Speedo on 108

How hard is it to replace the speedo on a 108? It is not the cable because the speedometer still works, but neither the trip odometer nor the odometer work.
Thanks
Tim

[MikeTangas]

No need to replace, just rebuild it or get it rebuilt. I had mine rebuilt by Palo Alto Speedo, been working great since. Steve Brotherton's shop also does the rebuilds. Do a search on speedo rebuild and you should find a link to Steve's shop.

[WANT '71 280SEL]

He has a used one though to put in. It is pretty much a straight-forward swap isn't it?
Thanks
David

[MikeTangas]

If he has a used one, it is a straight forward swap provided it is a 108 speedo. Customary caution needs to be used when pulling the cluster, two 10mm wrenches needed to disconnect the oil pressure gauge, plus the care to not kink/bend or break the water temp gauge capillary tube.

Now, how sure are we that the used one doesn't have the same odo/trip issues? I'd pop it in AND get the original rebuilt.

[psfred]

It's easier than that.

Speedo can be removed without disconnecting the oil pressure line -- drop the parking brake bracket, reach up and unscrew the speedo cable and the white plastic knob that retains the instrument cluster. Pull cluster out, reach around behind the speedo and remove the three phillips screws that hold it in and use a pair of needle nosed pliers to unclip the wire retainer for the cluster lamp. Gently remove speedo from cluster. You can pull the dash dimmer at the same time. Knobs for odo reset and dimmer stay on the cluster.

Once you get the speedo out, the fix is very easy. Get some locktite, low set (blue) is better, but either will work (red or blue). Push the shaft that goes through the milage nuber wheels all the way toward the metal drive gear (passenger side of speedo) and push the metal gear the other way for clearance.

Whittle down a matchstick or use a broomstraw and use the tip to tease a small drop of locktite down onto the shaft. Work the shaft back and forth to get some between the shaft and the gear, then use some paper strips to get all the excess out. Wipe the end of the shaft that goes through the sheetmetal flange clean, too. Adjust gear and shaft to original position -- if you leave the gear pushed over tight against the number wheels, they can all turn at once!

DO NOT get any locktite on the plastic gears or number wheels!!!! ONLY between the zinc gear on the outside and the shaft.

In a couple minutes, the locktite will set up and the odometer will work. Test by putting a tapered matchstick or similar in the speedo cable fitting and spinning it. Hole is square, whittle to fit. Spin to give positive speedo needle movement, otherwise the odo counts down....

I'd use a bit of rubbing alcohol to clean the number wheels, especially the tenths wheel on the trip odo while I was in there.

Installation of the now working speedo unit is the reverse. Takes about an hour if all goes well, longer if you drop the cluster bulb and have to fish for it.

If I ever get around to it, I have a spare speedo I will use for a DIY article.

Peter

[Tomguy]

Well, it does depend on which 108 the speedo came from, I would imagine - I would think the gearing in the 6 cyl's would be different from the 4.5's, not to mention the difference if it had MT or AT, M110 or M108, M129, M116, M117, or M130. 108 is a VERY generic term encompassing 250S all the way to 280SEL 4.5 (250S, 250SE, 280S, 280SE, 280SEL, 280SE 3.5, 280SE 4.5, 280SEL 3.5, and 280SEL 4.5). But if the part numbers on them match, then it'll work. Otherwise - no guarantee it'll be right, I'd imagine.

[250SE]

I remember several years ago I had issues with my speedo cable. The speedo worked just fine but it would squeal so loudly. The faster I went, the louder it got. So loud I couldn't even hear my stereo! It was horrible. I just went and disconnected the speedo until I had time to get it fixed. It was so embarssing. It has been about 4 years since the repair and it hasn't given me any problems. Although my car seems to think that 68mph is actually 80mph. I'll let her think she goes 80 on the freeway though.... :p