Speedometer cable/speedometer bounce woes
 

On my 300cd, the OE cable caused enough bounce on the speedometer needle that the cruise would surge due to the needle bounce. Last winter in very cold conditions it started to scream so I replaced it.

The first run with the cable and it was perfect - no bounce in the speedometer from barely rolling on up. The next day, it screamed when driving over 55.

It's all about the speedometer cable routing, the speedometer is great. It's just dangerous to adjust while moving, and inconsistent. Yesterday I got it to be real smooth and perfect from 25mph up. I can live with that - let's me run cruise control on the highway. Was perfect through when I pulled up my driveway yesterday. This morning, as soon as I backed out, bouncing was severe at all speeds. Even when I adjust it and it smooths out, after a little while it will get bouncy again.

I made sure not to overtighten the cable to the speedo...

What am I missing? Very frustrated. Would like to put kickpanel back...

Thanks!

have you lubed the cable? I've read in passing that it could be a cause, also pulling the cable up to create enough slack to pull the cluster can be a pinch point, go under the dash with the cluster in and push some of it back though and see if it helps

Cable came lubed. Read that it was recommended to put a drop of grease on the end so did that. Believe ATF creeps up. Old one's lube was fine even!

Btw, is there any mount point or clip that should hold it under the dash? None on mine. I get the feeling from tinkering that holding it in a certain spot would help - like zip tie it in.

I'm told part of the problem is the bushing in the speedo head itself binding in the threaded collar the cable screws on to. Read somewhere to lube this bushing. Routing the cable is important but I think the main culprit is this bushing. The tightness of the cable knurled knob should have no affect on this unless left too loose.

When you say "adjust", what exactly do you mean? I am curious. I a had a similar problem last year, only it happened on a 400 mile trip and I had to cut the cable, so I could drive the car home. The "scream" was so loud it was deafening.

Anyway, I had bouncing issues before the cable croaked. After replacing with a new cable I get a very slight tiny bounce that is barely visible at speed and a bigger bounce at speeds below 25 MPH (as you stated). On the cable I received (from this site), it said to lightly grease both ends of the cable before installing. So, I did.

Let me know if you figure it out. Sounds like we have the same or similar issue. I wonder now if I simply put off replacing the cable for too long and all the bouncing permanently damaged the speedo assy.

Interesting. Greased the cable ends thnking this would lube whatever was needed. Perhaps it can't migrate to this bushing.

I assume the bushing is what holds the female end in place/alignment on the speedometer?

Adjust = playing with the cable in/out of the firewall and side to side under the dash while driving sans kickpanel.

Somewhat dangerous and a hassle.

Currently have a Velcro ziptie with cable almost fully pushed out through firewall (no slack - almost), and tied to a bracket near the right side of the steering shaft passing through. That is, slightly held leftward of where it would nTurally lie.

I'm hoping that having it tied will add consistency of operation. Currently at speed Otis absolutely beautiful. above 50 you would almost think it is electric. However, below 45 it is terribly bouncy.


I greased both ends per the instructions - used Dow molykote 33.

I wondered about speedo bounce and figure it probably needs some speedo theory to troubleshoot (no swimsuit jokes please.)

How does the speedo actually work? The cable rotates from the tranny, that's clear enough. The cable has a square tip that fits into the bushing-thing on the back of the cluster, but then what? Is that bushing magnetically coupled to the needle? A spring? How does the cable translate consistent rotational motion to a relative position on the cluster?

I assumed that some bounciness was lack of lube between the round bushing in the cluster and the round housing in which it sat. Has anyone disassembled the speedo? Got pics?

I put a few drops of T-9 lube (bike shop; link: http://boeshield.com/) on the rear of the speedo cluster and that eliminated bouncing except at low speeds. I attributed that to initial static friction or some other low-speed phenomenom.

Where exactly did you put the drops of t9? I have some so it's worth a try.

The bounce and squeal is definitely cable routing/bend related though to some extent, as I can induce it or atop it depending upon how I press and move the cable under operation. Problem is, no one alignment is good for all speed conditions...

It's been a while, but I think at the yellow arcs in the pic. I think the brass outer piece is fixed and the inner metal cylinder rotates with the cable. I presumed there was a lack of lube or friction due to age between the outer brass collar and the inner cylinder.

The design is what makes me wonder how that translates to the needle. A spring causes the needle to return to zero, but what pushes it up? Magnets? Friction?

I was afraid of putting too much in and gumming things up inside, so it was literally drops, followed by some rotation with a small flat head screwdriver.

mines had bounce since I got it. when I did the manual swap it was bad with the 300D auto cable. I put a 240D auto cable in and it was better. I found that too tight a turn at the trans and at the speedo were the worst offenders. also there is a tie at the corner of the engine which needs to be in place to hold the nice arc from the bottom of the car to the fiewall entrance. Mine still jumps a little at low speeds but settles down around 25mph which is the best ive had it so I didnt mess with it. I assume I will have to do it all again when I get the 5 speed install complete this summer. FWIW I did install a different speedo to see, bounce was still there but it changes severity every time I touch the cable so there is no saying if its cable or speedo for me

Yak, youre the best!

Have been fiddling with the bouncing speedometer when driving. My use of the car is in spurts, and in the last week, it went 500 miles of interstate. I tried moving the cable and cluster any number of ways, ziptieing the cable in different orientations under the dash, etc.

I drove probably 300 miles holding the cable in different orientations. Some I could release and drive for a good while without any issue, very snooth... But the next time I drove after a stop, it would bounce.

I was at my wit's end, so pulled the cluster tonight and put about three drops of T-9 on the bushing. Seems super smooth and silent.

Before lubing that, the best orientations always had some cable noise. No noise now it seems...

Thanks!

Interesting... I may have to try that!

I put up a DIY for cable replacement - probably a good idea too...