a pain in the a$$ they are, you need to run a blanket or shield. I don’t know if this car had one, but I doubt it. I have no idea how fast this car is, my guess it’s just above the 10.99 e.t. that requires one. Most likely a 727. I could be wrong, but I don’t think 904’s explode like that.

Mine made a bigger mess than that , the hemi`s oilpan was laying on the ground holding the engine up.
Thirtyish yrs later (or whatever) when they finally redid the dragstrip, I was told there was still parts of my trans. in the grass outside the starting line .
 
There’s zero doubt that most of us were lucky.... some still dance with the devil. My first “enlightenment” was in the early 90s. Friends car launched and BOOM! the final autopsy was that the 8.75 broke first, shocked the sprag, and set up the chain of events we’ve all seen before. Does it happen EVERY time? No... In my early Mirada days, when a performance upgrade was finding a 3.91 chuck in the bone yard, I broke a couple gear sets. Not knowing any better we’d throw another set in and race on. My cousin met the same demise in Vegas at mats. Launched, 8.75 broke, shocked the sprag so hard it broke and cracked the case. Luckily the drum stayed intact.

We’ve run billet drums, blankets/shields on our 727s since that first experience. While it’s always a debate I feel the blanket, if made properly, is a better deterrent for containment. It’s ability to “absorb” the energy is greater over the “solid” CSR style shield imho. We run the CSR as it covers all aspects of the sub 10 sec rules, but on a 727 I’d prefer a blanket :).
904.... much smaller mass, it’ll stay together. Talked with Dave (Pro Trans) about this topic and he’d never seen one come apart either.
 
I ran 9.80’s to 10.40’s from the late 1970’s to early 1990’s with stockish parts in my big block 727’s. Probably my big savior was number one knowing most of the do’s and don’t’s with keeping them together. Good hardcore parts were expensive and hard to come by back then so we didn’t use them. Number two biggie for me was all three big block cars I owned back then had upgraded ujoints, driveshafts, and each had a Dana rearend in them. All weak links that when they fail cause possible 727 issues.
 
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