I'd switch to a th400 or powerglide before I'd run a blanket or shield again. Blanket is a nightmare with melted straps and acting like a sponge, and the shield is pricey. I'd do the above with a billet drum and proper VB on anything that's going to rev.

My thoughts; A Turbo 400 can spit a drum as well.

Buddy of mine had a healthy small block, 904 combo in a Dart. Broke the 8 3/4 under power. Fixed the rear and was out driving the car around. Had a very slight vibration. Called me and said he was going to the track and whether I though it would be OK. I told him to take it out and bring it to me. He said it drives fine. I said bring it to me.

Half the springs were crushed and the rollers were loose in the thing. Half the rollers were functioning well enough to drive the car around. Would not have survived the first hit. No idea what valve body was in it other than it was a manual.

A failed roller clutch doesn't necessarily mean the car won't move. And in a 727 with a stock drum, it would be a ticking bomb.

Have the trans properly built, install an aftermarket billet front clutch drum, a bolt in over running clutch helps. A low band apply valve body offers a tad more help in preventing over run clutch roller spit back.

A shield or blanket is “suspenders on a belt” after doing the above.

And of course, drive the car correctly.

You have to engine RPM way beyond what most decent street small blocks will turn to get a 904 drum to explode. Still better to fix it than risk other stuff falling apart with a vibration.

A stock 383 and 440 will rpm enough to get a 727 to grenade.

Never heard of a 904 coming apart like that. Not saying it never happened.

Yep.

I haven't read all the comments but This is sound advice , the only thing I would add is to use a Super Sprag , A+A or whomever else is making it , I think it's coan ??... it has more rollers and it's very hard to damage , if at all. A standard bolt in is for repairing stock sprags that are loose in the case , they do nothing to stop the rollers from rolling over . A billet drum won't explode , at worst it will deform from tests I have seen so it not going bang is what you are really after.

As mentioned in post #9. My car has damaged two Ultimate sprags. The Ultimate uses standard Ford C-6 rollers and springs. With a reduced diameter 727 inner race. Custom outer race.
Doug

Thanks Doug,sorry to hear that you broke them twice. I'll log into memory for future reference.

I don't think it matters what kind of sprague you. put it it if you rip some gears out. The sprague goes when it looses the load then gets hit. In other words, you rip some gears out and the engine revs then you roll forward a little and the pinion hits more gears with the engine revs, that's when it goes. There isn't a sprague or case on the planet that will take that inertia hit.

Several years ago at BG a NSS racer did exactly this and the stationary part of the sprague cocked in its bore, and that was that. And that was a super dupper sprague. Sprague was still good, but not the case.

. .

Never heard of a 904 coming apart like that. Not saying it never happened.

I use the CSR carbon shield on my cuda. I used to run a blanket, but switched to the shield b/c of the NHRA rules and it's the only thing that will fit w/o hacking up the trans tunnel.
I had a drum explode in 2008 and it made a huge mess, but the shield did its job. It did destroy the shield, but it kept the explosion contained.
This was no minor explosion either. The case, pan, and valvebody were in pieces and swept up off the starting line. Every bellhousing bolt had a small piece of case still attached to it.
Crawled under the car and you could see the clutches just hanging on the shafts. A piece of the drum dented and cracked a header tube, blew the whole floor pan upward, stopped when it hit the brake pedal.

After that I put billet drums in the new trans and my backup.

Glad to hear your shield did its job with the explosion. I hear over and over again that a carbon-fiber shield is no match for explosion shrapnel (??).

A few years ago I busted my 8-3/4 for the last time. Happened right at the hit, sheered the pinion right in half and turned the whole thing into a gravel box. I tore into the transmission after that and found everything to be perfectly fine. Foot was to the floor, coming off the two-step. I got out of it immediately, but the carnage of that incident was exactly the type that should have damaged the sprag. Somehow it was fine. Just lucky I guess. I installed a blanket after that incident feeling as though I was on borrowed time with the stock drum. Car also got a D60 after that.

I’m now in the process of installing a Transbrake in my 727. I’m going with a CRT unit. After a lengthy discussion with John, he convinced me that it was past time for a billet steel drum. I was going to go with one of his units, but then just last week out of the blue I found a brand new A&A Ultimate Steel Drum complete with retainer and 15-spring piston on eBay for a fraction of the retail price tag. I couldn’t hit the “buy it now” button fast enough on that deal. So I will now be running a bolt in sprag, a steel drum, and an LBA valvebody.

At the same time as this project, I’m also on a campaign to carve some weight out of my street-heavy sled. I weighed the blanket just last night…. 9lbs-3oz. Not as bad as I would have thought. I think it’s worth its weight. But it is also a giant PIA! I take pride in my car always looking clean and well maintained at the track. This thing never fails to hang down like some slob with his pants sagging off his ass. I don’t know how many times someone has come up to me at the track and said “there’s something hanging down under your car”. I’ll get under there with zip ties and duct tape, but the thing just always finds a way to hang down. Drives me nuts. Not to mention it also makes it nearly impossible to access the linkage, or numerous other areas.

So I’m on the fence as to whether or not it will be re-installed when the transmission goes back into the car.

Back to the original discussion…. I feel pretty fortunate to have been racing with a stock drum as long as I have with no issues, and feel really good about having that worry behind me now. FWIW: I start my burnout just out of the water in 1st gear, but immediately go to second as soon as the tires turn and hold it in 2nd at about 4500 until I feel it start to tug. Let off and roll forward to a stop. Straight back to 1st gear then let it roll forward in 1st to the beams. I try to do as small a burnout as possible, as I don’t think a big smokey burnout does anything for you with todays tire technology, and mostly I’m cheap and don’t like to have to buy tires.