Thread: What normally fails on a fairey/toro overdrive?

The splines on the socalled clutch sleeve and input shaft wear to the point of completely stripping.
The upper rear gear and its mate on the layshaft wear through the case hardening and the box howls/screams in overdrive.
forgetting to engage direct drive when starting off from a standstill can break the gears and/or split the casing.
Always carry the standard mainshaft gear and PTO cover plate with you in case of overdrive failure.
Bill.

Originally Posted by wagoo

The splines on the socalled clutch sleeve and input shaft wear to the point of completely stripping.
The upper rear gear and its mate on the layshaft wear through the case hardening and the box howls/screams in overdrive.
forgetting to engage direct drive when starting off from a standstill can break the gears and/or split the casing.
Always carry the standard mainshaft gear and PTO cover plate with you in case of overdrive failure.
Bill.

Thanks. So is it fair to say that the clutch sleeve and input shaft will still be usable as long as they have not yet stripped and the teeth are 3/4 intact (how do these strip when they are not meshing in and out all the time? Isn't it just a drive dog?) Some of mine seem worn on one side of each tooth presumably in line with the direction of drive. I also found the roller bearing on the clutch sleeve had flat rollers on one clutch and the output gear where the bearing runs has lines worn into the case hardening, supposedly when they are used in direct drive for a long time the bearing rubs against the inside of the output gear and causes this. Interestingly I have one clutch sleeve and input shaft with no visible war to the teeth and on a different drive, the output gear is perfect, so I may strip and build one good spare out of several donors, replacing any worn bearings at the same time.

Any idea what the deal is with toro overdrives? Nobody seems to want too much to do with them?

The critical component is the drive dog. The fine teeth will wear right off (probably avoidable by removing and regreasing every couple of years). Noise will result from worn bearings or worn (case hardening off) gears. In my experience they are always noisy!
Parts for the Fairey are available but expensive.

The overdrive is, as is stated suitable for use only in third or fourth, and using it in lower gears is likely to result in catastrophic failure. The oil capacity is small, and it is likely to chuck oil out the breather or transfer it into the T/C, leaving a shortage of lubrication. I have extended the breather so that oil pushed up it drains back rather than being lost, but I cannot emphasise too much the need for regular checks of the oil level, at least every 1500km.

The Toro appears to be much more robust, but parts are very problematical.

John

The needle roller bearing on the so called drive dog will wear chatter marks on the inside of the (hollow) drive gear sticking out the front of the overdrive box. Feel inside where this needle roller bearing rubs and if the area is rough/pitted and or grooved then the thing is useless, as you need to replace that main drive cog/shaft, Regards Frank.

Originally Posted by Tank

The needle roller bearing on the so called drive dog will wear chatter marks on the inside of the (hollow) drive gear sticking out the front of the overdrive box. Feel inside where this needle roller bearing rubs and if the area is rough/pitted and or grooved then the thing is useless, as you need to replace that main drive cog/shaft, Regards Frank.

There is just enough thickness of material in the hollow output gear to bore it out and fit a Torrington bearing . I did this about 20 years ago but sorry, I didn't record the part number of the bearing.
I now run an aluminium /bronze bushing in this location, but that is feeding into and out of a 2:1 crawler box, not an overdrive. I wonder whether the bushing would work ok with the 27% over drive, as the speed differential between the gearbox mainshaft and overdrive output gear would rarely get to 1000rpm ?
Bill.

I had a machinist look at fitting a hardened sleeve after machining for the sleeve it would have cost me more than buying a new shaft from Down Under or something like that in southern USA in the end I sold the box for what I paid, Regards Frank.

Machining and a a bush if flogged.....Nothing wrong with the materials used in a standard series installation........As hinted in the past, the little sods dont lubricate well at all.

I remove mine every 5 to 10k and pack the splines and rear bush with molly grease. I have toyed the idea of using a remote electric oil pump as I successfully have on my very hard worked LT230 so lubricates properly.

The main drive gear needs some extra oil holes to get some oil into that needle roller bearing, that was going to cost an arm as well, Regards Frank.