I have a 1985 D-100 Custom and looking for a drum to disc conversion for the rear brakes. My problem lies with this information:
9 1/4" rear end (confirmed by Dodge)
3.21 gears (confirmed by Dodge)
5 x 5.5 lug pattern
3 1/2" center diameter on wheels.
2.85" diameter on bearing registration
11" x 2 1/2" drums
I've checked with Summit, Leed Brakes, and with Wilwood, and have struck on at all three locations.

What am I missing, or is this a lost cause and I'm stuck with the drum brakes?

 

I would swap a 9.25 from a 2003 up 1500 with rear disks. Most from my area have limited slip differential especially if 2wd and your choice of gear ratio.

 

Iowan, that was something I forgot to include. I do currently have a limited slip. I would like to keep the original differential so i don't have to change the rear hub or drive shaft but moving up to an '03 with a 9.25 would be an easier solution. Would it be possible to just change the axles, and move the axles with disc brakes to my existing housing? I know the axles currently are (supposedly) 51.625 in and the axles on the 03 are 54.125. Since my drums are 2.5" deep, would that work for the difference in length of the axles?
I'm trying to save overall time and modifications if possible.

 

I dont know of anyone that makes a direct bolt in kit for those trucks..... Good Luck and keep us posted... Cheers

 

So for an update, I found that an '09 Durango has the same lug pattern, but I need to check and see if I can find one. (All the ones I've found so far have been cannibalized at the wrecking yards).
Also need to check the distance on the spring perches so I don't have to make any additional changes to the diff housing.
I know my 85 has the rear lower shocks mounts attached to the rear of the diff. 03 and above has the driver side lower shock mount to the rear facing and the passenger side to the front facing of the diff.
Don't know if the upper shock mounts will match.

Then, someone posted on one of the forum pages that I could pull a rear end from a late 70's to mid 90's Chrysler and it should bolt right in.
My problem there is, Chrysler has a 5 x 4.5 lug pattern. So, I either carry two spares or also change the front spindles to the smaller lug pattern.

The more I get into this, the more head scratching I do and the more headaches I get.

Thoughts?

 

No doubt that these conversions can get tricky at times.... All I can say, is when you pull the trigger on doing the switch, make sure you write in it a book that you have for the truck and keep it in the glove box so when you need to order parts you know what it can off of... Sometimes you just have to cut, chop. and fab. and rebuild... Get out the cutter and the welder.... Cheers

 

It would be great if you could document the process here also so others can see what they need to do to.

As far as using the later 9.25 differential you may need to buy a complete axle assembly and use axle brake brackets as needed to use the disk brakes from the 9.25 on your 8.25. What you might be able do use is the caliper and backing plates from a Jeep Liberty and the rotors from the latter 9.25 on your 8.25 axle. The Jeep caliper brackets should bolt to your axle housing but the trick is finding a rotor that fits over the axle and then fits the caliper. But that is a bolt on possibly.
if I was looking to do this swap though I would swap the complete 9.25 axle assembly with disks and the gear ratio, limited slip that you desire. The 9.25 is so much stronger and if you do any towing or performance driving there’s no comparison between the two axles the 8.25 is very weak.