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View Full Version : How to reduce slop on mainshaft?



airbornrover
05-21-2009, 05:59 PM
trying to rebuild gearbox nice and proper and noticed that i could push and pull the main shaft significatly(about 1/4 inch) when the pinion shaft is solidly in place. Looking at the parts catalog there are only two places on the main shaft that call for shims, doesnt seem like switching out to the largest thickness for both of them will take up enough of the slop. First time doing this. Am i overlooking something simple? Have not purchased any replacement pieces yet.

Thanks

Ren Ching
06-09-2009, 10:21 AM
first of all lets. clear up some terminology to make sure we are referring to the same parts. by pinion I take it you mean the input shaft or primary pinion which protrudes through the bellhousing and engages with the clutch disc.

the manishaft is located in line with the primary pinion (input shaft) and protrudes into the transfer box. when you remove the PTO cover off the back of the t-box you see the rear of the mainshaft. is this where you are finding the 1/4" fore-aft movement?

the shims on the mainshaft IIRC are there to correct the endfloat on the 2/3 gear "pack" and possibly the 1st gear as well.

if there is signficant for-aft movement of the entire mainshaft I would look to the large "special nut" on the back of the mainshaft, visible through the pto cover of the transfer box. this should be tight and held in place with a fancy lock washer. if that is tight then check the roller bearing between the two cases. there should not be this much play, if any.

also check the bearing between the primary pinion and the mainshaft.

let us know what you find...

rgrds,
dave in DC



trying to rebuild gearbox nice and proper and noticed that i could push and pull the main shaft significatly(about 1/4 inch) when the pinion shaft is solidly in place. Looking at the parts catalog there are only two places on the main shaft that call for shims, doesnt seem like switching out to the largest thickness for both of them will take up enough of the slop. First time doing this. Am i overlooking something simple? Have not purchased any replacement pieces yet.

Thanks

scatterling
06-09-2009, 04:41 PM
I just ran downstairs and checked the gearbox I put back together. There is zero fore and aft movement in the mainshaft. (The castle nut is tight)

airbornrover
06-10-2009, 08:51 PM
Just a little late on the info guys:)
Appreciate the info none the less thou. I had placed a thicker shim on the primary pinion so that was nice and tight. Should clarify that I was using an overdrive at the time that burned out due to me not topping up the oil enough for the overdrive. Didnt think that the nut would take up that much slack. Also the way i pictured it in my head if i were to tighten up the nut then it would pull the mainshaft more to the rear.

Either way, I went ahead and purchased a new tranny from RN.