Speedometer Driven Gear

[chevy97]

Ok so the Previous owner did a complete transmission rebuild and i guess didnt have the speedo driven gear so he just plugeed it with silicone so ATF wouldn't leak out but now explains why i dont have a speedometer functioning.
The question is now, can ya tell me what original gear was in place of it. Currenlty its a Th400 with the yellow drive gear which means its 19 teeth. Next is that on the housing theres numbers stamped that read 36,37,38,39 counter clockwise on it. Does that mean the possible driven gears available are 36-39 teeth??? Also i tried using the transmissioncenter.net website to calculate the gear needed but i cannot seem to determine the rear axle ratio as it was bed-lined and block certain numbers on the differential tubes, but i can assure its a regular 10 bolt diff with a NP-208 Transfer case. Should i just match colors of yellow to yellow?

 

[SlickGTP]

You're correct that that gear housing is for gears with tooth counts from 36-39. There's another one for 40+.

You really need to determine the gear ratio in the rear end before you can figure out which driven gear you need. There are a few different ways to calculate it.

Here's a thread that explains how to do it without removing the cover: How To Calculate Gear Ratio wo Removing Covers

 

[chevy97]

Okay so I got a new driven gear but when installed it won't spin even with cable disconnected. I tried two different setups both my original housing and 35tooth gear and another 40+ housing with 42 tooth gear and still no spin. I can see the drive gear spin inside the tranny but seems like it doesn't make contact with driven to spin cable. Am I missing something?

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[SlickGTP]

I went to compare your pictures to the ones I took while doing my speedo fix and from what I can tell, you're missing the drive gear. That small one is for the governor.

Here's the post where I have the pictures from mine.

http://www.gmsquarebody.com/forum/showpost.php?p=212800&postcount=34

 

[chevy97]

You know what, ur right that yellow gear I have isn't the drive gear and makes sense to my problems. I searched other posts on how to change and most come out with a 2wd but mine is 4wd, is it the same thing after I disconnect transfer case from tranny?

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[SlickGTP]

Aw hell... I wasn't paying attention to the fact you have a 4x4. For the 4x4s the speedo gears are in the transfer case itself. The transmission should've had a blank plug installed instead of the rtv'd gear housing.

I'd look on the tail housing of the transfer case for a similar gear housing with retainer plate.

 

[chevy97]

Yes, the transfer case does have a plug but the line is cut off. How does this setup work, is there an extension that runs fun T/C to cable ?

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[SlickGTP]

I have a feeling there's a longer cable that is used for the 4x4s. LMC Truck shows different numbers depending on several factors including year, transmission, and whether or not you have cruise control.