I have a 78 Monte and i have the ability to put a rearend out of an 86 SS in it. My question is, what ratio did the stock rearend have back in 86 and will it bolt directly into my car? The other question is, were all the SS rears posi or were some open? I don't have the rearend yet, so i wanted to know before I purchase it.

 

i cant tell you if it will bolt up...do you have the 4 link style or leaf springs (srry i'm not familiar with 78... more than likely it is a 7.5 10bolt rearend witch imho not worth dirt...

 

as for gear ratio?i want to say 2.73 but if you check out montecarloss.com and go in the tech section it should tell you and posi... i hig hly dought it unless someone put it in

 

All SS's 83-84 were 3.42:1 , all SS's 85-88 were 3.73:1. Posi was an option, If you have access to the car the rear is coming out of and the rear was never changed , look for G80 on the spid sticker inside the trunk lid. G80= posi. HTH

 

he is correct it should come with 3.73s and it could be open or posi and it will bolt right in. it looks exactly like the rear you have in the car.

 

I was told it is a 3.73 posi. I am going ot buy it if it bolts right in.

 

the monte man said it will bolt right it... do it

 

Yep no problems bolting it in, HOWEVER, it will have metric wheel studs in it. The original on a 78 is 7/16 standard. Scary part is they will thread on the metric studs and actually tighten up. For a little while! Remembered that the hard way at 65 mph and the lugs came loose.

 

you know what your right about that. i forgot that at one time i was running different lugs on the front and rear. im running the same rear but a couple years ago swapped to moser axles. how much are you paying for this rear? cause all honesty its not worth it your better off just buying an 8.5 for it or going to a yard and getting a posi carrier and a rebuild kit. im almost positive the housing is the same one you have just with a posi carrier and gears. the 7.5 has a small ring gear and 26 spline tappered axles c-clips and what have you. its not built to do much of anything but point a-b driving and once you introduce power to it and a wider tire its a bomb waiting to go off. upgrading it isnt worth it and in what youll spend you can get an 8.5 with a ring gear thats an inch bigger and has 28 spline axles add a c-clip eliminators and it should be able to handle 500+hp. just giving you my opinion. i bought mine for 150. blew it up bought moser axles and a 9* auburn carrier and it still isnt worth anything and i feel like an *** for not just spending a little more to get something thats worth while.

 

I ended up buying it. I got it for $125. I am not going to be putting a 500 hp motor in my car. I was just going to go with like a 355 with a little getty up cam in it. If I ever do decide to all out race this car, I'll be changing everything then. It is hard for me to tear apart a 84,000 original mile car, with documentation.