Transmission oil change

[Emcdawg]

I changed the transmission oil in my 84 manual 4x4 this weekend just because I had just bought the truck a month or so ago and didn't know how long it had been in there and there was some whining when you de-excelerated. There were a few shavings on the drain plug but not to bad, the old oil was terrible, thin and dirty. I used GL-4 and a few oz's of Lucas oil stabilizer and the whining is gone and it shifts a little smother but when down shifting the rpm's must be lower before it will go in gear without grinding. It's not a big deal but I wondered if anyone knew why?
I also changed out several of the remaining old vacuume lines and man did that make a difference! Thanks for all the great info on this page.

[Mark Mellott]

Check your clutch cable adjustment at the clutch release bearing fork to be sure that there is not too much free movement of the fork before it engages the release bearing into the pressure plate. The clutch disc may be worn down and the clutch cable may be a bit stretched, both of which will create excessive play in the release bearing fork. This excess play may not allow the clutch to fully disengage when you shift and so the gears will grind as they try to mesh in syncronization.

It is possible the gears are getting worn out and simply will not mesh in sync unless the motor speed is low.

Could be all of the above.

If it is a hydraulic clutch release system at the fork (instead of a cable) , and you fluid drips coming from the actuator cylinder that pushes a rod against the clutch release fork, then you need to replace this cylinder and bleed the lines with fresh brake fluid. If there is no sign of leakage but the rod does not fully extend when the clutch is pressed, then you may just simply have to bleed air out of the system much like you would do for the brakes.

[Rev_D21]

Glad to hear NICO helped you and your 720. As for the change in RPM for downshifting I am guessing that the new oil helped get internals working closer to how they should and now you don't have to rev as high as a result, you just need to get used it again.