Digging for info - front drum explosion on 727s

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a70duster

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Hello all, thanks to the internet a lot of us know that the factory front drum will probably come apart when the sprag fails. The driver has to be putting the pedal down while the transmission selector is not in 1st (no Low/Reverse band applied).

For all the drag strip failures, my question is this. Can these failures be tied to a valve body that didn't apply the low band in 1st?
 
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Most of all the big explosions that I saw were in the 1960s
when converters .were not very advanced and traction was
limited = Often racers would neutral start their race cars with
sometimes disastrous results.
I have broken the sprag a number of times with both style valve bodies
and never hurt the drum (Even the light Aluminum Drums). Maybe I was
lucky for a change.
 
GTX JOHN said:
Most of all the big explosions that I saw were in the 1960s
when converters .were not very advanced and traction was
limited = Often racers would neutral start their race cars with
sometimes disastrous results.
I have broken the sprag a number of times with both style valve bodies
and never hurt the drum (Even the light Aluminum Drums). Maybe I was
lucky for a change.
Click to expand...


Oops!


transmission explosion.jpg
 
a70duster said:
Hello all, thanks to the internet a lot of us know that the factory front drum will probably come apart when the sprag fails. The driver has to be putting the pedal down while the transmission selector is not in 1st (no Low/Reverse band applied).

For all the drag strip failures, my question is this. Can these failures be tied to a valve body that didn't apply the low band in 1st?
Click to expand...


Here's some info that may help.

Gallery: Bulletproofing a 727 Torqueflite With TCI Auto - Mopar Connection Magazine | A comprehensive daily resource for Mopar enthusiast news, features and the latest Mopar tech
 
I've read if you do a burnout always shift into 2nd after. If your don't ,when you launch it goes boom!!
 
If you have a small block, have you considered a 904? Smaller drum, much less chance of it exploding. Personally after 40+ years I never had or saw a 904 blow a drum. But it can still have sprag failures due to the usual reasons. Also has the option of a 2.74 low gear and combo will be about .15 seconds faster than a comparable 727 trans & converter.
 
I always do my burnout in second gear (manual valve body or trans brake valve body) then shift into high gear and always let off of the gas pedal (decelerate) when coming out of the water box. I always have a bolt in rear sprag and never do dry hops. In the 40plus years of drag racing I have never had a catastrophic transmission failure. If I brake a drive shaft / u-joint or rear gear I always dissemble the transmission and check the rear sprag for damage.
 
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^^^^ Dry hop with low band applied in 1st gear? Is that bad? Seems no different than launching the car???

Like you, I have a rmvb with low band apply (Griner valve body). Burnout starts in 1st, immediately to 2nd then 3rd, about 5500 rpm then let off throttle, roll out of box.
 
Demonx2 said:
^^^^ Dry hop with low band applied in 1st gear? Is that bad? Seems no different than launching the car???

Like you, I have a rmvb with low band apply (Griner valve body). Burnout starts in 1st, immediately to 2nd then 3rd, about 5500 rpm then let off throttle, roll out of box.
Click to expand...
Seems so much easier than doing a second gear burnout with a 5800 stall converter…. lol
 
I start and finish off in 3rd gear even with my 318 cars.
Never have a problem achieving a good burnout.
I always lift while tires are still spinning.

The problem with the 9/10 second Stock/SS cars is
that they occasionally explode the tires 20 or 30 ft out if we
hit a bald spot. If you do not react fast enough and lift
they will Hook Hard and bang there goes the sprag no matter
how good of a one is in the transmission.

It is never pretty when we take the trans back apart!
 
Not that it applies here since trans tech has advance so far, but many decades ago when guys were using ''stockish 727's'' i was told not to neutral the car at pre stage to ''clean it up'' as many did, but get into 1st gear earlier and go under power in to the lights for 2/3 ft or so. Just rambling, but if any one else remembers this let me know that i haven't lost what's left of my mind...lol
 
I have always put it in neutral when prestaged and check the two step
to make sure it is work and pump the brakes till they are rock hard.
Never had an issue with that myself as of yet.
 
If you aren't starting in second with a manual valve body, shouldn't you start spinning in first and shift into second without lifting? (Lower horsepower car)
 
That would be much better than ever letting
it hook while spinning in 1st, That is the kiss of Death
from Torqueflites!
 
A Glide is the right choice in a light and high HP race car.
It is also cheaper to build for racing.
 
-Boosted- said:
Seems so much easier than doing a second gear burnout with a 5800 stall converter…. lol
Click to expand...
My converter stalls at 5000 hence why I'm around 5500 in 3rd for the majority of the burnout. It's actually a simple process to start in first, shift to second pretty quickly and then to 3rd right away. It's not like you're very deep in the throttle! Then lift and release the line-loc and roll out of the box.
 
Demonx2 said:
My converter stalls at 5000 hence why I'm around 5500 in 3rd for the majority of the burnout. It's actually a simple process to start in first, shift to second pretty quickly and then to 3rd right away. It's not like you're very deep in the throttle! Then lift and release the line-loc and roll out of the box.
Click to expand...
I've yet to do a burnout or stage the car since getting it together as the weather conditions won't allow it....lol

Can't wait for good weather and the tracks to open up next year.
 
A Glide is the right choice in a light and high HP race car.
It is also cheaper to build for racing.
toolmanmike said:
How many glides do you own?
Click to expand...
I have raced several over the years.

I used to own Reed Whisant's (Sic) Old Pro Stock Arrow.
It had a 526 Bl in it and ran 8.21 @ 167 with a Glide at our bumpy old Vegas
track about 30 years ago. I had a couple of old Pro Stock Arrows.
I think that might have been the Arrpw that I sold to Brian at
Indio Machine Shop who still builds some of the very best Small
Block Mopars.

I also raced an A/ED with a glide in the mid 70's and a couple others
not as noteworthy.
 
Low band apply valve body
Bolt in sprag
Billet front drum

Problem solved.

I’ve considered the glide dozens of times. And I have as close to a bulletproof 727 in my car. However, if you have a 727, simply buy the billet front drum, low band apply valve body, and bolt in sprag. Those 3 pieces will cost less than converting to a powerglide.
 
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