7.25 to 8.25 necessities

[MOPARJ]

I am acquiring a 8.25 rear for my 73 Duster finally. I am getting the driveshaft that was in the donor car, so that should be taken care of. The new rear had 10" drums. I don't recall my size, but my car has front discs and rear drums, so maybe its a 10" setup.

I will not have the ubolts that came with the 8.25. Will my 7.25 ubolts work? Also, what else from my 7.25 rear and brake setup will work on the 8.25? What will I need to get or buy to make the swap work?

Thanks

 

[340mopar]

What is the donor car? if it is a Dart or Scamp the driveline will not work because of the different wheel base.


Chuck

 

[crackedback]

Get the 8.25 shock plates as they are different than the 7.25 setups.

 

[MOPARJ]

What is the donor car? if it is a Dart or Scamp the driveline will not work because of the different wheel base.


Chuck

The setup is coming out of a 73 Duster as well. It was originally a slant six car, but was converted to a 318/904 car, which is my combination right now.

Justin

 

[dgc333]

If you can get the shock plates grab them but if you can't just elongate the holes to accept the bigger u-bolt. U-bolts need a 3" inside dimension to fit over the 8.25, you can get Universal ones that the length will need to be trimmed on from your local NAPA or order the correct ones from your favorite mopar supplier.

If you are pulling the axles it's a good idea to replace the rubber brake hose that goes from the axle to the chassis.

The e-brake cables will swap over with no issues. If your car had front disks it likely had the same 10" by 2.5" brakes as the 8.25.

Good time to replace your rear springs or at least replace the rubber bushings.

 

[rumblefish360]

Like said above, the shock plates and U bolts are different sizes. 1/2 inch. It would be easier to grab the shock plates from the donor car.

Replaceables! Excellent idea!. Rubber brake hoses. From body to rear, wheel cylinders, etc....
This is the time to do it and do it right end to end. It'll just suck going back later.

 

[MOPARJ]

Well, I got the rear in the car this weekend and swapped of the brake parts over from the 7 1/4 to the 8 1/4, since they both have 10" brakes. The rear seems to spin well by hand, no terrible noises. Fluid looks ok, but I will change in a week or so. Brakes werent engaging as well as they should when I tested them last night on the jack stand. I will bleed them tonight, as there is probably an air bubble in the system. I dont see why they shouldnt be working. The wheel cylinders did not seem frozen.

The real issue I see is that the exhaust was built around the 7 1/4 driveshaft, but the 8 1/4 shaft that I got with the rear is a little thicker in diameter, so it ever so slightly touches on the left side in a two inch area of the shaft. It looks to be just enough to make some noise until I get it to the exhaust shop this weekend. I dont think it will do more than make noise.

Well, I will take her on the maiden voyage on the new rear this evening, if bleeding the brakes proves to be successful. We will see how it really performs and how healthy it is. Also, I will see how much noise the driveshaft/exhaust pipe contact will make. BTW, its a 3.21 open setup, which should be a better performer than the old 2.76 setup. I hope to feel some difference.

Just thought that I would update the project.....

-Justin

 

[rumblefish360]

Thanks for the update. I like to read them. You'll feel a difference in gear ratios.

 

[MOPARJ]

Thanks for the update. I like to read them. You'll feel a difference in gear ratios.

Well, just got back from a couple of trips around the block. Heard of clicking noises from the rear at first when pulling away from the driveshaft, but they went away. Seems fairly solid for a used rear. No clunking when shifting, just nice and smooth. At first the shaft was rubbing a little on the exhaust pipe, but not a much as anticipated and it even went away. I heard some creaking and movement, but I am sure that the rear still as to seat itself some more in the ubolts and what not.

I will come home this evening and retorque everything, including the ujoint bolts on the yoke and the ubolts. I will also regrease the ujoints, as they were the ones that came with the 8 1/4 shaft. The brakes are still self adjusting, as they are a little soft still. I transplanted a lot of my good 7 1/4 brake parts over and used my 7 1/4 drums, as they looked much better than the ones that came with the 8 1/4.

I will do these few things this evening, then take her out for a longer and little bit faster drive tonight to see how this new gear feels. I will repeat the check and drive process each evening just to be safe, as I want to take the car 60 miles round trip to a cruise in this Friday evening.

Ahhh, the trials and tribulations of Mopar car crafting.......my young gentlemans salery is suffering..lol....oh well...

I will update again after more driving....

Justin:thumblef:

 

[damnimcooltom]

Make sure you retorque the u-bolts a few times over the next coupe of months. They can stretch more with use, and you'll want to make sure they stay tight.