slipping odo in 126, easy fix?
 

is that just a matter of repositioning the gears and some crazy glue? or is it more like replacing wheels?

The W126 speedos usually require a gear replacement.

Henry are you going to autopsy? Mine went south last month I just threw another in until either I quit procrastinating about fixing it or someone else did an electronic speedo.

Try: http://www.odometergears.com/

If it is just the gear slipping on the shaft like the mechanical speedos do, I remove the gear and lightly "stake" the shaft with a punch and reinstall the gear.

W126 speedos are different.....
 

The W126 speedo is an electric speedo head and as such the odometer drive is configured differently from the cable driven units.

On my older MBs, I could broach some splines on the shaft after disassembly and the gear would get a new purchase on the shaft and this keeps it from slipping. I used a pair of pliers to slightly roughen the shaft, and I like this better than trying to use some glue in very tight quarters.

For the W126, there is a motor driven gearset that seems to have fragile gears. The gearset is easily accessable after speedo removal, just remove the metal cup the speedo is in and then a side plate external to the speedo frame, and the gears are revealed. I've disassembled quite a few speedo heads to gather a good set of gears, but replacements are available online, if you search a bit. I recall there's a company in Virginia, maybe Newport News or Hampton that sells replacements.

So, the failure mode on a W126 turns out to be not as easy or cheap as the older mechanically driven speedos....

Jim

it's really simple to remove and replace the gears though. all three of my gears were soft as bubblegum, and just about fell apart in my hands. the VDO oem replacement gears are available for around 20.00 each. there are also companies that remake the gears and sell them as a set for 65... not sure what is best way to go. oe, is junk, remade ones may be better, or not...
John

That's good information. I started to disassemble from the pictorial of D Giants and said whoo - this is different and stopped. Probably going to look like the picture of gear in link with teeth broke as it was just changing a group of "9" when everything stopped. If we get a rainy day maybe I will snap some pic's of the electronic speedo coming apart.
Good information guys!

hardest part I found in disassembling the speedo was getting those two plastic parts off of the circuit board so the speedo could be pulled out of the cluster.
not too bad. the gears are right on the outside of the speedo. the odd thing is, the gears that fail are connected to other gears that are made of a different kind of plastic, and those gears are STURDY!!! I wonder why they did not make it all the same... planned obsolescence I suppose.
John

oh, and another thing, most tell you to make the hooks to pull the cluster out, some say to just get under it and push it out from below. I found it simpler to grasp the lower edge of the cluster, and put thumbs on top of the reset button and clock set buttons and just pull it out.
worked well for me on both of mine!
John