Repair of odometer worm gear - PeachParts Mercedes-Benz Forum

HuskyMan · #1 06-09-2011, 02:33 PM

Here it is, my experience with repair of the 2" worm gear in the odometer of the 1984 300DT. I've found that the spindle on the top of the gear is prone to break rendering the worm gear useless which means the odometer stops working. OK, here's the repair:

First, follow the removal sequence shown on dieselgiant's web site for removing the instrument cluster. Remove the 2" worm gear, set aside. Go to your local home depot store and go to the hardware aisle. Home depot has large cabinets with drawers loaded with various hardware parts. You are looking for 1/16" X 1/2" Steel/Zinc Plated tension pins (they come two to a package). Also, purchase a small workshop bench vice while you are at the store (unless you already have one). Attach the bench vice to your work bench or kitchen counter top. Place a microfiber cloth around the worm gear and insert gently into the bench vice, tighten the vice but not too tight (you don't want to break the worm gear!)

Next, take a dremel tool and drill a small hole in the head of the worm gear, the hole should be either the same size (1/16") or slightly larger as the tension pin. next place some super glue into the hole you just drilled, then insert the tension pin. DO NOT hammer the tension pin into place! I made this mistake and ended up breaking a perfectly good worm gear, fortunately I had another laying around.

Lastly, place the worm gear back into the odometer drive, screw it all together and you are done. Allow the superglue to set up overnight before reinstalling the instrument cluster back into the car. Mine is working great with no problems!!!

note: this project would be easier if you purchase a dremel tool drill press from home depot along with a vice installed into the base of the drill press to hold the worm gear. This set up would allow a cleaner drill of the worm gear since the drill press holds the dremel tool rock steady while drilling.

Stretch · #2 06-10-2011, 12:42 PM

Sounds great - did you take any photos?

mccauleybil · #3 06-10-2011, 12:54 PM

Now that you seemingly have this procedure perfected, and have invested in the correct tools, are you willing to hang out your shingle? My guess is that I could follow your instructions, and have a 50+% chance of success, or pay you to further develop your learning curve?

Any interest in repairing my odometer?

vstech · #4 06-10-2011, 04:25 PM

instead of superglue, I'd use plastic epoxy. easier to work with, and more permanent bond.

Stevo · #5 06-10-2011, 04:32 PM

Quote:

Originally Posted by vstech

instead of superglue, I'd use plastic epoxy. easier to work with, and more permanent bond.

I'm always afraid of dripping a drop in the wrong place so I notch the shaft with a small set of bolt cutters. (very carefully

)

TX76513 · #6 06-10-2011, 05:45 PM

Attach the bench vice to your work bench or kitchen counter top.

Ya - then wait to get hit in head with iron pan

HuskyMan · #7 10-12-2011, 03:16 PM

OK, an update, the odo stopped working again so I pulled the cluster. Appeared to be the infamous pot metal gear that was slipping so I performed the diesel giant fix. Next, I noticed the Home Depot supplied 1/16" X 1/2" tension pin was not quite big enough to fit securely in the hole of the metal housing. So.....replaced it with a 3/32" X 1/2" tension pin. I had to whip out the dremel and drill out the previous hole I had made in the top of the plastic worm gear using a 3/32" bit, then install the 3/32" X 1/2" tension pin. Also applied a small drop of Gunk Super Oil to the tension pin to aid in lubrication because it is a tighter fit now. I did not use any super glue this time to install the tension pin as it fits snug, but time will tell if it is ok not to use an adhesive. I'll install the cluster in the car and give an update in a week or so. So far, the fix looks good...

PS I'm going to purchase the dremel tool drill press from Home Depot (abot $40). It would have made centering the hole in the head of the worm gear much easier. I was trying to do the repair on the "cheap" which can get you in trouble sometimes......

till next time, may the wind be at your back and may your sled dogs pull your sled steadily through the snow drifts......

HuskyMan

gsbaxter · #8 01-06-2012, 01:14 PM

While you've got it out, check and wipe all bulbs, inside glass and clean the speedo numbers with a q tip and alcohol.

And pulling the speedo cable a couple of inches through the firewall makes everything much easier.

Also--don't use any type of glue on the brass rod--roughing it up works just fine--I pinched the rod with the end of a regular set of pliers--did a great job.