kc8oye Posted April 21, 2005 Share Posted April 21, 2005 I scored a posi unit for my monte.. I think.. came out of an '85 buick LeSabre.. it's definately posi (even has the warning tag about using LSD fluid) both tires turn in the same direction and it's a !@#$ to try and turn it around on the ground it's definately a-body-style 4-link, (even tho the lesabre is a T-body (b-body maybe?)) I have two problems tho a) it's a 5x5.00" pitch circle (monte is 5x4.75") the shock mounts are in the wrong place, (they're on the front for the buick, back for the monte) now.. the housing itself appears to be identical to my 10-bolt housing... what are the chances of me taking the posi guts out of the buick and putting them in my housing with my axles? I'd like to totally rebuild the axle anyway, new seals, bearing inserts.. etc etc. I'm TOLD the buick has 3.73's and I definatley don't want those w/o an o.d trans. If I have to buy new 2.73's to fit the buick's carrier that's fine. and my last Q.. anyone interested in helping me tear both axle housings down and rebuild the monte's? Quote Link to comment Share on other sites More sharing options...
alex's72fgmc Posted April 21, 2005 Share Posted April 21, 2005 a) it's a 5x5.00" pitch circle (monte is 5x4.75") just swap out the axles just make sure they are the same spline count but see next answer below... the shock mounts are in the wrong place, (they're on the front for the buick, back for the monte) those can be removed and the other ones put on but i would rebuild the one that works on your car not this one due to the amount of work you have to do. now.. the housing itself appears to be identical to my 10-bolt housing... what are the chances of me taking the posi guts out of the buick and putting them in my housing with my axles? just check and see if the diff will fit into the rear axle housing of yours and see they may have a different diameter than the 70-72 axles "dont know but would not hurt to see. Alex Quote Link to comment Share on other sites More sharing options...
Grease Posted April 22, 2005 Share Posted April 22, 2005 If you dont want 3.73 gears ( sell to me ) lol if i remember correctly 2.73 will reqire a different ( series 2 ) carrier . you might go down to 3.23 gears on the carrier from the LaSabre.if doing all that work i would say just have a shop install the stuff in your housing.Though you do need to check the axle spline count .if thats not the same you'll need new side gears as well. mike Quote Link to comment Share on other sites More sharing options...
kc8oye Posted April 25, 2005 Author Share Posted April 25, 2005 sweet.. that's what I wanted to hear :0 thanks guys Quote Link to comment Share on other sites More sharing options...
Guest Posted April 25, 2005 Share Posted April 25, 2005 Hey Hey Kc you can't just change the gears from housing to another they have to be set up right or the first time you get on it bang there goes your rear the gears have to meash (hope I spelled that right)just right. boy I wish I know how to do that Dave Quote Link to comment Share on other sites More sharing options...
monzaz Posted April 28, 2005 Share Posted April 28, 2005 What year monte is this for? The rear is going to be much wider than a 1970-1972 rear. the upper control arm mounts are wider also. lower control arm bolts are larger and this is probably a 8.5 or 8.875 half breed 12 bolt with a ten bolt cover. You can not make a 8.5 diff fit a 8.2 or a 12 bolt from 70-72... Nor will the 12 bolt fit the old style 12 bolt. Can not be done. Now it is a totally different story if it is a 1973-1977 monte your working on. Until I know what year you have there is no definet answer...YET. Jim Quote Link to comment Share on other sites More sharing options...
kc8oye Posted May 17, 2005 Author Share Posted May 17, 2005 it's a 70-72 monte. Quote Link to comment Share on other sites More sharing options...
Guest Posted May 18, 2005 Share Posted May 18, 2005 Remember even if the gear wasnt the same series you could use a ring spacer. Just a thought... Quote Link to comment Share on other sites More sharing options...
kc8oye Posted May 23, 2005 Author Share Posted May 23, 2005 well.. let me rephase.. I am considering two options.. 1) using the whole housing as-is.. relocating any mounts as needed... 2) taking the posi unit out and putting it in my housing. as for option 2... how is it going to work if I change the whole diff as one unit, setting lash and what not as required... OR... using just the posi 'center section' and possibly finding a new carrier? or am I thinking of one piece as two? it's hard to do this w/o the axle infront of me.. can't wait to have i-net at home again Quote Link to comment Share on other sites More sharing options...
Guest Posted June 20, 2005 Share Posted June 20, 2005 You need to do a little more research, I will bet that you have a 8.2 10 bolt in your monte carlo, the 10 bolt out of the buick is more that likely a 8.5 in. rear, nothing interchanges sorry, please double check me though, as I've been known to be wrong, go to team chevelle they can help you over there also. Jim Quote Link to comment Share on other sites More sharing options...
big gear head Posted October 18, 2005 Share Posted October 18, 2005 These guys are right, the Buick rear end is probably the 8.5 10 bolt and you Monte Carlo rear end is probably the 8.2 10 bolt. You can not take the parts out of the 8.5 and put them in the 8.2. The upper controll arm mounts were changed in '73 to a 90 degree angle. The '72 and earlier rear ends had les than a 90 degree angle, so changing the brackets isn't going to work either. You could try something like ladder bars. As for the axles, if the Buick has the 5 on 5 bolt pattern then it probably also has the larger truck axle bearings, so swaping the axles won't work either. Don't mean to ruin your good mood, but I'd hate to see you go to a lot of trouble for something that won't work. There are some 8.5 rear ends that were installed in the '72 Chevelles and other mid size GM cars. If you can find one of them you could swap the internal parts and use it. If not then sell the gears and posi to someone with a second gen Camaro. Quote Link to comment Share on other sites More sharing options...
monzaz Posted November 18, 2005 Share Posted November 18, 2005 That is exactly what I was trying to get at. I guess if you want to go through all the work of relocating(replacing in some cases) the perches for the rear. You will also need to cut the drive shaft if you are doing this also...10 bolt 8.5 is 1" longer in the pinion housing area. your origial drive shaft will not work. Sounds like you should just find a better way and off the parts on ebay. 1971 1972 buick and olds a-body did come with 10 bolt 8.5 rears which will hold thoses gears and posi unit and will DIRECTLY bolt into your monte carlo. Hope that helps. I would just buy a 8.2 10 bolt posi and stick it in. less hassle. Good luck. Jim Quote Link to comment Share on other sites More sharing options...
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