63 speedo gear

[Joe L.]

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

Scott-----


As you mention, the speedometer DRIVE gear in the transmission is steel and is pretty much "indestructible". However, it can easily be installed at the wrong position on the main shaft. If it's off even a little bit, improper meshing of the drive and driven gears can occur. This is true of all 57-63 T-10's, 63-67 Muncies, and 71-74 Muncies. 1968-70 Muncies use a nylon drive gear with special retainer that ensures proper positioning of the drive gear.

If the 22 tooth green driven gear is the correct one for this car, it is available under GM #3860345.

[Rainer S.]

Re: 63 speedo gear

Joe,

Tires:P215/70R15, ratio is 3.70:1
Getting ready to pull the cable etc.
I will also pull the gear out, put blueing in it, to see, if I can verify, that the gears are meshing. Will have to pull the gear out again, to do this and look at the blueing. Hpoe the oil does not wash it off...

Rainer

[Joe L.]

Re: 63 speedo gear

Joe,

Tires:P215/70R15, ratio is 3.70:1
Getting ready to pull the cable etc.
I will also pull the gear out, put blueing in it, to see, if I can verify, that the gears are meshing. Will have to pull the gear out again, to do this and look at the blueing. Hpoe the oil does not wash it off...

Rainer

Rainer-----


Assuming that the transmission and its internal components are original to the car, you should have the correct DRIVE gear installed for the 22 tooth green DRIVEN gear.

By the way, for the original tire size, the 22 tooth green DRIVEN gear should provide reasonably accurate speedometer calibration. However, the 215-70-15 tire size has an OD about 1-1/2" less than the original tires. So, with your current tire size, the speedometer will not provide an accurate reading.

[Rainer S.]

Re: 63 speedo gear

OK, You transmission guys. This is down your alley.
1. Removed speedo gear and cable.
2. Lubed cable with grease
3. Re-installed cable and connected to gage, verified that the cable is not bottomed-out-have sm. amount of backlash, when pulling on cable, while installed at instrument.
4. Connected drill at transm. end of cable - needle moves steadily
5. Cleaned speedo gear teeth with solvent, put Dykem steel bue on the gear teeth.
6. Re-installed the gear back in and connected the cable at the trans.
7. Drove around the block, same thing, as before.

The needle fluctuates, then stops and only moves when accelerating. As soon as I let off the acc, needle goes to zero.
8. Removed speedo gear from trans and observed, that the gear mesh is inadequate, almost negligible. (see pictures)

That is my problem. The speedo gear does not have enough engagement with the drive gear in the transmission. Or the speedo gear has a different gear tooth spacing than the trans gear and does not match.
I can't use a larger dia. speedo gear, because the bore in the housing is just big enough for the gear I have. (Gear O.D: .863")
There is about .013"/dia. difference, between the speedo shaft (.303") and the speedo fitting (.318"). That play allows the speedo gear to move away from the drive gear, but only .006 to 007", not enough to cause the gears not to mesh, I don't think.

What could cause this condition ? I can't really see much of the drive gear in the trans. When looking at it with a mirror, the gear teeth look similar to the once on the speedo gear, but I am not sure. I can stick my finger into the hole and feel the gear, does not appear to be loose or sloppy.
Is there another gear I can try ?
I can bush the speedo fitting to tighten-up the looseness to .001" clearance (I am a Supervisor in a Tool Room).
But besides that, what else is there, I could try next ?
Could I have the wrong type of gear ?

Rainer

[Joe L.]

Re: 63 speedo gear

OK, You transmission guys. This is down your alley.
1. Removed speedo gear and cable.
2. Lubed cable with grease
3. Re-installed cable and connected to gage, verified that the cable is not bottomed-out-have sm. amount of backlash, when pulling on cable, while installed at instrument.
4. Connected drill at transm. end of cable - needle moves steadily
5. Cleaned speedo gear teeth with solvent, put Dykem steel bue on the gear teeth.
6. Re-installed the gear back in and connected the cable at the trans.
7. Drove around the block, same thing, as before.

The needle fluctuates, then stops and only moves when accelerating. As soon as I let off the acc, needle goes to zero.
8. Removed speedo gear from trans and observed, that the gear mesh is inadequate, almost negligible. (see pictures)

That is my problem. The speedo gear does not have enough engagement with the drive gear in the transmission. Or the speedo gear has a different gear tooth spacing than the trans gear and does not match.
I can't use a larger dia. speedo gear, because the bore in the housing is just big enough for the gear I have. (Gear O.D: .863")
There is about .013"/dia. difference, between the speedo shaft (.303") and the speedo fitting (.318"). That play allows the speedo gear to move away from the drive gear, but only .006 to 007", not enough to cause the gears not to mesh, I don't think.

What could cause this condition ? I can't really see much of the drive gear in the trans. When looking at it with a mirror, the gear teeth look similar to the once on the speedo gear, but I am not sure. I can stick my finger into the hole and feel the gear, does not appear to be loose or sloppy.
Is there another gear I can try ?
I can bush the speedo fitting to tighten-up the looseness to .001" clearance (I am a Supervisor in a Tool Room).
But besides that, what else is there, I could try next ?
Could I have the wrong type of gear ?

Rainer

Rainer------

I'd say the problem relates to a DRIVE gear that is not installed on the mainshaft in the correct position. It does not have to be far off to cause just the problem you're experiencing.

The OD of the DRIVEN gear you have pictured is the largest of any ever commonly used in any 1957-70 manual transmission. There is no DRIVEN gear that I am aware of that has a larger OD and which will properly mate with the existing DRIVE gear.

So, I'd say the only solution will be to remove the transmission, remove the extension housing, and adjust the position the DRIVEN gear.

[Rainer S.]

Re: 63 speedo gear

Joe,
I was afraid you would say that.... But you are probably correct.
I will put the fitting back in w/o the gear and connect the cable, at least I will be able to drive the car.
Will mull over when to pull the trans out.

Thanks for your help.

Rainer

[John D.]

Re: 63 speedo gear

Greasing cables. I still can't believe the number of people I talk to that don't lubricate the tach cable, the speedo cable, and the fuel injection drive cable.
I recommend disc brake wheel bearing grease on the FI drive cable. I guess it would work well on the tach,speedo cable also. I know that the old white lithium grease doesn't hold up very well.
Dow Corning #44 med temp bearing grease is good stuff but not readily available and expensive. Any brand of Disc brake wheel bearing grease will do.
Ranier I feel for you friend. Removing the tranny in a 63 isn't too bad of a job if you have a nice lift and a friend.
Have Werner do it. Much easier to sign the check sometimes. Good luck, JD

[Wayne M.]

Re: 63 speedo gear

......Is there another gear I can try ?
I can bush the speedo fitting to tighten-up the looseness to .001" clearance (I am a Supervisor in a Tool Room).
But besides that, what else is there, I could try next ?
Could I have the wrong type of gear ?

Rainer

Rainer -- You've received excellent information above, but removing a trans to re-position the drive gear on the output shaft is such a major job that I offer the following hypothesis as a long shot on your problem. I'm probably wrong, but here it is, FWIW.

Looking at the damage on your green plastic 22-tooth driven gear, it looks like there is sufficient contact between the two, but it seems the platic teeth are being distorted. Is it possible that the car (or tranny) was originally set up for a 4.56 final differential ratio ? In this case, the drive gear has SIX hypoid teeth, and not the eight teeth (in 2 different diameters) normally used for the 3.08 to 4.11 ratios in Corvettes.

First pic below is of a 4.56 drive/driven set; the 6-tooth drive gear was used on '57 thru '68 Corvettes. The 20-tooth steel driven gear was used from '62 to '67's, according to my P&A30B of 1970. A different 20-tooth steel was used on '57 thru '60.

Second pic shows the 6-tooth drive again, and TWO versions of the 22-tooth plastic gears; one of larger diameter for the smaller diameter 8-tooth drive, and the smaller gear to mate with the larger 8-tooth drive gear [the latter grey plastic gear is a more recent addition -- was not available up to 1970, at least].

Third pic is of a pair of 8-tooth drive gears; IIRC, a large and small OD, and an assortment of plastic gears. You can see the wear pattern on the blue and brown (small) gears when it was used on the small drive gear (still meshes, but wears, more quickly with a high cable load).

The 4.56 steel drive is the largest diameter of the three, at 1.922", and is the thinnest @ 0.453". The 8 tooth versions are 1.765"/0.531" for large plastic gears, and 1.850/0.610" for the smaller plastic gears. It's easiest to identify by caliper measurement of gear width. I don't know if you can get a needle nose caliper (if such a tool exists) through the speedo fitting bore, but that would provide positive identification.

Again, this is a long shot -- I would even try a small plastic gear; certainly won't hurt, and you could analyze the wear or speedo behavior and post result on the board.

[Scott P.]

Re: 63 speedo gear

Rainer, did you put in a new driven gear since you first experienced the problem. The teeth on the driven gear should look like those that Wayne showed in his pictures.

About the drive gear being in the incorrect location on the main shaft. You do not have to pull the trans to check it. I believe the correct dimension for the drive gear on the main shaft is in the Chevrolet shop manual for your year Corvette, I think it is about 10" or so. Study the cut-a-way drawings in the shop manual to be able to visualize the below operation.

Take the speedo bullet out. Unhook the driveshaft, Remove the yoke, now with a thin metal object, say a machinest ruler that is 1/2"x12", or a piece of coat hanger bent very straight or a piece of 1/16" gas welding rod, insert it from the rear until it bottoms out against the speedo drive gear. I have not done this before but Ive rebuilt lots of Muncies and I think it will work. If the dimension is way off then look at the shop manual some more and figure out why. There should not be anything in the way for this not to work. If the demension is right on or off just a little then you can proceed to another trouble shooting area.

When something goes bad or dosent work I always try to find out or remember what we last did to that part or system. If the speedo worked for a long time after your restroration then I say, gear and or cable housing problem. The reason the speedo is skipping or returning back to zero I think is because of the driven gear teeth being messed up.

Speedo cable housings are cheap at the local parts store, buy one the correct length and put it in and see what happens, along with a new driven gear.

Scott

[Rainer S.]

Re: 63 speedo gear

Wayne,

Thanks for such detailed description of the various drive /driven gears used on those transmissions. Pic's look good..
I have taken another pic of the gears out of my trans. The badly worn one was in the longest, it was green at one time, turned yellow from contact with oil. The green one shows the start of similar wear. Like your brown one in your pic #3.
I will try to look at my trans again tomorrow.
There is absolutely no way to get a sm caliper tool in the hole, to measure the width of the drive gear.
But, I have an idea, I will try to get an impression of the gear width and tooth count and spacing, by pressing a piece of paper against the drive gear, thru the hole, using a dowel. this may work.
That way I could verify the shape of the gear. If that does not work, I have another alternative I want to try. (Better than pulling the trans...)
Also, I may try a smaller gear, or one for the wider drive gears. Will see..

Rainer

[Rainer S.]

Re: 63 speedo gear

Scott, thanks for pointing out to look in the shop manual! I found the description of how to install the speedo drive gear. Also a cut-away section, showing the autom, trans with a section of the extension housing, which is similar on the 4-speed. I understand how to check the position of the drive gear from the rear of the ext. hsg, after removal of the driveshaft etc.
I now understand how this all relates.
If I remember, when locking into to approx. 7/8" dia hole for the speedo bullet, with a mirror, I noticed, the drive gear was not central to the hole. Maybe the pos is off. I will verify this tomorrow.
By the way, what holds the drive gear in place, just the press on the main shaft ? No circlip/shoulder ?
Judging by fig 36 in the manual, its pressed on, until the set-up dim of 4 1/2" is met...

Rainer

[Joe L.]

Re: 63 speedo gear

Scott, thanks for pointing out to look in the shop manual! I found the description of how to install the speedo drive gear. Also a cut-away section, showing the autom, trans with a section of the extension housing, which is similar on the 4-speed. I understand how to check the position of the drive gear from the rear of the ext. hsg, after removal of the driveshaft etc.
I now understand how this all relates.
If I remember, when locking into to approx. 7/8" dia hole for the speedo bullet, with a mirror, I noticed, the drive gear was not central to the hole. Maybe the pos is off. I will verify this tomorrow.
By the way, what holds the drive gear in place, just the press on the main shaft ? No circlip/shoulder ?
Judging by fig 36 in the manual, its pressed on, until the set-up dim of 4 1/2" is met...

Rainer

Rainer----


For all 57-63 T-10, 63-67 Muncie, and 71-74 Muncie, the transmission speedometer DRIVE gear is retained to the shaft by an interference (i.e. pressed) fit. No clip or retainer is used. However, the journal on the main shaft for the DRIVE gear is wider than the gear. So, the gear can very easily be installed out-of-position.

[Rainer S.]

Re: 63 speedo gear

I found the root cause to my speedo problem.
I rigged-up a mirror to have a look at the hole in the transmission, which the speedo gear assy goes in, and observed, that the drive gear is out of position in relationship to the centerline of the driven gear assy by approx. 1/2". (should be central)
The edge of the drive gear appears to be in line with the centerline of the bore. It is too far toward the engine.
Took a pic (don't know how I did it) with an almost straight on look.
I guess, the trans has to come out.
At I time, when I have the car almost completely done and prepared to have it re-judged, to get topflight (should get 95%) it's frustrating to have to take it apart again...
I don't want to tackle it in my Garage, so I might have to call Werner...

Rainer