Right now i have a 267 w/ th350, GM 7.5 rear with 3.90 or 3.93 not sure. I don't know thats what the guy told me, Its a daily driver/ Street project. Up coming shortly will either be a 350 or a 327 w/ double hump heads. Keeping the th350 trans in for awhile yet. Wanting to know what are my options for a new rear end. I'm the type of guy that will spend the money to do it once and be done. although im only 18, but i got it. Ive heard of doing the 8.5 GN rears, 12 bolts, and ford 9 inch. personally id rather do the 8.5 or 12 bolt chevy, unless a ford 9 inch would be the same amount of work for a better rear. Does the 8.5 make a clean swap? Does the 12 bolt need modifications for suspension? Is it just shortening if the drive shaft/ New longer one ordered? I need all the info about the rear end, work involved, what needs to be done to have everything tip top shape to make the best decision. Any advice on an engine would be helpful too. Whatever knowledge you guys have is beneficial. THANK YOU!
What are my rear end options?
- Thread starter 79BuOwner
- Start date
8.5 is pretty much a bolt in swap........some guys have used the ford fox body 8.8.......some fab work involved,but a very strong rear for a bit less than an 8.5........12 bolt a body rears bolt in but you have to use the coversion upper trailing arms and a 5.5 back space rim.......if your looking for a stock direct bolt in then the 8.5 would be your best bet......out of a grand national or a olds 442.......i am not sure of the drive shaft though...i had a local shop make one for me......i was lucky enough to get a 12 bolt that was only 1 inch per side wider than the 7.5 that i took out......used no hop bars and adjustable upper and lower trailing arms for my 79 bu.....463 inch bbc,10.5 comp. ,rec. port early 427 heads,lunati solid flat tappet cam,weiand team g manifold,holley 870 avenger carb,cd ignition,th 400 trans.....12 bolt rear with 4.11 gears and a full spool......street car..........
I have a 12 bolt from a 67 chevelle and all i had to do is get the 5.5 b/s rims, use the 12 bolt swap control arms, diff u-joints and i had the tooth pick original d/s removed and had a bigger one made.
Now with the 5.5 bs the tires wont rub the frame? Right now i have 14x7 rallys original with 245's on em and itsa bout 3/4-1 inch from rubbing the frame, alot of tire bulge. im saving to find a rear set of weld prostars, since i already have my fronts. either going with 15x8 or 15x10, saw the price new so wasn't gonna go that route, just wait till someone puts up a set of really nice used ones with a good B/S.
Also the 8.5 can still use an original B/S? I would assume the length to each end is the same as a 7.5..? if not little wider?
Also the 8.5 can still use an original B/S? I would assume the length to each end is the same as a 7.5..? if not little wider?
Also which cars carry the 8.5 and which carry the 12 bolt? just to get an idea of what id be looking for at a junkyard, although im sure most are already taken, but ya never know.
8.5= Grand National/ 442
12 bolt= 64-67chevelle (stock width?) 68-72(1" wider)
9"= after market
I'll double check the 12 bolt widths
12 bolt= 64-67chevelle (stock width?) 68-72(1" wider)
9"= after market
I'll double check the 12 bolt widths
"--------------------------------------------------------------------------------
I measure 1964-67 = 54 1/4" & 1968-72 = 55 1/4" backing plate surface to surface....................."
/\ From another site.
I measure 1964-67 = 54 1/4" & 1968-72 = 55 1/4" backing plate surface to surface....................."
/\ From another site.
so with an 8.5 rear and a 12 bolt from a 64-67 chevelle i would be able to use a 4.5 inch backspace rim? im concerned because rims are expensive and im not gonna buy two for the back which is what i need, then have to sell them just because of a new rear, thats pretty much wasting a thousand dollars. might be able to get my money back from the rims but who knows when il sell them, thats my concern. my 7.5 now has 3.93 gears so with a built 350 i should be fine for awhile with out mashing on the gas too much. till i get my stuff together and figur out whats going in. Also is the fox body 8.8 allow for the same backspace rims?
