this_is_greg

Rear-end oil recommendation for 1938 Dodge RC 1/2 ton pickup

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What oil is recommended for the rear-end on my 1938 Dodge RC half ton pickup?

The manual states "Powerful Extreme Pressure Gear Lubricants design specifically for Hypoid Gear Lubrication ....SAE No. 90."

Will modern 90w gear lube be ok this is old truck?

 

Thanks in advance.

   Greg

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Thanks Alan. Mine hasn't been rebuilt. It appears someone welded the two halves together. Not sure why someone would do that. Maybe thought that's how you stopped a leak???

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very odd....I’ve seen old gasket material swell up and look like it was welding metal, but once I pryed them apart it was clear it was swollen material.

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Maybe RTV or similar oozing out and not welds?

 

14 hours ago, this_is_greg said:

Will modern 90w gear lube be ok this is old truck

Please don't use that 90w slang. In oil speak, the W means something, basically behaviour when cold (think "winter"). If you want SAE 90 oil, say so. It will, of course, be much thinner when hot than when cold. The SAE 90W-140 behaves as SAE 90 when cold and 140 when hot. 80W-90 likewise.

 

I think you can go ahead and use 80W-90 (EP) as @Surf City '38 has said.

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You should use SAE 90 GL-4 EP (extreme pressure) gear oil, available at O'Reilly's and other chain stores.  These days the shelves are full of GL-5, which is for limited-slip, so be sure you get GL-4, which is much easier on any yellow-metal (e.g., brass, bronze) components that may be in the diff.   If  the diff is loose/worn, use 140 weight or mix half-and-half with the same brand's 90.

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Was just looking through an OEM Late 30s dodge passenger car shop manual and saw rear axle lube recommendation of 160 weight for summer and 90 weight for winter as required. That's 80 year old info based on the lubricants of the day. I really doubt anyone ever changed their axle lube twice a year. I'm going to put some modern 90 weight in mine and call it good! 

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12 minutes ago, John Dunn said:

Was just looking through an OEM Late 30s dodge passenger car shop manual and saw rear axle lube recommendation of 160 weight for summer and 90 weight for winter as required. That's 80 year old info based on the lubricants of the day. I really doubt anyone ever changed their axle lube twice a year. I'm going to put some modern 90 weight in mine and call it good! 

 

Since you will probably put more miles on it during non-freezing weather You should go with 140 gl-4 gear lube

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That makes good sense. Definitely not for cold weather use any more. There is a shaky looking old heater in the cab and I'm not even hooking up the hoses. 

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SOP used to be to drain a pint out of the differential and a 1/2 pint out of the transmission and top both up with coal oil/kerosene.  Then in the spring you drained both and put 140 or 160 back in.

In my personal experience at minus 40 degrees F if the unit is parked outside and there is a wind, the engine will start but the transmission and differential are solid.  After the engine is warmed up I could leave the transmission in neutral (always parked in neutral in the winter) and slip the clutch a bit to get the input shaft spinning.  Once the transmission was warmed up then you could drive away but usually had to stay in first for a mile or two.  Did this twice and then added coal oil and never had to do it again.

The coldest I drove the car in was minus 54 F and had no troubles.

Edited by Tinindian (see edit history)

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4 hours ago, JFranklin said:

 

 

Since you will probably put more miles on it during non-freezing weather You should go with 140 gl-4 gear lube

 

Yes , Greg and John. Hypoid gears shear the oil down. I have gone to 140 to stop a pinion seal leak on a disposable beater. Dried the old thing right out even with thousands of miles of subsequent use.   -  Carl 

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