Speedometer quit! - PeachParts Mercedes-Benz Forum

psaboic · #1 12-08-2016, 11:03 AM

Folks,

Gonna need a little help with this one. On the way to work this morning the speedometer in my daily driver 83 300D quit working. No speedometer, no odometer, no trip odometer....nothing. I was going about 40MPH or so and I looked down and the needle was bouncing around between 0-20 MPH, and then it just gave up.

I'm suspecting either a broken cable, or (God forbid) a broken drive gear in the tranny but after I take the instrument cluster out, is there anyway to check the cable without pulling it out of the cable sheathing?

Also, where on the transmission is the other end of the cable connected to.

In short, how hard a job am I looking at??

Thanks,

Glenn

BWhitmore · #2 12-08-2016, 02:32 PM

Pull the instrument cluster. Pull the oil pressure/water temp/fuel gauge from the cluster and reconnect the oil pressure line to this gauge while the gauge is resting in the dash opening. Take the car for a drive and you can see if the speedo cable is turning. More than likely you have a broken speedo cable.

psaboic · #3 12-08-2016, 02:57 PM

Thanks. Never thought about pulling the oil pressure gauge out of the cluster and then reconnecting it so I can drive the car a bit.

So if the cable is broken, how hard is it to disconnect the transmission end of it?

Probably going to be Saturday before I can work on it, as they are predicating an ice storm here tonight and part of tomorrow!

Glenn

BillGrissom · #4 12-08-2016, 03:02 PM

A broken speedo cable is an easy fix, at least in my U.S. cars. Auto parts used to carry a universal cable you cut to length and crimp a square end on. But, in my case the cable didn't die, but was murdered. Culprit was a wobbly bearing in the speedo which caused the spinning cup to grab, so good the cable broke and spared the speedo (had it re-bushed). Never dug into my M-B speedos, so don't know what is in there.

BWhitmore · #5 12-08-2016, 07:01 PM

The speedo cable connects at the left (driver's side) bottom of the transmission. IIRC the cable is held in place by a small tab with a bolt (10mm socket or wrench) . A little tight in that area but not too bad. The cable also goes through a holder near the front of the trans and also a plastic holder where the engine and trans join together (left side). When reassembly leave this holder unattached until the cable is attached to the speedometer. Reattach after inst cluster is reinstalled. By doing so you have more slack in the cable making it easier to attach the cable to the speedo.

HarvAMG · #6 12-08-2016, 07:41 PM

Pull the end of the speedo cable off the transmission and spin the little pin inside with your fingers. If it spins free, you have a broken cable.

Based on your post, I'm 99% willing to bet it's the cable. Make sure to find the correct part number. They are different between the 240D and 300D as well as auto and manual transmissions.

psaboic · #7 12-10-2016, 03:55 PM

Well, got some time to work on the car today. I took the instrument cluster out and removed the cable from the transmission end (what a PITA). Attached a small drill to the cable end under the car and had a helper watch the cable end inside the car. Result, no movement of the cable in the car so it looks like I have a busted cable. New one is on order from Pelican.

Maybe it is me, but it looks like a semi pain in the proverbial butt to replace the cable. What is the bst way to do it....hook up the transmission end first, then the instrument panel end, then secure it all down, or???

Any advice appreciated. Thanks,

Glenn

optimusprime · #8 12-11-2016, 06:53 AM

Remove the old inner part of the cable by pulling it down from the bottom of the car, or up .Make sure its all out of the outer part ,put both parts together and if all the bits are there .Grease up the new drive and feed it back in ..Pull the drive inner cable up from inside the car take it right out .Any bits in there will come out with the grease .Clean the drive and re grease it .You can do this as many times as you want to ..Pop it back in the outer cover .Fix it in to the console and all back in to the car ..But replace you bulbs in the speedo now you have it out .The hardest part is pulling the console out of the dash board .

charmalu · #9 12-11-2016, 11:36 AM

The cable isn`t that big a deal to replace. I will come as a complete assembly with a new firewall grommet.

Remove the old cable assembly, through the firewall with the grommet.

Fish in the new cable through the firewall and pop in the new grommet.
Attach the cable to the Spedo head, oil line and electrical stuff.

There is one plastic piece that connects the cable to the body to keep it from flopping around.
Push cable end into the Transmission, attach the bolt (10mm) and the metal tab. tighten it and you are done.

From my experience the inner cable does not pull out from the outer part.

BWhitmore · #10 12-11-2016, 11:58 AM

One thought - leave the plastic holder for the cable (found where the engine and transmission mate on the left side) unattached to the metal holder until the cable is attached to the back of the speedometer. By doing so you will have more slack in the cable which aids in attaching the cable to the speedo. Once completed re-attach the plastic holder to the metal holder (under the hood).

psaboic · #11 12-11-2016, 12:21 PM

Sounds good. To me the biggest PITA is the lack of room getting to the 10 MM bolt at the transmission end, I ended up removing the transmission mount and lowering the trans a bit to get more room.

Agree, it would be nice if you could feed a new inner cable into the already existing and routed outer jacket, but my cable does not seem to want to come out.

Glenn

charmalu · #12 12-11-2016, 11:49 PM

Quote:

Originally Posted by psaboic

Sounds good. To me the biggest PITA is the lack of room getting to the 10 MM bolt at the transmission end, I ended up removing the transmission mount and lowering the trans a bit to get more room.

Agree, it would be nice if you could feed a new inner cable into the already existing and routed outer jacket, but my cable does not seem to want to come out.

Glenn

For that bolt, I use a 1/4" ratchet with a short extension and 10mm socket.

charmalu · #13 12-11-2016, 11:55 PM

Quote:

Originally Posted by BWhitmore

One thought - leave the plastic holder for the cable (found where the engine and transmission mate on the left side) unattached to the metal holder until the cable is attached to the back of the speedometer. By doing so you will have more slack in the cable which aids in attaching the cable to the speedo. Once completed re-attach the plastic holder to the metal holder (under the hood).

I forgot to add that one part, to attach the cable to the cluster, then mount the cluster and last to connect the trans end.

When I pull a cluster, I first remove the cable from the trans end first to get the slack I need.

What Iam thinking, and what Iam typing don`t always jive. LOL

Whats with the smilies tonight? second time I couldn`t get them to work.

psaboic · #14 12-21-2016, 11:00 AM

Just to follow up. Followed the good advice here and replaced the speedo cable. All is good now. Installation went a lot smoother than removal for some reason