I'm going to change the gear oil in the rear axle on my 1955 F100 for the first time since it looks pretty dirty and I'm pretty sure it hasn't been changed in the last 20 years. I believe this to be the original. Is this what they refer to as a Dana 44? Also, is 90 weight gear oil is the best choice?

 

90 weight gear oil is the right stuff to use. The label on the bottle of modern gear lube will say 80w-90 or maybe 85w-90, but it's all good.

The picture looks like a Dana 44, and you should find a small 44 cast into the housing, typically found on the webbing around the rear cover.

 

If it's the OE axle, it's probably a Dana 41. The 41 was very similar to the 44. That really doesn't change anything, though. Run lube as per '52 Merc's recommendations.

 

1953/56 F100: The 1948/56 truck parts catalog says: Spicer (Dana) 44.

There's no Dana (Spicer) 41 listed. It's not listed in the 1949/59 car parts catalog, or the 1957/63 & 1964/72 truck parts catalogs, either.

 

back in the 1960's we use to put 90 in trans and 140 in the rear end. oils may be different now. i use a synthetic in my posi (trac lock)

 

Great thanks for the info!