Hello all,

Thanks to this forum I have accomplished so much with my 83 240d, and learned a lot about diesels along the way. As is with other 25-ish year old projects, I have run into a problem i cant find the answer for.

My speedometer has always been a "little" erratic, but for the most part accurate. Then out of the blue it dropped to 0 -- no speedometer, odometer, or trip meter movement. A review of my receipts shows the PO had a new speedometer cable installed about 18 months ago, but I checked it anyway -- it appears to be intact -- if you move one end, the other end also moves. I also used the matchstick trick in the back of the speedometer and got surprisingly solid needle movement (no erratic behavior like before). I am now worried that something is wrong in the transmission itself, but dont know where to begin/what to check. Based upon visualization, I assume that the 4-speed manual tranny tailshaft has to be removed to get to the speedometer gear(s) in there? Is there anything else I can check before I go there since it would appear that will be a LOT of work just to get to some plastic gears? I am at a loss and was hoping for an easy cable replacement or maybe a cleaning of the gears in the speedometer itself.....I searched the forum and it would appear cleaning the speedometer and replacing the cable are the most common problems.

ANY suggestions/thoughts/ideas would be most appreciated! Thanks in advance!

1983 240d 4-speed manual transmission, 245k miles

It sounds like you are on the right track in your tests.

I cannot imagine a faliled drive inside the tranny but your results point that way.

I have a spare tranny with other issues so I might have a part that would help you if you can verify that it is possible for it to fail as it appears to have done.

Tom W

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Sounds to me like its the speedometer. See this repair link:
http://diymbrepair.com/
I had the same problem when I bought my 240D. It was a simple repair, at least for me. Roughly 1/2-1 hour to pop out the gauge cluster. 1/2 -1 hour to get out the speedometer and the same to repair it. My gears were is good shape. The pot metal gear was spinning on the shaft. There are places that sell the plastic gears and a replacement plastic gear for the pot metal one.
Also, there are places on the internet that repar the speedos. I did use a place called Prowls in Lancaster Pa for a different speedo (VDO). I think you would be looking at $125-200.
Tom

Can you check to see if the shaft is rotating while you are driving? Also you can remove the tranny of the shaft and drive it with a drill to check the speedometer function.

I have the exact same problem on my 240D 4spd stick. I'd like to know how you solve this. If I get into mine before you do yours I'll post my results here too.

- Peter.

__________________
2021 Chevrolet Spark
Formerly...
2000 GMC Sonoma
1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021
2002 Kia Rio. Worst crap on four wheels
1981 240D 4spd stick. 389000 miles.
1984 123 200
1979 116 280S
1972 Cadillac Sedan DeVille
1971 108 280S

First and foremost, thanks to you guys for such quick responses and great ideas. Taking your thoughts to heart, I actually took the day off work today and accomplished the following:

1. I am able to turn the speedometer/odometer with a drill and torx bit -- the guage appears to work perfectly, matter of fact smoother than I ever remember when it was connected to the speedometer cable/tranny while driving down the road.
2. As I mentioned, I found a receipt for the cable replacement from the PO -- used good quality MB part and it appears intact. I even called up that mechanic (a really nice guy, would recommend him to anyone in need of an MB certified mechanic in Oklahoma) and he said that although he had only seen it a couple of times, there were small plastic gears in the tailshaft of the tranny for the speedometer as he recalled, although he wanted to review the FSM to be sure. He will be getting back with me sometime tomorrow, but at $75/hour, I feel this could quickly get out of control if I have to turn it over to him.
3. Haven't tried to jack up the rear of the car to see if turning the driveshaft turns the output at the tranny where it connects to the speedometer cable.

It would figure that my MB would be the one which would have a weird glitch.....are there really plastic/metal gears in the tailshaft of the tranny where the speedometer cable enters into the tranny itself? I really believe that it where the problem lies, but I am at a loss and question my mechanical ability to take the tailshaft housing of the manual tranny apart and successfully repair the problem. I am not yet willing to give up on the original speedometer and going with some crappy aftermarket speedo....unless of course someone here on the forum has already done that successfully with good quality stuff!

Anxiously awaiting your replies!