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Re: 727 explosion poll
[Re: SportF]
#2642098
04/06/19 10:13 PM
04/06/19 10:13 PM
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Joined: Jan 2003
Posts: 7,475
Minnesota
Hemi_Joel
master
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master
Joined: Jan 2003
Posts: 7,475
Minnesota
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If you rely on a mistake free existence for your safety, you are living dangerously. 
[img]http://i.imgur.com/boeexFms.jpg[/img]31 Plymouth Coupe, 392 Hemi, T56 magnum RS23J71 RS27J77 RP23J71 RO23J71 WM21J8A I don't regret the things I've done. I only regret the things I didn't do. "Wise men talk because they have something to say; fools because they have to say something. ~ Plato"
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Re: 727 explosion poll
[Re: farmboy]
#2642168
04/07/19 07:49 AM
04/07/19 07:49 AM
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Joined: Jan 2003
Posts: 2,915
A shed in England
Tig
master
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master
Joined: Jan 2003
Posts: 2,915
A shed in England
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Ring and pinion failure caused this, there's enough internet pics and scarey story's out there to make me put the good stuff in.  (LBA VB, super sprag and Steel drum) ![[Linked Image]](https://i.imgur.com/5O2t4Ss.jpg)
'74 Challenger..9.46 @ 145.9 1/4, 6.001 @ 118 1/8 so far. 4023lb !!! # N/A, Marsh performance 655ci, Indy Maxx, T/R, Indy 600-13 X's, Street legal, pump gas, full interior, Cal-Tracs, mufflers, 3:73's and real 10.5 radials.
9.51 @ 142.4 1/4, 6.003 @ 114 1/8 with our old mule KB, 572-13, 580 wedge.
RHD '68 Barracuda Fastback 323ci street/strip. Best ET 13.88 @ 99.03
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Re: 727 explosion poll
[Re: Tig]
#2642173
04/07/19 08:20 AM
04/07/19 08:20 AM
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Joined: Jan 2005
Posts: 2,540
Milwaukee WI
TRENDZ
master
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master
Joined: Jan 2005
Posts: 2,540
Milwaukee WI
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I responded to the poll with a no. I have seen what was left of a trans when they blow, but it never happened to me.
Im putting a clutchflite together here in the near future. It will have a good drum etc... I’ve been sold on that for a long time.
What I was thinking after reading through this thread though, is how can you know if the sprag failed without opening up the trans?(or having it open itself up) I had an A&A built 727 in the turbo car. I kept shearing pinions off of the rear end. The last one did some damage to the car( driveshaft whipping around) Anyway, after having that trans out a few times for inspection, I thought it would have been nice to know if the sprag is ok without going in.
Anyway.... since im going to be doing this trans, it would be pretty simple and cheap to install a drum speed sensor in the trans. With EFI, I can set my drum rotation limit to say 500 rpm higher than engine redline. If the drum exceedes that threshold, the ECU can shut down fuel/ ignition.
Good/ Bad/ Ugly? Anybody see a potential problem with doing this?
"use it 'till it breaks, replace as needed"
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Re: 727 explosion poll
[Re: TRENDZ]
#2642199
04/07/19 09:22 AM
04/07/19 09:22 AM
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Joined: Mar 2003
Posts: 2,491
PA
moparacer
top fuel
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top fuel
Joined: Mar 2003
Posts: 2,491
PA
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I have never blown one up but have seen guys blow them up and seen what was left after guys blew them up and all I have to say is that is enough to put the fear of god in you about blowing one up. If you break something in the drive train you pull the tans and check the sprag....PERIOD.
67 Barracuda street/bracket car 11.27-119
68 Dart 502 BB 8.70s-152
414 cid SB Dragster 7.65-174
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Re: 727 explosion poll
[Re: TRENDZ]
#2642285
04/07/19 01:19 PM
04/07/19 01:19 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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I responded to the poll with a no. I have seen what was left of a trans when they blow, but it never happened to me.
Im putting a clutchflite together here in the near future. It will have a good drum etc... I’ve been sold on that for a long time.
What I was thinking after reading through this thread though, is how can you know if the sprag failed without opening up the trans?(or having it open itself up) I had an A&A built 727 in the turbo car. I kept shearing pinions off of the rear end. The last one did some damage to the car( driveshaft whipping around) Anyway, after having that trans out a few times for inspection, I thought it would have been nice to know if the sprag is ok without going in.
Anyway.... since im going to be doing this trans, it would be pretty simple and cheap to install a drum speed sensor in the trans. With EFI, I can set my drum rotation limit to say 500 rpm higher than engine redline. If the drum exceedes that threshold, the ECU can shut down fuel/ ignition.
Good/ Bad/ Ugly? Anybody see a potential problem with doing this? The sprag can still let go.. are you talking a 727.. you can figure out the RPM that it can let go if you use 2.2 times the engine rpm to see if the rpm is lower than 12500 rpm.. thats basically the rpm that the drum can handle before centrifugal force lets go and it blows 
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Re: 727 explosion poll
[Re: J_BODY]
#2642306
04/07/19 02:32 PM
04/07/19 02:32 PM
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Joined: Feb 2003
Posts: 990
Addison,IL
OUTLAWSSAA
super stock
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super stock
Joined: Feb 2003
Posts: 990
Addison,IL
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How does “learning to drive” play into the rear gear breaking causing the event? Both situations I was present for were seasoned racers. Proper burnout, move to the line, bring up the rpm, green/go/BOOM!! in both of these situations they were foot brake cars so the preload was there. One a high 9 car, the other a 10 sec deal with NOS that wasn’t even used that day. Both 8.75 There is something your stock drum can do that a billet or aluminum can’t. In the event of mayhem you’ll have the chance to see  I ran a lightened cross drilled stock drum in the Mirada for many years. I broke a set of gears (8.75 of course) and threw another set in. I was lucky.... to be honest back in the day I didn’t have a clue. Chuck Lofgren was at the track the day my friend blew the floor out of his Challenger. He stopped by and took a look and educated us, matter of fact he pretty much assured us that the gear was broken even though it pushed back and towed back to the pits ok. He was spot on. I still say upgrade that 727 front drum. Cheap insurance. Think of all the bad things that “could” happen that are eliminated by this upgrade. This post makes all the cents in the world. I don't care if you've been running a stock drum for 150yrs. You shouldn't be running a race car with a stock drum. Your playing with fire.
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Re: 727 explosion poll
[Re: TRENDZ]
#2642316
04/07/19 03:01 PM
04/07/19 03:01 PM
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Joined: May 2003
Posts: 6,558
Downtown Roebuck Ont
Twostick
Still wishing...
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Still wishing...
Joined: May 2003
Posts: 6,558
Downtown Roebuck Ont
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I responded to the poll with a no. I have seen what was left of a trans when they blow, but it never happened to me.
Im putting a clutchflite together here in the near future. It will have a good drum etc... I’ve been sold on that for a long time.
What I was thinking after reading through this thread though, is how can you know if the sprag failed without opening up the trans?(or having it open itself up) I had an A&A built 727 in the turbo car. I kept shearing pinions off of the rear end. The last one did some damage to the car( driveshaft whipping around) Anyway, after having that trans out a few times for inspection, I thought it would have been nice to know if the sprag is ok without going in.
Anyway.... since im going to be doing this trans, it would be pretty simple and cheap to install a drum speed sensor in the trans. With EFI, I can set my drum rotation limit to say 500 rpm higher than engine redline. If the drum exceedes that threshold, the ECU can shut down fuel/ ignition.
Good/ Bad/ Ugly? Anybody see a potential problem with doing this? The only problem with that is it doesn't allow for inertia. Kevin
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Re: 727 explosion poll
[Re: Twostick]
#2642353
04/07/19 04:30 PM
04/07/19 04:30 PM
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Joined: Jan 2003
Posts: 3,830
N.E. Ohio
6bblFLASH
master
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master
Joined: Jan 2003
Posts: 3,830
N.E. Ohio
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No never broke one either. Have seen a couple friends blow them apart,,,,,,,,,ugly for sure.
My trans guy and very experienced racer said " if the output drags in one direction and freewheels the other,the sprag is working";
This what I check on a regular basis. So far I still need 2 shoes...........
70` Cuda`,440 6BBL Jerico,Dana 4.56 Still on 93 Pump Gas
9.87 @ 136/1.31-60ft.`09 Mopar Nationals PASSON PERFORMANCE "Stick-Shift" Champ!
2013 StickShift Challenge Winner@ Mopar Nationals!
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Re: 727 explosion poll
[Re: Twostick]
#2642449
04/07/19 08:52 PM
04/07/19 08:52 PM
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Joined: Jan 2005
Posts: 2,540
Milwaukee WI
TRENDZ
master
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master
Joined: Jan 2005
Posts: 2,540
Milwaukee WI
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So, if drum speed cuts fuel and ignition, how would drum speed ever exceed its programmed limit?
Even if the sprag is in a failed state, the drum would go 2.45 x engine rpm. But engine rpm is not the fuel/ignition cut determing switch, drum speed is.
Lets say I set max drum speed at 8000 rpm, if the sprag was in a failed state, engine rpm would only get to a little over 3,265 rpm before fuel/ ignition cut. A bit of inertia wouldn’t let it exceed the rpm limit, it would only prolong its deceleration.
"use it 'till it breaks, replace as needed"
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Re: 727 explosion poll
[Re: TRENDZ]
#2642454
04/07/19 08:58 PM
04/07/19 08:58 PM
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Joined: Mar 2006
Posts: 9,813
MI, usa
dvw
OP
master
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OP
master
Joined: Mar 2006
Posts: 9,813
MI, usa
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So, if drum speed cuts fuel and ignition, how would drum speed ever exceed its programmed limit?
Even if the sprag is in a failed state, the drum would go 2.45 x engine rpm. But engine rpm is not the fuel/ignition cut determing switch, drum speed is.
Lets say I set max drum speed at 8000 rpm, if the sprag was in a failed state, engine rpm would only get to a little over 3,265 rpm before fuel/ ignition cut. A bit of inertia wouldn’t let it exceed the rpm limit, it would only prolong its deceleration. If the engine was limited 3200 rpm you'd be pretty slow. Doug
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Re: 727 explosion poll
[Re: dvw]
#2642465
04/07/19 09:11 PM
04/07/19 09:11 PM
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Joined: Mar 2006
Posts: 9,813
MI, usa
dvw
OP
master
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OP
master
Joined: Mar 2006
Posts: 9,813
MI, usa
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There has been 1750 views to this thread. I'm sure some are double looks, stick shift guys, non Mopar owners, Late model non 727 owners, etc. We've had 20 votes saying the voter personally blew up a drum. My bet is just about anyone who experienced personal failure voted attesting to that fact. Lately there have been many posts of paranoia about 727's. Many of these posters with no personal experience. This was out of line in my opinion. Shields, bolt-in sprags are no more than band aids. If you are worried about a drum explosion skip right past them and buy a good drum. If you have enough power to break the drive train this is probably a good idea. But as the poll shows most 727 trans will lead a happy life when driven correctly.
Doug
Last edited by dvw; 04/07/19 09:16 PM.
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Re: 727 explosion poll
[Re: dvw]
#2642471
04/07/19 09:21 PM
04/07/19 09:21 PM
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Joined: Jan 2005
Posts: 2,540
Milwaukee WI
TRENDZ
master
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master
Joined: Jan 2005
Posts: 2,540
Milwaukee WI
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So, if drum speed cuts fuel and ignition, how would drum speed ever exceed its programmed limit?
Even if the sprag is in a failed state, the drum would go 2.45 x engine rpm. But engine rpm is not the fuel/ignition cut determing switch, drum speed is.
Lets say I set max drum speed at 8000 rpm, if the sprag was in a failed state, engine rpm would only get to a little over 3,265 rpm before fuel/ ignition cut. A bit of inertia wouldn’t let it exceed the rpm limit, it would only prolong its deceleration. If the engine was limited 3200 rpm you'd be pretty slow. Doug Yeah. Thats the idea. How fast would you try to go with a failed sprag?
"use it 'till it breaks, replace as needed"
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Re: 727 explosion poll
[Re: TRENDZ]
#2642496
04/07/19 10:15 PM
04/07/19 10:15 PM
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Joined: May 2003
Posts: 6,558
Downtown Roebuck Ont
Twostick
Still wishing...
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Still wishing...
Joined: May 2003
Posts: 6,558
Downtown Roebuck Ont
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So, if drum speed cuts fuel and ignition, how would drum speed ever exceed its programmed limit?
Even if the sprag is in a failed state, the drum would go 2.45 x engine rpm. But engine rpm is not the fuel/ignition cut determing switch, drum speed is.
Lets say I set max drum speed at 8000 rpm, if the sprag was in a failed state, engine rpm would only get to a little over 3,265 rpm before fuel/ ignition cut. A bit of inertia wouldn’t let it exceed the rpm limit, it would only prolong its deceleration. That drum and everything that is spinning with it at 8000 rpm has more than a little bit of inertia. I don't know how far past 8000 it would accelerate but I think it's going to speed up before it slows down. If you're up on the converter at 5500 when the sprag fails the inertia from the rotating assembly alone will be enough to spin it up past 8000 and it all happens in the blink of an eye. If you have a wheel come off a car at 60 mph, the first thing it does is pass the car because of the inertia. Kevin
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Re: 727 explosion poll
[Re: Twostick]
#2642501
04/07/19 10:27 PM
04/07/19 10:27 PM
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Joined: Jan 2005
Posts: 2,540
Milwaukee WI
TRENDZ
master
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master
Joined: Jan 2005
Posts: 2,540
Milwaukee WI
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The wheel passes the car because a 3 wheeled car slows down.😀
If the sprag has failed, the engine could never get to 5500 with my little trick.
If you set a 2 step rev limiter on a car to lets say 5000rpm, how high does inertia take that engine beyond 5000 rpm?
"use it 'till it breaks, replace as needed"
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Re: 727 explosion poll
[Re: TRENDZ]
#2642649
04/08/19 10:16 AM
04/08/19 10:16 AM
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Joined: Sep 2003
Posts: 19,307
north of coder
moparx
"Butt Crack Bob"
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"Butt Crack Bob"
Joined: Sep 2003
Posts: 19,307
north of coder
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i had a left rear wheel break the center on my wife's 76 chrysler, going down the interstate at 75mph. by the time it exited from under the 1/4 panel, it went straight up in the air ! you shoulda seen the cars behind me dodge that thing.  when it came down, it slingshotted over the guard rail into the woods. then there was the sparks from the u bolts grinding down on the concrete. luckily, no one was hurt, and no damage to anyone behind me. 
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Re: 727 explosion poll
[Re: BradH]
#2642721
04/08/19 12:43 PM
04/08/19 12:43 PM
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Joined: Mar 2019
Posts: 24
PA
1118Steve
member
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member
Joined: Mar 2019
Posts: 24
PA
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Never blown one up, and have been racing them for fifty years. Have only seen four come apart, and one of those were when we were doing neutral starts back in the late sixties. Don't screw around and do stupid stuff in low gear and you will be fine. Keep after your stuff,, don't do burnouts in low gear, and check it close if you have a drive line failure. But, it makes for good pictures and gets the kids all riled up on this board.......I'd be interested to know of those "it's gonna blow up" crowd have dual street/strip cars, out blowing the street tires off in low gear to impress the kids on Saturday, bolt some slicks on Sunday and the trans comes apart on the first hit because they overturned the sprag screwing around the evening before. You guys can hit the panic button, but I'll just keep doing it the way I've done for 50 years. .
Last edited by 1118Steve; 04/08/19 12:54 PM.
"Old Age and Treachery beats youth and enthusiasm"
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The last engine was only 7.10 in the 1/8th, the previous was 7.50. I go to the Mopar race at SGMP just about every yr, and dont recall seeing one blow there either
