G-Body Rear Diff Question

[1987Regal]

I plan on running a twin turbo small block and I need a rear diff that can handle some power. I need to know what rear diffs will fit into this car with minor mods and also what upgrades I need to do to the diff. I need to be sure that the rear is no wider than what the car came with stock.

1987 Regal

[Quick GN]

How much power you plan on running? I've seen low 10sec GN's with stock rear ends in them!!

[gmachinz]

I can set you up with gearsets and install kits if you are going to overhaul your rear diff. As started, stock 8.5's can handle a lot of power. Take a tip from the Buick guys and don't go any steeper than a 3.55 gearset or so for a nice, torquey RPM climb. -Jabin

[Bill Howell]

Several outfits make bolt in 9inch ford rears for those cars. That is what I have in the 80 malibu I am building. The original rears are probably ok but I did not want any issues as I add more power later. I know the Grand Nationals had the same rear but they didn't have the instant torque that V-8's have. I have two stock rears if you want them, you can have them.

[1987Regal]

Bill.....how much for the rear diffs and where are you located?


gmachinz....when I'm ready I will hit you up for some parts....thanks for all of your help

[Quick GN]

Grand Nationals had the same rear but they didn't have the instant torque that V-8's have

Have you ever seen a GN launch at 20psi on a trans brake???

[Bill Howell]

87 Regal
I am in Pigeon Forge, Tn. 37863 As previously stated, you can have them.

Quick GN,
I knew someone would say something about my statement.Yes, I know all about transbraking,boost and the torque created there, however I think he was talking about a street car and GM I am sure did not intend for those rearends to handle that type stress in stock form from the factory. Are you running a stock rear or have you beefed it up? If it is stock and takes that kind of punishment regularly, then I stand corrected. However, before I spend money beefing up my stock rear, I would rather have the 9". The added benefit was I got rear disks brakes with the package.

[Quick GN]

I think it depends on what you want and/or have. I think for general street use on street tires a stock GN rear will hold up to alot of power. Start adding slicks/trans brakes/ and boost and yes you will break it sooner or later, for that I agree the 9" would be the way to go.

[gen3bu]

my 79 malibu has a 7.5 inch rear and i thought the gn's all came with a 8.5 inch rear.
correct me if i am wrong. how much power will the tt sbc make. the 7.5 in my s-10 is taking @ 500 hp and still kicking, and it gets drag raced a lot with sticky tires. i am working on a dana 60 for my 79. it came out of a 468 cid w/8-71, 2 750 dp's, and a trans brake 1972 chevelle - it was an all out race car.

[RatMalibu]

gen3 is correct the 84-87 GN's and 84-88 Olds Cutlass 442 had the 8.5" 10 bolt....all other G-bodies had a 7.5" 10 bolt....the 7.5's are good for a stock engined car......8.5's are good for a fairly healthy car with some upgrades but if you're planning on alot of power I'd go ahead and move up to a bolt in 9"....you'll more than likely end up with less money in the 9" than a properly beefed 8.5"....especially since the 8.5's are near impossible to find for less than $800 anymore

theres the strange 12 bolt and also the bolt in dana housing to consider also but the 9" will be the easiest on the wallet I think

I'm running a 8.5" but I got it before they went way up in price.....I'm sure I'd be running a 9" at todays prices

gen3 the 7.5 in the s-10 is probably still alive because of the relativly light weight of the truck

hth

[Bill Howell]

gen3 the 7.5 in the s-10 is probably still alive because of the relativly light weight of the truck

That was my thought too Matt.

87Regal, I am sure the two rears I have are 7.5 but you can still have them.

Another benefit to the 9" is once you have installed it, if your car is multi-purpose, it is much easier to swap gears if you are so inclined. You just swap chunks depending on objectives. That is not that simple with GM rears.

[gen3bu]

gen3 the 7.5 in the s-10 is probably still alive because of the relativly light weight of the truck

hth

i weighed the truck last year at it tips the scales at 3560 with @ 1/2 tank of gas