I'm in the market for a posi rear end with disc breaks, and was looking around the Hawks site. The list several types:
82-88 10bolt posi discs
90-92 10 bolt G92 1le
93-97 LT1 disc with TCS
98-2002 LS1 dics with TCS

Now I know the 4th gen rears are ~2" wider so wheels may stick out, and all the ends are basically equally strong if they have 28 spline axles. But what is the rear difference between regular disks, 1LE, LS1, and this TCS option? Thanks for your help .

 

82-88 (Standard) Delco-Moraine iron calipers with 10.5" rotors. Gov-loc or Auburn limited slip. Least desirable.
89-92 (so-called 1LE) PBR alum calipers with approx. 11.7" rotors. Auburn. Better.
93-97 (LT1) Essentially the same as the 89-92 above.
98+ (LS1) PBR alum calipers, though they don't resemble the 89-97 version. I've read that the rotors are approx. 12". Zexel-Torsen. Best if for no other reason than the parking brake system.

I'm unfamiliar with the traction control system, but I assume it would have no function on a thirdgen car.

JamesC

 

So as I'm starting to look around, I'm really wondering at the up the overall cost of the replacement. It seems from a place like Hawks that most rear ends run ~$500 (including the 9-bolt), $800 for the 1Le. Generally on ebay, craigslist, or the boards here, a rear end can be found for between $250-400. A new Moser unit with (28 spline axles) without gears or breaks runs $1000- http://www.summitracing.com/parts/MSR-9B82-CAM/. In the case of the used rear ends though, if you need to start swapping out for upgraded axles, new break rotors, maybe calipers, and gear set (not always I guess?) what kind of cost can usually be expected? I don't really have a good sense of what condition these parts tend to be in and what needs to be replaced.

 

The following FAQ may provide some food for thought (you'll need more than just the rear itself):

https://www.thirdgen.org/forums/tran...-10-bolts.html

BTW, if you choose well, you shouldn't have to replace gear sets or axles. You can rebuild calipers and turn rotors, if need be. Pads aren't all that expensive.

JamesC

 

I went with a 94 z28 rear. $135 for the rear, $35 for e-brake cables, $120 for gear change (3.23 to 3.73 (used gears)), $110 for correct brake proportion valve.

I love the rear but I hated how much the wheels stuck out. So I bought a set of tires and wheels from an 02 WS6 for $500. Not too bad considering I need tires anyways and the ones I got were basically new. And since I went with these wheels, I spent another $50 in spacers for the front and $70 in new lug nuts.

Figured I would throw that up there just so you can get an idea of some of the costs.

 

So I'm not crazy about the idea of my tires sticking out a bit, but 4th gen rear ends easier to find than 3rd gen with disk brakes. I suppose it could look a bit mean...or hick...not sure yet.

My question- how much (qualitative) of a difference does the rear LS1 braking set-up make over the smaller 3rd gen set-up (12 vs. 10.5 in)? Considering that rear brakes only do 20% of the braking to start...
I know you can switch over but that gets expensive, especially if you can get it in the first place.
Thanks for the input so far. -Mike

 

Mike:

I live in Cary - be happy to meet ya sometime and show you my rear! Seriously - I'm available most anytime, and I have the 4th gen LS1 rear installed with my stock 16in wheels - so you can see the exact end result - just PM me or email me and let me know.

 

So from what I've read it sounds like the Eaton posi is better than the Zexel Torson? Potentially more maintenance but better adjust-ability and locks up better? I was a bit surprised to read that as the Torsen was on LS1 cars that put down over 300 rwhp and those were high-perf cars. Can I assume if you are not regularly auto-crossing it doesn't matter?

Also- anyone have thoughts on gear ratio for a currently most stock 305 TBI with an auto trans? I am scoping out a third gen rear with 4.00 gears with disks (~300), but fear those will be too steep (way to poor mileage and top end). People seem to suggest 3.75s as good all round, but I'm wondering if 3.42s would be better. If I get the rear I'm then looking for replacement gears too.

Thanks for the suggestions so far, they have been helpful.

 

Personally, I wouldn't go above 3.42 unless I was visiting the track alot - 3.73 and higher are going to kill mileage. I have 3.42 and they seem to be a happy medium between mileage and seat of the pants feel. I had a 1990 305 TBI car and I stuck a 3.08 posi in it and it helped accelleration off the line alot compared to the 2.73 peg leg, but the 3.42's I have now are alot more fun.

If it helps any, with my current setup (see sig), I get about 17mpg, and I run 3000 rpms in 4th (automatic) with TC locked at 65mph. Kinda like comparing apples to oranges since I'm a carbed 350, and everyone says my rpm's are too high for those gears, but I've checked and rechecked, and I am in 4th, and my TC is locked.

We'll chat more Friday!