Hi all, I'm about to change the oil in my 1991 2wd manual pickup (r150), it has almost 300,000 miles and the trans bearings have been making a mild grinding/whirring noise since I bought the truck about a year ago. I'm thinking as a band aid solution it might help quiet down the noise if I switch to slightly heavier oil (manual says 75W-90), I was thinking maybe 80W-90? Either that or maybe some Redline MT-90 with some lucas heavy oil stabilizer? (heard good things about the Redline). Has anyone tried any of this stuff to quiet a noisy trans? Thanks.

 

I replaced some 85W-90 with the purple stuff and the synchromesh collars are loving life. Cold morning notchiness is gone and she shifts consistently and it seems to make no difference when the operating temperature is cold or hot. The gear oil additive packages for the brass synchromesh collars is important and I bet Redline and Royal Purple are equal in supplying them.

I also have a W58 series in a Jensen Healey. It was an early Celica box with the aluminum center section plate from Craig's list. It is noisy and I have a bearing kit for it which is yet to be installed but have Royal Purple is in it and it is shifting cleanly and the noise has more to do with a Cube short throw shifter which has no rubber isolation in the gear lever stem. This makes a huge difference in the noise transmitted into the cab. So I would take a look at the stem and see if the isolation between upper section with the knob and the steel section that is fixed into the top of the gear box as a pivot point is still compliant. Or your truck may not have that isolation section as it is a pickup.