Need Help with Atlas HO Scale U36B Running With Growl

[davefoxx]

All,

As such is my life, the one locomotive that I have waited on for years (Seaboard Coast Line U36B No. 1776 in the bicentennial scheme) arrived last night.  It's beautiful, and the DCC and sound (ESU LokSound) work great.  But, it growls when running in the forward direction- loud enough that I noticed it over the locomotive's sound even before I turned down the volume.

Please note that I have sent already sent two locomotives back to the manufacturers this calendar year, and both corrected the respective problem.  I sent an N scale GP40 to Atlas, and it took exactly the promised twelve weeks to receive the repaired model.  I recently sent an HO scale GP40-2 to Athearn, and they took one month.  However, while both did make the necessary repairs with my only cost being shipping back to the manufacturer, I would prefer this time to fix it myself (if I can), because I don't want to risk damage of this limited production model in shipping and I don't want to wait twelve weeks to get this locomotive running.

The issue and my findings: As stated, the locomotive growls when moving in the forward direction.  It is quiet in reverse (never fails for a locomotive that should always be the leader, right?)  The growl is definitely in the driveline, because you can hear the rotational growling (if that makes sense).  I removed the shell and noticed that there seems to be excessive play in the worm over the rear truck, as if it needs more thrust washers.  I took the top of the truck's tower apart, and there are thrust washers in there and it is sufficiently lubed.  My guess is that it could use more thrust washers.  There is definitely more play in the rear truck than there is in the front truck, and, when I slowly reverse direction, I can see the rear driveline shift longitudinally by 1/32" or 1/16".  Am I right that thrust washers will correct this growling?  I guess what doesn't make sense to me is that any excessive play would growl, because, although the worm shifts longitudinally, by spinning, it should still be able to line up with the trucks gears.  Right?  I don't know. 

Thanks in advance for any help,
DFF

[k27463]

Dave -- if you pull the driveshaft/bearings out of the rear truck (I forget if the U36Bs use slip joints or hex driveshafts) and remove it, does it groan with just the front truck turning?

That's usually my test to see if there's a truck problem or something else.

[davefoxx]

Dave -- if you pull the driveshaft/bearings out of the rear truck (I forget if the U36Bs use slip joints or hex driveshafts) and remove it, does it groan with just the front truck turning?

That's usually my test to see if there's a truck problem or something else.

Aha!  Great idea.  I will try that tonight, but, if I were a betting man, I would wager that the sound disappears when the rear truck is dewormed.  This will also comfirm whether there's any problem in the bearings of the motor (but I don't think so).

Oh, and the U36B uses slip-jointed driveshafts

DFF

[wazzou]

Have you tried the Bearden method...oh wait you're in HO, nevermind.   

[davefoxx]

Have you tried the Bearden method...oh wait you're in HO, nevermind.   

DFF

[Atlas Paul]

You may also want to give a call to Don Fidecaro in our service department, he may be able to give you some tips as to what to look for.

[davefoxx]

You may also want to give a call to Don Fidecaro in our service department, he may be able to give you some tips as to what to look for.

Thanks, Paul!

DFF

[tom mann]

I once "fixed" an Atlas HH660 in the weirdest possible way.  Like yours, it ran horribly and made a grinding sound.  One night, I cleaned the track with a little bit of oil, and once the Alco hit the spot that had a little bit of oil on the rail, it almost instantly ran smoothly and quietly. 

[davefoxx]

I once "fixed" an Atlas HH660 in the weirdest possible way.  Like yours, it ran horribly and made a grinding sound.  One night, I cleaned the track with a little bit of oil, and once the Alco hit the spot that had a little bit of oil on the rail, it almost instantly ran smoothly and quietly.

This is why I never say, "I've heard it all."  Wish I could fix mine that way.  I'm off to the basement to try to get that worm out and see if that isolates the growl.

DFF

[davefoxx]

Dave -- if you pull the driveshaft/bearings out of the rear truck (I forget if the U36Bs use slip joints or hex driveshafts) and remove it, does it groan with just the front truck turning?

That's usually my test to see if there's a truck problem or something else.

@k27463,

That did it.  I pulled the rear worm and driveshaft out, and the locomotive is silky smooth.  In both directions.  So, as I surmised, it's not the motor, dry bearings, or the trucks.  So, do you think thrust washers will fix it?  I'll put a call into Atlas when I can find the time at work over the next few days, as suggested by @Atlas Paul.

Thanks, guys!
DFF

[k27463]

Thrust washers can't hurt.  And it's easy to revert if it doesn't fix it.

Other option would be to pull the other driveshaft and try it in that truck to see if it's the driveshaft/worm or the truck that's not correct.

I've only really done this with Athearns, as I've never actually had an Atlas that had any mechanical issues 

[Lemosteam]

DFF

Oh dear gawd.  I just fell out of my chair-  I use that line all the time when people try to be sarcastic with me.   

[davefoxx]

Other option would be to pull the other driveshaft and try it in that truck to see if it's the driveshaft/worm or the truck that's not correct.

@k27463,

I swapped the worms from end to the other, and, sure enough, the growling moved to the other end of the locomotive.  On a positive note, I can now run the locomotive in the forward direction without the growl.  Reverse, not so much. 

DFF

[Lemosteam]

Is there end or side play in the bearing blocks on that worm?

[peteski]

@k27463,

I swapped the worms from end to the other, and, sure enough, the growling moved to the other end of the locomotive.  On a positive note, I can now run the locomotive in the forward direction without the growl.  Reverse, not so much. 

DFF

So now that you've pinpointed the specific component, and you also have another like it which works correctly , compare them to see if you can see any differences between them.  They are simple devices - you should be able to discover if there are even minute difference between them.