PRO AUTO

iTrader: (1)

I currently have a M6 car with a 12 bolt and 4.10 gears that was set up by Strange but has busted the ring and pinion. The car has 419 rwhp with 390 rwt, cutting a 1.6 60' leaving around 4000 and I'm using a M/T ET Street tire. My question is how do I need to set up this rear end so that it will survive? I'm sure there are folks that have figured out how to keep these rear ends alive with 6 speeds, 12 bolts and more power than I have. Do I need to tighten up the backlash to prevent tearing up the ring and pinion? or what? The car is street driven some but not a daily driver at all, just an occasional cruise or True Street cruise.

Thanks for any help I can get with this.

Mikey 97Z M6

iTrader: (37)

If it were mine, I'd def aim for the tighter side of the backlash specs. I always setup my 9" with a tight backlash (M6 here also) and I drive it to/from the track. Richmond makes a "Pro" gear that would probably work good for your application (high shock situations). They are supposed to be less brittle, but from my understanding, they wear quicker. If you're only putting a couple hundred miles a year on the car, I don't really see that being an issue.

Good luck.

Mike

SWeiser31

iTrader: (9)

I ran a 12 bolt the last 2 seasons at the track. It took some pretty good abuse before a tooth on the ring gear finally broke. Last year was 6K launches on slicks with an extra 250lbs in the car. I've got a Monster level 3 clutch, which is a very aggressive clutch. I'm not making as much power as you but it did hold up fairly well considering. I had the backlash set at .002 or less and ran the Redline heavy shockproof gear oil. I also had a solid pinion spacer instead of a crush sleeve. That being said, I just put a S60 in it a few weeks ago. What clutch are you running?
edit: x2 on a pro gear. Not really made for many street miles, but some people do and don't have a problem. They will hold up to the power too.

blue99fbody

iTrader: (5)

i didnt set it up mine was setup from moser but ive been running 500-700whp on it for 3 years launching at 6k cutting as low as 1.4s on it and it has never broke (knock on wood) but whines like a ****. maybe give them a call and see what they are doing.

PRO AUTO

iTrader: (1)

SWeiser31, I'm running the LS7 clutch with the LS2 flywheel and 4.10 gears and launch the car at 4k any thing higher just blows the tires off, my mph is 117 but not running as fast in the 1/4 as you are and I don't understand why, the clutch seems to work good but it was much heavier than the stock one that I took out and it seemed to slow the car down some. I seen that you are running a 4.56 gear, just wondering if you are naturally aspirated and how tall of tire are you running, also, whats your rpm going thru the traps? I was thinking of running a 56 or 30 but havent decided for sure yet. What does your car weigh? Also, are you running Pro Gears? If so do you drive your car on the street any?

I will contact Moser and see if they will divulge any secret info. I had talked to a fellow along time ago when V8 Vegas had gotten so popular and he was running a stock rearend in it and I ask him how he was managing to do that and his answer was to set it up with 0 backlash.

Thanks for the advice.

SWeiser31

iTrader: (9)

My guess as to why mines a bit quicker is a combo of things. First I'm launching a little higher at 6k and it's hooking with the slicks. Second is the 4.56 gears, and third the faceplated trans. You have the higher mph because you get going a little slower, but come on strong at the big end. I'm naturally aspirated on a 28x10.5 tire going through the traps right at 6500. The car weighed like 3480 when I made that pass. I don't run a pro gear, but I thought about it before going with the S60. I know several people use them that go on drag week and don't seem to have any problems. They just won't last as long because they're softer. If you go with a pro gear, I would keep the trips as short as you can. As far as gear ratio, if you're staying N/A and can turn the rpm, I'd go 4.56 for sure with a 28" tall tire.

Gary Z

My Moser 12-bolt has survived serious punishment with no problems. More than 200 launches above 6k on MT 26x11.5-15 ET Streets cutting 1.5x 60s. Richmond 4.33 gears. I didn’t do anything special setting up the gears – just carefully followed Richmond’s recommendations. Pinion depth and backlash were within specs. I set the carrier bearings on the tight side. My 4.33s are not Pro gears. I went with the cheaper (harder) gear set thinking they might make less noise than my original Pro 4.10s – they don’t. I have a stamped rear cover with no extra carrier bearing support. So far, so good. Knock on wood.

SlickVert

iTrader: (5)

Normally the problem is the Clutch and Tire that cause rear-end and tranny failure.
The clutch needs to be softer hitting, most of these new type of 6 puck clutches hit way to hard.
Tires, need a tire with a large side wall so you have some flex. 28 x 10.5S x 15 is the minimum.
F-body suspension has no flex at all, need a soft clutch and your 60' will get better as well and a tire with some side wall.
4.56 gears is the way to go for sure. With 4.11 you are getting to much wheel speed with that stock T-56 first gear (2.66).
Best mod ever and most fun on street is a set of 4.56. Still can cruise at 70mph with a 26" tire under 2,000rpm.
Been there done that.
Good luck,

BlackScreaminMachine

iTrader: (17)

Dropping Race Weight out of the car does many things, one of which is less strain on the car and it's parts. I have never had a ring and pinion bust out of it but I have had 2 differentials **** out of it. Both Tru-trac before people were finding out how junk they are.

Since the shock of the launch is a big factor, I worry about even trying a Eaton HD posi, most go right to the spool. You really cannot use a Detroit Locker with the M6 so thats not a real option.

If your ripping out the pinion now, then there might not be much you can do. Maybe consider a 2 step to soften the shock.

I am running into the same issue now, I am at the point where a RMVB 4L80e might be going in.....

Gary Z

I seem to be doing every thing wrong. I forgot to mention, I have a Tru-Trac that has not failed and a Spec 4 (six-puck, solid hub) clutch. Maybe the reason my stuff has survived is that I don’t have 28-inch tires.

Gary Z

Now that I’ve given this subject more thought, I’m recalling some of the things I’ve learned. First, the obvious - Breakage is prevented by Slippage. Either the clutch or the tires (or both) must slip. I have learned to prefer tire slippage because clutch slippage greatly shortens clutch life. More serious M6 racers than me use slipper clutches and accept frequent clutch replacement because clutch slippage gives better sixty performance than can be achieved with tire slippage. I accept so-so sixty times because I hate replacing clutches. I’m on my fourth clutch. My Spec 4 is by far the most durable clutch I’ve had but it does not slip. If your clutch doesn’t slip you are always on the verge of wheelspin which will kill your sixty. I’ve found a happy medium where my tires slip enough to avoid breaking or bogging without spinning. Hope this helps. Good luck.

Doug G

.008 and OK so far. But as time goes by thats gonna open up

the 35 spline and spool should help me some ?

PRO AUTO

iTrader: (1)

Sounds like I need to go with a 56 gear and 28" tall tire, but your last sentence you mentioned the 56 with a 26" tire so I'm a little confused of which would be better for the strip? What kind of rpm's would it be turning with a 56 and 26" tire?

Thanks for all the help.

PRO AUTO

iTrader: (1)

Gary, what is your rpm through the traps with the 33 and 26" tires?

Gary Z

I trap at 129 MPH and 7100 rpm on nitrous and 120 MPH @ 6600 rpm N/A.

LosLs1's

iTrader: (21)

So it seems that I should be ok with running 4.30 and a 26" I have an m6 car... Safely saying that I hook the only flaw of my 8.8 is that I'm running stock 28 spline axles