Hey all...

How come on Hawksthirdgenparts.com, the rear end assembles are so different in price? I will be looking to swap rears sometime soon, and I was looking to get the best one for the price. My car is a 91RS with L98 swapped into it, with a stock 700R4. Right now, the rear is the 2.73, drum, "one wheel peel" non-posi.

On Hawks, they split them as:
82-88 10 bolt posi w/disc
88-89 9 bolt posi w/disc
90-92 10 bolt posi w/disc G92 1LE

I know that I want posi, but which one is the better, 9 bolt or 10 bolt (I dont know much about rear ends), and also, what would be a good gear ratio to get? The car is my daily driver, commuting in southern california traffic, so I would like something better than the 2.73, but nothing to extreme. Would an aftermarket be better than a stock replacement? My budget isnt all that big (thanks to the L98 swap), so if you think aftermarket is better, what is the cost?

And I know that I am not going to buy from Hawks, but I was using them to see what my options are. Once I know what I am going to get, I am going to shop.

Thanks in advance,

-Tim-

 

9 bolts are ultra rare, so replacement parts are hard to find and pricey.
They are however stronger.

At your power level, a 10 bolt should be fine.
3.23 gears are quite nice with overdrive, keeps it a nice highway cruiser. 3.42's would also work nice if you want a bit more snap off the line.

Do you really want/need rear discs? I wouldn't lose sleep over that, you're not gaining a whole lot in braking power, really you're only paying more because everybody and their dog jumps on the bandwagon of wanting rear discs. The stock discs on these cars aren't worth going out of your way to get anyway.

 

I dont really need the rear disc brakes, but it is something that I would like. Would the 3rd gen 10 bolt be stronger than the LS1 rear? I was originally looking at the LS1 rear, but heard a lot of bad things about how weak they are.

 

They're exactly the same size and strength-wise.
Except that the 4th gen rear is 2" wider, so your rear tires will stick out more. For pinner rear tires (215/65R15's) it looks goofy, but if you had fat tires out back it might look ok.

 

My tires are 245/40R17, on silver 17'' SLP ZR1s. Since the 10 bolts are weak and 9 bolts are hard to find parts, what would be a good alternative?

 

That's the age old question right there.

10 bolts aren't exactly weak like circus lemonade. They should be fine for what you're doing.

Your other alternatives are to fab up your own Ford 9", or GM 8.5" or 12 bolt, or buy a ready to bolt in Ford 9" etc. Price that out and you'll quickly want to stick with your 10 bolt

 

Getting back to the hawks listing

82-88 10 bolt posi w/disc <- Should actually be up to 89 since they have 26 spline axles.

88-89 9 bolt posi w/disc <- some of the 87-89 models have the 9 bolt like the Z28 with the L98.

90-92 10 bolt posi w/disc G92 1LE <- Exactly the same as the earlier versions except they have 28 spline axles.

As for the brakes, the PBR aluminum caliper brakes started around 89, maybe 88 and the 90-92 will have them.

In 1986, GM switched from 7-1/2" ring gear to 7-5/8" ring gear. All the internal parts are interchangeable so even the late model diffs are still called a 7-1/2" even though they're 7-5/8".

The fourth gen diffs are similar to the 90-92 diffs except they're wider.

The best factory diff to use is a Dana 44 but good like finding one. They came in the SLP Firehawk and were available over the counter from the GMPPC years ago. Chances are if you do find one in good condition, it will be about the same price as an aftermarket 12 bolt or 9". There are no other diffs that are a direct replacement for a third gen diff.

 

At what power level would the 10 bolt start becoming the weak point? Under any daily driver duties? Or only on the tracks?

 

If you break a 10-bolt in a daily driver, you have to do something dumb & stupid. Almost all 3rd & 4th gen cars have the 10-bolt and they are still running. So what are you concered about???

 

My old 10 bolt was beefed up and I was running into the 11's at 117 mph. I changed to a 9" when I installed a tranny with a transbrake.