Ball Bearing question.

JohnnieB

While ordering replacement bearings for the input shaft to my differential, I noticed the motor side bearing from EZGO is a Ceramic Hybrid ball bearing. Or at least the last line on the Additional Information tab says: "Made of steel with ceramic balls"
http://www.shopezgo.com/products/Bea...roduct_id=2298

That tidbit of information explains why and how I messed up the bearing in my differential; And I can accept the use of a hybrid bearing in this application, but I cannot figure out why EZGO put a hybrid bearing on one end of the input shaft and a regular (steel ball) bearing on the other end.

Anybody know, or have a good guess why they didn't use the same type bearing on both ends of the shaft?

BGW

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kellybell

I don't normally discuss balls with you, Johnnie B, but I will make an exception just this once. Perhaps someone has been there before you and replaced the bearing with an in correct one? Are there other signs that someone has been there before you? For instance, different colored wires, other parts obviously replaced?

JohnnieB

The cart was fresh off a 3yr lease when I acquired it and no signs of any wiring changes that I noticed. The motor has the be removed to change that bearing and I'm about 99.999% sure the motor had never been off since it was installed at the factory, so the bearing is most likely whatever EZGO (Dana/Spicer actually) put in at the factory.

A ceramic hybrid has less rolling resistance, better load and heat capabilities and can be operated at higher RPM. Mechanical Engineering isn't my long suit, but I'll accept the supposition that there is a reason to use the more expensive bearing in this application, but why just on one end of the shaft.

After in installed my new motor, I heard a rhythmic clunking sound and suspected I had screwed up a wheel bearing when the motor seized and I slid to a stop, but I traced the sound to the top of the differential.

I'm not 100% sure it is the bearings on the input shaft, but I did put a lot of stress on the shaft while getting the old motor off. Basically, I disconnect the cables top the motor and unbolted it from the differential. I couldn't get the motor off, the cart was sitting on the street in front of the house where the flatbed wrecker offloaded it, so I towed the cart to the
cart to the garage. When we got to the garage, the motor was lying on the rear axle housing.

Unbolted from the differential, the seized motor spun 12.44 times each time the tires revolved. I moved the cart slowly, but the rotating mass was imbalanced enough to wiggle the stuck motor off the input shaft.

The noise doesn't actually sound like a bad bearing. It is only there when the cart is moving very slowly. The ceramic balls are harder than steel, so my guess it that they made some indentations in the races and when the RPM gets high enough the balls don't drop in the indentations, sorta like a bumpy road is smoother when you drive faster.

Anyway, I'll know the bearings were bad if the noise goes away after I replace them.

kellybell

Can you take out the bearing and test them? I would suppose that would be equal to replacing them, as long as you had to do all the work in tearing it down. You could replace the bearing with a metallic part, but you would still have to tear it down.......

kellybell

"but why just at one end of the shaft". So, excuse me for not knowing, but that infers there is another end. Could the noise be coming from the bearing at that end? Perhaps this other bearing is worn, being metallic and wore out before the one in question? Just grasping at straws......

JohnnieB

Actually, I'd prefer to hybrid bearings on both end of the shaft, but I'm going to replace them with whatever EZGO ships.

Other than taking off the motor, which shouldn't be difficult, I lubed the splines with anti-seize compound, only a snap-ring holds the input shaft in the differential and in can be removed with taking the differential out og the cart.

JohnnieB

This isn't the input shaft for my cart, but the layout is the same. A bearing at both ends.
http://www.shopezgo.com/products/48-...-Gear-Kit.html

The motor shaft mates with splines at the left in the picture.
The hybrid bearing is the one on the motor side, the regular bearing is the one on the right side, which is smaller in diameter since it has to pass through the hole the larger one seats in.

You are correct, the bad bearing could be the one away from the motor side, it would have had the longest lever arm applying force to it while the motor was wiggling off.

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My problem isn't which bearing is bad, I'm replacing then both.

What is puzzling me is what was going on in the mind of the engineer that decided a hybrid bearing was needed for one end of the input shaft and not needed for the other end of the same shaft.

Personally, I would have used hybrid bearings on both ends of the shaft.

kellybell

Hmmmm. You know in the MG/MGB world, trading parts from other years is common. I wonder if EZGO imbibed in this kind of use-these-parts-up-before-we-open-the-new-ones?

kellybell

Are you sure the bearings in the axle aren't making the offending noise?

KLA

Hi JohnnyB,

It could be because the motor side bearing sees higher loads than the other side of the input shaft. Basically the engine torque creates a higher side load on on the bearing at the motor side because the intermediate shaft gear sits close to the side.
In addition that bearing has to support the rotor in the motor. So the torque fluctuations from the magnetic field switching also load that bearing.