Posi rear cover/girdle

[buzz77]

I was wonderng if someone could explain to me the theory behind the rear end cover girdle. What exactly does it do and how? And are they effective?

 

[CWPottenger]

I was wonderng if someone could explain to me the theory behind the rear end cover girdle. What exactly does it do and how? And are they effective?

Generally speaking cool looks.
That being said if you have a vehicle able to put down serious torque numbers and your tires hook very well then the girdle is designed to reduce/eliminate stress and deflection of the bearing caps in the rear end.

 

[Fox80]

If installed correctly, the "girdle" type cover can help to prevent a cap failure people make a big deal about the size of the ring gear, but most of the failures are either a all out cap failure or gear wear from cap/case deflection the above pic is of a Ford 9" circle track gear set, I assemble many many gears every year, and when properly set up this is the one thing that can't be avoided, the cover will use the support bolts to help prevent the cap from breaking under load, dirt circle track cars have very little traction compared to a street car, but even just occasional abuse can split a cap or distort a housing. I wouldn't say this is the number one reason for gear failure, that is improper set-up, but it does happen a lot, the housings in these cars were designed for 250hp max, even the beloved 8.5 shares all the parts of the 7.625 set-up, the first big power upgrade for a Ford 9" is a case with billet bolt through caps so every style housing has this weak point, and the girdle covers do help if done right

 

[buzz77]

Thanks Fox,
So I imagine the bolts on the girdle/cover are supposed to fit into those shallow grooves in the center of the caps? Would you recommend this for a 7.5 26 spline axle posi for our cars? I don't think ill ever approach more than 250hp in my car, Ill be lucky to get it at 200 someday.

Another thing. how much power do you honestly think our 7.5 rears can handle on the street,[not considering track use and burn outs using slicks]?

 

[Fox80]

I would put one on these cars, I have one for mine and it probably only makes 100hp at the wheels, it's not like you are talking a huge money investment. Every GM gear set I have ever done for me or other people I have put a cover on them, the gears in the above pic are two laps old in a heat race, you are looking at over $700 in junk for a broken cap. If you use a girdle cover, c-clip eliminators, a decent aftermarket axle, and jig up and weld the tubes so they don't spin, these rears can easily handle into the 11's /475hp. If I personally was to ever change out the housing in my car for more power I would go to a 9" only because of the c-clip GM stuff, the eliminators like to leak. The biggest thing I see on GM rears is guys don't get the pinion depth right, if your new to it GM rears can get frustrating because you have to handle the whole housing to set it, and keep pressing off the pinion bearing to change the shims, another reason the 9" is the better choice. With the bolt in 9"'s available today spending over $1,000 for a 8.5 just to get a ring gear that is a little bigger doesn't make much sense to me IMO, the pic shows a 9" case but it shows you don't need any expensive tools to do pinion depth, it's a cheap depth mic and a parallel bar, not the way I do them the pic is from a "class" when I was showing a guy how to do his own gears without spending big money on all the equipment that I have