7.5" rear behind a 455?

Bonnewagon

Bonnewagon

Geezer
Sep 18, 2009
6,470
113
Queens, NY
If I put my factory stock Pontiac 455 w/MY6 overdrive trans in my Bonnewagon might the 7.5" rear live? I know most would say "fugedaboutit". But I ran the same 7.5" behind a harsh Pontiac 400 for 10 years with no issues. I think it would help that I already have the same 3:23 guv-lock gears in it as I did then. The trans has a 3:1 first gear which adds up to 9.69 overall ratio. I feel 10 to one is ideal and this gets me almost that. Then the .75 overdrive reduces the 3:23 to 2:42 which is some nice highway gearing. And of course I am an "adult driver" and I don't do crazy clutch dumping anymore. What I am asking is would a 7.5" rear last during everyday normal driving? Someone on here posted long ago about running a 455 w/Saginaw trans and 7.5" rear. He said be nice to it and it will live. I would not want to search out an 8.5" rear if I don't absolutely have to.
 
Texas82GP

Texas82GP

Geezer
Supporting Member
Apr 3, 2015
5,235
113
Spring, Texas
Maybe do the budget 7.5 build, especially since you are proficient in setting up a differential? Go with the 4th gen Camaro limited slip dif and get the upgraded (GN) axles? Adult driven, my guess is what you have will hold up fine but I have no real world experience.
 
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Bonnewagon

Bonnewagon

Geezer
Sep 18, 2009
6,470
113
Queens, NY
Well in my salad days I ruined PLENTY of hardware. I learned the hard expensive way. Now I am very respectful of machinery and it's limits. That said I abused this 7.5 pretty well behind the 400. Even the Guv-lock was fine. Which by the way is really nice in the snow. When I rebuilt it there was no damage inside. All I did was tighten up the backlash.
 
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565bbchevy

565bbchevy

Geezer
Aug 8, 2011
6,833
113
Michigan
I abused my stock 7.5 that had an Auburn carrier and 373 gears behind a 496 BBC for many years, I never ran sticky tires and also never had traction and it held up until I later sold it and went with a Moser 9".
 
Bonnewagon

Bonnewagon

Geezer
Sep 18, 2009
6,470
113
Queens, NY
I abused my stock 7.5 that had an Auburn carrier and 373 gears
See, that is what I mean. Usually when I hear of a 7.5 or any other rear breaking it is a case of a big motor trying to push dead gears. Change to better gears- take the strain off- live a long time.
 
ssn696

ssn696

Comic Book Super Hero
Supporting Member
Jul 19, 2009
3,960
113
New Mexico
Find another 7.5 and put it in the shed as insurance. I always thought that G80 in G body was an Eaton-style clutch pack, not the clockwork locker used in the pickups.
 
500/600

500/600

Master Mechanic
Supporting Member
Nov 17, 2018
440
93
West Virginia
Your own signature contains good advice...……………………….'get the right tool for the job'.
 
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