C70 transmission noise help

[jd730]

    In the middle of wheat harvest here and my truck's tranny is getting noisey.  1980 C70 tandem w/ 366 and a 5 spd.  Reverse and 1-4 are noisey with 5th quiet.  PTO is also noisey when lifting a load.  Truck does not jump out of gear.  Hard to describe noises with print I know.  Any ideas where to start looking?  Do I plan on a total rebuild and if so how much am I looking at?  Truck has about 45,000 miles.

Thanks

John

[BA Deere]

Could it be low on oil? Maybe 5th gear spins enough lube up where 1-4 don`t.  Maybe try "Lucas oil treatment" to cripple through.

[Pat in CMO]

 Probably the input bearing if it's quiet in 5th. I 5th gear the mainshaft is locked to the input shaft and drives straight through so there is no side load on the bearing from the load driving through the countershaft.  Patrick

[jd730]

Thanks for your reply, I'm thinking you may be right, also when lifting the bed the pto is quite noisey as well and vibrations can be felt in the shifter.

Thanks,

John

[jd730]

Oil level is full, checked it right before harvest started.

Thanks,

John

[nitefarm]

Had one one time that  a snap ring slipped out of groove. G.M. fixed with pipe spacer to keep gears apart instead of snapring.