Quick Question

[msbaugh]

Working on a quick 15 minute job today... I'm just swapping the speedo gear on my 727 after I put the new 8 3/4 in.  I'm trying to get my speedo more accurate after the swap. 

Check the pictures, the old (blue gear) is quite large in diameter while the new gear with the correct number of teeth (red) is much smaller.  It's the right tooth number but it's so small that it doesn't even seem to engage in the splines on the transmission.  Where the heck can I get the right toothed gear that will engage correctly? Are they supposed to vary that much in size because it doesn't look like it's big enough at all.

Thanks fellers

[msbaugh]

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[DocMel]

When it comes to speedo gear changes, you will find that the gears that you change out will always be in the same diameter, just a different number of teeth on the outside edge : I believe you dont have the right model gear.

[daveh]

I agree with DocMel.  Tire size is also going to be a factor in what gear you choose.  Good luck. 

[cudazappa]

in order to keep the correct gear tooth pitch (because the worm gear in the transmission remains constant) the only way to change the tooth count of a speedo gear is to reduce or enlarge the gear size appropriately.

A 34 tooth gear will be larger than a 32 tooth gear.  If they kept the same diameter, the teeth pitch would change and not engage the worm gear in the transmission.

The speedo gear mount has an offset hole for the gear to go in.  When installing it, have the gear as far away from the worm gear.  Once inserted, turn the mount into the worm gear gently turning the gear ("wiggling" it back and forth radially) at the same time so that the teeth will engage the gear.  If you do it too tight you will eat up the gear.  If not tight enough, you will eat up the gear.  Not engaged, you don't get a working speedo.

I'm not near my FSM but I'm sure the procedure is explained.

[msbaugh]

in order to keep the correct gear tooth pitch (because the worm gear in the transmission remains constant) the only way to change the tooth count of a speedo gear is to reduce or enlarge the gear size appropriately.

A 34 tooth gear will be larger than a 32 tooth gear.  If they kept the same diameter, the teeth pitch would change and not engage the worm gear in the transmission.

The speedo gear mount has an offset hole for the gear to go in.  When installing it, have the gear as far away from the worm gear.  Once inserted, turn the mount into the worm gear gently turning the gear ("wiggling" it back and forth radially) at the same time so that the teeth will engage the gear.  If you do it too tight you will eat up the gear.  If not tight enough, you will eat up the gear.  Not engaged, you don't get a working speedo.

I'm not near my FSM but I'm sure the procedure is explained.

That makes a lot of since, thank you for the heads up. I realize now that the diameter would have to change in order to incorporate the different tooth counts.  Intuitively it makes perfect sense. I did not notice the offset hole so I did not see a way to line up the smaller gear.  It makes since now though, I will have to take the housing back out and try to see how it needs to be positioned to line up, thanks!

[anlauto]

When it comes to speedo gear changes, you will find that the gears that you change out will always be in the same diameter, just a different number of teeth on the outside edge : I believe you dont have the right model gear.

This is a false statement.

The gears all have different outside diameters depending on the number of teeth. As mentioned above, the mounting housing has four different mounting locations to allow for the different size gears.

[msbaugh]

That did the trick!!! For some reason though the speedo doesn't work in reverse! I don't really care but is that normal?

[anlauto]

Yes that's normal...

[msbaugh]

Yes that's normal...

I guess I just never noticed before haha