Have a 1990 4WD p/u with a W56 manual transmission, and the truck has about 265,000 miles. I understand that it is pretty common for these to whine, especially 5th gear, which is what mine is doing. Have heard everything from a transmission rebuild is in my immediate future, as well as they can run like this for a long time before any real trouble will occur. My question is, would it be beneficial to do anything in the mean time, or just drive until it craps out? Was thinking about doing a fluid change since it is about time for that. Is there anything that might prolong the life other than using what the manual says to use? Read that some people have had luck with a Lucas additive and other things similar to that, but I do not have any first hand experience with that.

Thanks!

 

Change the fluid if it gives you peace of mind. I say rock it till it breaks.

 

try a quality, heavier weight gear oil - like Redline.