Motor Turn - But not enough torque to move

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This has got to be a strange failure mode.

I was riding my 2000 TXT electric cart down the road normally. I applied the brakes in a moderate to heavy stop. When I went to start again the cart would not move.

Batteries were low on charge at the time so I started by recharging the batteries over night. The next day - still no movement.

I then jacked the rear end up I found that the wheels would move when pressing on the accelerator. However, if I held the wheel with my hand I could prevent it from spinning. Even when holding the stopped wheel I could still hear what sounded like mechanical motion within the transaxle.

Batteries may be close to end of life. I measue a no load voltage of 37.4 and a load voltage (with the rear end jacked up and the accelerator pedal pushed down) of 30.0.

Because of the timing of the failure, I tend to think I have a mechanical problem - maybe partially striped gearing in the transaxle, but part of me thinks an electrical problem might be the root cause and the timing of the failure was coincidental.

Any thoughts or direction?

 

[dougmcp]

Check the brake hub spline to axle connection, it is likely stripped.

 

[[email protected]]

dougmcp,

I appreciate the suggest.

I pulled the brake hub and the axle spline gear looks fine. I also removed the transaxle gear box cover and inspected the entire drive train. All of the gears look good.

There must be a clutch mechanism between the motor and the drive chain that is slipping. I can't think of any other explanation.

Any other suggestions?

psites

 

[HotRodCarts]

If the splines in both hubs are good it could be the motor coupler. You would need to pull the motor to check that.

 

[Andy4639]

You need to look at the Hub while it's on the cart. With the cart jacked up and wheel off have some one press the gas and see if the nut spins and the hub doesn't. If so then you have bad hub. if it doesn't either the input shaft or the coupler is bad.
You will have to pull the motor to check both of them. if you could hold the wheel and herd the rear end still moving it's got to be one of the three.
Coupler is on end of motor when you take it out.
Input is after the motor is off it's the gear that the coupler mates to.

 

[[email protected]]

Nuckem' Race Team,

The axle spline gears look in good shape so I am following up on the motor coupling and the input shaft. It is not obvious how to remove the motor from the transaxle. Can you give me any direction on what is involved in doing this? I have removed three bolts from the transaxle casing that attach to the motor. I have also removed the wiring to the motor windings.

The entire motor will now rotate freely about its main shaft, but it will not pull away from the transaxle. Is there a trick to disengaging the motor from the drive gears?

Also, can you give me any direction of what to look for indicating a bad motor coupler or input shaft. Particularly the motor coupler - what does it look like and how does it work? Is there any on-line documentation on this area of the golf cart?

Pete

 

[Andy4639]

If you have the motor rotating freely then take a rubber malet and bump it around the edge while holding the weight of the motor it should come off with a couple of taps. NOTE make sure you hold the weight of the motor through this process.

Coupling: This is made to the end of the motor shaft when it comes off.

Input shaft: This is the gear the coupling attaches to when you make the motor back up to the rear end. It takes a pair of snap ring pliers to take the ring out of the casing then just pull the input shaft out. You will need to know which one you have in order to get the right one there are two of them. Count the teeth to know.

 

[MikesMotorToys]

You checked both rear brake hubs / splines?

 

[HotRodCarts]

Thats normal on an open rear end. Did the other tire spin when you held the tire? Like MMT said make sure you check both hub splines.

 

[Andy4639]

If he did it right and held the wheel and watched the nut, to see if it turned on both sides then it's got to be one of the other two. If the nut did in fact turn it's the hubs. I can't say for certain what he has but I feel he has done it the way it should have been done.

 

[MikesMotorToys]

I see - I've never had an EZGO motor coupler go bad in all my years in the business. But I have seen plenty of mis-judged drums, though...

 

[Andy4639]

I have never had a coupler go bad either, but I have had to replace a input shaft on my 89 Ezgo. I would think the only way a coupler could be bad is it was ran loose at some point but then you have other problems!!!

 

[[email protected]]

I am reasonably sure that I have checked the spline gears correctly and eliminated them as the failed parts. One other symptom that I think enforces the motor coupler or input shaft as the problem is that when I put the cart back on the ground and press on the accelerator pedal - the transaxle gears do not move. I can physically look at the gears since the transaxle cover box is off. The transaxle gears "cog" slightly (rotate maybe a degree or two and return to their original position). The net effect is no rotation of the transaxle gears. During this test I can hear motion in the motor.

I am going to attempt to pull the motor sometime this afternoon. I will let you know what I find.

Thanks for the help.

Pete

 

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********************************
* Final update on this problem
*
********************************

It turns out that the search for a mechanical problem was a wild goose chase. Two symptoms lead me down the mechanical path that turned out to be false:

1. The failure was instantaneous (making me think it had to be mechanical)
2. There was a sound in the drive train that seemed to sound like rotational motion (which I interpreted as slippage somewhere in the drive chain).


After confirming that the spline gears on the axles were good, that the planetary gears in the transaxle were good, that the input shaft was good, and that the motor coupler were good I was left with a big question mark - but from this I was sure that the problem was not mechanical.

I poked around the forum some more and found a post that had semi-similar symptoms. That post was by "gatordp" titled "Cart only moves at lowest speeds", dated February 18th.

The solution to gatordp's problem was a failed battery. I followed up on this lead and found that I had a battery that went to 0 volts under load.

Evidently, I must have had a plate or other structure in the battery that instantaneously failed.

One thing that I did learn from this process that would have easily isolated the problem is that there is a view port on the back side of the motor that lets you look at the state of the motor shaft. The view port has a plastic cover that is easily removable. If I would have looked at this view port first I would have seen that the motor shaft was only shuttering when I tried to accelerate, but was not actually turning. This in turn would have isolated the problem to something pre-motor.

I attempted to show a picture of the port . . . but it doesn't look like this post arrangement accepts picture attachments.

 

[dougmcp]

Thanks for following up and reporting the fix.
Normally, the batteries and connections are the first thing to check but based on the original post the batteries were charged and the motor spun.
Holding the wheel and still having the motor turning suggests brake hub problems.
Glad you go it fixed.