# 4 gear help



## 2racer (Jun 15, 2008)

Bought a new auto world 4 gear nice cars. Anyway was trying different bodies on and now the gears are rough between the back gear and the crown gear any ideas why ? I really didn't do anything .


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## Joe65SkylarkGS (Feb 15, 2010)

Well the crown gears in them are very sensative. Once you spin em up and drop it on the tires accidentaly, it's usually enough to mess up the gear mesh. And once that happens, it will never mesh smoothly.

You have to be very gentle with them bud. Sorry.


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## sjracer (May 25, 2008)

Actually some bodies are a tighter fit than others. You don't want a body that fits to tight, snug yes tight no, because it has an adverse effect on the chassis. Some people trim bodies to make them fit looser. Check the threads on hobbytalk regarding tight there are several things one can do.


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## 2racer (Jun 15, 2008)

Thanks I will try a new crown gear


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## alpink (Aug 22, 2010)

it has been suggested, elsewhere, that using an original AFX crown gear works very nicely. not my idea, just passing the news on.


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## wheelszk (Jul 8, 2006)

PMed you.


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## wheelszk (Jul 8, 2006)

I mean alpink.


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## alpink (Aug 22, 2010)

got it, thanx


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## Bill Hall (Jan 6, 2007)

alpink said:


> it has been suggested, elsewhere, that using an original AFX crown gear works very nicely. not my idea, just passing the news on.


Yeah works great! Unless your rule set dis-allows. 

I have a crudeo...er....video somewhere. I like this mod for the Specialty set up as it gives them a bit more leg. Obviously it could belabor the initial giddy up of a dragster tired car depending on your setup....both occuring due to the change in tooth count.

It's not a direct fit...but it has always solved the chronic gear skipping BS for me, even with early non-screw gearplates.

Trim the shoulder away...AND open the outside edge of the crown window on the gear plate...OR thin the back side of the gear so that it will fit in the existing window. I use the xacto for all trimming.

NOTE:I have had a couple where I've had to add some shim back in after cutting all the shoulder away, and some had to have it all cut away. So I usually dont remove the shoulder all in one bite...about 3/4s if memory serves. Then I scuff the final fit in on a chunk of 600 paper.

To really get one slickered up, I like to slather up the new modified crown, pinion and gearplate with some toothpaste and lap in the whole nine yards forwards and backwards.

Here they are...begin at post 642 link #3 @ http://www.hobbytalk.com/bbs1/showthread.php?t=215904&page=43

Four gear 101 stuff: http://s44.photobucket.com/albums/f30/modelmurdering/?action=view&current=MOV06500.mp4


__________________


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## Bill Hall (Jan 6, 2007)

*Back wheel modification*










Use low speed and cut a groove to establish the back lip into that wide shoulder. There's a line if you look close.










Cut a bevel on the outside of the initial groove.










Then roll the edge out and away from the back lip.










Cut the remaining shoulder down to the outer rim diameter.










Install your full width tire. The PVT specialty offering in this case.


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## dlw (Aug 17, 1999)

One thing to check is the play of the rear top gear held by the rivet. If there is a lot of play, you can give the underside of the rivet a few gentle taps of a punch, or some careful squeezing in a press. 

That should help your gear mesh problem.

Afx crowns have a slightly larger diameter than AW crowns.


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## 2racer (Jun 15, 2008)

Thanks for the help but it still has to same problem I think this one is a parts donor .


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## pshoe64 (Jun 10, 2008)

Have you tried lapping in the gears with a mild abrasive? MAAS, Simichrome or even toothpaste applied to the crown and cluster gears and then ran on low voltage to smooth the gear mesh may help. I do this process on all my "racing" chassis to help smooth things out. Be sure to clean all the abrasive out when done and lightly oil the gears.

-Paul


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## Bill Hall (Jan 6, 2007)

It's quite possible that you introduced something into the works when changing bodies around. Remember that it doesnt take much to wad up the gear mesh. Just a nick or a snaggle of flash can upset the applecart. 

Flip the gear plate over and carefully inspect the pinion in good light. As it is somewhat hidden from view it's a great place for gremlins to hide. Also introduce a new crown gear into your diagnostic tests and observe the results. Be sure that the crown gear hasnt been moved/slid too close to the pinion. Push the crown back towards the inner chassis housing and see if it doesnt relieve a bind caused by pinched teeth. 

If you've got it narrowed down to the driven cluster and crown with the body removed; you have either a boogered crown....pinion or both; a hidden foreign object mucking up your werks, or perhaps insufficient clearance between the back of the rear wheels and the chassis housing.

Try hosing the area down and blowing it out to remove any foriegn objects that may have worked themselves under a gear or deep into the root between the teeth. Hold the chassis up to a desk lamp and make sure you can see light between the chassis and the back of the rim through a 360 degree rotation. Do not assume that you have clearance or that the rim's back surface is completely flat. 

Even as a last resort, whether you find something or not; you should take Shoe's advice. Like pancake chassis in general, most every four gear will benefit from a good lapping, save for a scant few exceptions. I've had PLENTY of "gritchy" set ups come back to respectability via proper lapping.


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## slotcarman12078 (Oct 3, 2008)

Just for giggles I did a little test. I got some NOS Aurora mag 4 gear chassis ( without basket handles) and dissected a new AW 4 gear. ALL the parts transferred without a hitch. So if you guys are looking to swap over the internals, go for it. The one I did runs smooth!!


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## Marty (Oct 20, 1999)

Bill Hall said:


> Use low speed and cut a groove to establish the back lip into that wide shoulder. There's a line if you look close.
> 
> 
> 
> ...


Don't the tires now ride on the rail instead of the track surface?

Marty
Marysville, OH


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## Joe65SkylarkGS (Feb 15, 2010)

Marty said:


> Don't the tires now ride on the rail instead of the track surface?
> 
> Marty
> Marysville, OH


Marty this is the only problem I been having doing this. So you have to narrow the rubbers too. A new exacto blade will chew it up like a wet noodle so be careful and a steady hand is needed here. Spin it up on a dremel watch the rotation and tilt the blade opposite to the rotation so it don't grab the blade and then make your cut. No biggie.


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## Bill Hall (Jan 6, 2007)

*Apologies and "your results may vary disclaimer"*

Marty: Yes! Please accept my apologies. The tires do ride on the rail....and off the rail. As with any modification your results may vary. Regardless, it doesnt seem to matter much on my original L&J track. The cars hook up instantly and zip smoothly around the track. We took the rear guide pins out and allowed ourselves to touch the rail years ago. I never give it that much thought; but probably should given the status of modern sectional track. 

For the record: I've massaged all my rail joints years ago... and in keeping with slot-car 101 doctrine I roll both the inside and outside sidewall on every tire I install before it ever hits the track. It doesnt take much, just a kiss with some 220 keeps your car from catching the edge and high siding when it crosses the rail. I will also add that the PVT's soft compound, and thus more forgiving nature might have an awful lot to do with the overall excellent ride that I experience. As a side note, most all of my tire abnormalities and handling issues went away when I changed over. ESPECIALLY my four gear units that were twitchy, tippy, and generally unpredictable on EITHER rim style, while running brand X or brand Y tires. 

In retrospect, I can see that this modification may not meet muster with some of the modern sectional track with taller rail heights. This is not inconcievable, as I have had "set up" type issues with other cars I've traded or sold with friends who have modern sectional track with rail heights equal to the model railroad standard ......as well as conversley related issues with track having lower rail heights.


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## Joe65SkylarkGS (Feb 15, 2010)

Bill Hall said:


> Marty: Yes! Please accept my apologies. The tires do ride on the rail....and off the rail. As with any modification your results may vary. Regardless, it doesnt seem to matter much on my original L&J track. The cars hook up instantly and zip smoothly around the track. We took the rear guide pins out and allowed ourselves to touch the rail years ago. I never give it that much thought; but probably should given the status of modern sectional track.
> 
> For the record: I've massaged all my rail joints years ago... and in keeping with slot-car 101 doctrine I roll both the inside and outside sidewall on every tire I install before it ever hits the track. It doesnt take much, just a kiss with some 220 keeps your car from catching the edge and high siding when it crosses the rail. I will also add that the PVT's soft compound, and thus more forgiving nature might have an awful lot to do with the overall excellent ride that I experience. As a side note, most all of my tire abnormalities and handling issues went away when I changed over. ESPECIALLY my four gear units that were twitchy, tippy, and generally unpredictable on EITHER rim style, while running brand X or brand Y tires.
> 
> In retrospect, I can see that this modification may not meet muster with some of the modern sectional track with taller rail heights. This is not inconcievable, as I have had "set up" type issues with other cars I've traded or sold with friends who have modern sectional track with rail heights equal to the model railroad standard ......as well as conversley related issues with track having lower rail heights.




Now thats a mouthfull Bill!!!!! :woohoo:


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## pshoe64 (Jun 10, 2008)

Well stated Bill. I'm confused on the concern about tires hitting rails. Any car that power-slides a turn is going to go over rails. I guess I considered that normal operation and just set my cars up for it. Like Bill said, soft tires are the ticket. I love the big meat tires on any rim, but there's something extra cool about those specialty rims fully loaded with tread.

-Paul


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## slotcarman12078 (Oct 3, 2008)

I would assume with a harder compound, the only thing the tire would be grabbing is the rail. My L&J rail is considerably higher than, say Tomy rail. I did a little comparo today and the difference is about double rail height on the L&J. I guess that's why any car with any kind of magnetic down force get's stuck so bad...


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## 2racer (Jun 15, 2008)

The arm plate must be the problem. I traded the plates on different cars and everyone that had that plate skipped. So I finally started crown gears first the new ones and back to the old. I finally used a spacer by the gear the fix the problem. Thanks for all the ideas thats what makes this site so good.


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