What Weight Oil in Engine and Diffs?

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renovate7
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What Weight Oil in Engine and Diffs?

Post by renovate7 » Sat Aug 19, 2017 5:17 am

I'm getting ready to change my engine and diff oil. The book calls for straight 30 in my original 270 engine and 90 weight in the differentials. The engine has excellent compression and uses no oil. Any harm or is it a good thing to use 15/40 in the engine and 85/140 in the differentials?


70th Division
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Re: What Weight Oil in Engine and Diffs?

Post by 70th Division » Sat Aug 19, 2017 8:11 am

Hello,
I don't know about the specifics of oil.
Personally I would try to keep as close to original as possible. especially since your engine works perfect now.

I do know that you Never want to use a detergent type oil in an old engine, in particular CCKW/DUKW engines.


Ray

renovate7
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Re: What Weight Oil in Engine and Diffs?

Post by renovate7 » Sat Aug 19, 2017 1:02 pm

Thanks for the replies. Someone else PM'd me with info and I think I'm going to stay with the 30 non-detergent and 90 weight as the book calls for.

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Re: What Weight Oil in Engine and Diffs?

Post by nhs275 » Sat Sep 02, 2017 5:45 pm

15/40 Rotella is a fine replacement for SAE 30 in a vintage engine so long as the engine is not a sludged up mess. If you pull the rocker cover and there is any sludge buildup, do not use a detergent oil until you get rid of that sludge. If you use a detergent oil in a sludged engine, the detergent works on the sludge (good) but the oil filter traps it (good - except too much sludge clogs the oil filter - very bad). Use of a detergent oil in a new rebuilt 'old' engine isn't a problem at all.

A straight mineral oil should be used in vintage transmissions and transfer cases with straight cut spur gears. The detergent additive tends to foam with the agitation that comes with straight cut spur gears in old truck (and jeep) transmissions and transfer cases. This manifests as oil being pushed up through the shift cane joint. Use of detergent oil in hypoid differentials is fine - caution should be used for double reduction differentials in heavy trucks. That said, foaming from gear agitation is a problem that shows up only at sustained high speed. If your truck is used only for parades and is trailered to the parade, or runs on surface streets to the parade/event, use of a detergent oil in gearboxes is just fine.
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nhs275
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Re: What Weight Oil in Engine and Diffs?

Post by nhs275 » Sat Sep 02, 2017 5:49 pm

Neglected to clarify - 'straight mineral oil' has no additives, and no detergent. When I need straight mineral gear oil, I visit the local oil distributor.
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1944 Converto T6, property tag ID CV38 Shangri-La

Dr Deuce
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Re: What Weight Oil in Engine and Diffs?

Post by Dr Deuce » Mon Sep 04, 2017 3:39 am

And don't forget to add the Zinc if you use modern motor oil. They took the zinc out for 'pollution' reasons. Solid lifters that slide on a cam lobe should have it as I am told.
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Re: What Weight Oil in Engine and Diffs?

Post by nhs275 » Mon Sep 04, 2017 11:03 am

The product Camguard is recommended for piston aircraft engines - in particular for its corrosion inhibitors and additives to reduce cam lobe wear. I am not an employee, not a distributor and not connected to this company in any way. I am a member of the experimental aircraft association which is where I ran across this product.

https://aslcamguard.com/
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Re: What Weight Oil in Engine and Diffs?

Post by Joe Gopan » Thu Sep 07, 2017 4:43 am

The OE use in WWII era tactical wheeled and tracked vehicles was Detergent. The information can be found in WWII Army Motors.
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