Speedo gears for TH400

[J Banning]

I have a TH400 in my T-Type. I'm running a 3.42 gear and 28” tall tires. The speedo reads about 20mph high (says 80 when I’m going 60).

I currently have the following in the trans:

• 18 tooth metal drive gear
• 34 tooth green plastic driven gear
• “36-39” stamped aluminum driven gear housing

QUESTION: What parts do I need so my speedo will read accurately, and can I keep the 18 tooth metal drive gear, or do I need a new one?

Thanks,
-Banning.

 

[J Banning]

Looking at TCI's web site, these look exactly like the pieces in my trans...

1. The drive gear is the meal gear that appears to be pressed onto the output shaft of the trans.
2. The driven gear housing is the aluminum housing that the speedo cable screws onto and then fits into the tail shaft of the trans.
3. The driven gear is the green plastic gear that slips into the driven gear housing. It meshes with the metal drive gear.

Any help would be much appreciated. Thanks.
-Banning.

 

[jakeshoe]

You need a 44 tooth driven and the appropriate sleeve.
If you factor in any tire growth a 45 tooth may be better, you are borderline.

 

[J Banning]

Thanks for such a quick reply.

I'm having a hard time figuring out what drive gear (metal gear) I'll need to go with the 45 tooth driven gear and appropriate housing. Where can I buy these?

 

[1of1547]

TCI has both their part #'s and GM part #'s on their list. Just click on the part #'s page.

 

[J Banning]

...can I keep the 18 tooth metal drive gear, or do I need a new one?

 

[jakeshoe]

You initially asked what you needed to get your speedo correct with your existing drive gear. I answered it, what else do you need?

 

[J Banning]

if I don't need to change the drive gear, then great, I'll go ahead and order the 45 tooth driven gear and 40-45 tooth housing.

Thanks again for the help.

 

[SSedan64]

NovaResource.com - Recalibrating GM Speedometers

TCI - COMPONENTS: Speedometer Gears