1991 Ranger - 131,000 miles - Transmissin noise???

Hello,
My dear old Ranger has started a fairly loud squeaking when I start it cold. The squeak seems to come from the back of the engine. It goes away after about 15 minutes when the engine heats up, The frequency also increases as the RPM and the speed of the truck increase. I'll have it checked next week, but I'm afraid it may be the transmission. Any ideas???
thanks, and I'll buy another Ranger when this one passes on.
:disappoin

I would guess the clutch/throw-out bearing area.

thanks for the help, I'll let you know what they find