M1009 Speedometer Cable Replacement?

[Sharecropper]

OK, using the time-tested formula of "# of Drive Gear teeth X axle ratio X (20168 divided by tire diameter) divided by 1001 = # of Driven Gear teeth to use", I determined this: 15 (drive gear teeth) X 3.73 (M1009 rear axle ratio) x 616.99 (20168 divided by your tire diameter of 32.6875) divided by 1001 = 34.48. Or put more simply 15 X 3.73 X 616.99 divided by 1001 = 34.48 required teeth on driven gear for accurate speedometer output.

So you will need to use a light green 34-tooth driven gear GM 9774413 or an orange 35-tooth driven gear GM 9780387. You will also need the GM25512340 sleeve with either of these driven gears. All this is readily available on Ebay. PM me and I will send you a link because the SS website police don't like for us to post links to active Ebay auctions (so dumb).

 

[Sharecropper]

OK, using the time-tested formula of "# of Drive Gear teeth X axle ratio X (20168 divided by tire diameter) divided by 1001 = # of Driven Gear teeth to use", I determined this: 15 (drive gear teeth) X 3.73 (M1009 rear axle ratio) x 616.99 (20168 divided by your tire diameter of 32.6875) divided by 1001 = 34.48. Or put more simply 15 X 3.73 X 616.99 divided by 1001 = 34.48 required teeth on driven gear for accurate speedometer output.

So you will need to use a light green 34-tooth driven gear GM 9774413 or an orange 35-tooth driven gear GM 9780387. You will also need the GM25512340 sleeve with either of these driven gears. All this is readily available on Ebay. PM me and I will send you a link because the SS website police don't like for us to post links to active Ebay auctions (so dumb).

I just looked and I have a new 25512340 sleeve in my spare parts bin which you are welcome to if you want it. All you will need will be the driven gear. If you plan to keep running your same tires & wheels I would get the light green 9774413 driven gear. If you change to larger tires in the future, it is a simple calculation to determine which driven gear to use with that specific tire circumference.

 

[HelluvaEngineer]

Didn't the M1009 have 3.08 axle ratios? As a spot check, unless the stock gear was way off, if using the adapter, I can do the ratio of the tire diameters and apply that to the gear ratios I would think, since that's a simple linear ratio. That gives me 38.9.

 

[Sharecropper]

Didn't the M1009 have 3.08 axle ratios?

Dang. Good catch. I stand corrected. Let me re-work the calculations. For some reason I was thinking the M1009's were running 3.73 gears.

 

[Sharecropper]

Holy Mackrel. Using 3.08 gears in the equation, you would need a Yellow 28 tooth driven gear without the reducer adapter that you removed. Is that what you said you had? If so, try using the Yellow driven gear without the reducer adapter and see how the speedometer reads. If you do not have the Yellow 28-tooth driven gear, I just looked and there are several on Ebay. Just search "yellow 28 tooth driven gear".

 

[Sharecropper]

Just following up on this. What sleeve do you have? The Yellow 28-tooth driven gear will require the GM 25512340 sleeve. As previously stated, I have one of these sleeves in my spare parts bin which you are welcome to if needed. It is new in the GM box. Let me know.

 

[HelluvaEngineer]

It has the stock grey sleeve. I'm still waiting on the order of the gear and carrier that I posted above. I'm still planning to try it with the adapter so I don't have to open the case. It may be the weekend before I can follow up.

 

[HelluvaEngineer]

Finally, an update on this. It's been raining every day for a week.

I just put everything back together with the new driven gear, housing, and cable. I have no reading on the speedometer. This doesn't surprise me though, because I noticed there is nothing driving the speed adapter from the end of the driven gear. Unless it's a press fit (doubt), now I think I lost a square pin that is supposed to drive everything. Does anyone with an M1009 know if there is something connecting that driven gear to the adapter? Thanks.

Edit: I guess tomorrow I will connect the new cable directly and make sure that works.

Edit2: Yeah I found list one listed as a Mopar part. I am completely missing that drive shaft. I'll search the ground but I think it's gone. I could make one from cutting off a section of the old speedo cable.

 

[Sharecropper]

Finally, an update on this. It's been raining every day for a week.

I just put everything back together with the new driven gear, housing, and cable. I have no reading on the speedometer. This doesn't surprise me though, because I noticed there is nothing driving the speed adapter from the end of the driven gear. Unless it's a press fit (doubt), now I think I lost a square pin that is supposed to drive everything. Does anyone with an M1009 know if there is something connecting that driven gear to the adapter? Thanks.

Edit: I guess tomorrow I will connect the new cable directly and make sure that works.

Edit2: Yeah I found list one listed as a Mopar part. I am completely missing that drive shaft. I'll search the ground but I think it's gone. I could make one from cutting off a section of the old speedo cable.

View attachment 947593

Did you try connecting the cable directly to the transfer case without the adapter? I'm interested to know what your speedometer will do in that configuration. Try it and report back please.

 

[HelluvaEngineer]

Did you try connecting the cable directly to the transfer case without the adapter? I'm interested to know what your speedometer will do in that configuration. Try it and report back please.

It keeps getting better and better. I connected the new cable directly to the xfer case and went for a drive. Nothing.
So I had my tools with me and I disconnected the speedo so that I could see the cable. No rotation. Put my fingers on it while I drove. Nothing. So my guess is that the 39T is completely incompatible with whatever drive gear I have and the info that decision was based on is garbage,

Interesting side note: I just found out that if you replace the alternator lights with LEDs, your alternators won't work.

• The GEN1 and GEN2 lights are part of the excitation circuit that "wakes up" the alternators when the ignition is turned on.
• With incandescent bulbs, current can flow in both directions through the filament, and the bulbs provide enough resistance for proper alternator excitation.
• LED bulbs are polarity-sensitive and allow almost no reverse current flow, so they block the alternator’s feedback voltage after startup, and sometimes don’t allow enough current to initiate charging in the first place.
• With LEDs and the voltmeter disconnected, the system can't back-feed enough current to self-excite the alternators—so the alternators don't start or stay charging, and the lights stay on.

 

[royalflush55]

It keeps getting better and better. I connected the new cable directly to the xfer case and went for a drive. Nothing.
So I had my tools with me and I disconnected the speedo so that I could see the cable. No rotation. Put my fingers on it while I drove. Nothing. So my guess is that the 39T is completely incompatible with whatever drive gear I have and the info that decision was based on is garbage,

Interesting side note: I just found out that if you replace the alternator lights with LEDs, your alternators won't work.

• The GEN1 and GEN2 lights are part of the excitation circuit that "wakes up" the alternators when the ignition is turned on.
• With incandescent bulbs, current can flow in both directions through the filament, and the bulbs provide enough resistance for proper alternator excitation.
• LED bulbs are polarity-sensitive and allow almost no reverse current flow, so they block the alternator’s feedback voltage after startup, and sometimes don’t allow enough current to initiate charging in the first place.
• With LEDs and the voltmeter disconnected, the system can't back-feed enough current to self-excite the alternators—so the alternators don't start or stay charging, and the lights stay on.

Sounds like your drive gear for speedo is garbage. it must be worn down enough to not turn the driven gear.

 

[Sharecropper]

Ditto on what Flush said. From what I am reading, your drive gear inside the transfer case could possibly be shot. I know it's a pain to get to and to see it, but you really need to remove the sleeve and inspect that drive gear as recommended in my earlier post. You can't get your head and eyeball up in there to see, but you can shine a light in there and hold your phone up to take a photo of the gear. If in fact the drive gear teeth are missing or worn-off, you will have a choice of 1)- either doing without a speedometer reading while driving or 2)- going into the transfer case to replace the drive gear. Here is what a new drive gear looks like -

 

[HelluvaEngineer]

Thanks guys. I looked at it with an inspection mirror a while back and it looked OK.

I just had a chance to go out there and look at it again. I used a nub from the end of the old cable and the driven gear would not turn by hand, so that was good. I reattached everything and I was very careful to feed the end of the cable into the driven gear. After that, the speedo started working. I suspect what happened is that the end of the cable slipped over the side when I installed it the first time.

The speedometer is now nice and smooth. I only took it around the neighborhood but it doesn't look that far off. I will try it with the phone GPS this week and see if I need the reducer. Again, I did change the gear to the 39T. It looked a little low to me but that seems incorrect as I thought the adapter was a reducer. I'll wait until I can get some actual data and report back.

Thanks again for the help.

 

[Sharecropper]

Thanks guys. I looked at it with an inspection mirror a while back and it looked OK.

I just had a chance to go out there and look at it again. I used a nub from the end of the old cable and the driven gear would not turn by hand, so that was good. I reattached everything and I was very careful to feed the end of the cable into the driven gear. After that, the speedo started working. I suspect what happened is that the end of the cable slipped over the side when I installed it the first time.

The speedometer is now nice and smooth. I only took it around the neighborhood but it doesn't look that far off. I will try it with the phone GPS this week and see if I need the reducer. Again, I did change the gear to the 39T. It looked a little low to me but that seems incorrect as I thought the adapter was a reducer. I'll wait until I can get some actual data and report back.

Thanks again for the help.

Before you reinstall the reducer, let me know how far off your speedometer reading is and I will calculate which new driven gear you will need for accurate speedometer reading without the reducer.