Speedo gears in a T400

[gnxtc2]

Anyone know how to figure out what speedometer gears I need?

Trans: 400
Rear Gear: 3:73
Tires: 325/50-15

When I had the trans apart, there was a plastic gear on the tail shaft (drive gear) held in with a clip. I think the color was greenish. Went to TCI's website and it stated that the replacement gear was steel and press on. My drive gear was a slide on on held in place with a clip.

Forgot what color the driven gear was.

Thanks

Billy T.
gnxtc2@aol.com

 

[Fuelie600]

You can go directly to your GM/Chevrolet dealer for the plastic gear. They are around $7 ea.. I went with the tallest gear possible for my set up( color pink ). You will need to see how off your speedo is, then count the trans gear teeth ( the one the external plastic gear rides against ) to see what you will need. There is only so much wiggle room for changing the ratio, before the internal gear will need to be changed out. A GPS is a helpful tool for calibrating your speedo. I'm still about 10% fast and my calibration, but it will do. I can't slow it down any more with out changing out my tailshaft and internal gear. Brian

 

[gnxtc2]

I'm trying to figure it out before I put any fluid in

Billy T.
gnxtc2@aol.com

 

[Fuelie600]

OK, I see. There are many variables ( trans ratios ect), and when I had Vince Janis build my 400, he got it close with the info I gave him. I still found that when I actually hit the road, there was some dialing in to do on the speedo calibration. Best of luck, Brian

 

[chris718]

rear end ratio x # of teeth on drive gear divided by tire diameter in inches x 20 .2

 

[fgordon]

I'm trying to figure it out before I put any fluid in

Billy T.
gnxtc2@aol.com

Try this link, it may help.

TCI - TECHNICAL INFORMATION: Speedometer Gears

 

[gnxtc2]

Went to the TCI site.

Tried plugged in the drive gear teeth size and the calculator came up with "N/A"

So what I decided to do is start from scratch.

Planning to use a:
40 tooth (black) driven gear
and
15 tooth drive gear. TCI states that this gear is metal and brown/gray in color. From doing some research, I have an early model 400 with a plastic drive gear held with a clip. I guess a trip down to the GM dealer will have to be made. I hate doing to the dealer with no part numbers.

Unless someone has some other tips.

Billy T.
gnxtc2@aol.com