How to swap different types of rears into G-bodies

81cutlass

Comic Book Super Hero
Feb 16, 2009
4,366
113
Western MN
$2200 new is cheap?

A 8.8 is cheaper than that by far, like sub $1000. It's just the geometry sucks since the upper control arms are at different angles and locations than a G body so they force usage of conversion arms which screw up the instant center and suspension geometry. You can fix the geometry but its still not right. 4 lug also is a bummer so you need axles if you want to run GM pattern.

A 12 bolt is better but they aren't falling out of trees anymore.
 
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Reactions: 1 user
Oct 14, 2008
8,324
113
Melville,Saskatchewan
I would like to fit this rear end in my G body.....:banana:

Reminds me of my wife. I got her rear in my G body once last year. Maybe with new paint? She likes her rear in the Challenger GT, don't blame her. It didn't help the tail pipe fell off:(.
 
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Reactions: 1 user

81cutlass

Comic Book Super Hero
Feb 16, 2009
4,366
113
Western MN
8.8 from a fox body-$250
5 lug 31 spline moser axles-$270 new summit
31 spline posi carrier and 3.73 or so gears, buy salvage yard explorer rear- $200
8.8 swap arms from baseline suspensions- $320
3rl or 1350 yoke-$50
Gear install kit for 8.8-$100

That looks like $1200 total, and not NEARLY full scrounger value parts. No weld option.


You still need to buy a driveshaft and brake lines for any rear you do so you cant count that. You do have to buy ford lug wheels which also sucks for some people and backspacing, but most g bodies have 14
s anyways so the chance you buy new wheels anyways is high enough that thats a zero factor in the decision.

I am not a fan of 8.8 geometry which is why I don't have one in my car, but its a cost effective option for someone keeping under the 800hp range.
 

gnvair

G-Body Guru
Sep 1, 2018
978
93
Southern New Jersey near Philly
I think a fair price comparison is when starting with all new items;
Do the cost calculation of a 9" with all new supporting hard ware such as new center, new carrier, new ring and pinion, axles, bearings, brakes, etc.
Then do the calculation of a used 8.8 housing with new 31 spline carrier,new ring and pinion, new axles (stock 28 spline are fragile), new bearings, brake items and control arms (since you need them to bolt it in) and spring perches.
What I just said for the 8.8 could also be applied to the 64-77 A body rear ends such as the 12 bolt, 8.2, 8.5 etc.
 

Rob-Legacy1

Apprentice
Sep 11, 2016
66
18
New Braunfels Tx
The link I posted has all new parts limited slip , disc brakes, ring and pinion of your choice direct bolt in for Gbody 5x4&3/4 bolt pattern for $1895 . Which I'd say is pretty inexpensive. It would cost you a lot more to have me install a 8.8 in your car than it would that 9". At some point you have to value your time
 

81cutlass

Comic Book Super Hero
Feb 16, 2009
4,366
113
Western MN
Absolutely, a 9" can be a great option, I just think the assumption is when you buy a quick 9" you are getting all new parts, you don't. Not that anything is wrong with used, I prefer OEM used parts over new aftermarket alot of times due to the known quality and testing the OEM's go through that aftermarket groups aren't required to meet, but it's something to be mindful of.

A new center housing piece is an additional $100 (the base price includes a used unit)
A base 9" carrier made from grey iron is included which quick themselves only rates to 450hp. The good daytona bearing support nodular iron case is another $350
9" rears have the low pinion design which although is awesome for strength, is poor for power efficiency and they take additional power to turn.

A Ford 8.8 and GM 12 bolt are very similar in design and even share carrier bearings.

A GM 8.5/8.6 10 bolt is again similar in size and power capability as 8.8 and 12 bolt, its just that they don't come in widths and configurations that apply to G bodies very well.

Every rear axle option has its benefits and negatives and each person has to look into each option as to weather or not it is a good fit for what they want to do. Power, budget, amount of factory style fit wheels and efficiency of the axle are all factors people need to consider.

Saying "put a 9" into it" or "put an 8.8 in" is like saying "put a SBC in place of your 307 olds", the SBC can and often is a good choice, it's just people have CONSIDERABLY less brand attachment to their rear axle than they do their engine.


The issue is 9" cores are drying up, 12 bolts are rare these days, and the days of affordable GN/442 8.5's are long gone unless you get lucky.

The 8.8 has slightly replaced the 9" these days as the go to rear end for many applications in and outside of the G body world, but it's not the "Halo to do" rear axle and takes upgraded parts just like 9", 12 bolt, and 8.5/8.6 options.
 

Rob-Legacy1

Apprentice
Sep 11, 2016
66
18
New Braunfels Tx
I don't believe 9" parts are anywhere near drying up. Every heavy racing type still use them and every part is available new. and while the center section maybe used it was the only used part and not a wear Item. I have nothing against the 8.8 it's a fine differential but at the end of the day is not a great deal over a 9". The 8.5 is ridiculously expensive and unless restoring or you already have one is not a good option for cost saving. the 12 bolts are good aswell but still much more expensive than a 9". At the end of the day it is a personal choice. I was only giving my opinion and based on the article link posted in the og post the 9" I linked to was less expensive. if you have the ability and equipment to do it yourself you may be able to save some money but what value is your time.
 

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