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Transmissions and Rear Ends Three on the tree or four in the floor? Shift it all here.

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  #1  
Old May 29th, 2020, 10:16 PM
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Default SM420 and 44Axel

What gear oil for both? I have 80w90 Valvoline not syn ,am i in the ball park??
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  #2  
Old May 30th, 2020, 02:01 PM
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Default Re: SM420 and 44Axel

Yes you are. I personally use straight sae140, but that can be hard to find.
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  #3  
Old May 30th, 2020, 02:13 PM
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Default Re: SM420 and 44Axel

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
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  #4  
Old May 30th, 2020, 02:29 PM
tbucketnut tbucketnut is offline
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Default Re: SM420 and 44Axel

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)
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1953 Chevrolet 3100
261 cu inch, SM420
Finished Cab off restoration

1964 GMC 1000
305 V6, SM 420
Restoration is now started
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Old May 30th, 2020, 03:38 PM
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Default Re: SM420 and 44Axel

Thanks Steve, dont think my 63 has posi so should be fine with Valvoline 80w90 in tranny & diff. jf
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Old May 30th, 2020, 05:53 PM
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Default Re: SM420 and 44Axel

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.
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Old May 30th, 2020, 10:10 PM
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Default Re: SM420 and 44Axel

Tough story Lewis, thanks for sharing history ,what a nightmare. jf
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  #8  
Old May 31st, 2020, 12:04 AM
tbucketnut tbucketnut is offline
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Default Re: SM420 and 44Axel

So free lube but the rear end carnage was on you then.
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Gig Harbor, Wa

1953 Chevrolet 3100
261 cu inch, SM420
Finished Cab off restoration

1964 GMC 1000
305 V6, SM 420
Restoration is now started
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  #9  
Old May 31st, 2020, 02:26 AM
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Default Re: SM420 and 44Axel

Does the 1963 Dana 44 have a drain plug? and is an additive needed? 2WD 1000 Thanks to all JF
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  #10  
Old May 31st, 2020, 05:54 AM
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Default Re: SM420 and 44Axel

Yes tbucketnut, it is.
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