Transmission Oil Level

Question for Fix My Hog

Hi. I have a 2008 Road King Police (FLHP) and after every ride, there’s a quarter-size oil drop just below the primary case, near the drain plug. When I checked the transmission oil level, it was low so I changed it and filled it full. So I’m thinking maybe a shifter or transmission case seal. Before I do any unnecessary work, can you tell me how to systematically diagnose and troubleshoot such an oil leak? Tips and tricks?

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Fix My Hog Answers

First, it is important that you check transmission oil level per your manual, some models and years are with the motorcycle upright & level and some on jiffy stand. If you overfilled the transmission case the excessive oil may be flowing out through the transmission vent. This might be the oil that you are seeing on the ground. Otherwise, start simple. Make sure that the oil is not leaking from the derby or outer primary cover gaskets. If none of these, your leak might be orientating from an inner primary seal or transfer seal.

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6 Responses to “Transmission Oil Level”
  1. Dave Roberts
    Dave Roberts

    In regards to the oil leak under the 08 Road King Police, what about the simplest fix of a seal around the drain plug? With careful scrutiny we should be able to observe not only where the drip is from but the source of the leak.

  2. Stan Stolarski
    Stan Stolarski

    I have a pristine 1992 FLSTF . . . Also have a tiny leak (nickle size) after riding that appears to be around the center of the large outer primary. Fluid level OK. Will changing the large primary gasket as well as the derby O-ring & inspection gasket take care of this ? Thanks !!!

  3. JimmyRay

    I’ve seen some questions on here that are common sense to but that’s because I bonded with my Scooter since day one. It’s a good thing, good site.

  4. Roger Baker
    Roger Baker

    You should read your owners manual on checking fluids. My 2019 Road King tranny oil is to be checked on level ground while leaning on the jiffy/side stand. Primary oil is checked on level surface with bike standing straight up. READ THE MANUAL!

  5. Michael T Conley
    Michael T Conley

    Harley told me it was base cylinder gaskets outer primary and oil filter bracket. I chased it down to iner primay o ring. A 90 deger adaptor for presure washer let me clean area to chase leak.


    In the service manual indicates that it should be messured on the jiffy stand. cuote When checking the transmission lubricant level, the motorcycle
    should be leaning on the jiffy stand. Allow a short period of
    time to equalize lubricant level in the transmission compartments