Posted by Vaughn on Friday, September 01, 2006 at 11:46AM :
In Reply to: Gear oils for our old irons posted by Mike (Montreal, Quebec) on Thursday, August 31, 2006 at 11:05PM :
I've been using the later gear oils in my transmission/transfer case and differentials of previous jeep (48 Truck) and current 56 PW for 30+ years. I can't say I have experienced any problems with bronze bushings or sync rings over the years. All seem to have normal wear for what they are designed to do when the units needed rebuilding. I use SAE140 in the tranny (sliding gear)/TC and SAE90 in the diffs.
I think there are trade offs between what is not added and additives to oils. Additives today prevent oxidation and oil breakdown to eliminate gear contact minimizing teeth wear of the more expensive parts.
A person who rarely drives a vintage vehicle may want to consider oils with no additives. It's not so much the oil, but the moisture that builds in the units and acts as a catalyst for the creation of acids that eat at the bronze in vehicles that aren’t driven much. If you have to have a bronze part made, then it might be prudent to change the oil every time you use it. The bronze parts for the PW are available and not expensive. Even in today’s cars/trucks, there are bronze parts and they don't use oils that are designed for older cars.
I guess it’s a decision each one has to make based on the use of the vehicle, availability of parts and what they feel comfortable doing. As for me, I will stay with the oils that have the protective additives so I can get the most out of the most expensive parts.
To prevent the tranny/TC and diffs from run hot, fill the unit to the recommended 1/2" level below the filler plug. Anymore than that is considered overfill that will cause the unit to heat.
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