Rear end swap questions

[robhowardiii]

hi I recently picked up a 68 chevelle 8.5" rear-end. I know all this has probably been answered before but I cant find it. my questions are
1: can I use the same spring mounts on the axle? (they are off to the front not dead center on top the axle)
2: do I have to shorten the driveshaft like a g body 8 1/2" swap?
3: as far as control arms go do I have to change the lowers or just the uppers (with the spherical joint)

now the last question is, is it worth it? I have a 7 1/2 now with 2.41 gears open diff the 8 1/2 is a 308 and I cant seem to find a gbody 308 in my area. I picked up the 8 1/2 for free and its in good shape. I also picked up a set of iroc wheels that need spacers, so if I am going to drop $ on spacers I am thinking why not just swap the rear and its like adding a 2" spacer on each side and killing two birds with one stone as far as my rear gears (and I don’t know how to set up gears so swapping gears will be expensive)

 

[jdietschweiler]

Where's your location? I happen to have a 3.08 posi just sitting on my trailer. I don't need it I'm going 8.8.

 

[pontiacgp]

you can use the same mounts but the car will sit a bit higher,

I'm not sure about the driveshaft, I have the 8,2 rear and I used the same driveshaft I used with the 7.5....JBrue would know tho,

you can force the uppers to work but it's alot better getting the conversion uppers. I'm using the UMI and so is Jbrue..the lowers work

your sway bar will work but it's a bit of a struggle to get it in..

the 68 rear is 4.5" wider than the 7.5 rear, I have the 67 so mine is 2.5" wider but JBrue has the 68-72 version so you can take a look at his car to see how it looks...I forget what his backspacing is

you will also need a conversion u-joint for the rear, Napa has them but they arn't cheap

 

[robhowardiii]

How do the spherical joints hold up? That's my concern with the umi ones. I was talking to someone with a 79 malibu who has no spheres on his 12 bolt swap I think they wher pmt brand. He says he has no binding. Second does anyone have a part number for the u joint? I called napa and they had no clue what I was talkin about.

 

[pontiacgp]

Spherical joints have been used in various applications including aircraft for decades so it's the quality of the joint that determines how it will hold up. I'm using the Roto joint and I have only had them on for 1/2 a season. As I mentioned JBrue is using the UMI conversion uppers and he's got alot of power under the hood that he uses so he can give you a better idea on how they are holding out. Ask Ramy who's the Product Development Engineer at UMI and a member here, he'll give the straight goods on the products.

 

[UMI Sales]

Spherical joints have been used in various applications including aircraft for decades so it's the quality of the joint that determines how it will hold up. I'm using the Roto joint and I have only had them on for 1/2 a season. As I mentioned JBrue is using the UMI conversion uppers and he's got alot of power under the hood that he uses so he can give you a better idea on how they are holding out. Ask Ramy who's the Product Development Engineer at UMI and a member here, he'll give the straight goods on the products.

Thanks GP.

Our upper conversion arms are the key component (of our product line of course) to getting the rear physically into the car. The cars we've built here have had both factory G-body lowers and our adjustable G-body lowers.

Let me know if you have any specific questions and I'll be happy to work on an answer.

ramey

 

[robhowardiii]

got rear in haven’t got the upper swap arms yet (long story not to happy with iceman wish I had bought umi) but now onto the next issue. I am doing all this mainly to put a set of iroc rims on. I went to put them on and they seem to have a smaller hub diameter then the axle. anyone run into this? what’s the best way to overcome it? I was thinking die grinder and make the hub circle on the rim a little bigger but there has to be a better way.