tuxedo

Hey guys. I had my cluster rebuilt around 6 months ago. Probable only have around 150 miles on it so far. Between winter and Corona the car has been in the garage like all of us have been in the house. Anyway on the last couple of short drives I noticed the needle will not come to rest at zero. I can back it up and it resets to zero. But if I drive it and then come to a stop it comes to rest around 5+mph above zero. Any ideas on what that's all about?

I also put a Tremec TKO 5 speed in the car at that time. As you know pulling the cluster for this is a PIA and it may just fix itself once I drive it more. But am wondering if any of you have been down this road and had any thoughts.
Tux

Nowhere Man

I would make sure your speedo cable is free and not binding up

Dennisscars

I am making the assumption it is still a cable driven speedo. I'd remove the cable at the trans, pull the inner cable out an inch or so to disengage from head. If it's still not zero with no outside influence, which should be slim since the cable is not directly attached to the mechanism. Spinning makes a magnetic field. I'll leave it to others to explain the science.
I would surmise that when they rebuilt it the needle was placed back on not at zero at rest or it's somehow slipped/moved (again, slim).

And while you have it loose would be an equally advantageous time to clean and lube inner cable for good measure. Too heavy of a grease not better. Which usually a dirty/binding cable jumps erratically from it winding up and sproinging ahead. (one of those technical terms)

tuxedo

Thx Dennis. Yes it cable driven. I understand what you are saying and will try that as its an easy test. I appreciate the feedback. With being stuck at home I can at least accomplish some of these projects. Not sure why it did not have the problem from the start but as you said it could have slipped.

tgtexas02

The speedo cable or transmission will have no effect on a needle returning to zero. When the internal magnet is not spinning inside the speed cup, the needle returns to rest based on a spiral tensioned spring and a "fixed" tang stop. To me, there is not enough tension on the spiral spring to insure a return to zero. You can simply remove the needle and set on zero but this might also alter calibration and is a lot of effort. Then check speeds by timing on a mile length of highway and at 30, 60 and 90 mph. Personally, I would contact the folks that did the original work and see how helpful they are. If I had done the work, I would tell you to return it to me and not at your expense.

65GGvert

Sounds to me like there's a slight bind or rub in the needle or shaft. If backing up makes it drop, try a light tap on the dash, if it drops to zero, I'd leave it alone unless it got worse. It may loosen up on it's own. If it's right at higher speeds, you don't need it at 5, and you can tell if you're stopped or not.

tgtexas02

As far as backing up and it returns to zero, the magnet is spinning in reverse and obviously that attraction on the speed cup pulls it back to the stop...hence, rests on zero. I feel strongly that spring does not have enough tension but it could be be catching on something? Whatever it is, it isn't right.

buns

For future reference, a picture of the spring>

DansYellow66

Possibly the needle is hitting the lenses before returning to 0 mph? Seems I once had this happen on one of my small gages but I thought there was more clearance on the large speedo/tach. If it jumps slightly when taking off from a stop I would check for this.

tgtexas02

I don't see a lot of choices for you except to live with it, attempt to fix yourself, send it back to original restorer, or pay another restorer to fix. What are your thoughts?

edit: Earlier I mentioned simply "remove" needle and set to zero. You do not have to remove the needle to do this. I should have said "rotate the needle counterclockwise until set on zero"; however, this approximate 6 mph offset correction will most likely result in similar offsets at higher speeds. This procedure will not damage anything. If you were backing up at 25 mph, your needle stays on zero because of the stop tang. Without the stop tang, your needle would continue to rotate backward just like it does when going forward. Not trying to get too technical...don't get over your head.

tgtexas02

FWIW. Quoted from AC Service Bulletin 3D-425, dated April, 1967, pg 7:

"2. Inadequate Zero Bank

(Pointer or Cylinder does not return to zero.)

(a) Weak, broken, or improperly adjusted hairspring.

(b) This paragraph applied to cylinder (drum) type units and not (needle) pointer units.

(c) Pointer improperly set. (The viewing angle should be the same as when mounted in car.) Remove pointer and reset at zero mark on face dail. Check for bank.

(d) Front jewel too tight, resulting in speed cup spindle end play being too tight.

(e) Dirt or grease in mechanism. Disassemble and Clean."

tuxedo

Bill,

You have a keen understanding of the internals of the gauges. I will see if the original gauge restorer will take it back for R&R. He should, but I am not looking forward to pulling the cluster. I am still working and moving to another house right now so not much time for this right now along with the Corona disruption. Looks like you are down in Galveston and I am in West Houston. Do you work on these gauges etc? I think you do?

Tux

tgtexas02

Need to change my profile as we sold the Galveston place on bay side of 61st Street and kept our Belton house. Yes, I do work on these gauges but not as a business. I have what I call a collection of C1 speedos, tachs and small gauges. For me it is much like the guy who has a collection of corvette models/toys. It is one of my hobbies. I have thought of offering this service once I finish my 58 body off which is nearly there?

In your situation, it is a lot of effort to pull your cluster, probably get charged shipping to and from who ever does the fix, and put your cluster back in. Done properly, I am of the opinion that re-tensioning/adjusting the spring needs to include a calibration check which might necessitate a magnet re-charging and a complete re-calibration? That is why I suggested talking to the original restoration shop and see if they have any suggestions for you? Just trying to give you some insight if you talk to them. If they are resistant to not really helping you, I would just move until you just cannot stand it not being on "Zero", have the time to remove, and send to someone else. You might be my first customer if you can wait?

GordonR

In the mean time download a "speedometer app" on your cell phone and check your accuracy.

tuxedo

Cluster will be pulled this week and the original restorer of the speedo will take it back and fix it. So on my way to getting it back to normal.

TUX