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Thread: Oil film on top cover of T9.

  1. #1
    Join Date
    Dec 2014
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    Default Oil film on top cover of T9.

    I recently noticed a pretty uniform film of oil on the top cover of my T-9. I know that there is a small breather hole in the cover (original from the manufacturer). Have I overfilled the gearbox? I believe that I have a liter or so of Lubrimoly 75-90 GL-5 in it. There’s is no leakage from anywhere else on the motor or the transmission. I guess that when I next pull the drivetrain, I will install a hose and route it to a catch can. Ant other thoughts on it?

  2. #2
    Join Date
    Dec 2013
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    Quote Originally Posted by papak View Post
    I believe that I have a liter or so of Lubrimoly 75-90 GL-5 in it.
    I thought that GL-4 has to be used in the T9. GL-5 will eat up the syncros...

  3. #3
    Join Date
    Aug 2008
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    Iowa
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    Ferdl is correct, although it takes a while. EP (Extreme Pressure) additives are aggressive toward yellow metals (copper, brass, bronze). GL4 gear lubes have half the amount of EP additive as GL5, making them more suitable for manual transmissions.

    It seems unlikely, given the size of the breather hole, but I suppose it is possible that the gear lubricant is foaming and escaping out the top that way. Foaming is often the result of moisture contamination or cross-contamination with another fluid. Perhaps an oil change will fix it.

  4. #4
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    I may be wrong on the grade of lube. I'll have to check my notebook. There is only 1600 mi on the drivetrain. It's interesting because there is NO evidence of seepage anywhere else.

  5. #5
    Join Date
    Sep 2007
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    Houston, TX
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    In my experience when a T9 is over filled the oil leaks out of the selector shaft at the front of the gearbox and drips on the ground under the joint between the bell housing and gearbox. I have never seen one leak out of the small breather hole on the top cover, I suppose it is possible but I haven't seen it. And, unless you have added a fill plug on top cover of the gearbox, as many have, it is hard to over fill it from the normal fill plug on the side of the box as it runs out when it is at the correct fill. I guess you could have the gearbox really un-level as you fill it but it would have to be really out of level. Are you sure it is not coming from a breather hose on the engine, or some other source?
    A little over a liter if the box is dry (if it is a refill a liter would be good) is the correct fill amount for the Type N T9 five speed

  6. #6
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    Dec 2014
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    Los Angeles
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    This is the driest engine rebuild I think I have ever done. Nary a drop from anywhere. Nothing from the bottom of the bellhousing but an occasional drop from the output shaft seal when I park it facing uphill after a blat. I do have a fill plug on the top cover. I plan on replacing it with an Earls adapter and a -4 breather hose before I put it back on the road.

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