my B body 8 3/4 into A body swap

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duster731

young gun
Joined
Mar 30, 2010
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Location
Venus Texas
Ok so I am finishing up my swap tonight and I would like to document my swap so you guys doing it or thinking about it get more of an idea and what's needed and used for the swap..... at first i knew nothing about this swap i didnt even know what a 8 3/4 looked like but now i can answer alot of questions about it and learned all of my knowledge from this site to be able to do this swap and know what to look for at pick a part,

It probably has been documented already but at least you get more info and know what exactly was used on my swap.

Parts I collected over a couple months period was
1) 68-70 B body rear end housing and axles got from a member here (crackedback) drove an 1 1/2 away for a good deal lol - 150$
2) a overhaul rear end gaskets/green bearing kit complete shipped to my door from Dr diff -95$
3) 323 open third member 741 drove to applevalley to grab this from a member her an hr away -50$
4) 391 open third member 741- free
5) clutch type sure grip shipped from a member here thank you-260$
6) braking hardware including metal brake lines,housing breather, tee, backing plates, brake shoes,drums and the hardware- free :)
7) rubber brake hose for the rear end from autozone - 20$
8) new u bolts from autozone -10$ ( I had a 20$ store credit so for two they were 15 plus tax for 4 about 32$
9) shock mounts from pick a part - 10$
10) new spring perches eBay but from jegs - 15$ I think or 20$
11) 2 new rims from summit 120$ shipped
12) 2 new kyb gas a just shocks summit - 75$
13) need new leafs and will be getting some soon
14) driveshaft shortened 60$
15) install green bearings 40$
16) adjustable pinion snubber from summit 72$ shipped

I'm pretty sure thats it now for the swap....... Pretty simple first thing was cleaning the housing up sandblasting anything I can, now the b body rear spring perches need to be moved in an 1/2 on each side that would put you to a body specs 43 in center of hole to center of hole the b brig is 44 in...... I set my pinion angle to 5 degrees up which is stock location anywhere from 3 to 7 should be fine on the pinion angle

Next was primer and then 2 coats of semi gloss black it came out really good
IMrear1.jpg


Now my original plans was using the 323 gears but I found out that my 7 1/4 rear was already 323 and thought they were 276 so I stepped it up and found a ad on my local Craigslist.. it was a complete 8 3/4 out of a truck unknown ratio and condition so I drove over and picked it up for the braking hardware mainly..... Knowing that trucks came with bigger brakes and lower gears for towing purposes I took it apart and found out it was a 391 open 741 and had 11 inch brakes on it so I took everything off of it I paid 100$ for the rear complete and I sold just the housing for 100$ so thats how I got some parts for free if you were wondering. (note) all brake parts interchange from rear to rear as long as its lbp to lbp and sbp to sbp and the size varies of course...... i reused my emergancy brake lines they fit perfect...

I posted a help wanted add on c.l for help on installing a sure grip carrier into my third member and a half Hr later a guy emailed me and said he can do it so I git it installed and Fe did it for free......
thirdmember.jpg

:computer:
Next was assembling I got my axle bearings installed for 40$ at a local tire and brake shop. I installed the third member and then the axles seals, then backing plates then axles of course with the gaskets.
Now was the swap

Out the old one
IMrear2.jpg


In the new one
IMrear4.jpg


I used 2 pins to make the center hole on the spring perch mate tight with the pin on the leaf springs so there was no slack in between them
IMrear6.jpg

IMrear5.jpg


Here's the dimension of the u bolts they were the same size as the stock ones

IMrear7.jpg

IMrear8.jpg


I also ordered traction bars from summitracing just to try em out

shocks.jpg


Last but not least was rims I ordered some earo racing rims from summit they were lime 54 a price I like them and there 4 in offset so including the 1 1/2 in longer on each side they will stick out an inch or so.. I don't mind but others like it tucked in so you would need 5 in offset or more
rims.jpg


I got my driveshaft shortened to 49 in from center of u joint to center of u joint and I still have an extra 1 3/4 of suspension play on the slip yoke....

And that ladies and gentleman is my swap tonight I'm going to pick up my drums I'm getting them turned and also need to get my rear rubber brake line.... After I finish it I will post pics of how it sits and looks, hope this helps those that struggle or looking for more info.. if you have any questions post em thanks........ :)
 
Looking good Brandon. Nice that you have two gear sets for cruising and running the strip.

My 2 cents. Send the traction bars back, not needed on a Mopar.
 
Ya there probably more for looks I installed the 391 for now to see how they are ive never experienced with other gears... Thanks
 
Nice Job!

There are a couple of things that you might want to check. The thrust buttons in the suregrip, have they been removed? You wont need them with Green bearings. Also make sure you put suregrip additive in when you fill up the chunk. Did you replace the axle seals?

When you install the e brake cables, you will want to back off the adjuster under the car. If not you will get one brake assembly together and wonder why the other side is such a bear. (Don't ask me how I know)

And as far as the wheels with a 4" backspace they will sit surprisingly good. I was worried about mine sticking out, and they don't I'm running stock Rallye wheels on the rear with a 4" backspace and it sits great. Mine is a Dart Sport. When I go to a wider tire I will need to increase the backspace so they don't stick out.
 
Kool thanks for the info
For the thrust pins I didn't remove them because you don't really need to with stock axles only on Aftermarket axles due to Aftermarkets tend to be a little longer so more splines can come in contact..
as far as additives I bought some gear oil with limited slip additives in it and was good for sure grips LSD and posi.. and its synthetic

I did replace the axle seals and man o man one side took about four of them before the fifth one went in good lol good thing they were 1.70$ at kragen. I havnt put the brakes in yet but I am tonight and probably notice what you went threw lol
 
If you back off the adjuster under the car you won't create new words LOL. One side will go in fine, it's when you get to the other side you can't pull enough cable through the guide to get the shoes to sit properly.
 
I didn't get it finished tonight it sucks working 12 hrs a day every other weekend and so I painted my brake drums Orange lol and I had to go back to autozone and spent 50$ on braking hardware, brake adjusters, brake fluid and cleaner so tomorrow I should finish it after work and then ill take pics
 
When I installed the braking hardware and the shoes I didn't have to mess with the e brake adjusters under the car it went on very smooth
 
That's cool, I know on mine I sure did, I couldn't even come close to getting the one side together.
 
Do you have to shorten the drive-line?
And shock plates, B-Body are different?

BTW, very nice job and write up.
 
Thanks for the driveshaft I shortened it to 49 in and I have about 1 3/4 of suspension play on the slip yoke..
All of the car 8 3/4 rears use the same shock plates
 
"I set my pinion angle to 5 degrees up which is stock location anywhere from 3 to 7 should be fine"

Not an expert by any means but did you mean to say 5 degrees down?
 
Nope thats what I thought at first but then I talked to Dr diff and made sure I was on the same page and he said up meaning when the rear end is upside because ur welding the perches on the tip of the pinion should be facing down as soon as ur done welding and turn the rear to the right side up the pinion would be 5 degrees up
 
Got it, rear end upside down.

Can you post a pic showing the tire clearance to the rear springs?
 
The traction bars have a caution for driving. A guy looked at my Duster at a car show and said he had a 70 Duster 340 once upon a time but it got totaled. He said the traction bars got hung up on the railroad track and before he could get train stopped it hit the car. Can't have much worse day than that.
 
Ooooo thats sucks..


On a side note went cruising in the duster just now after work and man a total night and day difference in traction, hooking, and burning out with the adj pinion snubber a sure grip and traction bars now I just need new leaf springs so I can fit some 275/70/15 under her
 
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