Hi. I’ve rebuilt my 1960 Dommie 99 gearbox and it’s all working fine (on the bench). However, the gearbox sprocket has a bit of resistance to it when I turn it. I undid the sprocket nut and the the force required to turn the sleeve gear was reduced to what feels ‘normal’ to me.
The ‘problem’ (if it really is one) only appears when the sprocket nut is tightened up to 60 or 70 foot pounds. (Haynes manual says 80 but I can’t get it that tight). It’s seems as if tightening the sprocket nut is pulling the pinion side of the sleeve gear tightly against the bearing’s inner/outer race inside the gearbox, or the bearing is being clamped too hard between the sleeve gear sprocket and the steel spacer ring - is any of that possible?
I’ve replaced the sleeve gear bearing and oil seal plus the steel spacer ring that fits into the oil seal and sits behind the sprocket. The steel spacer is a moderately tight (snug) push fit in the oil seal but turns within the oil seal when the sprocket is turned.
I have no idea how turning the sleeve gear felt originally as the gearbox was full of crud when I got it so nothing worked.
Am I overthinking this - is it a non-issue? Is this ‘normal’? Will things free up a bit once the gearbox has been used for a while?
Any ideas gratefully accepted.
Regards
Tony
Seal thickness?
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Hi George, Thanks for your…
Hi George,
Thanks for your reply. The sprocket turns fine until the nut is tightened fully. It seems to be that the sleeve bearing is being squeezed between the sleeve gear pinion and the spacer ring for some reason.
Regards
Tony
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The sleeve gear should turn…
The sleeve gear should turn as easily when the sprocket nut is fully tight as when just finger tight. What I think George is suggesting is that the spacer ring is tight in the seal so, when the nut is loose, the spacer stays with the seal and sleeve gear turns within the spacer. Alternatively, the sprocket could be rubbing against the outside of the seal when fully tightened. Removing the seal will eliminate this possiblity.
The bearing inner race is not going to distort 'cos you tighten the nut up fully. So any difference you notice will be:
- the sprocket rubbing against something (seal or shell)
- the spacer dragging on the seal or the bearing cage
- the bearing being so tight that the sleeve gear was turning inside it
- the mainshaft so out of line that pulling the sleeve gear straight locks it up.
The spacer and/or seal could be wrong. Are they from Andover? The bearing might not be fully seated in the shell. Gearbox might be a basket case.
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Hi Stan, thanks for your…
Hi Stan, thanks for your reply and useful suggestions.
I took the nut and sprocket off and removed the seal, then put the spacer ring and sprocket back on. I tightened the nut fully and found that the sprocket turned very easily.
I then put the seal back in with just the spacer ring inserted. Turning the ring with my fingers was almost impossible so I put the ring on my lathe and removed 2 thou from the outside diameter. That allows the ring to just turn within the seal but it is still a snug fit.
With the sprocket back on and the nut tightened, the sprocket is still a bit stiff to turn but at least I now know that it’s the rim of the spacer ring rubbing against the oil seal and nothing more serious. I imagine things will loosen off a bit once the gearbox has had some on-road use.
Thanks again.
Regards
Tony
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Hi,
To eliminate the easy things first, can you remove the oil seal and its housing, then refit the spacer/sprocket? If it is still stiff to turn, then it suggests something isn't quite right inside. It should turn reasonably freely.
If it is now free to turn, then it suggests that the culprit is the seal housing binding or seal drag causing the problem.
Regards, George