Gunreaper

Ok I have a rear diff question. I have a 1989 camaro 5.7 tpi. I have a 383 stroker being built and a built 700r4 stage 2 trans. Motor is rated right at 500hp with holley efi on it. While I am waiting for that I am working on the rearend.

My diff tag say 2.77 series 2. My rpo tag shows GH3 = 2.77 gears and G80= limited slip

I am not racing the car but will want to be able to get on the throttle some. Do I need an entire rear end with 3.73 posi gears or can i rehear this diff?

midias

You do not need those items but you may want them. G80 means you have a "posi" that being said your gears have nothing to do with it being "posi" or not. 3.73 is not going to make it stronger. Sounds like you might have a 9 bolt parts for that are expensive and the cone style posi units are usually shot by now. Pop the cover and see what you actually have. If you do have a 9 bolt it is probably cheaper to get a 8.8 built up properly. If you are truly putting out 500hp I probably would not run a 10 bolt either

big gear head

If you want to use any gears around the 3.45 or 3.70 area then you are going to have to get a 3 series Borg Warner differential. There is also a Truetrac type differential available for this rear end now, so you might want to look into that. There is a thread on this sight that covers the conversion to this differential.

GeneralDisorder

iTrader: (1)

It is a fairly strong diff. Will probably be alright for the street with street tires. You will want to do some 3 series gears and the Torsen carrier from Australia.

Parts are not that hard to get. All the rebuild parts are easily available, several gear manufacturers offer a 3.70 set, and now you can get the Torsen carrier from Australia. Mine works great - no complaints.

GD

Gunreaper

do you guys think my 2.77 gears will be ok while just getting the motor running and setting up the holley efi? Or is it going to trash on me as soon as I pull out of the driveway?

DEADWOLF

Look at the rear cover on the differential. If it has 10 bolts it is the 7.5/7.625 ten bolt rear which can survive behind 500 ft lbs of torque with a harder street tire. If it has 9 bolts in the cover then it is the 7.75 Borg Warner rear which is stronger and if built right can survive 500 ft lbs of torque with a softer street tire. The torque is what reeks havoc of the rear end.

I've got a 10 bolt with 4.56 gears in my 1990 firebird. Current build for next year is a SBC at around 450 Hp and torque. I've actually been considering building a 327 short stroke motor to reduce torque and put my hp in the 7000+ rpm range due to the low gear. Then next winter I'll upgrade to either a Dana or fore 9".

I've also got a Borg Warner in a second project car that I am looking at building for the wife. I'll probably keep it in her car as I plan to LSx engine it for ease of starting and driving.

midias

I cant imagine a reason why they would. In your mind are numerically higher gears stronger?

DEADWOLF

Lower gears let a less powerful motor get you out of the hole Quicker. My car is primarily a drag car that is barely street legal and may see 1000 miles a year on the street. With that in mind 4000 rpm on the interstate is fine for the limited amount of time it will be on the interstate. At the end of the 1/4 mile if I am close to top speed I'm doing good, but if I run out of gears at the 1/8th mile point then I'm geared lower than I need to be.

Gunreaper

So my 9 bolt rear diff is strong if built right. What parts are needed to do that? And I see 8.8, 10 bolt, and Ford 9" Diffs. I guess I'm a little confused on what fits and or what has to be modified to make fit

big gear head

The 2.77 gears are actually stronger than a 3.70 gear. It's not going to break, but it won't make your engine feel strong like the 3.70 will.

Gunreaper

So if I keep my rear end and go to 3.73 posi gears what would make it last?

big gear head

I would recommend an aluminum cover like the TA Performance cover with the preload bolts. If I remember correctly the 9 bolt has small 3/8 bolts in the bearing caps, where the other GM rear ends have 7/16 bolts.

GeneralDisorder

iTrader: (1)

You need the 3.70 gears (not 3.73 - Motive, Yukon, and others are all the same - same factory in China making all of them), Australian Torsen carrier, rebuild kit, and the TA rear cover. And it has to be setup correctly - which if you have to pay for that makes it probably not worth it. Just buy an aftermarket rear already setup from Moser, Strange, Hawk's, etc. I did it all myself and still spent well over $1000. Just the Torsen carrier landed from AUS is about $500.

GD

Gunreaper

Can I even put 3.70/3.73 gears in my 9 bolt diff with a series 2 carrier?

GeneralDisorder

iTrader: (1)

No. Not at all. And the factory cone type LSD carrier is worthless anyway so you wouldn't want to if you even could.

GD

howie099

9 bolts and stronger than the 10 bolts of the 80's the F-bodies came with like everyone else said. You most economical way to go is the torsen diff and 3.70 gear I just bought a torsen from AU for like $507 dollars. You can get other ratios from the website 9bolt but they are all used. Your engine is 500HP at the crank or the wheels? I still bet you kill the trans before the 9 bolt 700's are weak even if you build them up good for hwy not the track.

With the 2.77 gear you will not be off the line fast and you will be good for hwy driving, but I am sure that diff is worn out so either rebuild it for the estimated $1000 w/parts or do a swap to an aftermarket 9" or 12 bolt. Can do a 4th diff also they are like 1/2" wider probably as strong as the 9 bolt but parts are everywhere for them in the US. If you are not using a transbrake & in the 11's in the 1/4 mile you are will be good with 9 bolt. Get the aftermarket diff cover w/bearing supports that will make it stronger and weld the tubes to the diff on the 9 bolt and call it day.

Gunreaper

485 at crank so probably around 400ish at wheels. The trans is built by mad dog transmission. Its stage 2 for 500hp.

howie099

Rebuild the 9 bolt if you want to change the gear ratio. If is good you won't hurt it if you just change the fluid if the posi cones are good. Matters what u want to do with the car and what your budget is for it. I rebuilt mine and after this one I will go to the aftermarket ones.