PS2 Diesel motor/driveline noise

first of all are you sure you did n have the motor aligned correctly  and all screws tight on mounting, and did you do a through cleaning of the gears, sometimes you can get small gravel or rocks etc from you track that you may have added details and some of the gets caught up in the gears, have seen sometimes  the gears don't mesh correctly due to there being worn?

Alan

After you reassembled did you see if it made the same noise in reverse as well.

I did not totally disassemble the truck. I just pulled the motor out and checked for smooth running of the gears. I didn’t think of it being worn, because according to the Odometer it’s only got 27 miles on it, now I know the odometer and chrono are estimates at best. This engine just has not got that much use on it. Now that doesn’t mean some foreign material did not get in there or there is a bad gear. I thought I had read somewhere on the forum that MTH might have had a spacing problem that was corrected by shimming. I could not find any such article anywhere. Starting to think I dreamed it. 

It also does it in reverse. It only does it at slow to slow/medium speed. 

I don't remember any specific mention of a problem with MTH diesels.  YES it is possible that the worm is pressed on too far, or not far enough.  And it's also possible that you could get lucky and correct it with shimming.  You could also make it worse.

Inspect the spur gears on the wheels, and the intermediate gears along the side of the truck to make sure they aren't split, and there's no ballast or foreign debris in there.  

If they all look good and the noise really bothers you, then I would get a new exact replacement motor from MTH.  Swap it in and see if the problem goes away.  If it's still there, then get a new exact replacement truck block from MTH.  If you change the head and the handle, it isn't your grandfather's axe any more.

Swap the truck blocks. If the noise follows the truck block it's a truck issue. If it stays on the same side it's a motor issue. 

a1hobo posted:

... I thought I had read somewhere on the forum that MTH might have had a spacing problem that was corrected by shimming. I could not find any such article anywhere. Starting to think I dreamed it. 

I don't think you're dreaming.  There was an issue 5-10 years ago where some MTH diesels exhibited jerky slow speed (less than 5 sMPH) operation.  If I recall correctly, the "solution" was a thumbnail sized thin piece of cardboard (or whatever) shim placed between the motor and the truck such that the motor does not mount exactly straight up and down but instead "leans" ever-so-slightly forward or backward (think Leaning Tower of Pisa).  However, I don't recall there being a clunking noise issue so may be something altogether different.

I believe I am nailing it down to the mating of the worm gear with the truck. There seems to be movement up and down of the motor shaft. It’s not what I’d call excessive. For right now it may be something I just might have to live with for a bit. 

Maybe it just needs run, like really fast, you know to loosen things up a bit ??

Sometimes the noise can be corrected by shimming between the motor and motor mount on one side so the worm leans into or away from the worm driven gear.  It's a trial and error proceedure.  The shim is very thin; I start with mica insulation used to isolate voltage regulators.  If that doesn't solve it, you may need a new motor. Sometimes the worm is not cut correctly and replacement is necessary.

beer cans can be easily cut to provide the shim material

Just for the sake of curiosity, I experimented with how snug I tighten the motor down. It did change the noise sounds, but still there. So I believe we are on the right path to the noise coming from the mating of the worm gear and truck. Next up is the shimming idea. 

I had to shim a couple to get proper operation, it's been a few years and I don't remember the exact models, but it's a real thing.

John do you remember was it a equal shim all the way around the motor or just lean the worm into or away from the truck gear? 

It was not a shim all the way around, in both cases I needed to cant the worm slightly to correct the engagement.  I believe both times it was too tight and I had to tilt it away slightly to relive the binding.  I used very thin brass stock, it didn't take much movement to fix the issue.

Thanks, I was leaning toward the thought of too tight. The reason being, when I let up on how tight I tighten the motor screw down the noise would let up some.