Speedometer Gear Wearing Out After 50 Miles

[Tuck73]

I have replaced the speedometer gear twice. The second time, I replaced the speedometer cable as well. I can go about 40-50 miles and it will quit working. I pull the gear and it is worn just enough that it won’t work. It’s not completely chewed up but more worn. I purchased the gear from Tom’s. How do I know if I need a 6 or 7 spline gear? I’m assuming g the one from Tom’s is the wrong one or else I have a bigger issue. Also, the transfer case has recently been rebuilt.

 

[Viperwolf1]

Might be something wrong with the drive gear on the output shaft. If you remove the driven gear you can inspect the drive gear. That's the gear with either 6 or 7 teeth. If it's plastic it can be identified by color. If it's steel you'll need to remove it to identify it.

To replace the drive gear the entire transfer case doesn't need to be removed and disassembled, just the rear output housing.

Sent from my SM-G781U1 using Tapatalk

 

[Broncobowsher]

Viperwolf has a wonderful chart that shows what gears work together for a given tire size and axle ratio. Since you will be replacing both gears to resolve this issue just pick the pair that are best matched to what you have (or plan on changing to)

 

[Viperwolf1]

Viperwolf has a wonderful chart that shows what gears work together for a given tire size and axle ratio. Since you will be replacing both gears to resolve this issue just pick the pair that are best matched to what you have (or plan on changing to)

Good point.

 

[.94 OR]

Any chance there is an issue with the cable? Could be causing an increase in friction that eats up the plastic gear.

 

[DirtDonk]

Definitely check the cable.
Even a new one could feel perfectly good when you’re spinning it by hand but if it’s just slightly too long, then when you put it in it could be binding.
Granted, it’s unlikely you had two cables with the same problem, but it’s not impossible.
Especially if both are replacements?

 

[Tuck73]

Any chance there is an issue with the cable? Could be causing an increase in friction that eats up the plastic gear.

I have a new cable. I’ve tried three gears. Two on the old cable and one on the new. Same issue on both.

 

[Tuck73]

I will try to look at the drive gear this weekend. Not sure what I’m looking fo but will give it a shot.

 

[MikeCon]

I have replaced the speedometer gear twice. The second time, I replaced the speedometer cable as well. I can go about 40-50 miles and it will quit working. I pull the gear and it is worn just enough that it won’t work. It’s not completely chewed up but more worn. I purchased the gear from Tom’s. How do I know if I need a 6 or 7 spline gear? I’m assuming g the one from Tom’s is the wrong one or else I have a bigger issue. Also, the transfer case has recently been rebuilt.

Did you pull cable out of shield and lube it? White grease

 

[Broncobowsher]

I thought the cables took graphite for lube?

 

[blubuckaroo]

What would happen if you used the wrong driven gear for your drive gear?

 

[.94 OR]

What would happen if you used the wrong driven gear for your drive gear?

Speedo would be off, unless you are suggesting using one from a totally different application.

 

[DirtDonk]

Nothing. I believe that all of the different driven gears with the different tooth counts are compatible with both tooth counts on the drive gear.
Could be wrong, because that's been just an assumption of mine, but I have not heard of anyone not being able to swap both gears around to achieve the desired ratio for their new differential gear ratios and tire sizes.

Paul

 

[69_Sport]

There are two types of these Ford gears. The difference is in the angle of the teeth. There are left hand and right hand styles. You can tell the difference by holding them up next to each other and examining the teeth. One will curve to the right, the other one to the left.

Are you sure you have the correct one? You may have one with the correct number of teeth, but the wrong style.

It has to do with the original use for the gear and which side of the transmission it was located.

 

[blubuckaroo]

There are two types of these Ford gears. The difference is in the angle of the teeth. There are left hand and right hand styles. You can tell the difference by holding them up next to each other and examining the teeth. One will curve to the right, the other one to the left.

Are you sure you have the correct one? You may have one with the correct number of teeth, but the wrong style.

It has to do with the original use for the gear and which side of the transmission it was located.

Thanks. This is exactly why posted the "rhetorical question."

 

[Broncobowsher]

There are actually 4 different speedometer gears, not counting tooth count. The two different helix directions, those depend on if the driven gear is located above or below the output shaft. The other one is the support nipple on the end, there is a short and a long version.


So long as you are getting parts from a Bronco vender there is nothing to worry about.

 

[DirtDonk]

So long as you are getting parts from a Bronco vender there is nothing to worry about.

Haha! Good one…
Wait. Did I say that out loud?

 

[Rustytruck]

if you pull the gear out of the transfercase and leave it hooked up to the speedo how hard is it to turn yhe cable?

 

[Seventee]

There are two types of these Ford gears. The difference is in the angle of the teeth. There are left hand and right hand styles. You can tell the difference by holding them up next to each other and examining the teeth. One will curve to the right, the other one to the left.

Are you sure you have the correct one? You may have one with the correct number of teeth, but the wrong style.

It has to do with the original use for the gear and which side of the transmission it was located.

This is the problem I had years ago. A vendor was selling the wrong pitch gears, which at the time I determined was for a 2wd manual transmission and not a 4x4 transfer case. I went through a gear in about the same amount of time as the OP and was baffled until I compared the replacement gear to my original and noticed the pitch difference.

 

[77BroncoWag]

Is it cable replacement time if the speedo bounces a lot? for example the needle goes up and down 30mph to 40-45mph driving at a constant speed