9 1/4 brakes on an 8 3/4 housing

[JDMopar]

Will 9 1/4 rear end brakes from an 88 D100 work on an 8 3/4 truck housing? I know I will probably have to drill the bottom hole in the backing plates, but is the offset on the 9 1/4 backing plates going to work with the 8 3/4 axles? I have the correct 8 3/4 axles for the XL bolt pattern on the brakes....5x5 or 5x5.5 (?), which is the same as the front rotors on the truck. The 9 1/4 in the 88 D100 is a one legger, and has Bonneville gears in it (2.45's). I want to put the 8 3/4 truck rear end in it with 3.55 or 3.91 Sure Grip so it has a little more ooomph to it. Thanks.

 

[Garrett Ellison]

Some dimensional measurements from the Strange custom axle order form. I'm pretty sure that the brake offset is the same after the bolt pattern and center register diameter change, but I would measure what you have between the two first.
Axle Offset (Brake Gap) with Chrysler or Mopar Rearends Measured from outside face of axle flange to the outside face of the housing end. On Chrysler/Dana/Mopar type housing ends, F is obtained with the backing plate and gasket installed or combined thickness accounted for. If aftermarket disc brakes are being used then it’s best to remove the axle bearing and supply the B dimension to ensure proper fitment of axles. Chrysler/Dana/Mopar common F dimensions: 2.3125, 2.423 or 2.673

 

[Garrett Ellison]

I forgot to mention, you probably need the brake width to match on the two axles.

 

[JDMopar]

Thanks Garrett. I'll double check all that before I go to the expense of new axle bearings on the XL bolt pattern axles. The truck will likely be next winters project, so I'm trying to get all the ducks lined up and quacking beforehand! Hey...next time you're at your buddy's place with all the trucks, see if he has any extra towing mirrors for an 81-93. The ones with the 3 stainless arms and the rectangular mirrors that swing in and out. I'm over y'alls way semi regularly and could run pick them up if they're reasonable. Thanks for the help.

 

[moparmarks]

I have. The brake width is determined by the backing plates, not the axles. 8.25, 8.75 and 9.25 all can use the same brakes.