Cascade Crew

Alphius · Posted: Sun Mar 09, 2008 3:04 pm Post subject: 18 tooth speedometer gear

I decided I actually want to know how fast I'm going in my car... Rolling Eyes

I need to get a driven speedometer gear for a T5, same gear as for a T10, Muncie, or TH350. If anyone has an 18 tooth (brown) speedo gear laying around... let me know cause I could use it. From anywhere on the internet it's looking like about 20 bucks including shipping.

Thanks!

Al Hasse · Posted: Sun Mar 09, 2008 3:11 pm Post subject:

I need to do the same thing once I finish up this rear end swap. I haven't figured out which gear I need yet, I'm going from a 3.08 to a 3.23.

Twilightoptics · Posted: Sun Mar 09, 2008 4:38 pm Post subject:

I didn't think th350 and std transmission gears meshed properly. And there are tons of driven gears.

Alphius · Posted: Sun Mar 09, 2008 6:34 pm Post subject:

Hmmm, well according to a couple places on the internet Rolling Eyes

a TH350 and all the others I said (T10, Muncie 4-spd) use the same style of gear. Seemed kind of odd to me, but I think I'm gonna end up having to buy one expensively. Just seems kind of pointless to me to spend upwards of 15 dollars for a little tiny piece of plastic with teeth on it.

The one I need I already said is the 18 tooth driven gear, which should be a darkish brown color. I'm going to have to drop by the GM dealer or pay 20 bucks for one online though I think... GM will charge me just as much though Crying or Very sad

EDIT: Never mind guys, I found an eBay store that sells them for cheaper. Now I guess we'll find out for sure if a TH350 gear will fit a T5...

Alphius · Posted: Thu Mar 20, 2008 1:12 pm Post subject:

Got my new gear! Made and ordered for a TH350, works just fine for my T5. Good info to know I guess...

Anyway, now I'm ecstatic... I have a new 145 speedometer and it shows the right speed too Very Happy

I managed to get my calculations right too, which is good cause I must have done them 30 times just to be sure... Laughing

Al Hasse · Posted: Thu Mar 20, 2008 1:20 pm Post subject:

What rear end gear do you have and what size tires. I need to calculate mine too, might even need the same gear....

Alphius · Posted: Thu Mar 20, 2008 5:52 pm Post subject:

Hey Al, I have a 3.23 rear end and 25.6 inch diameter tires, so my correct speedo gear combo was a 7-tooth drive gear on the output shaft and an 18-tooth driven gear...

Stock with 3.73's the car had a 7-tooth drive and a 21-tooth driven.

A stock 3.08 car has an 8-tooth drive gear, and will therefore need a little different toothage on the driven... Correct me if I'm wrong, but your car will have 3.23's with the new rear end in it, right? If so, and according to your tire and wheel height with 17's and a 245/45/17 tire, you will need a 20-tooth driven gear for your 8-tooth drive gear.

Tire height is almost 25.7, rear end ratio is 3.23, drive gear has 8 teeth.
You need a 20-tooth driven gear for a TH350.
Here's the formula if you want to plug it in yourself also (I may have forgotten something about your setup Embarassed

):

Speedometer Gear Teeth = (Drive Teeth * Rear End Ratio * 20.2) / Tire Height

Good luck with it Al! Will I be seeing you at Cows this year? I can't wait to meet everyone... and cruise with a bunch of thirdgens Very Happy

I've been lurking around here long enough to almost feel like I know everyone... Laughing

Al Hasse · Posted: Thu Mar 20, 2008 6:27 pm Post subject:

Thanks lots. The drive gear was the only part of the equation I didn't know. When I get a chance I'll pull it out and see what driven gear is in there Smile

Yes, I will be at cows, my vacation request has been approved. If you bring your dad with you, he can bring his classic with him, the guys would like to see it.

Al Hasse · Posted: Fri Apr 04, 2008 7:12 am Post subject: