Rear end limits

[Dave Vince]

Anybody out there with some stories on the limits of the junk rear they put in these Camaros. Some GM corporate jerko should be shot for putting that piece of junk under these cars. A friend of mine who had an early 80s El Camino, which he said had the same rear, reached the high 7s' in the 1/8th. Then blew when it was pushed harder than that.

[joe ws6]

all depends i think. If your running slicks and a stall its histroy i believe. All kinds of people will say how good and far their rears went, then theirs the rear ends that broke on stock cars. But i know if you are thinking about anything big, well just junk it.

[casey02ws6]

It depends on whether your are an A4 or M6. A guy in our club is running 10s on his stock rear end. It is an A4 though. M6s have been known to grenade the rear end at or near stock power levels. You should be OK unless you run sticky tires and / or an aftermarket clutch. Street tires and the stock clutch will usually give up before the rear end.

[Joe 1320]

These are the same rears as in the S10. Not the same 10 bolt as the 8.5 inch from years ago. These 7.5 inchers don't have as beefy of a case and the internals are a little smaller. Autos tend to be a little easier on the rear than a stick. gummy tires put added stress on the internals too. I've got 140K miles on my 97, much with many bolt ons and all I ever did was do gears, bearings and seals. The pinion bearing went south at about 100K miles so I did the gear then. I'm in the high 12s, low 13s on street radials and the rear is holding. It's the dump the clutch and powershift guys that break the rears. The secret is finding the extra tenth or two elsewhere and not abuse the driveline. I will say that I added a T/A specialties differential girdle. It is a large cover with built in preload bolts and cap to help keep the internals in line. Flex is bad.

[Joe K. 99 Zeee!!]

I will say that I added a T/A specialties differential girdle. It is a large cover with built in preload bolts and cap to help keep the internals in line.

Drain hole is an added bonus! Next time I change out my rear diff oil I'll probably put one on.

[Dave Vince]

Rear

Thanks for the replys. Mine is an A4 with stock converter. 60' are a dismal 2.0 even with the MT radials, which hook pretty good. I do have the TA cover on the rear as I do not trust the rear at all. I launch the car at idle as it gave the best times that way. Ran 8.57 at 86mph 1/8th mile. The speed indicates that its making decent power, but the et is weak for the mph. Had a 72 Nova that ran 88 mph in the 1/8th and that ran high 7s' low 8s' in the 1/8th.

[Kevin - Blown 95 TA]

Dave, are your tires spinning to get you that 2.0 60?

[Injuneer]

I really don't think a condemnation of GM is valid. Their obligation was to put a rear under the car, that in normal service, with the stock parts, was reliable. The 10-bolt seems to meet that criterion, albeit just barely. When someone decides to make more power, abuse the driveline with sticky drag radials and beefy clutches, and a lot more HP, it is the owner's responsibility to upgrade the drivetrain components to match the demands their modifications are putting on it.

Could it have been better? Yes. Would it have increased the price of the car? Yes.

I ran the stock rear with the M6, bolt-ons and a 125-150 shot of nitrous. The car ran in the 12's with the nitrous. I just didn't do 5K clutch dumps off the line. When I decided to up the ante, start using slicks, start spraying it sooner, I invested in a 12-bolt. Avoided problems so far.

Would have been nice if they put the 12-bolt in it from the factory, but would every buyer have been happy paying $1,000-1,500 more for the car new? Particularly if they never planned to race it, mod it or hammer it?

Just a thought.

[drifts14x]

So, not to thread jack or anything, but how much extra is it to buy a 12-Bolt? Is it really so big a deal that it's worth complaining about? I am not really happy about having to replace the rear-end, but who doesn't like a good weekend mod? BTW, Is there any certain donor vehicle to get the 12 bolt off of, or do you guys have to take one for a really old (67-75) Chevy vehicle and modify it to fit your car?

[Injuneer]

The 12-bolts used in the older GM cars will not work in a 3rd or 4th Gen, because they lack the mount for the torque arm. You could add a mount, and somone here did it, but he said even though he saved maybe $500, he would not do it again. You may also have to narrow them, you will have to add all the brackets, probably need to rebuild the posi (if it even has a posi), etc. 99% of us buy a new 12-bolt made specifically for the 3rd and 4th Gen F-Bodys. A Strange or Moser 12-bolt will run you anywhere from $2,200-2,600 plus shipping. They are good for 800-1,000HP, assuming you get the right options.

[Dave Vince]

Reply

Kevin with the MT radials there is very little wheelspin. The initial launch is pretty good, I leave at idle, but then it flattens out until about 4k rpms, where it comes alive. Moser has a 12 bolt package available at a starting price of 1768.00. Includes posi unit, axles, pro street gears, cover, bearings, assembly. GMs thoughts on this weak sister of a rear are exactly as Injuneer put it. When asked why they put such a weak unit in they said either the clutch will slip or the tires will break traction. An excuse to put the cheapest thing they had in these cars. There was a time when you would actually have the option to purchase a better rear for your car, but Im talking ancient history now. Injuneer where did you get 1,000 to 1,500 more for a better rear. I know they would try to get us for all they could, but if Ford could put the reliable 9" in their cars why couldn't GM come up with something similar. I guarantee it was some Corporate bean counter deciding that one, not an engineer.

[Injuneer]

According to the Moser website, the lowest price 12-bolt for an F-Body, with a posi is $2,249. You can get one with a spool for $2,009 but that's not practical for the street. The 33-spline axles and HD Eaton posi run the bill up a bit, as will the ABS reluctor(s). Maybe some of the dealers sell them for less.

My number for OEM cost was a guess, knowing what axles, a good Eaton HD posi and a set of 8.875" gears would have added.

Even the Mustang didn't get the 9-inch. The 9-inch was out of the really heavy sedans and the trucks, just like the GM 12-bolt. The F-Body was a parts bin car. How else could you explain the radically different front and rear wheel offsets on the 3rd Gens, and mismatched front and rear hub diameters on the early 4th Gens.

[Dave Vince]

Moser

My price for the Moser unit was from a recent issue of Chev high performance. That was a base model with no upgrades. It was probably a special sale. The 9" was put in the heavier cars, we took one out of a 70s' Thunderbird which we put in our Nova. That T bird was a big boat. We finally blew the caps off the 9" with a 400 fogger shot on a BB and had to go to a aftermarket nodular. Manufacturers will cut costs wherever they can to make more profit. My guess is that it would cost between 50 and 100 dollars for a manufacturer to go from the puny 7.5 to a decent 8.8. It would be nice to at least have the option to upgrade. My guess is that they would charge about 10 times what it cost them or about 500 - 1000, if they even made it available. You are thinking aftermarket prices not the manufacturing level. You would still get the cheapest Posi and axles however.

[N20LT4Bird]

The 12-bolts used in the older GM cars will not work in a 3rd or 4th Gen, because they lack the mount for the torque arm. You could add a mount, and somone here did it, but he said even though he saved maybe $500, he would not do it again. You may also have to narrow them, you will have to add all the brackets, probably need to rebuild the posi (if it even has a posi), etc. 99% of us buy a new 12-bolt made specifically for the 3rd and 4th Gen F-Bodys. A Strange or Moser 12-bolt will run you anywhere from $2,200-2,600 plus shipping. They are good for 800-1,000HP, assuming you get the right options.

I had about 1400 into this rear when I was all said and done and that was with the best of everything as far as internals go. It was a LOT of work and unless youre doing it more for the challenge (as I was), its much more efficient to buy the Moser or Strange rear.


http://f-body.com/forum/showthread.p...highlight=pics

[Dave Vince]

Rear

Thanks for the info, I would personally opt for the Ford 9" if I was going to put some serious power in this car. With an aftermarket case, axles and a back brace the 9" can take 1500 hp. I have no plans for such insanity with this super hard to work on F body. I will go to a full chassis race car again if I want to go crazy quick. Going from a stock chassis car to a race chassis was worth a full second in 1/8th mile ET with the same driveline combo.