Speedometer Does Not Work

[vicnation]

I've spent the last hour trying to determine why my speedometer doesn't work. It hasn't in quite a while. I have replaced the cable. I can spin the cable from the transfer case end and the speedometer does work. There's a part sandwitched between the cable and the T-case housing and I'm not sure what that is. However, the internals seem to spin normally.

Could it be the gear in the T-case or something else?

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How do I get the gear out and how would I determine what part I need to replace it with? The truck has 32" tires but is otherwise stock. It has 3.07 gears, a TH350 and a NP203.

 

[chengny]

There's a part sandwitched between the cable and the T-case housing and I'm not sure what that is.

That is a speedometer calibration box (not OEM) to correct speedo cable rpm for oversize tires.

Here is a 205 set-up - similar to yours:

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How do I get the gear out

Use a big wrench and unscrew that coupling nut (actual term is sleeve). The sleeve has an internal o-ring that acts as a seal to prevent gear oil from leaving the T/C case and entering the speedometer cable housing.

how would I determine what part I need to replace it with?

Just get the gear used with stock tires. The speed compensator is matched to the degree of oversize of the tires. No need for a special drive gear.


One thing you mention isn't right:

However, the internals seem to spin normally.

Unless you are Superman, if you can spin the output shaft, that isn't "normal".

The speedometer drive output assembly is essentially hard coupled to the speedometer gear which is locked to the T/C's rear output shaft. If you can "back feed" through the speed compensator...something is broken. It could be the speedometer drive shaft shaft (shown above) is parted or it's gear is stripped, the internal speedometer gear could be stripped or it isn't locked to the rear output shaft.



First you have to take the assembly apart and see what is wrong.

 

[vicnation]

Thank you for the information. I'll pull it apart and look at the driven gear.

When I said the internals seem to spin normally, I was referring to the gear calibration box. When one side spins, the other side does as well.

What should I be looking for when I remove it? A stripped driven gear? When ordering a new one, do I just count the teeth or go by color?

Thanks again...