8.75 A Body Rear End

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J's1970Duster

J's1970Duster

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I'm putting together an 8.75 rear end for my 1970 Duster. It came with backing plates, axels, but no perches. I obviously have to make sure that the axels are still straight and useable, also I know I have to replace all the bearings. What I'm not sure of is what kind of bearings to buy.

Are all 8.75 bearings the same size?
I've heard a lot about green bearings, are these the best?

Any and all answers are are all welcome. I'm new to all of this fun stuff, and trying to build my first MOPAR.
 
When you say all the bearings I assume you mean "ALL" the bearings in the 3rd member as well as the axle bearings. If that's the case there are 3 cases (741, 742, and 489) and they all take different bearings. There are also 2 different types of sure grip units (cone and clutch), if yours is a sure grip and each have their own bearing sizes. I'm not positive but I believe the open differential takes the same side bearings as a clutch type unit. As for the axle bearings, imo there's nothing that will outlast the factory tapered bearings but the newer style of "green" bearings work good also and make it easy to R&R the axles. If i were you I'd talk to Dr. Diff about what you need. You'll be hard pressed to find someone with more knowledge and good business character than Cass and his prices are always good. Here's a link to his website

www.doctordiff.com
 
Sorry, my third member has already been rebuilt with sure grip and 391 gears in a 489 case. Not sure what type of bearings were used for that. I'll look into both types of bearings for the axels.

Thank you for the information Fishy68.
 
Also I believe that the housing I have 54.25 inches long. If I'm not mistaken that's the size of a factory B body rear end. Will this work in my duster???????
 
J's1970Duster said:
Also I believe that the housing I have 54.25 inches long. If I'm not mistaken that's the size of a factory B body rear end. Will this work in my duster???????
Click to expand...
I think that is out of a 65-67 B Body yes that will work for Your Duster you just half to move the Spring perch's in a little bit which you said they are not on The Housing so that will save some work.
 
J's1970Duster said:
Also I believe that the housing I have 54.25 inches long. If I'm not mistaken that's the size of a factory B body rear end. Will this work in my duster???????
Click to expand...

That's about 1-3/4" wider than a A-body housing. It'll work ok if your wheels have enough inboard offset to make up for it. If not they may stick out of the wheel wells
 
J's1970Duster said:
Also I believe that the housing I have 54.25 inches long. If I'm not mistaken that's the size of a factory B body rear end. Will this work in my duster???????
Click to expand...

Yes, it will work. You'll need to install the perches at 43" c-c for the stock A-body spring location. Not sure what your plans are for the car, but if the axle doesn't have perches on it now would be a good time to install a 1/2" spring offset too.

As Tracy pointed out you may need more backspacing on your rear wheels, since you have a wider rear axle. But, this depends on your plans (I'll explain).

I have a 68-70 B body 8 3/4 in my Duster. It's 54-15/16" wide, so even wider than the one you've got. I ran my car with stock police rims for awhile, 15x7" rims with 4.25" of backspace and 225/60/15 tires. Even though they were stock rims with the stock backspace, I still had no problems running them with 225's. But that was absolutely as big as I could go for tires on those rims, I was at the limit for clearance on the quarters without trimming back the quarter lip. You'd have a little more space than me with the narrower B body rear, if everything were perfect it would be an extra 11/32" per side to the quarters compared to what I had. That might let you run a 235.

With the right backspace though you can get a 275mm wide tire on a Duster with the stock spring locations and no modifications to the wheel wells. Just depends on what your plans are for the car. If you wanted to center the wheels to maximize your tire size, you'd need more backspacing than the stock rims have. What size rims/tires are you looking to run? I could figure out some ballpark backspacing numbers based on what I'm running on my car.
 
J's1970Duster said:
Also I believe that the housing I have 54.25 inches long. If I'm not mistaken that's the size of a factory B body rear end. Will this work in my duster???????
Click to expand...

Absolutely!

I installed one in my Dart Sport, with 10" wheels and 5 1/2" backspace. I think it fits great.
 

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Thank you everyone for your info. Now I have another question about the break line. Since I now know that it's an b body rear end. What is the proper length of of the break line? I've looked on Doctor Diff and it lists many different lengths for this style of rear end.

Do I need to but the backing plates back on to get the correct measurement?
 
Dr. Diff uses the drum-drum measurement on his axle line selector. You want to use the 59.5" measurement for the brake lines on the axle.

Or just call Cass (dr. diff) and tell him you've got a 65-67 B body 8 3/4, he should be able to point you in the right direction. :thumbup:
 
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