SM420 and 44Axel

[jmfurgason]

What gear oil for both? I have 80w90 Valvoline not syn ,am i in the ball park??

[LEWISMATKIN]

Yes you are. I personally use straight sae140, but that can be hard to find.

[jmfurgason]

Thanks Lewis ! why does the container say for topping off only and not for synchromesh ? appreciate your answer, there is a lot of info out there ,not all correct. Louie thanks you as well, be well be safe. jmf

[tbucketnut]

I run 90 weight mineral oil in my SM420, in my 1953, it has the early style synchros. The 64 GMC I use multipurpose gear lube, same as you can run in your rear end too, unless you have a powr-Loc rear end (posi)

[jmfurgason]

Thanks Steve, dont think my 63 has posi so should be fine with Valvoline 80w90 in tranny & diff. jf

[LEWISMATKIN]

I can tell both of you about a bad experience with power-lock spicer carriers. I built one for another truck i owned and was using genuine gm posi-trac fluid. I ran the axle over 1.5 years and didn't change the fluid. One day, on my way to a funeral home, i made a sharp, rh turn. I heard a loud "bang" and lost all motion with the truck. I got it back to dad's shop, removed the inspection plate, and found that the slip agent in the lube had failed. I had broken the head of the pinion gear off the pinoin shaft, and cracked the case of the rear axle, which dad had to weld up. I started to research why the lube failed, and discovered gm recommended a 12-month replacement for the lube if the posi-trac fluid was used. As i think about it now, i laugh at my self, although it wasn't funny at the time.

[jmfurgason]

Tough story Lewis, thanks for sharing history ,what a nightmare. jf

[tbucketnut]

So free lube but the rear end carnage was on you then.

[jmfurgason]

Does the 1963 Dana 44 have a drain plug? and is an additive needed? 2WD 1000 Thanks to all JF

[LEWISMATKIN]

Yes tbucketnut, it is.