The last time I changed my transmission fluid on my 1990 LS400, I noticed that my drain plug was stiff as I unscrewed it and as I screwed it back in. Usually once I turn it a half a turn or so I can turn it the rest of the way with my hand, but this time I had to use the socket all the way until it fell out. It just feels stiff.

Is this a common problem? Does anyone know what caused it or how to fix it?

Should I run a tap through my drain plug hole and run my drain plug through a die? Or would it be cheaper to replace the plug? Or is the problem the pan? Has anyone had this happen before?

If I just need a new plug, has anyone had any success getting an aftermarket plug, or is it a dealer-only item?

Thanks for your help.
Curt

 

The drain plugs on both my LS behaved the same way. I replaced with a new plug and it was still the same so I inclined to believe that was normal...unless some else want to correct me. Anyone?

 

Try spray some WD-40 and let it soak in for a few minutes. Same applies to any tough nuts and bolts. You can also try apply some spark plug grease on the thread of the new tranny drain plug, though I have never tried it.

I'd advise against using U.S.-made aftermarket parts on foreign cars, especially parts that require tight tolerance.

 

Dont put anything on the thread, unless you want it swimming around in your transmission fluid. I dont think its a problem that its tight... thats how mine was the last 2 times i drained. Your fine man.

Just make sure you dont over torque it.

 

The spark plug grease will stay in the thread and won't swim around in the tranny fluid. Otherwise it wouldn't be used in the spark plug thread because it could flow into the cylinders. Right?

Other greases won't work because they can't take the heat.