Trans speedometer gears

R

rfpowerdude

Member
Joined
Oct 13, 2005
Anyone know a good source with a good selection of drive and driven gears? I need to get a 13 tooth drive and a 31 tooth driven gear for a '78 Cutlass Salon into which I put a rebuilt KZF 200-4R (one of my other cars). I have a 3.08:1 geared posi rear so the speedometer reads way low. This trans was an Olds 442 app with 3.73:1 rear originally. Since GM speedometers want to have 1001 revs/mile, the gears can be calculated by:

Speedo Revs/mile =(20168*DiffGear*DriveGearTeeth)/(Tdiam"*DrivenGearTeeth)

...then rearrange for the missing info.
I have a 26" tire.

Rockauto used to have a lot, now they have nothing. Anyone know a good source with a good selection?
 
The 13 tooth drive (governor) gear is the most common, you are in luck there. driven gears are much cheaper to buy new than a drive gear which is probably discontinued anyway. Let me go hunt for part numbers...
 
13 tooth drive gear is part number 8634934 and is discontinued from gm, list price was $26.56 at that time. It is called white in color, more of a natural clear plastic color

31 tooth driven gear had 2 gm numbers, again "white" in color. I "think" 403417 is just the gear without the bullet, list price was $8.28 when it was discontinued. I "think" number 25524926 is with the bullet, list price was $65.72 (!) and it says "trade" which I don't know how to interpret, but you'd have to be nuts to pay $65 for it anyway. Back when I made these notes, TCI part numbers for those 2 gears were 880041 for the gov. gear, and 880037 for the driven gear. Have to call them for availability. Any trans shop should be able to help you find them, the 3.08 ratio was common. The gears you are taking out are actually much more desireable than the ones you are installing, someone might trade you (myself included if they are the right gears).

I didn't run the calculator to verify tooth count I just looked up the gear tooth count you gave me.
 
Thanks a bunch amigo, I will have the pan off this weekend and I will report on what gears are already in there. Yes, maybe we can make a trade! :D
 
If you need NEW gears, I do not have them. I have some good used gears, and I am fairly certain I have the ones you need.

Send me a PM if no one else jumps in here. I know most all of the 200-4r builders will have a PILE of those gears laying around. It's one of those things that is useless until you don't have the right ones, and new ones are mostly gone. There should be a driven gear that would match the red 12 tooth drive gear also.
 
Ya, a green 29 tooth driven gear would match the 12 tooth red drive gear for my application. Used gears are fine, this installation will probably only be in this configuration for a coupla years...
 
My only 13 tooth drive gear that's NOT in a trans has a little too much wear on it to be considered "sellable" by my standards, and I don't have a 31 tooth driven gear even if I tore into a core for the drive gear. I DO, however have a nice used red 12 tooth drive gear and green 29 driven if that will work for you. PM me a cell number and I can send you a pic. Your current drive gear should be a green 10 tooth, if you can run a calc. and see if the driven gear range goes low enough to use it, that'd save you some trouble pulling the governor out but I doubt it goes that low. I cant calculate with the various formulas tonight because all that stuff is at work.
 
A 3.73:1 rear uses a 10 drive like you said. The driven one is probably a 29 since that's what calculates out. With a 3.08 gear and a 10 drive gear, a 24 driven would be necessary. However, I have to pull the governor anyway since the governor spring is probably laying in the pan. I figured since I will be in there fixing the governor spring, I should also do the speedo gear change. Is there a 24 driven gear available? If so, that would be all I need. If not, I would need the 12 drive gear. THEN, my 29 driven would be right.

I am tearing into it on Friday morning. I will post back once I know what I have. Thanks!
 
24 doesnt exist from the info I have. 18, 19, then 26-31. i assume 18-19 are for diesels/crazy tall gears.

If you just need a drive gear I can do that too.
 
Well, the reason this all started was because I had high rpm only upshifts. My searching around here taught me that this was most likely the governor spring fell out. This past weekend, I got the pan off, governor out and YEP, the spring was in the pan. I pulled the governor, and put the spring back in. I then put a drain plug into the pan so I wouldn't have to deal with that again when I replace the speedo gears. I put it back together and started on the drive home. The shifting was completely back to normal until I got halfway home. It did it again, except this time, I can't get it to shift out of 1st at all. Plus, there is no engine braking on coast down at all. I am thinking the spring came off again and one or both check balls are in the pan. When I first pulled the governor, the check balls also fell out. What holds these captive so they don't fall out while driving? When I get the governor out for the second time, I want to put it back together one final time and be done with it.

Any suggestions?

Also, I could really use the red 12 tooth drive gear now... :)
 
rfpowerdude said:
Well, the reason this all started was because I had high rpm only upshifts. My searching around here taught me that this was most likely the governor spring fell out. This past weekend, I got the pan off, governor out and YEP, the spring was in the pan. I pulled the governor, and put the spring back in. I then put a drain plug into the pan so I wouldn't have to deal with that again when I replace the speedo gears. I put it back together and started on the drive home. The shifting was completely back to normal until I got halfway home. It did it again, except this time, I can't get it to shift out of 1st at all. Plus, there is no engine braking on coast down at all. I am thinking the spring came off again and one or both check balls are in the pan. When I first pulled the governor, the check balls also fell out. What holds these captive so they don't fall out while driving? When I get the governor out for the second time, I want to put it back together one final time and be done with it.

Any suggestions?

Also, I could really use the red 12 tooth drive gear now... :)
Click to expand...

The governor ball checks are held in by the weights. If they get bent they can fall out. Chances are the governor is damaged. You should use an 8-32 set screw to hold the spring in place in the future. PM me if you want the gear.
 
bison said:
The governor ball checks are held in by the weights. If they get bent they can fall out.
Click to expand...

So, when the balls are in place, no matter what orientation you hold the governor in your hand, the balls should not fall out even as the weights are flopping around? Mine did.

I will do the screw thing on it for the spring, but weigh it first before the screw is added so I can grind some weight off of it before I put it back together.
 
rfpowerdude said:
So, when the balls are in place, no matter what orientation you hold the governor in your hand, the balls should not fall out even as the weights are flopping around? Mine did.

I will do the screw thing on it for the spring, but weigh it first before the screw is added so I can grind some weight off of it before I put it back together.
Click to expand...

Thats correct. The balls should not fall out. I use nylon screws and they weigh about .2g when cut down. No need to grind. The hole is already the correct size for the 8-32 tap.
 
Ooh, the nylon screw thing is a great idea.

I will have to take the governor apart and slightly bend the tabs in that hold the check balls in place. They seem to be too far out since the balls can fall out if you alternately swing the weights all the way in and rotate the whole assembly upside down.
 
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