Just a little info that might help.
I have never been satisfied with any aftermarket heavy duty rear axles for G bodies.
-Gn/442 8.5 is tough, but hard to find and drum brakes, high cost. $750 is what I see them for. Not a sustainable option really. Taking apart a low volume specialty car for a part doesn't lean toward good results in the future.
-8.8 fox body is strong, affordable, easy to find, but 4 lug axles and have to buy baseline arms which mess with the suspension geometry. I know they "correct" it but moving the UCA mounts from the top of the housing to the side right above the axle tube doesn't help. The LCA mounts move inward meaning you cant run a factory rear swaybar, often have 2.70ish gears, still drums (so c clip elim's), and I think it just results in wheel hop and instant center issues. I havn't built a car with one but it seems like its 50/50 vs people that are successful and not. Can do the ranger and aerostar axle swap for cheap but still wrong bolt pattern, or money for custom axles. About the only pro I see is it's the right width and has 4 link bars. Also they use a diferential flange instead of a GM style so thats another part.
-93 mustang has a similar rear (that is 2" wider or so) with disks, 5 lug and often better ratios, but still wrong bolt pattern so custom axles, and same control arm issues.
-66-67 chevelle 12 bolt, how many 66-67 12 bolts still exist? Not enough to make it easy to find for the average person.
68-72 12 bolt? Same deal as other chevelle, tough to find, not that cheap, wrong width, drums, probably wore out.
Aftermarket 9", sure if you have an 800hp car and $2000 laying around. $300 housing, and axles and carrier and gears and brakes. I built a 9" before on the cheap and it was still $700 and has 5x5 axles, and open 2.73 gears. 9" rears arent exactly plentiful anymore either.
Best option I see that is available in junkyards today is the 98-02 Zr2 8.6 rear. They are 30 spline 5x4.75 axles, 3.73 gears, disk break, have 1350 input yoke, and are SUPER plentiful. I have over 25 of them for under 300 bucks (as low as $150) within 200 miles of me at salvage yards.
The overall best option is a manual 4.3 4wd 98+ s10 has an 8.5. They do not come in any blazer despite what salvage yards will tell you. Only 4wd s10 4.3 I have verified. I can't find one either, they are stock width within .5".
Only bad news on the zr2 rear is they are 4" wider than stock G body rear and they have a gov lock diferential instead of a true posi. Good news is since most G bodies have 15x7 wheels with 3.5BS or so, a 16 or 17 inch wheel in c5 vette or 4th gen f body wheel will fit. They are available aftermarket in like a 15x9 and 7" BS at summit for race wheels too.
So my build began with a 98 sonoma zr2 rear. Reportedly they turned from 8.5 to 8.625 (same rear just bigger gear, maybe metric cover bolts?) in 99 but have not confirmed. Mine is english thread.
Cut off leaf perches and panhard bar.
I designed, programmed the CNC, machined, and welded up a plate to bolt the housing. This is what your UCA will attach to. The force on a launch is compression on the plate so they won't break. I did the materials/stress analysis, it's fine. 🙂
The plate retains the exact left right position of the UCA, it moves them up like 1/8" over stock because the housing is just bigger.
Sliced and bent the ears
Welded it up!
Welded on $100 9" lower brackets, modified upper for my plate, and spring perches.
I did all the welding and assembly on this last night after work in 3 hrs. With the fixture I plan to make it would be 1.5. No exotic cast welding. Retains stock control arms and sway bar. Awesome features you pay $800 for at some aftermarket product.
If you are bound and determined to run stock width you can for $300 or so. Axles are available on summit. Just have to cut the housing down 2" on each side.
I have been hinting I have this planned for the last few months. Here it is!
I have never been satisfied with any aftermarket heavy duty rear axles for G bodies.
-Gn/442 8.5 is tough, but hard to find and drum brakes, high cost. $750 is what I see them for. Not a sustainable option really. Taking apart a low volume specialty car for a part doesn't lean toward good results in the future.
-8.8 fox body is strong, affordable, easy to find, but 4 lug axles and have to buy baseline arms which mess with the suspension geometry. I know they "correct" it but moving the UCA mounts from the top of the housing to the side right above the axle tube doesn't help. The LCA mounts move inward meaning you cant run a factory rear swaybar, often have 2.70ish gears, still drums (so c clip elim's), and I think it just results in wheel hop and instant center issues. I havn't built a car with one but it seems like its 50/50 vs people that are successful and not. Can do the ranger and aerostar axle swap for cheap but still wrong bolt pattern, or money for custom axles. About the only pro I see is it's the right width and has 4 link bars. Also they use a diferential flange instead of a GM style so thats another part.
-93 mustang has a similar rear (that is 2" wider or so) with disks, 5 lug and often better ratios, but still wrong bolt pattern so custom axles, and same control arm issues.
-66-67 chevelle 12 bolt, how many 66-67 12 bolts still exist? Not enough to make it easy to find for the average person.
68-72 12 bolt? Same deal as other chevelle, tough to find, not that cheap, wrong width, drums, probably wore out.
Aftermarket 9", sure if you have an 800hp car and $2000 laying around. $300 housing, and axles and carrier and gears and brakes. I built a 9" before on the cheap and it was still $700 and has 5x5 axles, and open 2.73 gears. 9" rears arent exactly plentiful anymore either.
Best option I see that is available in junkyards today is the 98-02 Zr2 8.6 rear. They are 30 spline 5x4.75 axles, 3.73 gears, disk break, have 1350 input yoke, and are SUPER plentiful. I have over 25 of them for under 300 bucks (as low as $150) within 200 miles of me at salvage yards.
The overall best option is a manual 4.3 4wd 98+ s10 has an 8.5. They do not come in any blazer despite what salvage yards will tell you. Only 4wd s10 4.3 I have verified. I can't find one either, they are stock width within .5".
Only bad news on the zr2 rear is they are 4" wider than stock G body rear and they have a gov lock diferential instead of a true posi. Good news is since most G bodies have 15x7 wheels with 3.5BS or so, a 16 or 17 inch wheel in c5 vette or 4th gen f body wheel will fit. They are available aftermarket in like a 15x9 and 7" BS at summit for race wheels too.
So my build began with a 98 sonoma zr2 rear. Reportedly they turned from 8.5 to 8.625 (same rear just bigger gear, maybe metric cover bolts?) in 99 but have not confirmed. Mine is english thread.
Cut off leaf perches and panhard bar.
I designed, programmed the CNC, machined, and welded up a plate to bolt the housing. This is what your UCA will attach to. The force on a launch is compression on the plate so they won't break. I did the materials/stress analysis, it's fine. 🙂
The plate retains the exact left right position of the UCA, it moves them up like 1/8" over stock because the housing is just bigger.
Sliced and bent the ears
Welded it up!
Welded on $100 9" lower brackets, modified upper for my plate, and spring perches.
I did all the welding and assembly on this last night after work in 3 hrs. With the fixture I plan to make it would be 1.5. No exotic cast welding. Retains stock control arms and sway bar. Awesome features you pay $800 for at some aftermarket product.
If you are bound and determined to run stock width you can for $300 or so. Axles are available on summit. Just have to cut the housing down 2" on each side.
I have been hinting I have this planned for the last few months. Here it is!
