This applies to all Big Haulers with the latest Bachmann drive system.  These units are identified by the small offset bump in the bottom cover directly over the rear drive axle and the plug directly to the rear of this offset bump. In general, these are referred to as Generation 5 & 6 Big Haulers [Gen 6 being the 10 th Anniversary Big Haulers.  The new and highly detailed Big Haulers originally did not come with any operating instructions so click here to get on online version. The later versions were repackaged.

In running some of the 4-6-0's, it has been noted that there is some excessive wheel wobble that can occur. In looking at Fgure 1 below, not the direction of the wobble that has ill effects on smooht running. 
When looking at the wheels It is normal to have some driver wheel rotational looseness on the #1 &  #3 axles. This generally does not have an adverse effect on performance.




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Big Hauler Wheel Repairs




First, the #1 and #3 axles are solid axles.

The center blind driver [#2 Axle] is made up of 2 steel axle ends pressed into a plastic center section.  This is a carryover from previous 5th generation Big Haulers that have this latest drive system.  There generally never is any rotational play on this center axle, between the drivers.

The Celcon bushings are the reason for the rotational play between the two wheels but as previously stated, it does not affect the performance of the engine.

Any side to side wobble of the #1 & #3 driver wheels can be attributed to the Celcon bushing being loose.  This side to side wobble  may be due to the following:

   1. Mounting screw that holds wheel & Celcon bushing
in place is loose.Solution - remove mounting screw,
use LOCTITE 222 on threads, reinstall and
tighten mounting screw.

   2. Screw mounting hole in center of axle is too shallow causing mounting screw to bottom out before wheel is tight on the axle. Solution - tap axle mounting hole deeper or slightly shorten mounting screw, LOCTITE, reinstall mounting screw and tighten.

   3. In extreme case the Celcon bushing is undersize on its outside dimension with result the bushing "flats" are not a tight fit in the driver wheel hub.  Solution - replace with a correctly sized new Celcon bushing, LOCTITE, reinstall mounting screw and tighten. This may warrant you sending the Big Hauler to Bachmann

4. Insert a nylon washer between the screw head and the Celcon Bushing.

When any of the three possible solutions are completed there should be no side-to-side wobble of the driver. Only a slight amount of rotational looseness should be present.

Side Note:  The drive gear turning on the axle may be caused the extreme heat that is experienced in some warmer climates but that is not always the case.  The Gen 5 Big Haulers seem to have more of a tendency to have this gear slipping occur.  Pulling 10 cars on a slight grade can create this axle/gear slip.  Pinning the gear is the accepted fix.

Figure 1
In the above photo, after removing the bolts that hold the side drive rods on.  A small wrench or flat blade [non serated] pair of pliers can do the trick.
The Celcon bushing [labeled Plastic spacer in above
photo] along with the screw, is what keeps the wheel mounted firmly in place.  There should be no side to side wobble as noted in figure 1.
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Notice that I am placing a small plastic washer on top of the bushing.  DO NOT USE BRASS or metal washers.  You can find these small washers at Lowes and Home Depot.