Changing from 8.25 to 8.75

[Mikes270dart]

Is there any parts from the 8.5 in my 74 dart that can be used on a 8.75 housing, specifically backing plates and brake hardware. I am going to have to redrill the axles for BBP.

 

[R4Sedan]

If you mean 8 1/4 rear??? Then yes. Drums backing plates hardware etc... If you have SBP rear then nothing.

 

[Mikes270dart]

Had a brain fart. 8.25 is correct

 

[72Dart6pack]

Please do more homework before you start on this project. Backing plates do not fit from the 8.25. And redrilling the SBP to the BBP is a very poor judgement thing. Good luck on your quest.

 

[R4Sedan]

That's right backing plates will not fit. I was thinking 8 3/4 to Dana. But if you have 8 1/4 shouldn't you have BBP.

 

[AJ/FormS]

8.25s were BBP, yes
The driveshaft might work; they are of similar length.
The brakeshoes and hardware and cable I think will work.

So I think a better question is what won't work?
And the answer is the drums and backing plates. And I think the brake Tee,vent is in a different spot.
FWIW
The 8.25 can take a licking on the street with street tires.

 

[70aarcuda]

I took an 8 1/4 out of my 73 Duster and bolted in a 8 3/4 housing...with BB axles ..and used the backing plates from the 8 1/4.....and used the same drive shaft...

what does not fit...cause I been driving it for 12 yrs......

 

[R4Sedan]

^^^^^^ Thanks for clearing that up.....I was doubting myself cuz what someone else said..

 

[toolmanmike]

Had a brain fart. 8.25 is correct

I changed the title for you. tmm

 

[72bluNblu]

You can't use BBP brakes on re-drilled SBP axles. SBP axles have a different flange offset than BBP axles do. If you re-drill SBP axles for the 5x4.5" pattern you have to re-drill SBP brakes.

However, backing plates for a BBP 8.25 are the same for an 8 3/4 with BBP axles (not re-drilled!). The only difference is that some the 8.25" housings only had 4 bolts to mount the backing plates, vs. 5 bolts for the 8 3/4 housings. But if you drill the 5th hole the backing plates bolt right on, the other 4 have the same pattern. BBP brakes all use the same axle flange offset and can be swapped between the later 7.25" BBP axles, the 8.25, 8 3/4 and Dana, with the only issue being the 4 mounting holes vs. 5.

 

[R4Sedan]

@72bluNblu. What a wealth of knowledge.

 

[Mikes270dart]

Ok so I have this complete A Body 8 3/4 drum to drum SBP. What would be the best way to put this rear end into the 74. The car currently has a 8 1/4 BBP. Can't find a A Body 8 1/4 with a sure grip.

 

[R4Sedan]

Unless your building a big HP motor, I would just keep the 8 1/4. Contact Cass Dr. Diff. He could get you a sure grip and whatever Ring gear you want. There even some guys on here that will probably be able to help.

 

[66fs]

It is relatively easy to add a sure grip to any rear since you do not have to set pinion depth. Just check the backlash on the existing rear and adjust to the same after you replace the carrier.

 

[66fs]

Ok so I have this complete A Body 8 3/4 drum to drum SBP. What would be the best way to put this rear end into the 74. The car currently has a 8 1/4 BBP. Can't find a A Body 8 1/4 with a sure grip.

Get a set of Big Bolt custom A body axles and use your 8 1/4 brakes as 72bluNblu said.