on certain axle type of uk Mitsubishi fd25n axles (not rubber block type) I have had new Mitsubishis delivered with too many shims in the back axle pivot.over time they can creak loudly or even seize up causing the truck to stick in the leaned over position and not be able to rock on the back axle to accommodate camber or potholes. this could be the reason why one wheel is worn more as its been driving mainly on that wheel till it has worn down and now not able to gain traction thus spinning.

jack up the back end and see if the back axle pivots

yes uneven tire wear is not uncommon on lifttrucks
especially if the operators in the past had poor driving practices and did alot of directional changes without using the brake allowing the tires to spin. Being a limited slip differential usually one tire will spin and most of the time it will favor one side over the other. Is it possible that an odd tire was installed on the lift prior to you getting it? sure it is. Can this cause driving anomolies like you describe? i suppose it can to a degree. I've been on lifts with tires worn like this that drove fine but while driving the lift would bob back and forth due to the uneven tires... its a tell tell sign the lift has been driven abusively. So yes... put tires on the lift... both tires... never replace a single tire as it creates unlevel travel which will be translated into uneven forks....
It makes operating the lift difficult when entering pallets...

Well, it's possible that a whole inch difference in tire height might be what you are up against.
But, consider also that there may still be a frame geometry issue that is simply causing one drive wheel to bear more weight than the other one, and the tire bearing the least amount of weight will wear out faster than the opposite because it will be spinning or slipping most of the time (especially when the forks are unladen).

As I looked over the lift, noticed something that seemed odd and measured the wheels. One front tire is worn 1 inch shorter than the other. My guess is someone put a used tire on. I removed both front wheels, raised the front end without the tires on, and engaged the transmission in both forward and reverse gears. The hubs turned as they were supposed to both ways. I also inspected the hubs- and nothing seems out of the ordinary I am ordering a set of new tires , guessing that with one wheel worn away and not letting the lift sit on on the floor properly has something to do with this problem. Any thoughts on this? Thank you for your information.

Yes swoop, definitely time wasted. Only redeeming factors I can apply to the incidents are that it is a company fleet shop, so there was not a paying customer being abused by getting billed for the time Technically, our employer was being "billed", but considering how often management gleefully wastes resources themselves, it does not seem so vilifying.
The other redemption is that it really did provide some OJT about the principles of weight distribution and traction of a 4 wheeled lift truck. That lesson itself is priceless.

I know I have hijacked this thread from its original poster and I apologize for that, but I want to add one more off topic item here.
This is something that might be of help to any of us at some point in time. It will be a rare occasion that this might be needed but if it is ever needed, it might save the day.

Where I work, we utilize a "drive on" ramp/rack for most of our scheduled PM work. We have only one ramp/rack, so it is a sort of shop rule that we don't put a truck on that ramp/rack and disable it so that it can't be moved off again. Doing that will prevent anybody from using the ramp/rack for PM inspections and service.
An employee placed a truck on the rack and proceeded to remove a king pin and knuckle from one end of the steer axle.
This was a truck sent to us from a different terminal and was not one of our typical trucks, as such, we DID NOT have the needed parts in our stock, and the dealer did not have them either.
So, our rack was tied up and unavailable for other jobs until parts arrived (ETA 3 days).
To make this truck "moveable", I first lightened the truck by removing the counterweight and stowing it outside of the building. Then, I jacked up the damaged end of the axle high enough to cause the wheel on the opposite end to clear the rack. Next, I snaked a length of heavy chain around the frame of the truck above the axle on the damaged end (looping the chain below the radiator). finally, the chain went under the damaged axle end and hooked back onto itself, taking up as much slack in the chain as I could. Then I lowered the jack and the chain became taut, with the damaged end of axle suspended in the air, all the weight of the truck back end was resting on the good end and wheel.
The truck was now a driveable (but not useable) 3-wheeler.
The truck was driven off the rack like that and parked out of the way, and then I disabled the ignition to ensure no further attempts at using the truck could be made by anyone.
With the counterweight removed from the truck, the drive axle and mast weight dominated the frame geometry thus the drive axle was able to pull because the truck had no tendency to"tilt over" to the side that was missing a steer axle wheel.
This will not work unless the counterweight is removed.

L1ftmech...
no worries, nothing personal taken out of that... after i read your post i realized what you were saying :o)

anyway that sounds like some of the pranks we used to pull in the shop back in the day... heheh

today if someone did that in the shop the tech's might have a laugh about it but the management wouldn't like it much as it wasted time because of having to find the problem and if discovered it being a prank they would have had meetings for 3 months about shop safety and wasting time on the clock. lol
great story though ;o)

swoop, my dissertation was not aimed at you or anyone in particular.
It was aimed squarely at getting past the mindset that this is a drive axle issue. The spinning drive tire might only be a symptom while the real issue may very well be in the realm of frame geometry as the cause.
Absolutely nothing wrong with yanking the axle shafts out for an inspection, but I offer a few alternative tests, which require the truck to remain fully assembled to accomplish.
And you are right about "vague description", but that may be more from his unfamiliarity with fork lift terminology and mechanical testing than being intentionally sketchy.
Anyhow, I'm not trying to one up anybody. just trying to cover all the bases.

Let me share this tale of 2 incidents that happened in our shop some time ago involving 2 other mechanics.
You have probably heard of them previously. Their names are Mechanic A and Mechanic B.
Mechanic A had jacked up one side of the frame to replace a defective wheel bearing on the right side steer axle end.
In the course of his work, he uses a 1/2" thick piece of steel bar as a drift to hammer on the damaged inner bearing race which is stuck to the spindle.
After freeing the race, for some reason he lays the flat bar on the axle beam, right under the axle stop, and forgets about it.
After he assembles the new parts and lowers the truck to the ground, the truck will not move because the right drive tire is just barely touching the floor.
He puzzles over the problem and is just about ready to pull his hair out when he comes to me and wants some help.
I did not see him leave the bar on the axle but after I saw the wheel spin, I walked about 20 feet to the rear of the truck and told him to come look.
The truck looked like it was leaning to the left.
I told him something was not right about that and wondered if he had somehow gotten the wheel crooked or I don't know what.
I told him to jack it back up and let's have a look.
He jacked it up and when I looked it over, I spotted the flat bar.
I pointed to it and said "what is that for?".
He said "my bearing knocker".
He pulled it out and everything returned to normal.
So, Mechanic A is impressed with his new found knowledge and one day he catches Mechanic B with a jack under the left side of a truck while he is working on some brake issue.
Mechanic B is away in the parts room. Mechanic A gets his bearing knocker and places it on top of the steer axle under the axle stop and walks away covertly.
Mechanic B puts the truck back together and lets it down.
Yep, left drive wheel spins itself silly.
Mechanic B actually locates the sabotage pretty quick and while Mechanic A is laughing his head off. Mechanic B takes the bearing knocker and pitches it into the dark depths of our scrap metal bin behind the shop.

It could be that the thingamabob in the whathamacallit is discombobulated! LOL

gee L1ftmech, his vague description of the problem only led us to throw out possible scenarios... but you're right, if an axle was broken the lift would not move at all... (maybe) i've seen some axles broken but still allow the truck to move, it just didn't drive right but was usually accompanied with some bad grinding or knocking sounds when the axle slipped.

Anyhow....
with the broken axle scenario aside....
i think he should still pull it apart and see whats going on in there. Maybe even drain the differential fluid and see if metal is in it, could be a spider gear problem in the carrier assy. Ya never know buddy ;o)

Anyway the part about checking the transmission fluid?
There should be a dipstick in the top of the case just to the right hand side on the top cover.... as far as i know that is the only place to check the fluid level. The recommended types of transmission fluid they say to use are:
Esso Automatic Transmission Fluid, Mobil ATF210, ATF220, or Shell ATF Dextron. Generally Dextron III will work fine.

But without a truck serial number its all just a GUESS as to what we are dealing with!

A "broken axle shaft" will not result in one wheel turning.
A broken axle shaft will result in NO WHEELS turning because a conventional differential requires that there be traction on both axle shaft ends to operate and provide movement.
A broken axle shaft will cause all motion to be concentrated to the output side of the differential where the broken (or missing) axle shaft is located. Or, a similar scenario can be created simply by removing either axle shaft from the truck. When you do that, the truck will not move under its own power because all the differential parts are free to turn uselessly inside of themselves.

The more important aspects of trying to determine why this truck only wants to spin one wheel can be tested in this manner.


And beware that you are doing tests where the vehicle might suddenly attain traction and thus move or jump off of a jack or a wooden block, so keep everyone clear from standing in front of or behind the truck.

With wheels off the ground, can you easily rotate both wheels by hand? If so, when you rotate one wheel clockwise, does the opposite wheel want to turn counter clockwise? If so, it is unlikely that a dragging brake is part of the problem. And the CW vs. CCW rotation confirms that differential is sound.

If you jack one wheel off the ground (with the opposite wheel still firmly on the ground) and engage drive, does that wheel rotate easily, or does the engine sound like it is under some load?
Next, if you move the jack to the opposite wheel and repeat the test, does that wheel spin easily, or does it require a lot of accelerator pedal to spin it?
If either wheel requires a lot of accelerator pedal to incite rotation, there may be a problem with the brakes dragging on that wheel.

If, when you jack either drive wheel clear of the ground (with the opposite wheel still on the ground) the wheels spin easily.........the problem is not in the drive axle at all.
If this turns out to be the case, then there is a problem in the frame geometry of the truck, which is causing one of the drive wheels to be "unloaded" when the truck is on level ground.
The reason for this is that the steer axle is mounted to the frame with a flexible/pivoting "trunnion" at the center of the steer axle beam. This allows the truck frame to adjust its angle slightly as ground/pavement/surface conditions and elevations change in order to keep the left and right drive wheels BOTH pressed evenly against the traction surface.
Problems of this nature are worse when the truck has solid rubber tires. Pneumatic tires are more adaptable to uneven traction surfaces. But, on really poor or rough surfaces, just having one of the pneumatic steer tires under-inflated can cause some traction problems too.

I have seen a truck (not Clark brand) where a steer axle king pin bearing failed and ate up the steering knuckle and axle end allowing the left side of the axle to settle much closer to the ground than the opposite side of the steer axle.
The result was that the entire frame of the truck got light on the right hand side.
That truck would spin its right drive tire at the slightest provocation..........until you picked up some weight with the forks.

So, you are going to have to do some careful testing and inspecting, maybe at both ends of the truck to find out why it spins one wheel.

If you have not tried lifting something (heavy) to weight the drive axle (increase traction), you may want to do that too.
If you load the drive axle and traction increases, that pretty much points to a frame geometry issue as the cause.

agreed....
like edward said, sounds to me like a possible broken axle shaft or maybe some brake hardware issue, maybe.

The quickest way to check the axles is to just pull them out and see if one is broken or damaged in any way. It doesnt require any special tools to do... jack the wheels off the floor and block the truck up, remove the bolts around the axle flange on the hub... smack the flange with a hammer to get it to break loose... then pull the axle out. (in most cases this works) (in rare cases you may have to use a snatching tool to get the axle out if the flange is not made onto the axle shaft)

Once you do that and verify the axles, you've gone this far you may as well go ahead and pull the hubs too and check the brakes and hardware.

it is normal for any 'standard' (not limited slip) differential to turn/power which ever wheel turns easiest, so it is not abnormal to only have 1 wheel turn while in the air. what happens if you jamb a board under the 1 wheel that turns easiest? the other wheel should start turning. if it does not, then you have something wrong with that wheel, my instant wag would be that one of the brake shoes or related hardware in the wheel brakes has become defective and will need to be replaced. pull off the drum and inspect the wheel brakes and park brake cables for proper operation.
Can you describe for us a little more what you mean by "not engage the right way"? you may have a broken axle shaft.
in any case, I would want to visually inspect the brakes on any older lift I put into service and did not know any history about, and pulling both brake drums off and doing an inspection to be sure the truck was going to be safe to use will give you the information about the brakes and axles you will need.