source for 12 tooth motor gear in gauge cluster
 

Hey guys, I've been gathering the gears necessary to repair the gauge cluster for pocket change. I got the gears that sell on other websites for $50 + for less than 20 shipped from half way around the world. Put them in and they were all a perfect fit except for the motor gear, which is too small. I will make a how to once I can put together a complete list of parts needed, I have looked and almost exhausted myself searching for a 12 tooth gear to fit on the 2mm shaft and drive the odometer + trip meter, radioshack doesn't have one, and I don't want to order random gears from everywhere to see if they fit. Part of the problem was the motor gear was desintigrated and I couldn't measure it's dimensions.

P.S.
For those who can't wait, here's where I found the two step gears:
gizmozone dot com

Answer
 

If you don't get an answer, look here.
http://www.peachparts.com/shopforum/diy-links-parts-category/188540-instrument-cluster-odometer-speedometer-tachometer-links.html


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Someone might have an old head unit as a part source.

odometer gears dot com

I think they have done the research & sell ~ $3 wholesale cost for $65 as a kit.

Perhaps we can figure out the specs.

Part Search and CAD

Exactly,
all my gears cost less than $5. If we were to set up a group buy I could get everyone gears for $7 shipped to their door, the only problem is finding the motor gear. Unfortunatly I tried rushgears.com, no luck. I believe the gears are all metric. I measured all the shafts at 2.0mm, and they all fell pretty close to even mm sizes in every aspect. They don't have the correct tooth count in metric, only in standard. So I suppose the search continues :(

Edit:
All of my gears cost me around $10, and I think I may have found the remaining 12 tooth gear, right here:
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11193

Some loctite 609 should hold it tight on the shaft, and it should last forever! I'll let you guys know how it goes!

I've been pleased with other micro hardware I've bought from these cats Precision Mechanical Components Timing Belts Pulleys Spur Gears Couplings Bearings Sprockets Retaining Rings Brakes Helical Gears Clutches Universal Joints

^ Thanks, looks like they have them, right here: https://sdp-si.com/eStore/Direct.asp?GroupID=338 for the 12 tooth motor gear, will search more for the other gear & post a link

Edit: seems they only have the motor gear, but for a good price, thanks!

P.S.

as far as I can tell the module for the gears is .5, and all the shafts are 2.0 mm, let me know your findings if they are any different

How do you determine the tooth count when the gears have turned to dust.

I've yet to find that info.

If you have the device and one gear, you can find it from GEAR RADIUS 1 plus GEAR RADIUS 2 = SHAFT SPACING, or MISSING GEAR RADIUS = SHAFT SPACING minus KNOWN GEAR RADIUS. If you have neither gear, you are shunted onto the "trail of tears" siding.

Note that the outside diameter of a spur gear is LARGER than the pitch (the actual spot of true contact) diameter, or the pitch diameter is smaller than the measured outside diameter. Just to keep things interesting. The pitch diameter is what is used to order/specify the gear, NOT the outside diameter. Or instead of pitch diameter, you can specify it as module (spacing, or pitch) and number of teeth. Same-same.

For very small gears (with few teeth), it helps us that the variance from one tooth causes a perceptible change in the gear size. Such as, from 9, to 10, to 11 teeth makes a visible error. If it was, say, 99-100-101, you would be hating life to try to guesstimate that dude.

Odometer Gears - Mercedes-Benz - 126 Chassis 79-91 Diesel

If you read, you will discover that thare are two types of the bigger gears. The gear on the motor, is always 12 tooth, no mater what. Upon dissassembly of my odometer, the larger two gears were largely intact, just missing a tooth or two each. I was able to determine how many teeth they should have had quite easily. I was then able to measure their diameters, widths, bores, etc. and order the correct ones. However I had to guess on the motor gear, and I was wrong.

But Boisebenz is also correct. There are formulas for spur gears, I just tried using logic I'd learned during some projects in my younger years.

I was wondering what the E3 tooth count would be for the 3.07 vs 2.88 diff W126s.

just nice to have the parts in hand before pulling the cluster.

On other cars I've messed with (70-83 Datsun Z(X) is example) the speedometer drive is mechanical and the required speedo drive gear is determined by the differential gearing. The Datsun drive gear is located in the trans.

Where is the pick up for these cars? It may be that the speedo is the same and rear end ratio is compensated some place else.

Hi

I just did a tooth count on a 88 560SEL speedo:
Black gears 48/12 and 44/34
Clear gear 48/16
White gear 26

And then on a 300SD unknown year.
It 's the speedo that reads up to 85 Mph:
Black gears 48/12 and 48/36
Clear gear 48/12
White gear 24

I need a set of gears for a 82 300SD (Speedo reads up to 120 Mph)
Don't know the tooth count yet, but if you guys do a group buy please let me know.

Hello,

On my 84 300sd with the highest written number on the spedometer being 120 (125 indicated by the line count), I had a 12 tooth motor gear, and 12/48 for the two gears right after it. I know there may be other factors like gear ratios, manual / auto, etc. but that's what worked for me on my automatic.

I would organize a group buy if anyone was interested, it should save them lots of $$ on shipping, but I'm not sure the places I've found have a gear for every mercedes spedometer, I'll have to take a look and see if they have ones with all the different teeth counts.

Just ordered motor gears, can post up a how to when I'm finished

Cheers,
Mike

I ordered the 12 tooth 1.9mm motor gear from your site, gizmozone, and it is a good press fit on the 2mm shaft. Also ordered the other 2 compound gears from them. I did this on my 500sec and only have about 1K miles on it but so far it works. They don't have the 15/48 tooth compound gear required for the 120 MPH SDs. Thanks for sharing your research.