Rear End

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Grasshopper

Grasshopper

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I was hoping to find out the size of the rear end in my stock 71 Scamp w/225/6. Is it 8 3/4?
 
Very unlikely should be a 7 1/4

You can tell by seeing if the cover plate on the rear of the axle has bolts or if its smooth
 
7 1/4 will have bolts on the cover. 8 3/4 will be smooth with no cover. It could be a 8 1/4 which looks a lot like a 7 1/4 but one of them has a plug i think...not really sure though.
 
This should help you out. I believe the 8.75 axle tubes are 3"

attachment.php
 
salinasjoel said:
I thought 8 1/4 came in 73?
Click to expand...

You are correct. I have seen a few cars with 8 1/4's that poeple swapped in way back in the day and didn't know what was going on. Think about how many people back in the 70's and 80's were destroying 7 1/4's and just throwing anything under their car they could find.
 
Thanks Saetun, this helps quite a bit. Do you think the brake line patterns are the same or close enough? I am ordering new lines that say they fit the car with a 8 3/4 axle.
 
are they totally different where it is not worth trying to mount or do you think they are close enough to adapt?
 
Saetun said:
This should help you out. I believe the 8.75 axle tubes are 3"

attachment.php
Click to expand...

To respond to the OP's question: Without a measuring tape, there's no telling. Anything that will let you sit behind the wheel and close the door will work. JK ;-)

This is a great chart. Note the differences in the shape of the rear cover and the number of bolts holding it on. The 8¼ axle has 3" diameter axle tubes. This means it would be necessary to swap the clips and the plates (saddles that are bolted between the axle and the spring and the lower shock mount) when going from 7¼ to 8¼ axles.

Axles in the Mopar world are known by the diameter of the ring gear. The 7¼ was used in /6 cars and V-8s with automatic. (I had a 66 273-4V and a 904 w/ 7¼ open rear.) It was used after 72 on /6 A-bodies w/o disk brakes. These were SBP axles. Sure Grip and a variety of ratios were available. There are BBP 7¼ axles out there. They are a direct bolt in for the SBP axles.

It is impossible to convert a SBP to a BBP 7¼ axle. The axle tubes and shafts are longer on the BBP axle. The brake backing plates have a different offset from the axle flange, too.

I have not seen an 8¼ axle on a 72. I've seen them on 318 and later disk brake cars. There are some different ratios still available in the aftermarket.

The 8.75 (sorry no 3/4 ASCII character) is sort of a holy grail for A-bodies. These things are hard to find. I've never seen one on a A-body that was SBP. The ones I have seen were SBP with aftermarket shafts for BBP. Most have used C or B body drums and backing plates. Tube diameter is 3".

If you opt to change the rear end type, you will also have to have your drive shaft shortened. The other alternative is to find a drive shaft from a 2 dr ht or 4 dr sedan that has the rear axle you want. The wheel base on these cars is 111 inches, the Duster/Demon/Dart Sport have 108 inches.

IMHO, unless you are planning to compete in speed trials with the car, I'd concentrate on getting it to run properly, with all the accessories working, and looking good. If this is a daily driver, I would underline and bold it.
 
Not even in 1973, did i ever see 8 1/4 in a slant six car , and i had lots of them .But i am in Canada too, U,S could be different. In an A body that is
 
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