1998 Ford F150--128,000 miles


I drive a 98 Ford F150–Manual. It has about 128,000 miles. When I backed out of the garage today, I noticed a small amount of a clear oil like substance on the garage floor. It was located in the center of the truck back where the drive shaft goes into the rear axel.

I would be greatful for any type of input.



Check the flexible rubber brake line going to the rear axle assembly.


The oil in the differential is really stinky. At the mileage it is probably not clear any more, though.

It doesn’t stink, but there is a “oil” smell to the substance.

If it’s clear and rear axle, you’ve got a leaking brake line somewhere.


Perhaps. And it’s an excellent idea to make that assumption until otherwise proven, brake leaks being as dangerous as they are.

However I’m betting on the pinion shaft seal.

If it was a pinion seal it would be black and smell like 90 wt axle grease. The only other clear thing back there is fuel that could possibly be leaking.


smell like grease,90w has a smell in and of its own.(when was it serviced last? (we don’t know ,do you?) master cyl low? (we don’t know) do you? need more info to assume and disagree.

synthetic will not turn BLACK,and smells diff’

Even new gear oil for differentials isn’t clear, and old stuff is most definitely black, having just changed out my truck’s rear differential fluid.

I too would bet on brake fluid. Have a look at the brake fluid level in your master cylinder. If it’s lower than usual, there’s your problem.

it must be brake fluid. if you are not sure, take off the master cylinder cap and compare the two odors. i have a 1989 f-150 with 170k miles on it and i already had to replace rusted out brake lines not to mention rusted out gas tanks.

Hi Skip-- I looked under the truck to see where the drip was coming from and it looks like it is forming a slow drip from the bottom of the gas tank. It is clear and feels like oil and when I smell the “liquid” it smells like an oil field. Does any of this make sense?