9"/12 bolt/10 bolt swap

[grizwald]

what did you guys have to replace to change to your 9", 12 bolt, or 10 bolt (8.5)? i'm trying to figure out which way i want to go and of course, cost is an issue. i don't want to choose one route because it seems to be a better deal only to have to change a bunch of other things. i know i'll be doing brakes, but what else? i currently have a 7.5 stock rear with umi tubular upper and lower control arms (not adjustable) and stock springs.

 

[bowtie81]

i have a 12 bolt from a 66 chevelle. i had to change the u-joints a parts store can set you up with that, b/c the 12 bolt is wider you'll have to change the offset on your rims. with a 15x8 i went with 5.5b/s with a 1/8 spacer and it fits a 275-60-15 tire perfectly with no rubbing. and i put the 12 bolt swap control arms on. the control arms were about $200, rims were $400 from summit, spacers were $10, whatever the u-joint costs. and it bolted right in with no hassle. keep in mind it takes less power to turn a 12 bolt than a 9". and in my opinion 12 bolts are just as strong as the 9 and plus the 12 is a bit lighter. theres a guy in sarnia here running a 12 bolt in his chevyII running 7's and that 12 bolt hasnt given him an ounce of problem.

 

[grizwald]

that's the only reason i'm considering the 12 or 8.5 10 bolt. if it didn't take more power to turn the 9", i'd go that way without even thinking about it. from a cost standpoint, they're not too much different. i would more than likely pay to have one narrowed to fit my car rather than buy new rims as it's more than likely the sale cost. did you have to get a new driveshaft?

 

[bowtie81]

i changed the driveshaft before that, i seen too many guys twist the original. i got mine out of a 81 chev pick up and had a machine shop cut it down to size and true it back up. works perfect.

 

[lilbowtie]

My vote would be for the 9in. I put a bolt in Moser using GM back plates, brakes, and drums. Had to have a drive shaft made. As far as the HP loss 2% won't make or break you. I also run a turbo 400 that takes more HP.