Bruce M

I have a 1990 Cummins with a Dana 70 rear end.
My sister got me used drums and backing plates off a Dana 80 or 70.
They have 13" shoes by 2-1/2" wide.
Have an extra 1991.5 Dana 70 rear end which I took off one drum and backing plate.
put the backing plate up to the flange and the drum on the hub with the wheel studs that are used on the later rear end.
The backing plate needs a 2" spacer between it and the flange it bolts to on the early axle to fit
The outboard drum moves the tire out about an 1".
Has anyone used outboard drums on the early inboard axle?

Bruce M

I just measured the late outboard drum which is 5/16" thick at the bolt circle.
If the thickness if the hub flange is 1/2" or less the tire should move out 3/4' or less.
The new backing plate has a hole in the center about 1/16" less then the existing backing plate which I think is used to center it for the 4 bolts holding it to the existing flange with a shoulder.
Also the bolt circle has a slight difference which I don't is a problem because of the flange shoulder.

bigragu

Bruce, if you figure it out, please share with the world, as that is a much desired mod. The last guy that started a tread on this, the tread just died, and no one knew if it ever became.

Thanks for your efforts

u2slow

I think a 2" spacer at the backing plate is asking for trouble. You want to weld the flange on at the right depth. Studs need to be addressed... 9/16" for the larger drum holes, plus longer, and different profile because the drum is on the other side of the hub flange.

I've put a 2ndgen diff my truck, and have extra 10.25" Ford diffs around. Either one is easier to swap in than the brake change being proposed.

Bruce M

I went to autozone on line and it looks like the 1995 dana 70 and 80 use the same drum and shoes, so the backing plate should be the same for both.
Using the existing 9/16" studs off the 95 rear end the drum fits perfect, but it would be nice to have a little more non-threaded surface through the drum.
That tells me that the hub flange on the later model could be a little thinner then ours?
The backing plate spacer should be around 2-1/16" long with an inside diameter to match the old backing plate on one end and the other end to have an outside lip to match the later backing plate.
Matching the 4 holes on the old axle flange drilling through the spacer into the new backing plates will be the same bolt circle as the old axle which is a fraction different bolt circle.
The only thing that will change is the new backing plate holes not the 1990 axle.

oliver foster

I am watching this tread, but I have just swapped a 2nd gen axle into the 1st gen in the past to make this happen.
I have a Dana 80 under my [white] '85 crew cab.

Bruce M

A flange can be made out of steel plate and welded to the axle to match the later backing plate, but what about heat treatment and distortion?

u2slow

I've cut flanges off other diffs and they usually get mangled. They're only mild steel.

Two threads that deal with welding on a new flange... (albeit for a disc swap)

Pirate4x4.Com : 4x4 and Off-Road Forum - Powered by vBulletin

fordmann.com | F-350: Sterling Rear Disc Conversion

samiam4

Are you using the 1995 style hub? We the brakes. I would use a spacer. If the move is 2 inch, maybe a new flange can be made and welded on. How do you figure the depth?

Pm me, I might be able to help w a new flange.

Alec

I was thinking about doing this swap a while ago . . . but then I decided to do a D80 swap instead.

I think it is worth looking into swapping to the DRW drum and backing plate -- though it looks as though the flange on the axle tube would have to be moved in, instead of out, to accommodate this.

u2slow

~2" less space to plumb and bleed your wheel cylinder is going to be interesting...

Bruce M

Alec,
I will be using the drum number 123.67027 that you show in your thread with the existing hub and 13" backing plate.
Need to machine the hub flange a little on the O.D. to fit inside the drum.
Am looking into the flange that U2SLOW was talking about making and welding on the axle tube instead of the 2" spacer using the existing axle flange.
First I will have to put a single phase motor in my 13" South Bend lathe.

Bruce M

Machined 90 hub a little on the flange O.D. so it fits the 95 drum perfect.
Now I have to look for a steel plate 3/4" thick with a 5-3/4" O.D. an an I.D. of
3.0 inches or so.
If I knew how to add pictures that would be nice

Bruce M

I am going to try and show the pictures of the 95 drum connected to the 1991.5
3.54 ratio rear end and the backing plate flange being machined on my lathe.
Sunday I will pull the hub on a 1989 rear end to see if the axles where the backing plate flange goes are the same as the 1991.5 before I finish the bore on the flange.
By the way the picture of the drum is a movie.

Bruce M

Found that the axle where the flange goes on the 1989 3.07 ratio and the 1991.5 3.54 ratio are the same diameter.
The bolt circle for the 1995 backing is different.
Still have to finish the O.D. and cut the top of the flange.
Did not have a thick enough plate to add a stop for the bolt heads.
Attached are pictures.