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Pilot Bushing Question

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Trevor Jessie

Trevor Jessie

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OK, I pulled my engine because the clutch had been slipping. I assumed that it had got oiled and glazed. Surprisingly, it look pretty good. However, when I pulled the tranny the pilot bushing was on the input shaft (not stuck in the crank like usual). So I'm assuming that it has "spun" inside the crank. Nope. It won't go back in without being driven. And it is loose (very loose) on the tranny input shaft. What gives?

BTW, this is a datsun transmission with Rivergate clutch.

I can't find my calipers, but does anyone have a theory?

And... what is your recipe for getting oil into the bushing?
 
Temperature I would guess. Try freezing that bushing or frosting it over real good with some of that de-duster spray for cleaning off a keyboard with the can upside down so it comes out as a liquid and freezes, then it should press in or fall in. Most of those bushings are oil light bronze with oil impregnated in the metal. They do funny things some times, as long as it can't come out when the tran is in then I would not worry about it. I had a car once with a worn out pilot bearing and still drove it for months. That bearing has got to be worn out real bad to cause much issue. I noticed a vibration from the clutch at times and would had to just tap the clutch at higher speed and the vibration would go away as the shaft self centered from the speed.
 
OK, but why was it on the input shaft where it has excess but not stuck in the end of the crank where it is still an interference fit?

I really need to do some measuring. This is not making sense to me.
 
Trevor
I just put grease in the crank-hole and let it lube itself. This may not be the correct way but it has worked for many years for me.
Bill
 
Was there excess grease in the hole where the bushing goes? Pushing the input shaft in with too much grease will pop the bushing out of the hole.
 
Bill, I was always told that grease will lube the outside of the metal, but will not penetrate it. So... once the grease gets hot and runs away there is no lube left for the bushing... then it can heat up and fail. I dunno. I'm going to get a new bushing and compare it and reassemble and try again.
 
It would make sense that the ID would be loose on an worn pilot bushing. I think there is .002" to .005" clearance between bushing and input shaft stock. It shouldn't hurt the crank even if the pilot spun in the crank for some reason. The softer metal will give. I've seen pilot bearings ruin cranks but never pilot bushings.
There doesn't seem to be much lubrication for the pilot bushing during operation. The oil impregnated bronze doesn't really need any. Most of the time the crank and input shaft are locked together anyway. (Except when you are sitting at a stop light) I take mine out of gear to protect the thrust washers (1500) anyway.
FWIW
JC
 
Well after doing some measuring, it appears that the pilot bushing came out of the crank and had been spinning freely on the input shaft. The gearbox oil did not have any signs of metal flakes, so I'm hoping that everything is relatively fine inside. How in the world did it come out of the crank? I can only get it to go back by drifting it in. Did the crank get that hot? Should I add a bushing to the input shaft to keep it from sliding back again?
 
Think I would just press it in and press on.
 
I just looked at one I have in the shop it is an olite bushing.I would replce it. If it came off now it will do it again. Press in a new one and maybe just a smear of a good moly grease. and call it good.
 
When the tran is bolted up, can it even come out enough to do any harm? How long is that tip on the input shaft compared to the bushing? Maybe you should put two bushings on the shaft, one to hold the other from coming out.
 
That is what I'm thinking Kim. As I measure there is ample room for the pilot bushing to slide back if it becomes free. However, if I place a bushing on the input shaft to make up the difference, it could not slide out.

I've never seen a pilot bushing come out of the crank without being severely worn or busted.
 
Trevor Jessie said:
That is what I'm thinking Kim. As I measure there is ample room for the pilot bushing to slide back if it becomes free. However, if I place a bushing on the input shaft to make up the difference, it could not slide out.

I've never seen a pilot bushing come out of the crank without being severely worn or busted.
Click to expand...
I have not seen it either, but putting that extra spacer bushing on there will give piece of mind so it can't happen again.
 
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