I have a 99 Z28 with 6 speed and after getting a whole new rearend installed under warranty at 50K it has been making a lot of noise lately again. I am at around 78K now.

I jacked up the rear today and just spining one side it sounds awful. The brakes pads seem to drag more than normal with e-brake off. But also there seems like a lot of slop in rearend and noise.

Maybe the gears were not setup right or is it the limited slip part?

How much is going to cost if I replace it myself with something more beefy? What should I replace it with?

Thanks

The 10 bolt is only as strong as its 7.5" ring gear, which cannot be made any stronger...M6 cars seem to be much harder on rear ends. If you are at all serious about modding it and running it, then I'd suggest saving for a 12 bolt or a 9"...

--Alan

Does the whole axle have to be changed to go to 9" or 12 bolt? Why is it called a 12 bolt? M6 a 6 speed? I have not be hard on it at all. I commute in it about 40 miles a day. I really think it is crap compared to how easy I am on the car. I always have the clutch out all the way before I get on it.

10 bolts are not known for their strength. They can brake with very little power and the right traction. M6 is a 6 speed, means "manual 6", think of it that way.

The whole thing has to be changed because well....the whole thing is different. The 10 bolt is called a 10 bolt for a reason. It has 10 bolts holding the hub cover on. 12 bolt has 12 bolts. That is not the only difference, the 10 bolt ring gear is 7.625" on 4th gens, and 7.5" on earlier years. 12 bolt has a 8.5" ring gear. The bigger the ring gear, the easier it is to move the axles, then making it stronger and last longer. 9" rear axles are called that because...you guessed it...the ring gear is 9" in diameter. 9" axle = ford, 12 bolt = gm.

So the bigger the ring gear the easier the car can move and transfer power, essentially making it stronger and last longer.

Also 12 bolts have I think 36 spline axles going into the carrier, where newer style 10 bolts have 28. The older 80's 10 bolts had 26 splines. Not to mention the bigger the axle the more heavy duty everything is built.

So I can go back to the stealership and have them redo it but this time pay for the whole kabob or do it myself.

Would I be able to pull the third member and take it to have new gears put in?

Anybody had any longterm luck with a certain brand of gears?

Because we have the same rear ends as the s10 pick-ups do.

GM = General Mistake, that's why.

No and no.

Good post with minor errors. The 12-bolt has an 8.875" ring gear. Stock 12-bolts have 30 spline rear axles.

Axles are 24-pitch. So, a 1-inch axle has 24 splines. The distance between the centerline of adjacent splines remains constant, so as the diameter of the shaft increases, so does spline count. For example, a 35-spline axle has a major diameter of 1.500 inches; a 40-spline axle is 1.708 inches in diameter. A 28-spline is ~1.17" diameter.

The diameter at the bottom of the grooves between the splines is the narrowest part of the shaft and therefore weakest part of the axle. That is why most axles that twist do so at the splined end. They may also break at the shoulder, at the bearing end.

Rich

So what is the process to replace the ring and pinion if the 3rd member can't be removed?

Why did they put such a weak setup with a LS1 in front of it? Did the SS & corvette get the same setup?

So basically if I want to fix it right so it will last the only option is change the whole axis out to a 12 bolt?

Pretty much, a 12-bolt or 9" are the 2 strongest options for your '99 F-body. You can "upgrade" some of the parts in the 10-bolt, but it's still just too small for the job.

Oh, 1 more little correction to the information above, the TRUE meaning of "10 bolt" or "12 bolt" refers NOT to the number of bolts holding the diff cover on, but the number of bolts holding the Ring Gear onto the Carrier. While I think that the # of cover bolts may usually correspond, in the older (60's / 70's) diffs, I think there were 12 bolt covers with 10 bolt ring gears? Something like that ... they weren't the same #.

In fairness to the General, the stock rear is perfectly adequate behnd a stock motor on street tires. Anything stronger is going to be more expensive, heavier, or both. If you have already broken a stock rear, don't bother to upgrade it. Get a 12-bolt or 9" as suggested.

Rich

Maybe so, but how big was the ring gear? If the ring gear had 8.875" diameter than it is a 12 bolt period. Does not matter what number of bolts hold the ring to the carrier. Hell, it could have 50 bolts holding the ring and 10 holding the cover, does that make the 50 bolt axle the strongest axle? 50 bolts with a 7.625" diameter, compared to a 12 bolt cover/10 bolt ring with an 8.875" diameter?

Just something to think about.

Cause they are stupid.
Even Ford is smart enought to put a very robust rearend in the Mustang.

Say what?!

Dude, all I was talking about in my post was clarifying the designation of "10-bolt" or "12-bolt" diffs. People always refer to them by that, but somebody mentioned the number came from the number of bolts holding the cover on, which is incorrect. I wasn't making reference to the # making a strength difference. Hell, the 10-bolts used in some 1st-gen and most 2nd-gen cars were actually very tough units ... but they used an 8.5" ring gear.