7.5" rear. Variatiions between a 75 housing and a 76 and up?

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7.5" rear. Variatiions between a 75 housing and a 76 and up?

Postby hoffbug » Wed Oct 08, 2014 9:24 pm

Can someone explain to me the differences between a 75 7.5" rear end housing and a 76 and up?

Im now hearing that they are not the same and that 75 Vega and Monza are unique to that year only..
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Re: 7.5" rear. Variatiions between a 75 housing and a 76 and

Postby hammerdown7 » Wed Oct 08, 2014 10:20 pm

The only differences I'm familiar with is the position of the panhard rod mounting bracket and the larger brakes after '75.

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Re: 7.5" rear. Variatiions between a 75 housing and a 76 and

Postby hoffbug » Wed Oct 08, 2014 10:38 pm

What is different? would the same rod and body mounts from a 76 work with the 75 housing?
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Re: 7.5" rear. Variatiions between a 75 housing and a 76 and

Postby hammerdown7 » Wed Oct 08, 2014 10:51 pm

The '75 bracket is angled to connect the panhard rod, the one with the bend in it, from the axle to a bracket welded into the front part of the left rear wheel well. The '76 bracket is angled slightly toward the rear of the car and mounts to a bolted-in bracket on the back part of the left rear wheel well. The '76 pan hard rod is straight, the '75 has a hump in it to go over the differential. A couple of pictures would be most helpful here but I don't have any.

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Re: 7.5" rear. Variatiions between a 75 housing and a 76 and

Postby hoffbug » Wed Oct 08, 2014 10:59 pm

Thanks Dick


Are the panhard brackets welded to the rear end housing? If so would the bracket off of a 1976 6" rear be the same as a 1976 7.5 rear?

Are the mounts for the torque are the same from 75 on up?
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Re: 7.5" rear. Variatiions between a 75 housing and a 76 and

Postby hammerdown7 » Wed Oct 08, 2014 11:12 pm

The brackets are welded to the axle. My guess would be that a 6.5 bracket would be very close if not the same as the 7.5 bracket on '76's. The torque arm mounts with 4 short bolts on the 6.5 and screw into threaded holes on the housing, two from the top and two from the bottom, the 7.5 uses two long bolts that pass through the housing mount with nuts and washers on the either the top or bottom, depending on wether you run the bolts up or down. It's easier to push them up from the bottom if the axle is mounted in the chassis, at least that's how I do it.

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Re: 7.5" rear. Variatiions between a 75 housing and a 76 and

Postby hoffbug » Wed Oct 08, 2014 11:16 pm

OK.. Ill have to take a good look at this stuff and see what I can do.. The donor 7.5" rear came out of a 75 Cosworth and Im trying to fit it into a 77 chassis.
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Re: 7.5" rear. Variatiions between a 75 housing and a 76 and

Postby Monzamaddogger » Thu Oct 09, 2014 6:28 am

You could try to change the panard bar mount on the body end to a '75 mount (if you could ever find one).
-Adam

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Re: 7.5" rear. Variatiions between a 75 housing and a 76 and

Postby hoffbug » Fri Oct 10, 2014 4:26 am

So I guess this begs the question.. Does one style have a performance advantage over the other?
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Re: 7.5" rear. Variatiions between a 75 housing and a 76 and

Postby hammerdown7 » Fri Oct 10, 2014 7:33 am

Handling-wise I would say they are the same. The '75 design probably leaves a little more room to route the exhaust. One thing you may check out is possibly using a rod end on the '75 axle bracket. There may be enough angle available on the rod end to compensate for the difference in the axle bracket angle.

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Re: 7.5" rear. Variatiions between a 75 housing and a 76 and

Postby cjbiagi » Fri Oct 10, 2014 1:18 pm

I think one main difference is that the later design with the straight rod has a bolt on body bracket than can be shimmed to allow you to center the rearend. The 75 with the curved rod had a welded on body mount (or just part of the chassis) so there was no ability to adjust the rearend. The "official" GM adjustment was to bend the rod to make it longer or shorter to move the rearend one way or the other, very tricky at best. I ended up cutting off the end of the rod where it attaches to the rearend and threading it for a male Heim end, this allows me to now have a adjustable panhard bar. If you find that your rearend is centered then it is not a issue, however when you start to put on wider wheels and tires the off-center postion that is common rears its' ugly head. I used a very hgh quality teflon lined Heim end since it is a important chassis component and under a lot of stress during cornering, don't cheap out there.
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Re: 7.5" rear. Variatiions between a 75 housing and a 76 and

Postby dindin » Fri Oct 10, 2014 2:06 pm

cjbiagi wrote:I think one main difference is that the later design with the straight rod has a bolt on body bracket than can be shimmed to allow you to center the rearend. The 75 with the curved rod had a welded on body mount (or just part of the chassis) so there was no ability to adjust the rearend. The "official" GM adjustment was to bend the rod to make it longer or shorter to move the rearend one way or the other, very tricky at best. I ended up cutting off the end of the rod where it attaches to the rearend and threading it for a male Heim end, this allows me to now have a adjustable panhard bar. If you find that your rearend is centered then it is not a issue, however when you start to put on wider wheels and tires the off-center postion that is common rears its' ugly head. I used a very hgh quality teflon lined Heim end since it is a important chassis component and under a lot of stress during cornering, don't cheap out there.


Don't they make an adjustable panhard now for the 1975?? I thought I was them from a couple different vendors.

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Re: 7.5" rear. Variatiions between a 75 housing and a 76 and

Postby nutt » Fri Oct 10, 2014 2:08 pm

I've got the bolt on attach bracket w/shims, the through-bolted torque arm and a slightly bent panhard bar. I'm assuming I have the later style and someone modified the bar?? It also is a 4.11 posi with the little tag so I'm also assuming that's factory. It also has 5 lug axles which I'm not too sure if they were ever available or someone modded them to S10 versions. They aren't metric lugs however. Correct???
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Re: 7.5" rear. Variatiions between a 75 housing and a 76 and

Postby cjbiagi » Fri Oct 10, 2014 9:21 pm

Yes, there are aftermarket adjustable panhard bars in both styles now. That is another option.
Regarding the next post, I don't know what you mean by a "slightly bent" panhard bar. The 75 is a curved design, the 76 and up is just a straight bar. If yours is actually slightly bent then it sounds like something happened to it.
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