All 55 and 56 Mercury used a Dana/Spicer 45 and 5x5" bolt pattern.

1952 to 54 Mercs used the Ford pattern 5x4,5".

Later Mercs used 5" for big cars, but also used 4,5", and later even other bolt patterns.

Useful link: http://www.carnut.com/specs/gen/merc50.html

Edsel used both 4,5" and 5".

The Dana 45 was developed to be stronger than the Dana 44 (which was used on 1954 Mercs and earlier, and later on low performance cars like the Dodge Viper .


Would be very interesting to see what went wrong with your rear end.

1955 Mercury

Reply and a bit of an update:

The axle is definitely a Dana 44. Don't know if it's original, but it fits properly and the ring and pinion wedding day was 1/6/55. My car appears to be a bit of a chimera; the trans is a B-W T-85 w/R11 OD. Supposedly Merc didn't start using those until the '56 model year. My car was built very late in the '55 MY, so maybe the line started using the T-85 a bit early?

As to the axle problem, it appears the fault lies with the lowering blocks that were on the car when I bought it. They didn't fit properly and were completely worn out, allowing the rear end to squirm around and occasionally cause a binding situation where the driveshaft goes into the trans. After a lot of online shopping I was not able to find replacement blocks that would bolt directly in. I finally got a set of adjustable blocks from Speedway and a machinist where I work is making the necessary modifications to make them fit. Film at 11...

Rear end:
Are you really sure that it is a Dana 44? It is very difficult to see the difference between a Dana 44 and Dana 45.

All 1955 and 1956 Mercury passenger cars used the Dana 45.
1955 Mercury used the stronger BW T85 with R11 overdrive. 1955 Ford used the weaker transmission.

Problem solved, that is the important thing .

1955 Mercury