8.5 rear end identification

[Travis Clark]

If you have your G body 7.5 rear why not compare width measures of the two rears. Also I'd suggest you remove the cover to see if the spider gears are welded together. I worked on a circle track team and since we were not permitted to run a posi or a spool we welded the two pinion gears to the side gears, commonly known as the spider gears. I don't know any circle track that allows a posi and with that rear end it must have been on a lower class division so I doubt it has a spool. I would also check the right axle that takes all the load in circle track for a groove in the axle caused by the axle bearing. Then after you do that you can always sell the gears to the circle track guys cause it would be the right gearing for that tack.

Roger that Sir, I thought I measured from backing plate to backing plate on the El Camino but I may have misread the tape due to the car being currently intact. Seller advised that he used the carrier for his wife's circle track car so it has no carrier, which was fine with me because I wanted to get the housing powder coated and go with all new parts. Not being mechanically inclined, upon originally seeing the listing for the 8.5 it appeared to be the same type of rear end so I purchased it trusting the guy that it came off of an 80 El Camino. It was not expensive enough to be upset about, lesson learned. I have seen that people modify housings by narrowing the axle tubes which seems like a lot of work if you do not know anyone who does such. I drove my El Camino from Louisiana to Stockton California to give me something to do in my downtime. I've always wanted to update the transmission and rear end and figured that this was a good time as any so I have a 700R4 and wanted to go bigger with the rear end.

 

[pontiacgp]

The shortening of axle tubes is usually on a Ford 9". The axle splines on a GM are cold rolled so you can't cut them and machine them like you can with a Ford axle. That rear end may have come from an 80 El Camino but it didn't leave the factory when new with that rear end. All El Caminos came with a 7.5 from factory. There is a member of this forum that is running a rear from the 68 to 72 version of the Chevelle that is 4.5" wider than the G body rear, his screen name is JBrue. My 67 Chevelle rear is 2.5" wider than a G body rear. Here is a picture of JBrue's Monte

 

[1bad79]

If you have your G body 7.5 rear why not compare width measures of the two rears. Also I'd suggest you remove the cover to see if the spider gears are welded together. I worked on a circle track team and since we were not permitted to run a posi or a spool we welded the two pinion gears to the side gears, commonly known as the spider gears. I don't know any circle track that allows a posi and with that rear end it must have been on a lower class division so I doubt it has a spool. I would also check the right axle that takes all the load in circle track for a groove in the axle caused by the axle bearing. Also lay a straight edge along the axle tube to make sure it has not been bent bouncing off a wall. Then after you do that you can always sell the gears to the circle track guys cause it would be the right gearing for that tack.

In Michigan we call that a Lincoln locker

 

[Travis Clark]

If you have your G body 7.5 rear why not compare width measures of the two rears. Also I'd suggest you remove the cover to see if the spider gears are welded together. I worked on a circle track team and since we were not permitted to run a posi or a spool we welded the two pinion gears to the side gears, commonly known as the spider gears. I don't know any circle track that allows a posi and with that rear end it must have been on a lower class division so I doubt it has a spool. I would also check the right axle that takes all the load in circle track for a groove in the axle caused by the axle bearing. Also lay a straight edge along the axle tube to make sure it has not been bent bouncing off a wall. Then after you do that you can always sell the gears to the circle track guys cause it would be the right gearing for that tack.

I just took off the cover and the carrier is gone as expected. I guess I can order a 9 inch Ford (made for a G Body) but I wanted to have a GM 8.5. Eventually I will build a 454 so I wanted to have a durable rear end to support it. I've heard guys rebuilding the 7.5's but they are limited from what I have read and most car guys back home don't share secrets about getting power to the ground other than beefed up transmissions and posi units. At least I know the 700R4 is legit because I pulled it myself from a coworkers husbands custom Camaro with a Currie rear end.

 

[Travis Clark]

The shortening of axle tubes is usually on a Ford 9". The axle splines on a GM are cold rolled so you can't cut them and machine them like you can with a Ford axle. That rear end may have come from an 80 El Camino but it didn't leave the factory when new with that rear end. All El Caminos came with a 7.5 from factory. There is a member of this forum that is running a rear from the 68 to 72 version of the Chevelle that is 4.5" wider than the G body rear, his screen name is JBrue. My 67 Chevelle rear is 2.5" wider than a G body rear. Here is a picture of JBrue's Monte

Oh wow. Thanks for that information Sir. Surely you guys had to modify the rear in some way to accept the wider axles. That's awesome.

 

[pontiacgp]

Oh wow. Thanks for that information Sir. Surely you guys had to modify the rear in some way to accept the wider axles. That's awesome.

The rear end was not modified in my GP or in JBrue's Monte. The conversion uppers from UMI fit the 64 to 72 Chevelle rear end to a G body. JBrue used the stock lowers.

The 8.2 rear I have is rated for up to 500 hp so the 8.5 would be higher than that. I would never try to build a 7.5 to handle power.

 

[Travis Clark]

The rear end was not modified in my GP or in JBrue's Monte. The conversion uppers from UMI fit the 64 to 72 Chevelle rear end to a G body. JBrue used the stock lowers.

The 8.2 rear I have is rated for up to 500 hp so the 8.5 would be higher than that. I would never try to build a 7.5 to handle power.

Got it. So if I were to order replacement axles, gears and carrier, the rear wheels would be set wider? I would order the axles for a 71 Chevelle? Did you guys have to increase your rear wheel size because I am currently using the 14 steel stocks.

 

[pontiacgp]

Got it. So if I were to order replacement axles, gears and carrier, the rear wheels would be set wider? I would order the axles for a 71 Chevelle? Did you guys have to increase your rear wheel size because I am currently using the 14 steel stocks.

the brake drums on your Chevelle rear end are interchangeable with the G body drums . The problem you may have is the backspacing may not be enough on your rims

 

[Dinosport]

Not to high jack but I have a couple of questions that might be useful for Travis as well. How well does the 12bolt work on the car with the conversion uppers. (Wheel hop, travel etc) compared to having a Gbody rear? For me it's easier to find a 12bolt with a posi, put 373's in it. I can have the housing shortened and just buy axles for a fraction of the cost of buying 9".

 

[Andebe]

One question. Who is Roger?