monsterjam5000

im going to rebuild my rear end with a higher gear and new posi, i want a 373 or 411 leaning more towards the 373. if i do this will i have to reprogram the computer so my shift points stay the same.

i dont want any problems and dont know how the computer will react to the rear gear change.

also will the gears and posi from my 1979 camaro 7.5 ten bolt fit my 1991 forumla firebird?

big gear head

The '79 Camaro doesn't have a 7.5 rear end. All Camaros from '71 to '81 had the 8.5 rear end, so no, the gears will not fit.

monsterjam5000

Ine must have been changes before I bought the car, my 79 had a 7.5 ten bolt. With a 373 posi. I put in a 411 posi, And did no know if the 1991 formulas had a 7.5 ten bolt.

big gear head

Someone could have installed a '76 or later 6 cylinder Nova 7.5 in it, but that would require moving the spring perches. No 2nd gen Camaros had the 7.5 rear end. Your '91 will have the 7.6 (same as the 7.5 but a little stronger) 10 bolt with 28 spline axles.

monsterjam5000

So any 7.5 gear and posi will fit? What does it usally cost to have new gears and posi installed in a rear end? Don't want to get ripped off.

monsterjam5000

Also does the computer have to be reprogrammed for the electronic transmission. And fuel injection?

big gear head

Yes, 7.5 or 7.6 gears and differential can be installed in the '91 rear end, as long as the diff is 28 spline and the correct series for the gears that you want to use. Look through this. It will answer a lot of questions. https://www.thirdgen.org/forums/tran...-10-bolts.html

ninetyone

iTrader: (2)

Are u running tpi? If so, it will not like 373 or 411. You will be quicker with 342 or 323.

monsterjam5000

why will it not like 373 or 411 thats the info im looking for i dont want to install something and make my car slower. i have the 373 and posi so i wanted to use them because its cheaper to use what you have instead of buying new.

ninetyone

iTrader: (2)

Why? because you have a certain usable powerband. The lower gears like 373 will get you to the max of your powerband tooo quickly. Basically, throwing you out of where your max torque and hp is.

ninetyone

iTrader: (2)

the problem is mainly with the tpi intake, but you dont really want to change that either until you get better heads and cam IMO.

monsterjam5000

well with any gear change do i have to reprogramme the computer

monsterjam5000

i found a 323 rear end from a 1994 camaro will that fit my 1991?

TheMonster

Yes it will, search, there is a ton of info about the 4th gen rears.

ninetyone

iTrader: (2)

yes, it will fit,but it will stick out in each side a few inches. If u don't care about posi,any 3rd gen v6 firebird rear will bolt right in.They were all 323 and 342. Check the thirdgen link on installing 4 th gen rears,and sell the 373 you have.

ninetyone

iTrader: (2)

what kind of car do u have? what have you done to it already?

monsterjam5000

if i go with a v6 rear end i would like to use a spool how well to they hold up?




also will i need the computer reprogrammed

ninetyone

iTrader: (2)

not too sure about the spool.Are you driving this on the track? you do not need to reprogram the computer. I think that is mainly for a cam swap.

84 z28

Spool is a no no on the street.

big gear head

A spool is dangerous on the street. It stresses the parts (axles, studs, wheels...) too much and stuff can break. You need a limited slip differential (posi) on the street so that it will give when you turn corners and not stress the parts.

cel19

Hey, got a question. Goin to rebuild the rear end in my 87 camaro for a street/ strip. Going with an eaton limited slip 28 spline with moser 28 spline axles and 3.73 ratio. Transmission will be a 700R4 built to withstand 800 horses. Personally I think it's a sweet setup. Some input of opinions would be awesome though, like if its a good combo or what not.

big gear head

If you are planning on building the original 7.5 rear end that is in your car you are going to blow it to pieces with 800 HP. You need a stronger rear end!