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Thread: Gear Oil

  1. #11
    Senior Member
    Join Date
    Nov 2019
    The hydraulic oil like the Rotella HD I mentioned is probably no more than 30 wt. but it is used in heavy equipment with ring gear and pinions, power shift transmissions, etc with extended continuous use under high temperature conditions. I think it would work in a jeep tranny.

  2. #12
    Super Moderator bmorgil's Avatar
    Join Date
    Dec 2018
    Northwestern Ohio
    The real trick here is to match the EP ability of the oil/lube to the application. Here it is important to remember to much EP capability (as intended for use in sliding hypoid applications), inhibits the synchro's ability to engage the next gear and "clutch". This causes more gear clash than normal and wears the clutching gear teeth faster. In addition the shift will be "stiffer" and slower than it was designed. The brass facings will become glazed making things worse. Most will never hear the excessive gear clash, there is usually to much other noise. This damage is subtle.

    GL-4 gear oil does have some EP. It is not so excessive that it causes shift issues. GL-5 is tops on the EP additives list, and is intended for the high sliding friction of a Hypoid gear set. The reverse error of putting a low EP in a Hypoid gear set is obvious and happens quickly. It is a total failure. The failure analysis in the Tech Section has some good pic's. If you make a mistake and use a high EP in a cone style synchro, life isn't over. Many have done it. Some don't notice. A sharp transmission re-builder familiar with old school synchro's, would know immediately.

  3. #13
    Thanks ya'll for your wisdom. I'll try the 40 wt oil.

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