6-18000 b6 switcher worm gear slipping

It has a plastic worm gear?

Yes, plastic /nylon gear on the axle,inside the gear box; the "worm" is also plastic/nylon.

Is the gear on the axle off axis for the worm?  is it sliding around on the shaft?

Yes, plastic /nylon gear on the axle,inside the gear box; the "worm" is also plastic/nylon.

Yes, it was off axis; so I pried it back on center; and it worked well for an instant; then it just worked its way back to one side. It actually worked well in forward only and lurched in reverse, then the motor just spun freely' and the gear was back to one side.

Do you eat bread?   I cut these in a circle for shims and then slip them on axles.  They work great for truck gears, as well as your issue.  Stack them to hold the gear in the correct position, problem solved.

Yes, plastic /nylon gear on the axle,inside the gear box; the "worm" is also plastic/nylon.

Ok; so I stack the bread clip spacers inside the gear box,on either side of the worm gear; great! I will try that!  I have read posts suggesting shiming with bread clips between the frame and wheel, but it did not occur to me that the same could be done inside the gearbox. Hopefully the gear will still be able to get a good grip on the sinstered axle and it is not too far worn. Oh wait... now I get it... I do shim between the wheel and frame with the bread clips...and that keeps everything in alignment...or do I shim inside the gear box?

If the gear is always moving to one side and isn't able to move to the other side, just do it on that side.  Obviously, if it wanders around all along the shaft, then you'll have to do both sides.  I just fixed a K-4 that had the exact same issue, a few bread closures, it's as good as new.  I'm talking about shimming inside the gearbox, because that's where the problem is.

If the gear can't get a grip on the axle, shimming isn't going to help, then it's time for replacement.

Thank you John. Can't wait to give it a try. First time I have posted with a problem, and a quick response and solution from the train repair guru himself. I am a big fan of all your informative posts.

jeffrey O'Brien 082418 posted:

Yes, plastic /nylon gear on the axle,inside the gear box; the "worm" is also plastic/nylon.

@jeffrey O'Brien 082418 I'm shocked at this.  I wanna see pictures! 

For those unfamiliar with the classic Lionel B6, the worm gear is on a lower layshaft driven by a spur gear train coming down from the motor.

I know that ONE of the spur gears is nylon, I think the pinion on the motor shaft, or perhaps an intermediate gear.  And i guess it's possible that the worm WHEEL on the center driving axle is nylon, although I would be surprised if this were true.  But if the worm wheel is nylon, the worm itself should not be.  Best accepted engineering practice is that the worm and worm wheel should be of dissimilar materials.  Then again, this wouldn't be the first time a manufacturer of 3-rail O gauge ignored best accepted engineering practices 

The original worm is multi-threaded and back-drivable (wheels can turn the motor.)  I know some folks were disappointed that these switchers did not run as smoothly  or slowly as expected.  Since you're not the first owner, is it possible that a previous owner changed the worm and worm wheel for a different combo, as described in this post, perhaps in attempt to get a lower gear ratio?  The factory gear ratio is 14.77 to 1.  Is that what yours is?

Maybe that's why these are going so cheap. I missed the above model (or one just like it) by one bid - but there are several right now in the $170 range.  I just assumed that they were bulletproof like the 1939 version, and the market was just saturated.

jeffrey O'Brien 082418 posted:

Thank you John. Can't wait to give it a try. First time I have posted with a problem, and a quick response and solution from the train repair guru himself. I am a big fan of all your informative posts.

Better save the accolades for when my suggestion works.

David Johnston posted:

I have two such 1989  6-18000 switchers my original which I bought new has hundreds of hours on it and the worm wheel shows no signs of wear. I did swap the pinion on the motor shaft and it's mate to raise the final drive ratio a bit and both pinion and spur are now brass I did that when the loco was nearly new.  The B6 I bought on eBay was heavly used and both nylon gears look fine.  Lionel did use nylon on some intermediate idle gears on a couple of locos that have cause problems. However as far as my B6s are concerned they seem to be doing fine.  I have a couple of General Models brass kits which I built back in the sixties and they have some sort of pressed fiber gears not too different from the Phenolic board used in electronic boards and they have been in use for over fifty years. 

   I think what drives the value of the 1989 B6 down is that both MTH and K-Line made B6s with modern electronics and if I am not mistaken Lionel has made their version of the K-Line B6 also. All that and it is a bit of work to cram TMCC into a B6 I've done two. Well I'm about 50% through the second one.  Photos show an LCRU2 just laid in the boiler to assess whether once the e-unit and smoke unit were removed there would be room for it and a fan driven smoke unit, there is. I built this one to try and get my original, which has all ERR boards, back from my brother. I still have to install the RS 2.5 board in the tender and add another 5 pin plug under the loco and make a 10 pin pigtail to mate with the plugs on the loco.   I may make a new tender floor out of aluminum and use it for the RailSounds heatsink which should save a bit of space inside but only if I have to.  I also added a coil coupler and pickup roller to the original trucks.   As heavy as the B6 is it has a lot of power that it cannot use and I plan to cast some lead weights to fit in a couple spaces in the boiler and make a pair of air tanks of lead  for under the cab.                              j

I would agree with what you said David, about the value of the 1989 B6's being driven down by the more recent releases.

I also have one of the 1989 releases and it is a good runner.

As with everything, caveat emptor/buyer beware.

I would suggest that anyone interested in the 1989 release look for descriptions saying that the locomotive actually runs or runs fine. There are enough of them listed on eBay to allow for weeding out the ones that might be risky purchases.

To the original poster, hope the shims work and nice work-around offered by GRJ.

Tom