AF Big Boy Problems and Solutions
A collection of QC and Operating Issues and Solutions

I am compiling these issues from personal experience and also from contributions from other owners.

Please email me at with your experiences and how they were resolved and I will add them for others to research. Include as much detail as possible!

 Does it happen in Command mode, Conventional Mode. Forward, reverse, type of track and switches used.  Were you able to repair it yourself and how. Photos can be added too.

Problem Solution
From Carl T
Found  the power pickup terminal connection on the pilot truck loose. Causing no problems but needed retightening.
Tightened terminal screw
From Carl T
Reduced the intensity of the marker lights in the tender to a more realistic level
Added a 10K resistor in the marker light connection.
From Jim E
The problem is that I do not have reverse. It acts like it is "locked" in "forward". The manual says the "program/run" switch can be used to lock in one direction by moving it to "program" , but I have it set in the "run" position.


This seems to have resolved itself, and
I have no idea why. I am using a late (circa 2004) Lionel CW-80 transformer that has the whistle/horn/directions buttons and should be compatible electronically. I also noticed today the directional light on the tender is working today, indicating that it is in reverse.
That did not work last night, either.
From Jim E
I found out what the little nut driver is for. Saw a screw lying by my track after shutting down the BB. After a close inspection, I was missing two side rod screws on the right side. Luckily, I found the other one as well. The little nut driver fits the side rods. I also found one loose side rod screw on the left side.
Re-installed screws.




From Lou T
I was having trouble with the BB tender going through Tom's turnouts and also riding up the rails on curves when going in reverse. I'm using SHS flex track with a minimum radius of 24" on one curve only.



The problem of going through the turnouts was to re-gauge the tender wheels using a 23/32" piece of plywood between the wheels as a gauge.

To solve the backing problem, I moved the flanged wheelsets in one space on both ends of  the stationary truck and put the blind wheelsets on each end. This shortened
the wheelbase on the stationary truck thus making it eaiser for the stationary
truck to negotiate the curves in reverse.
From Joe P
The tender coupler keeps riding high to the point that no matter how many cars I have behind it they come uncoupled. The couplers are not opening, just the coupler on the tender ends up higher than the coupler on the cars. When
coupling, the top of couplers are flush and then at startup the tender coupler jumps 1/2 to 3/4 of the coupler up.

I also discovered the spring for the front hook that holds the wireless tether wasn’t installed correctly . All this caused was the hook to sit high and into the body when not hooked up to the engine.
I compared the problem tender to the non-problem tender and discovered that the
coupler mounting bracket was bent and the screws that mount it to the fixed truck were not tight (allowed the bracket to swivel left to right also).

Fixed this also


From Scott G
Big Boy stopped smoking a few days ago and I think the heating element may have burned out. I've tried the restart procedure several times to no avail.






Called Lionel tech support concerning the smoke unit in my Big Boy. The gentleman I spoke to was very helpful. He said that it sounded like the element had burned out and that it was possible that the voltage regulator
circuit (located on a separate board somewhere else in the locomotive) had failed, causing much higher voltage to be passed to the heating element than intended. He recommended measuring the voltage across the heating element terminals with the engine running to see if it was too high (correct range is 4-5V). He also is shipping me a replacement element, but unfortunately, the 6 ohm replacement is out of stock so he is sending an 8 ohm version.
From Ken O
Noticing that there was some sparking action going on in the curves at the rear axle of the tender. If the train is going slow enough, the "shorting" can get severe enough to short out the transformer. When I look at the tender wheels at the rear axle, I notice the residue on the inside of the wheel from the "shorting".
Found the screws that hold the coupler mount to the  truck frame were loose causing the coupler to droop and short.



From Don
The "locked in neutral" does seem to be what's happening. I tried changing the Program / Run switch and the Odyssey on-off in all combinations but to no avail.
The DCDS-J board driver board has a black connector in the middle that needed to be reseated. Seems to fix the problem.


Jim K
My front drive mechanism has developed problems after about two hours of running. It appears the worm gear has slipped on the motor shaft. I removed the loco body and the cover plate on the driver chassis to observe the
mechanism in action.. It must be keyed in someway because you can turn the motor flywheel weight by hand and the motor shaft rides up slightly and then the worm gear shifts back about a 1/20 of a rotation and the spur gear does not rotate. It makes a rattling sound when it attempts to move under its own
track power. The front drivers appear to be totally dis-engaged from the motor while on the track. They rotate freely but only if pushed by the rear drivers. OK in reverse
Sent to Lionel,









From Harold H
Ran in conventional mode for about 15 min,all seemed fine. Moved Legacy control from main layout to xmas layout to run bigboy. Ran fine in cab one, then hooked up 3 flyer passenger cars (660 series) Ran until engine stopped with rear drivers spinning and front ones locked up. Reversed engine it moved a few inches and it locked up again(front drivers). I noticed it ran fine if I lifted the front of the engine so the drivers were off the track. Also found screw on track. It came from under cab. Replaced screw..
Repacked engine and sent it back to Lionel for repair.






From Bob B
Issues going through combined switches and tight radii curves.
Swapping the last two axles of the tender makes going through combined switches and tight radii curves way easier/better.
From David H.
Gaining experience with mine and those of two friends in the club this past weekend. Have mine up on rollers with boiler shell off to check if all plugs are seated properly and if I have a whistle vs smoke problem or not (i.e. using the whistle
decreases smoke output). Similar notes on the t-truck wires, lack of wheel contact on rails, and "retarded" front driver set as compared to

 Here are some of my observations:
T-truck wires: poorly routed, and stiff wiring. Mine swept out and back under the fireman and in contact with the t-truck wheels.

T-truck rear wheels off the rails: Two have had this including mine.  Then carefully bent the hook so it slips into the slot, but there's no pressure between the two tow bar sections at that point - just a nice full level insertion. Otherwise if the hook is too low and put into the slot it lifts the back of the t-truck and you have a teter-totter effect resulting in rear t-truck wheels off the rails.

Front power truck - - mine would lag behind the rear when on the rollers and run at slow speeds, and even momentarily stall, then get going again
while the rear was just purring along the whole time. I found they are particularly sensitive to linkage alignments and looseness, especially
that of the secondary piston rod and its links and pivots.







to sweep out under the engineer without wheel rubbing. Should have at least used super-flexi wires. Won't stay up inside cab. Curious to
hear how hot glue measure works.

I very slightly bored out one of the clear plastic washers at the front of the t-truck which otherwise failed to float up and down on its post restricting upward travel particularly (tipping the truck down in the front, up in the rear). Made sure the shape of the sheet metal bar provides level pressure to the truck pivot point, and that the tongue from the tender (with the slot in it) was straight out from under the
tender (mine was bent down some). Then deburred the edges of the hook (so there's smooth easy travel within the slot). Mine now sets fine on the tracks with  full four wheel contact.

Check that all linkages fhave free motion and lube pivots lightly with 108. But especially that secondary piston and everything associated with it. Hand turn the flywheel slowly and check with each small advance that all push rods are aligned straight and linkages have slack (almost a wobble) to them. If any feel tight (not necessarily locked, just restricted or stiff instead of free) ease them up. Mine now keeps pace and moves
smoothly with the rear.

From Jim E.
I noticed on my BB that both the trailing truck of the loco and front truck of the tender were not resting on all four wheels of either truck. It was due to two things, the first being that the "hook" from the loco has to be pushed all the way down into the slot of the tender, otherwise it binds and holds the tender up a little, making it "tipsy". Also, the wires from the trailing truck were fished through the spring area of the truck. I think.
 Once I made sure the wires were above the truck and helping push it down, the truck "seated" itself better on the track. This also helped with some power interruptions i was having. I'm very concerned about trying to bend/straighten any of that link because of the wireless tether.

From Steve B.
I was also dismayed by the wires going up into the cab from the trailing truck. No matter how many times I pushed them back up they just kept working down and caused interference with the movement of the truck. Maybe the restriction of movement of the trailing  truck kept the lead truck of the tender from moving properly. It shouldn't be so since the draw bar is free moving, but who knows. I think I will push
the trailing truck wires up into the hole and apply some hot glue to keep them there when I get it back. That very well may have been the culprit in my derailment.
From Carl T.
Noticed a sparking on the loco between the right front valve hanger and the boiler occasionally in curves.  The boiler measured a short  to the left track pickup. It is supposed to be isolated.
Found the short in the smoke unit. the element was touching the smoke unit case.

Moved the position of the element to fix. 

Carl T.
The loco was only doing 3 chuffs per revolution instead of 4
Adjusted the chuff micro switch by slightly bending the micro switch arm in a downward direction.