Another possible cause of cam sensor wear?

Mike T

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May 3, 2013
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I have a new GM old stock sensor in my car that started making a ticking noise. The noise started at around 5000 miles.

Out of curiosity I put a worn cam sensor in the lathe (chucked at the drive gear) to determine if it was vertical or horizontal shaft movement causing the noise. Immediately you could see a tremendous amount of run out. The entire sensor body at the cap end was moving approximately .065

3 sensors total were checked with the same results. All were ran in my car which has a little higher than normal oil pressure so I assumed possible bent shaft.

Upon disassembly I finally found that the drive gear and the shaft are nowhere near a perfect slip fit.

It would appear that the roll pin is all that determines how straight the gear to shaft alignment is. My theory is once the roll pin has been exposed to stress the gear gets locked at a crooked angle to the shaft.

More variables here but I believe the drive gear is pushing off of the cam gear causing the shaft to wobble in a elliptical pattern.
IMG_20190411_141329893.jpg
 
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earlbrown

runs with scissors
May 26, 2001
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lagrange, GA
I'd deburr the other end and flip it. That way you chuck can get a better bite, and then put a dial on the shaft at the gear and the gear ends themselves.


How true is your dependent chuck?
 

Mike T

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May 3, 2013
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I've chucked it several different ways and from both ends. The shaft alone runs true, the gear alone runs true.
The misalignment occurs from the sloppy gear to shaft fit. I haven't reinstalled the roll pin to see if the pin pulls the gear crooked of if it's a product stress in a running engine.

I mocked up the entire assembly in a front cover with pump gears and even the way the oil pump shaft mated was a little askew
 

Mike T

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Picture this... gear chucked up/locked in a rigid mount, slip the shaft into the gear (without the roll pin) and the cap end of the shaft will move 1/16 of an inch side to side.
 

earlbrown

runs with scissors
May 26, 2001
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lagrange, GA
Have you rotated the gear 180 on the shaft and duplicated the results?

I'm wondering if the OD and the ID are concentric.

Then again they might not care. Both the cam gear and the pump shaft are located with the shaft's bores. The gear doens't mesh against the cam to a bottomed out scenario so I guess a little runout really won't show up. Then again 065 thou is a MILE on a part that small.

I'm kinda wondering if there's a burr on the ID of the gear during initial machining and the fit between the gear and shaft is a very sloppy fit. Then again a .0325 burr is one hellova booger.
 

Chuck Leeper

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Is the ft cover a "gennie article"?
Many of the offshore covers are bored off location, and causing sensor issues.

In the "FWIW dept", many yrs back, Kendall Fredrick made a crank driven pump, using a late model and a stock cover. Don't know how far the project went. Haven't seen Kendall on here, for many yrs. A good project for Earl!
 
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Mike T

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it may need to be a little loose to accomodate "sloppage" in the other parts

:)

I thought of that as well Bob but it doesn't float smoothly, it seems to cock a bit and stay there.

A precise slip fit would be far better for the pin.
 

Mike T

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Is the ft cover a "gennie article"?
Many of the offshore covers are bored off location, and causing sensor issues.

In the "FWIW dept", many yrs back, Kendall Fredrick made a crank driven pump, using a late model and a stock cover. Don't know how far the project went. Haven't seen Kendall on here, for many yrs. A good project for Earl!
I'm probably not describing the run out in the best way.


With the gear end chucked up in the lathe and spun the opposite end whips around 1/16 of an inch. The run out is exaggerated because or the length of the shaft.

When it's chucked at the cap end the shaft runs true but you can see the gear has a slight wobble. It's not nearly as noticable because of the length of the gear.
 

Mike T

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Dam , that’s a good find ! Going to pull mine tomorrow and chuck it up and dial the shaft .
Slop or wobble load on the pin can’t be good !
If you have a spare it would be interesting to see if it's the same.

I would hate to have you pull yours out of a running car just to check something that we haven't determined to be critical.

Actual run out at the gear isn't going to be all that much.
I guess how tightly the gears mesh is going to determine how much lateral force is being applied to the shaft and housing bushings.
 

Mike T

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May 3, 2013
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I'd deburr the other end and flip it. That way you chuck can get a better bite, and then put a dial on the shaft at the gear and the gear ends themselves.


How true is your dependent chuck?
Earl I'm sure you have a spare cam sensor laying around why not chuck one up and let me know what you find.

also in case there's any confusion I haven't been grabbing it by the gear itself there's a nice step at the base of the teeth
 
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