Pre "8 & 3/4" Rear End Interchangeability

[jboymechanic]

I just picked up a 1954 Dodge truck with 4.72 gears in the rear which makes driving on the highways almost impossible without people flipping me off. I also happen to have a 1956 Imperial that had 3.07 gears in it before I updated the whole rear end. Long story short, will the 3.07 diff out of the Imperial fit in the '54 Dodge truck? Both have 8 & 3/4" diameter ring gears and 10 studs to hold the diff to the axle housing. The imperial had a 16 spline axle, I have not torn the Dodge apart to find out so I thought I would ask the folks here to see if any one has experience with such a swap.

[Scruffy49]

If the flange to flange distance is close, and a 56 should be a big rear end, just swap the whole mess. That way you don't have to worry about it. You're in luck to a point, your truck and your donor should have normal u-joints, unlike the ball and trunion type in the earlier trucks.

[jboymechanic]

You are correct that both have "normal" u joints as they don't use the ball and trunion joints, but the front u joint (on the Imperial) is an odd size that I'm still looking for.  Back to the rear end, I was hoping to keep the original rear end in the truck as the Imperial axles have a different bolt circle (5 on 5.5") and the spring perchs are on the opposite side of the axle housing (bottom side for Imperial and top side for truck).  I didn't realize that my '54 Dodge wasn't a pilot house era truck, but I believe that the diffs in the trucks were the same from '53 to '56. 

 

Not to get off subject, but the Forward Look era began in 1955, so what the heck era or design family is a '54 Dodge truck considered?

[Young Ed]

54-56 trucks are C series trucks.

[jboymechanic]

Well I was by the truck tonight and took some pics.  Although the truck and Imperial diffs are the same size, they have different bolt patterns to hold them into the axle housings.  Oh well.  The truck does share the same 5 on 5.5" bolt pattern of the Imperial (I thought it was 5 on 4.5") so maybe I'll just swap the whole assembly.  

 

Also, I think I discovered that the truck has fluid drive (if that is the correct term for a clutch and torque converter mounted in tandem).  Couldn't really tell, but the bell housing is really long, longer than any that I've ever seen.  Might be hard to tell by the picture.  Any way, seems to me that fluid drive would be an odd choice for a truck.  Could this be factory?

 

[Merle Coggins]

I didn't know they carried the FD into the C-series, but maybe they did. That option first came available for trucks in 1950, with a 3 speed as standard and a 4 speed as an additional option. (My truck has FD with a spur gear 4 speed.) Then in '53 they offered the M6 trans and dubbed it the "Truck-O-Matic. I was under the impression that the full automatics were available for the C-Series... but I've been wrong before. (I once thought I was wrong, but I was mistaken)

 

That definetly looks like a FD bell housing, with a 3 speed trans.

 

Merle

[Scruffy49]

Should be 5 on 4.5 for 1/2 tons. 5 on 5 for 3/4 tons... 5 on 5.5 is Ford or Willys, usually. Could explain the big bolt pattern, a 48-52 F1 rear is almost a perfect bolt in...