Kato n scale SD40-2 mid trucks

[Southern1970]

Hi all.  I purchased a Kato SD40-2 mid off eBay second hand.  when I try to run the locomotive the trucks sound really rough.  When I pulled the drive tower apart it looks like something is missing to hold the drive shaft and worm in place.

As per below photo is something missing from the truck/drive shaft?

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Cheers
Allan

[peteski]

Assuming that the black worm cover snaps and stays in place on the truck, the only thing that's missing is the outer bearing for the worm shaft.  That will make it run really rough since the worm will be wiggling around (to use a highly technical term).  Someone took the truck apart and lost the bearing.

That part is not sold separately. You will have to buy the complete truck from Kato. Well, unless someone here has a truck they parted out  and has a spare bearing.

[u18b]

as Peteski said.
Missing the outer bearing.

You will probably have to buy a whole new truck to get a bearing.

[mmagliaro]

There is a small white plastic nylon bushing on each side of that worm (at least, there's supposed to be).  You can buy the whole truck, OR... Kato actually sells just that worm+bushings+cup as a separate part (part number 929362).   It's cheaper and their website claims to have them in stock.  And if you're wondering... I knew this because it's a good source of mod 0.2 worm gears.

[jagged ben]

Originally these had the brass bushings (one seen in the top photo) and a super thin plastic washer between each brass bushing and the worm.  Then I guess at some point they started using plastic bushings instead.

[peteski]

Originally these had the brass bushings (one seen in the top photo) and a super thin plastic washer between each brass bushing and the worm.  Then I guess at some point they started using plastic bushings instead.

Are you saying that the current production of these uses plastic worm shaft bearings (bushings) and  not brass?  All the ones I ever worked on were brass, but those models were several years old.

And I didn't realize the worm assembly was available separately.  That makes the repair even cheaper (except for the shipping cost).

EDIT:  I looked at the currently available post and it does in fact have plastic bushings.  Interesting.  I'm sure they cheaper to make.  Even Kato seems to be cutting costs.

[delamaize]

Order This:
https://store.katousa.com/product/worm-gear-and-bushing-assembly-does-not-include-universal-n-scale/
Or this:
https://store.katousa.com/product/sd40-2-mid-truck-silver-w-wormgear-and-driveshaft-n-scale/

That will solve the issue.

Hi all.  I purchased a Kato SD40-2 mid off eBay second hand.  when I try to run the locomotive the trucks sound really rough.  When I pulled the drive tower apart it looks like something is missing to hold the drive shaft and worm in place.

As per below photo is something missing from the truck/drive shaft?

(Attachment Link)

Cheers
Allan

[Chris333]

Why do they sell SD40 wheels with both centered and offset gears?

[Southern1970]

Thanks all.  It confirmed my suspicions.  Will check out the Kato parts store.
Cheers
Allan

[jagged ben]

Why do they sell SD40 wheels with both centered and offset gears?

You mean SD40-2 specifically.  The SD40 only uses the offset gear axle

The centered gear wheelsets are used in the 'Mid-Production' SD40-2 with the sprung middle axle ("shock absorber").  Also a few other models like SD70ACe and I believe some SD70Ms.  The 'early' SD40-2 uses the same offset gear axle as most other Kato US locos, such as SD40, SD45, U30C, C30-7, C-449W, AC4000, ES44AC, etc.  (Okay I'm not so sure about passenger diesels but I think they also use mostly the offset gear type.) The gears also have different teeth.

[peteski]

Why do they sell SD40 wheels with both centered and offset gears?

Yes, like Jagged Ben mentioned, there are 2 different truck designs.  The older one is the same deign used on all low-friction truck design Kato used for decades.  In those the worm is mounted in the chassis and the worm gear is a actually a double gear, requiring the truck's internal gears to be offset.

The new version of the trucks used in the redesigned chassis has the worm mounted in the truck. No more double gears - all the gears are positioned in the center of the truck.  The worm gear now meshes directly with the idler gear.  All the gears also have finer pitch.

[delamaize]

Thanks all.  It confirmed my suspicions.  Will check out the Kato parts store.
Cheers
Allan

Order This:
https://store.katousa.com/product/worm-gear-and-bushing-assembly-does-not-include-universal-n-scale/
Or this:
https://store.katousa.com/product/sd40-2-mid-truck-silver-w-wormgear-and-driveshaft-n-scale/

That will solve the issue.

[Southern1970]

I was thinking of how to avoid paying $25usd shipping (to Australia), and wondered how I could fabricate a bushing.  Was going to consider styrene cut down and then I found my old accumate couplers that I cut off atlas trucks when I body mount micro-trains couplers.  I thought the part below would work (middle item).

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I used a 1mm drill bit in a pin vice to drill all the way through.  Then cut the extra material with a pair of nail cutters (bought then specifically to cut plastic parts), to leave a small flange around the outside.

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Last picture shows end result.  New bushings installed in each truck and the Kato SD40-2 runs smooth with no rough noise.

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[peteski]

Excellent!  Very creative, and inexpensive solution!

I didn't realize you were down under, but even in the States, shipping charges for a small item like that seem to have become unreasonable.

I'm curious, does Kato have a local presence (website/office) in Australia?

[Southern1970]

Excellent!  Very creative, and inexpensive solution!

I didn't realize you were down under, but even in the States, shipping charges for a small item like that seem to have become unreasonable.

I'm curious, does Kato have a local presence (website/office) in Australia?

Thanks Peteski.  I’m not aware of Kato having local presence in Australia, but several hobby shops here do stock their products.