Transmission marks ?

[karterphil]

So i've just inspected my transmission as i started to rebuild the motor and i have found an issue. The teeth on one of the sliding drive gears have odd marks which almost looks like they haven't been engaging properly as the marks are on most of the teeth on the gear. Also there are the same sort of marks on the tips of other gears which i think may be down to violent, clutch less shifting. Both types of marks are visible in the pics.

Im pretty sure i will need to replace this gear and therefore the c-clips that hold the gears on.

looking for some advice on what may have caused these marks?

Also, The gear that engages with this one has none of the marks mentioned and looks to be in good condition.

 

[007blaster]

Looks like some piece of metal or something got trapped on that gear and started chewing it up. Is every tooth on that gear like that?

 

[karterphil]

Looks like some piece of metal or something got trapped on that gear and started chewing it up. Is every tooth on that gear like that?

Almost every one yes, but that one in the pic is by far the worst one, the rest just have some small marks.

 

[karterphil]

I have just bought a new 3rd pinion gear (the marked one) from good old ebay uk for £15.99 ($26) so im pretty pleased with that, now to find the cir-clips i need. phhhh

 

[joeak47]

Also there are the same sort of marks on the tips of other gears which i think may be down to violent, clutch less shifting.

Why would you shift without using the clutch??? I always use the clutch when changing gears. Or...did you purchase it this way?

 

[karterphil]

I bought it this way, i always use the clutch, i have reason to suspect that it may have been mildly abused in its previous life due to newbies riding it

 

[davenichole]

yeah that looks rough. too bad you do not live close. i've got about 4 transmissions just laying around.

 

[karterphil]

yeah that looks rough. too bad you do not live close. i've got about 4 transmissions just laying around.

Yea, i do hate living here sometimes.

 

[Blaaster]

I could be barking up the wrong tree, these signs are familiar to me.

I have seen this many times, and is caused by placing the ground electrode of an electric welder in the wrong place when welding.

If the ground is placed in a position where it has a poor current path to the point of weld, the current will find the path of least resistance and arc over which in this case fusing a gear cluster.

The marks on the other gears are from wear transfer.

If indeed this is caused by arcing, I would suspect damage to bearings as well, it would pay to remove the bearings ad inspect them.

 

[karterphil]

I could be barking up the wrong tree, these signs are familiar to me.

I have seen this many times, and is caused by placing the ground electrode of an electric welder in the wrong place when welding.

If the ground is placed in a position where it has a poor current path to the point of weld, the current will find the path of least resistance and arc over which in this case fusing a gear cluster.

The marks on the other gears are from wear transfer.

If indeed this is caused by arcing, I would suspect damage to bearings as well, it would pay to remove the bearings ad inspect them.

That is quite a thought blaaster !
I will inspect the gear clusters closer for any other signs of arcing

I will be replacing all bearings in the motor with this rebuild just for peace of mind

 

[Blaaster]

The old brain just kicked in again and there was another time that I have seen similar marks on a tooth face.

The vehicle had been trailered a long distance with the tranny in gear.

The continuious backward and forward movement with the gears engaged chafed the teeth.

There was no lubrication present as the box was not turning so no oil was being picked up.

Needless to say I never ever transport any vehicle unless it is in neutral.

I am liking this thread as lessons may be learnt. Never weld unless the ground electrode is at the piont of weld. Never leave a vehicle in gear, especially a Diesel (but that is another story).

 

[karterphil]

The old brain just kicked in again and there was another time that I have seen similar marks on a tooth face.

The vehicle had been trailered a long distance with the tranny in gear.

The continuious backward and forward movement with the gears engaged chafed the teeth.

There was no lubrication present as the box was not turning so no oil was being picked up.

Needless to say I never ever transport any vehicle unless it is in neutral.

I am liking this thread as lessons may be learnt. Never weld unless the ground electrode is at the piont of weld. Never leave a vehicle in gear, especially a Diesel (but that is another story).

That is definitely a possibility or at least something along those lines. I:I

The quad served a lot of its life on a friends farm with some of his friends (quad newbies) riding it about and towing stuff like sledges with it, so i think the tranny may be where all this farm "work" is showing in the form of wear.

 

[Blaaster]

Are there any signs of water in the box, gears left meshed for a period of time in the presence of water can also exhibit the same marks, due to oxidation.

 

[karterphil]

Are there any signs of water in the box, gears left meshed for a period of time in the presence of water can also exhibit the same marks, due to oxidation.

when i stripped it a couple of months ago, the oil was dirty black but i didnt see any water

 

[karterphil]

Upon further inspection, im pretty sure that this was down to some kind of metal crap in the oil, but the question is where did it come from ?

 

[Blaaster]

Residue plucked from the gears when they rotated after welding.

 

[Larry's Shee]

Wouldn't the gear it meshes with have simular damage if from welding? Almost looks like a defective gear to me.

As to shifting damage, it shows up on the dogs of the gears as the teeth are always engaged.

 

[Blaaster]

Wouldn't the gear it meshes with have simular damage if from welding? Almost looks like a defective gear to me.

As to shifting damage, it shows up on the dogs of the gears as the teeth are always engaged.

Agreed there should another gear with a mirror image of the damage if it was caused by any of the ways mentioned.

Is there a meshing gear with similar markings?

 

[best]

Your gear:

What you are seeing is the case hardening flaking off, often called spalling.
Usually it is from too much load, and would usually also show on the mating gear.
Here is a classic example:

These gears are made of a high quality allow steel intended and heat treated to be tough.
In the heat treatment process the gear is subjected to additional carbon that will harden a very thin skin on the surface of the gear.
This is "case hardening", tough core to resist breakage, hard skin to resist wear.
These pictures show where the hardening is in a cut section:

Since this is limited to a single gear and not its mate, I'd suspect it is a manufacturing defect.
I'd suspect that the failure in this link is similar to your gear:

http://products.asminternational.org/fach/data/fullDisplay.do?database=faco&record=1748&trim=false

This link describes how it likely happened:

Diagnostic Tool Helps Develop Profile for Induction Hardening Process - Gear Solutions Magazine

Good job to find it and replace it, especially because you are going to be increasing the power and the load on those gear teeth.

You might find these pages interesting too:

GEAR FAILURES
ScienceDirect.com - Wear - Gear tooth contact analysis and its application in the reduction of fatigue wear

Steve

 

[Blaaster]

I at first glance though it could have been a defect or spalling, but the circled defect looked like a raised portion had been plucked from a mating gear due to fusion.

That is why I immediatly thought of welding malpractice, I have witnessed it so often.