Been looking around for differential swaps.
Guys been swaping 8.5 g bodies to get rid of the 7.5 but still weak and command 1500 and up.
The other option is a 8.8 or 9 from a ford but need to be modified heavily to work.
Today came across guys swapping 12 bolt gm, they say they are a direct bolt up but need new upper and lower control arms for the swap. And with that said, they are an inch wider but is actually better for control. Or can you shorten the housing and axles?
Any truth and info greatly appreciated

 

The 68-72 8.5" 10 bolt and 12 bolt rears are the same width, so whatever you would do to install a 10 bolt is the same thing you'd need to install the 12 bolt.

So how much power are you pushing that an 8.5" 10 bolt isn't strong enough?

 

Currently I have 10 bolt 7.5 inch rear end in my 1980 g body, which will be desperately needed to be changed out.
Was looking for 10 bolt 8.5 for g body but they sell for 1500 and up and arent much stronger and need to be built.
Next option is 9 inch ford built to fit gbody.
A 12 bolt is heavy enough and will bolt in but are a bit wider than the g bodies. So would need to cut the housing and change axels.
And to answer your question, 450 hp 490 tq

 

I'm certainly not an expert on rearends, but I have never heard that an 8.5" 10 bolt isn't much stronger than a 7.5" rear.

 

This has been coming up just about since the G-body cars were new. There is NO 68-72 A-body rear that is a "bolt in" to the 78-88 A/G-body cars. For starters, the early rear is several inches wider. More importantly, the upper control arm attach ears on the center section are in the wrong place and at the wrong angle. Uninformed swappers have forced the G-body arms to fit, which binds the suspension. You can get conversion upper control arms with ball joints instead of bushings that fix the binding, but the geometry is still off - and the rear end is still too wide. And finally, have you priced A-body rear axles lately?

 

[QUOTE=joe_padavano;1229204]This has been coming up just about since the G-body cars were new. There is NO 68-72 A-body rear that is a "bolt in" to the 78-88 A/G-body cars. For starters, the early rear is several inches wider. More importantly, the upper control arm attach ears on the center section are in the wrong place and at the wrong angle. Uninformed swappers have forced the G-body arms to fit, which binds the suspension. You can get conversion upper control arms with ball joints instead of bushings that fix the binding, but the geometry is still off - and the rear end is still too wide. And finally, have you priced A-body rear axles lately?

Was a complete rear end that was forsale for $500, should of snagged it.
Yes I know it's wider, but should be able to cut the housing so its the same and change out the axles??
UMI Performance make upper and lower control arms to allow the conversion
https://www.umiperformance.com/home/...ntrol-arm-kit/

Any way I look at it, I need something. My 7.5 will blow, chasing down an 8.5 g body rear end isn't easy and command 1500. Some say the 8.5 g body won't take the punishment either so needs to be built.
So my 2 options are a custom 9 inch or a gm 12 bolt.

 

Could go Dana 60 also: https://www.strangeengineering.net/p...g-mounts.html/

 

So $500 for the A-body axle (if you're lucky), $400 for the UMI arms, and who knows how much for the shortening and the new axle shafts. And that assumes the A-body axle is posi and the ratio you want. A-body axles with good ratios and posi tend to sell in the $800 and up range. Sounds like there's no difference in the price to get one of the rare G-body 8.5 axles, plus you're still stuck with the incorrect suspension geometery. The UMI arms only fix the binding. The ears on the center section casting are still in the wrong place.

 

Yah - 12 bolt chevys are not discount rears ...a housing is 1000.00 in this neighborhood... Ohio
I built these 10 bolt 8.5 for years here example pictured...BUT we can not find 7.5 rears to even chop up to make our custom 10 bolt 8.5 rears.

Just finding rear wheel drive car rears is difficult in the yards around here.

12 bolt chevy will swap in and yes there are conversion swap upper and lower as stated...BUT as another said where are you with money and then a used 12 bolt or anyother used rear ...WHERE ARE you at. If you have enough power you think your going to grenagde a 8.5 well you better set aside some money and get a newer good customer rear...especially if this is a keeper car it is money well spent

we sell new moser g-body rears 2350.00 cash drive in price
our custom 8.5 rear which is bolt in no mod rear too is 1750.00 has double adjustable uppers which is what makes it a direct bolt in
width is same lower bracket stock perches stock ...

 

I am sending you a PM right now!!!!!

 

Monza is a good guy that I've dealt with. I'd go for the Ford 9in.

 

monzaz supplied me with all the necessary components to build my 7.5 .It sits behind a 455 in the neighborhood 400 hp 500 ftlbs torque and its holding up well.I haven't put sticky tires on it with hard launches though.im in it for about 800 .(built it myself)I guess it will depend on how you drive it.I see grand national rears for sale once in awhile ,i wonder how they differ from the stock gbody rears?

 

well thats interesting, a 7.5 holding up. Whats special inside?

 

Moser axles , trutrac posi carrier from an s10, nitro 323 gear set .It has to be set up right , and like I said it’s doing great on the street .Just another option for you to consider

 

[QUOTE=deadeyejedi;1229471]Moser axles , trutrac posi carrier from an s10, nitro 323 gear set .It has to be set up right , and like I said it’s doing great on the street .Just another option for you to consider

Does the true trac make noise since its all gearing in their?
I looked at this option, but people are saying it wont hold up. But I guess it does

 

It’s not noisy at all I push it pretty hard . Time will tell how it holds up got the summer out of it including some impressive burnouts at the Adirondack nationals in lake George ny .