Rear Axle and Disk Brake Conversion

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rp23g7

rp23g7

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So i found a totaled 74 Duster that had a /6 in it. Planning to to the rear axle and disk brake swap on my 71 Scamp.

Is there anything i should know besides the obvious before i start? Is the rear axle a straight swap? Do i need to modify anything?

I assume i can set them next to each other and swap out the front end items by eye, or take pictures.

Does anyone have any pointers? Anything i may run into that i may need to do?
 
Assume The Totaled Duster Had A 8 1/4 And Your Car Has A 7 1/4. The Swap Should Be Pretty Stright Up Accept For The Bolt Patten Difference.
 
im doing the same thing from a 74 dart sport to a 74 duster... and would also how bad the disc brake swap is gonna be.
 
you will need new u bolts since the 7 1/4" axle is 2.5" in diameter and the 8 3/4" axle is 3". cut the driveshaft to fit. b,c,e or truck rear backing plates, drums, brakes, etc.
 
ooops.. i just noticed i put 8 3/4" not 8 1/4". the same should still apply. the front disc is an easy swap. loosen up the torsion bar adjuster bolt, and swap out spindle, uca, etc. put the spindles to the rear on the 71 so it doesn't hit the sway bar, the 72-earlier go to the outside of the strut rod.
 
redfastback said:
you will need new u bolts since the 7 1/4" axle is 2.5" in diameter and the 8 3/4" axle is 3". cut the driveshaft to fit. b,c,e or truck rear backing plates, drums, brakes, etc.
Click to expand...

I have always made it a rule (for myself) to use new ubolts anytime a swap is made. This comes from one semi-bad experience.

Hey redfastback: One of these days, we should attempt to get all of the Bay Area folks together.
 
Hey redfastback: One of these days, we should attempt to get all of the Bay Area folks together.[/QUOTE]

we should. good idea. you going to monterey bay mopars on the 11th?

i too always change the ubolts. i almost always have to cut them off anyway.
 
Just did these swaps on a 71 Dart from a '73 Dart. Rear came out of a '75 Scamp in the scrappie as the '73 Dart had the same 7.5" rear as the '71 Dart did. Wanted to upgrade a bit to an 8 1/4 rear.

I wrote my observations on doing the swap here on the board. I'd have to do a search to find the post for you. Basically though the rear was a direct bolt in. The only issue I had was that the emergency brake cable system was different between the two years I used. I just swapped the emergency brake cables off of the car I was putting the rear on to get them to work.

U bolt wise I used the ones that came off of the donar car. Will probably upgrade to new ones when I replace the knackered springs that are on the car.

Driveshaft had to be sortened when changing from a 7.5 rear to the 8.25. Also check the u joint matches or you will need to get one. There is an adapter joint availabe if needed. Numbers are posted on this site. For my swap of a 8.25 into a 7.5 car the shaft had to be shortened 1.5 inches (I actually went slightly more, but don't remember the number, it is in my post that I think is called rear swap findings or something like that).

Oh, one last note. Make sure to get the rear brake hose off the donar car if you are not using new (highly advise new). The hose end will match the fittings on the rear as others may not.

On the front brakes I did a straight swap onto the '71 off the '73 Dart. Rebuilt the suspension and brakes as I went. For whatever reason, I did not have an issue with the calipers in a different position. The '73 was a factory disc brake car and that is how they were on the car. No sway bar mounting so bit of a puzzle from other posts I'd read where the spindles needed to be swapped from side to side so the calipers would mount on the hose connection side. Someone posted hose numbers on here also or at least a car to use to buy new hoses from what I remember. The hoses they listed allowed a straight swap of the brakes with the caliper towards the front and just was a longer hose to reach across to the caliper from the mount. From what I understand the issue of the caliper being in the front is that it may create clearance problems if you have a front sway bar and are turning at full lock.

I swapped everything over from the upper and lower control arm out. This gave me the chance to rebuild everything and not have the other car down in the process. Just swap the rebuilt bits on when done. I also swapped the proportioning valve and the master cylinder off of the donar car.

Think that is about it. Was a bit of work on my own to do, but was not really that difficult and was by everything I remember a pretty straight forward bolt in.

Cheers
 
Redfastback, I dont really understand your post. I am swapping the whole axle, it is still complete with backing plates, Ubolts etc. Are you saying usually have to cut them because they are rusted?

Is the driveshaft longer then my original?

Put the spindles to the rear? Meaning swap left and right?
 
"ooops.. i just noticed i put 8 3/4" not 8 1/4". the same should still apply. the front disc is an easy swap. loosen up the torsion bar adjuster bolt, and swap out spindle, uca, etc. put the spindles to the rear on the 71 so it doesn't hit the sway bar, the 72-earlier go to the outside of the strut rod."

PLEASE ENLIGHTEN ME ALSO!

IF YOUR GETTING ALL THIS STUFF FROM THE OTHER CAR. MEASURE YOUR DRIVE SHAFT AND THEN MEASURE THE ONE IN THE DONAR VEHICLE IF IS DIFFERENT GRAB IT TOO...I ASSUMED YOU WERE TRYING TO DO THIS ON THE CHEAP.SO I JUST FIGURED YOU WOULD GRAB ALL THE BOLT FROM THE DONAR TOO...SORRY I DID NOT ELABORATE
 
It is possible that the rear in the Duster is a 7 1/4. I have a LBP 7 1/4 out of a disc brake /6 car. Not all disc cars are 8 1/4's

Chuck
 
Certainly right on the 7.5 rear deal. Got a neighbour with a later Duster and it is a 7.5 rear large bolt pattern. In fact, the '73 Dart parts car with a 318 is a 7.5 rear car. Bit of a let down as I was hoping that it had at least an 8.25 so I could swap it along with the front discs. Oh well, fun of the game.

On the drive shaft. You may indeed be able to use the one of of the donar. Clarification needed is what rear is being swapped for what rear and also what trans is in the cars. Both my cars had 904 transmissions. One a 318 car and one a /6. Thus, when I went from the 7.5 to 8.25 rear (did not get the driveshaft when I pulled the rear out of the Scamp at the scrappie worse luck as it was a 904 as well) I needed to get the driveshaft shortened so that it would fit. Hope that helps.

Cheers
 
Dusters have a 108" wheel base and a Scamp has a 111" wheel base like a Dart so the driveline will not be the same or correct length.


Chuck
 
Thanks everyone, How can you tell a 904 apart from a 727? My car as well as the duster had /6's.

I am doing the swap more for the power brakes, disks and large bolt pattern wheels, rather than the larger rear, as i may just leave the 6 in there and do the intake/exhaust mod later.
 
never mind on that last question, i found the answer. Another question though. Everyone says the drive shaft needs shortening. What part was longer, the shaft on the axle or if the car has a 727, the tailshaft?
 
The pinion shaft is shorter on the 7 1/4 than the 8 1/4 and the 8 1/4 is shorter than the 8 3/4. The 727 tail shaft is longer than the 904. Then there are the two different wheelbases on the '67 up a-bodies, so depending on which axle, which tranny and which wheel base car you have there are quite a few driveline lengths that would be required to fit any given car with a given combo.


Chuck
 
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