63 speedo gear

[Rainer S.]

I have a 63 SWC with a B/W 4speed. My speedo stopped working, removed the speedometer fitting assy. Found, that the plastic gear (Green-22 teeth) was worn (flattened) on one side, less that 1/2 way around. What would cause this wear ?
The gear was not in there very long, has less than 200 miles on it, since I had it installed, when I had the car worked on.
I have ordered a replacement fitting and gear from Paragon. The old gear was slightly sloppy in the fitting, but otherwise not too bad, aside the wear on the teeths. The long shaft of the plastic gear was not worn.
Just curious, what did the damage...

Rainer

[William C.]

Re: 63 speedo gear

How many miles had you gone since the gear was installed? Sounds like a kink in the cable or a mis-match between the size of the drive and driven gears.

[James J.]

Re: 63 speedo gear

Have checked to see if the cable turns or is it bound? If the gear stopped turning I would think that would wear a flat spot in the gear.

[Rainer S.]

Re: 63 speedo gear

Bill,

I have driven the car only less than 200 miles, a new cable was installed at the same time the gear was installed. I checked the cable, it is not kinked. I was able to pull it out of the casing, there is a stop on the cable on the only the gage end only.
I am unable to look at the mating gear inside the trans, even with different mirrors. I will have to look at the gear with a small camera, in order to see the mating gear teeth. (Don't have a camera)
One small issue, which may have contributed to the wear, could have been, that the seal on the fitting was not seated all the way. The gear stem was not engaged with the seal, installed. When receiving the new fitting and gear, I will compare the old and new fit...
How could I verify the mating gear, with out removing the trans ?

Rainer

[James J.]

Re: 63 speedo gear

Seems likely that if the speedo gear was not fully seated and therefore not properly meshed with the driving gear the plastic speedo gear would wear quickly.
I don't know of any way to check the transmission gear without removal.
Maybe someone else can help.
Let us know what you find out.

[Joe L.]

Re: 63 speedo gear

Bill,

I have driven the car only less than 200 miles, a new cable was installed at the same time the gear was installed. I checked the cable, it is not kinked. I was able to pull it out of the casing, there is a stop on the cable on the only the gage end only.
I am unable to look at the mating gear inside the trans, even with different mirrors. I will have to look at the gear with a small camera, in order to see the mating gear teeth. (Don't have a camera)
One small issue, which may have contributed to the wear, could have been, that the seal on the fitting was not seated all the way. The gear stem was not engaged with the seal, installed. When receiving the new fitting and gear, I will compare the old and new fit...
How could I verify the mating gear, with out removing the trans ?

Rainer

Rainer-----


What color/tooth count was the driven gear which was removed and replaced 200 miles ago? Was it the same as the failed one that you just removed? What is the rear gear ratio of the car?

[Rainer S.]

Re: 63 speedo gear

I don't know what color the gear was, that was removed. I didn't ask at the time. I will ask the shop, they may remember. I didn't want to bother them, since it was over a year ago, when I had it serviced for F.I issues, at which time I asked them to check, why my needle fluctuated when driving.
When I got the car back, the speedo worked, until it failed to work this week.

Rainer

[Rainer S.]

Re: 63 speedo gear

Well, I installed the new speedo gear and the new speedo fitting, but have the same problem. Needle fluctuates, erratically, then stops after (1) mile of driving.
Removed the gear again, no damage.
Connected a drill on the cable (still connected at the speedometer gage).
Needle moves, but not steady, in low rpm, more steady in higher RPM.
Re-connected cable again at trans, drove the car, still same, needle fluctuates, moved to the approx speed on the dial, but when I let off on the gas, the needle goes to "0" and does not move, until I accelerate again. Then after a mile, needle stops, and will not budge again.
Is my problem in the gage or in the trans ?
If someone could lend me an old, working gage, I can connect it to the cable, while connected at the trans and monitor, while driving (supported under the dash). I would be glad to pay shipping both ways (or buy the gage, if it's not too expensive).
I don't want to guess, where the problem is, either way, it's a big job, either removing the trans or removing the dash to fix this problem.
Not knowing, how the speedo works mechanically, or how the driving gear in the trans is mounted, on a spline or what, could it be slipping ? I have no idea, what could be the root cause.

Rainer

[Jack H.]

Re: 63 speedo gear

Essentially, the cable from the tranny spins a wheel inside the tach/speedo constantly. The wheel has a permanent magnet on it. There's a pre-defined air gap between the wheel/magnet and the pointer needle drive shaft where a corresponding magnet OR magnetically responsive metal 'pickup' is mounted.

The pointer needle tries to 'follow' the rotating magnet falling out of synch against its damping mechanism and then, briefly, falling back toward zero.

The next revolution of the drive magnet picks up the pointer mechanism pushing it back/up. The faster the revolution of the drive magnet, the higher on the scale the pointer needle climbs to.

Those who engage in speedometer/tachometer repair and calibration have precision equipment to spin the speedo head and observe the pointer needle's position. They can adjust the air gap as well as re-magnetize the system to obtain the necessary calibrated accuracy.

One way to check out your system is by connecting a donor speedo to the drive cable and seeing how it responds. The drawback is there's not typically enough 'extra' drive cable to connect to a second speedo that isn't physically located in the instrument cluster!

So, if you figure you have to pull the speedo anyway, why not simply walk it into a local speedo shop and have them run calibration/diagnostics on your unit? They need periodic cleaning & internal lubrication anyway...

Here in Denver, we're fortunate because we have a United Delco dealer who also does both speedo/tach and radio repair. Often, they have parts that've been LONG discontinued within the GM parts system. So, it's pretty simple to do the check out.

The most common malady is lack of periodic maintenance (lubrication) for the speedo cable. You can wind up with high friction and torn/frayed portions of the cable (inner sheath as well as internal drive cable).

Plus, the drive end of the cable is essentially 'square' intended to insert into its mating connector firmly without slippage. If that end is deformed (disconnect and visually verify), it can explain speedo/tach pointer needle anomoly issues...

[Rainer S.]

Re: 63 speedo gear

Thanks, Jack.
That was a very precise explanation, on how the needle gets to move. I was always wondering, how works, I new it wasn't a mechanical connection, like at the trans end. Now I know..Almost like a reverse electric motor principal...
I am almost convinced now, that my problem is in the gage.
Do I have to remove the gage cluster completely, in order to remove the speedo gage, or can I pull it out far enough to do it in the car ?

Rainer

[Dan H.]

Re: 63 speedo gear

Hi, had a similar problem after installing a new cable. Found out later you must check to make sure the end of the cable that goes into the speedometer doesn't bottom out. If this happens it creates a bind on the speedometer wearing out the bushings etc very rapidly resulting in 'contact' between the magnet and housing, causing irratic needle etc. bounce. Just make sure after rebuilding the speedo that the cable has enough room not to bottom out when tightened up. Rebuilding the speedo and tach can result in a change in the depth the speedo cable needs for clearance. Test the cables on the instruments before they go back in the car, much easier that standing on your head! Grind the end of the cable to provide the clearance/depth required. Good Luck!!!
Dan

[Rainer S.]

Re: 63 speedo gear

Good point, Dan.
The speedo cable end, which goes into the instrument has a stop crimped on the cable, which, if to long, would bottom-out. Yup. That's what I will go after next.
Hope that's it, it would make sense,since I had my cluster and all instruments restored by a reputable Vendor in MD. and have not seen too much use since...
I will check it out tomorrow. Will let you know, how I make out...

Rainer

[Scott P.]

Re: 63 speedo gear

Rainer, If the shop that last serviced your 63 just installed a speedo cable they may or may not have lubricated it. A dry cable will cause the speedo or tach needle to bounce. Have you lubed it yet. You must take it loose from the speedo to do this part of the job.

The cable housing needs to be removed and possibly replaced because if your needle bounces and a cable replacement does not solve the problem, with some grease on it, the cable housing is probably worn internally and causes the cable to bind up as its turning. This binding up can kill the speedo driven plastic gear, as yours did.

Lots of times speedo cables housings have been replaced and are too long or too short resulting in cable bind also so find out what your cable length should be and you can get a replacement at your local parts store, a little longer is better than too short. Make sure that the replacement cable housing has the same size threaded nuts on the ends as your existing one does. You can order a gray 63 cable from the catalog companies if you want that orginal looking part and it should be the correct length except that the 63 BW T10 cable went in from the drivers side and the later 63 muncie went in from the passenger side so the length will be different. (I think that last statement is true)

The drive gear in the transmission is steel and should not be a problem.

If while the speedo was working sort of ok and the speed it exibited seemed ok with you then you can just replace the bad gear with the same color and tooth count as it was. Some transmission repair shops or transmission parts houses or speedo repair shops have these gears. I am pretty sure you can buy it from GM if you know a GM parts guy.

The seal in the speedo bullet that your driven gear goes into is not your problem although it should be in the bullet far enough to do its job.

Scott

[Rainer S.]

Re: 63 speedo gear

Scott,

You brought up a good point about the cable lube, or lack off.
When I had the cable out for inspection, it was not lubed, dummy me, I never thought about putting some good lube on it.
When I remove it tomorrow, I will do that. I know what you mean by seating the seal. I did that already. The seal was not in the speedo bushing far enough,(bullet, as you call it) and I pushed it in where it should have been.
Not having a lubed cable in the housing may explain, why the gear was bad, when I first removed it. May even have worn the cable housing)
I now have a new gear installed, will lube the cable and verify the lenght of the cable, from the stop, to make sure it does not bottom out in the speedo gage (instrument).
I'll do anything, to avoid pulling my dash out...

Rainer

[Joe L.]

Re: 63 speedo gear

Scott,

You brought up a good point about the cable lube, or lack off.
When I had the cable out for inspection, it was not lubed, dummy me, I never thought about putting some good lube on it.
When I remove it tomorrow, I will do that. I know what you mean by seating the seal. I did that already. The seal was not in the speedo bushing far enough,(bullet, as you call it) and I pushed it in where it should have been.
Not having a lubed cable in the housing may explain, why the gear was bad, when I first removed it. May even have worn the cable housing)
I now have a new gear installed, will lube the cable and verify the lenght of the cable, from the stop, to make sure it does not bottom out in the speedo gage (instrument).
I'll do anything, to avoid pulling my dash out...

Rainer

Rainer-----


What is the rear gear ratio of this car and what size tires do you have on it?