Fluid Leak Question

[Broadwaydan]

I am getting ready to finish install of insulation and carpet in the cockpit. I was unfastening seat bolts under the car and noticed some greasy fluid on the ground (very little) and some residue on the transmission support a-frame and the mounting hardware in that area. There was not a lot anywhere, but this is the first time I have seen this. Car has been driven go-kart multiple times and is just back from getting final alignment. I got under it today and it appears that it is transmission fluid, and appears to be coming from in or around the speedometer sending unit (driver side). There appears to be some fluid when I look up inside the sending unit. There are no fluid leaks anywhere else on the transmission or anywhere up or down the length of the car based on my inspection. It is all centered at and below the sending unit. I double-checked that the fastener for the unit was tight. I was able to turn it maybe 1/32 of a turn, so really don't think it was loose. Any thoughts on how or why this might be happening? Thanks.

[CraigS]

Kind of normal for the standard cable units. Mike Forte has a replacement cable unit that actually seals. If yours is electrical i am not familiar.

[DVANSLEEN]

Mine had a small crack in it and the "O" ring was bad. Replaced with a Ford unit and leak went away. Check the "O" ring first.

[Broadwaydan]

Mine had a small crack in it and the "O" ring was bad. Replaced with a Ford unit and leak went away. Check the "O" ring first.

Thanks for the suggestions. I pulled the sending unit out today and checked it. The o-ring looked ok, although it does not seem to protrude very far outside the diameter of the unit itself. But, there is a small amount of pressure I can feel when I push it back into the transmission opening. Next time I drive it (may be a while) I will check for leaks again, and replace the o-ring.

Is the black o-ring in the center of the unit body the only one that should be there? I am surprised there is not an o-ring or gasket where the unit meets with the tranny housing. I also had a red o-ring inside the plastic bottom part of the housing, along with a very light cotter pin. Not really sure why this is there or what it does. I tried to attach some photos, but the files are too large. Not sure how to do it otherwise.

[GJerry]

If the o-ring looks ok but the diameter is larger than the diameter of the unit itself then it should be replaced with the correct size o-ring. It may have been replaced by someone else who thought it was "close enough". I think you can get one from Breeze Automotive.

[Broadwaydan]

If the o-ring looks ok but the diameter is larger than the diameter of the unit itself then it should be replaced with the correct size o-ring. It may have been replaced by someone else who thought it was "close enough". I think you can get one from Breeze Automotive.

GJ - thanks, I understand your point. The o-ring is tight around the unit at the ID. The outer diameter is what I meant is barely larger than the unit diameter. I am thinking it just may not be making a tight enough seal with the opening in the transmission. Maybe need one with a bit larger OD.