915 gear end play

[doug petty]

Does anyone know whats the minimum amount of end play that can be run on the gear stacks of a 915 gear box before you would have a seized up gear. Im talking about between the gear & the thrust washer. My bentley manual has no specs on this. In my vw days the hot setup for a much improved shifting would be .001 to .002 & adding a few more oil grooves the both sides of the gears. Is this feasable to improve the shifting of a 915?

[Jim Sims]

I do not understand how increased gear set axial play would help shifting in a 915 as the gears are always in mesh ("shifting" is done by sliding the operating sleeves onto the "dogteeth" on the face of the gear). Increased axial play would allow the gear teeth to slip sideways past each other a small amount and thereby effective reduce the gear tooth width to carry the loads. This would be a small effect though. All it seems increased axial play would do would be to delay the shift and increase the shift throw a minute amount and maybe result in more gear noise and wear. This evening I'll look in the factory shop manual and see if there is an axial play specification; I don't recall one. Cheers, Jim

[john walker's workshop]

being that there are no plus or minus sized thrust spacers, the gears all have the same end play. if there is galling on the gear or the spacer, you deal with that, and then everything is back to spec, so you would never see anything getting on the tight side. seizing is usually because of not enough oil.