Heavy Duty Rear End?


Active Member
I'm aware of many builders retrofitting a F*** 9" in the GN. My question is, why not go with a bigger GM rear? A 14 bolt with 3.73 gears cost me $100 & it measures only 1" larger externally. It also has huge brakes.
Out of what vehicle? 1" wider is harder to deal with than 1" narrower. Most guys go with a 9" because there is a HUGE aftermarket for all the parts. Axles are available in 40 spline, strong spools, great limiterd slip options, HUGE selection of gears and gear alloy's (drag gears are softer), ect. If you NEED a stronger rear end, the Ford is hard to beat. Strange offers a Dana 60 that is bolt-in, and a 12 bolt, too. What did your 14 bolt come out of, and where is pinion location comparede to a stock 10bolt. THe stock 10 bolt 8.5 will live a long time in a 9 second car properly built.
As Ken said above me the 9" and 12 bolts you can buy that bolt in.

I don't know anyone that sells anything drag race oriented for a 14 bolt, it's a truck rear end. Never seen anyone sell one that's a bolt in housing for a G-body either.

What is it a leaf spring rear end?? Your $100 is still a long way from making it work in a G-body.

Only bad thing about using the stock 8.5" is if you are building a FAST car (we're talking 8's maybe 9's here) then by the time you spend your money upgrading the 8.5" to live you could have sold the 8.5" and built a 9" or 12 bolt and you would get away from the wimpy axle tubes on a 8.5".

In the 10's or slower you're wasting your money to upgrade, IMO.
Oh and Ken I disagree with the 1" wider is easier to deal with then the 1" narrower, you could always have a rear end guy cut an 1" off. I would think it would be harder to add an inch.

Or you could use different wheel in which case an inch either way would matter.
Thanks for your replies.

Currently, I'm not upgrading the GN/TR. The 14 bolt, 8 lug is a bolt in for my preowned Silverado which had rear end issues.

Looking at the rearend got me to thinking outside the box for the GN/TR.
Which 14 bolt? The 10.5" full floater or the 9.5" semi floater? You can convert the 10.5" to the truck 5 on 5.5" lug pattern. But, it's a floater axle and you can't do anything about the masive hub that has to stick through the wheel. There are no off the shelf 5 lug wheels that will fit over the hubs without machining (extra money). Your limited on gearing options. 3.73,4.10,4.56,4.88,5.13 It takes a minimum of a 16" steel wheel to fit over the standard drum brakes. Changing to disks so you can run a 15" wheel will cost you more. The other problem is none of the brake setups will clear the stock frame rails on a G-body or most any car for that matter. The drums are close to 8" wide on each side and the width from backing plate to backing plate is less than the width of G-body frame rails. A complete 10.5" rearend probably weighs twice what a 9" weighs.

The semi floater came in a 5 lug (5 on 5.5") under the SS454 trucks, but those are rare and expensive. You can get an 8 or 6 lug version for a little cheaper and convert it, but your still limited on gear options. Gear sets and posi units are expensive for the 9.5".