TH350 speedometer gear Q

[84ZZ4]

I just got around to pickup up a TH350C to replace my dying TH250C. It came out of an Olds Delta 88 with a 307 Olds motor.

Problem is, I'm trying to find out what speedometer gears I need. I found the calculator on TCI's web site, but the answers it is giving me are conflicting.

I need a set of gears for 3.42 gears and 26.2" tires. I come up with the following combinations:

Driveriven

17:44.7
10:26.3
9:23.6
8:21.0
7:18.4

Problem is, it looks like the smaller gears are designed to be used with the chevy-style tailshaft with the smaller gear housing... is that right?

 

[Nordbert]

Yes, the smaller numbers are for Chevy. I'd look at the gears you
have now (if the speedo is correct) and either use them or buy new ones like them. You can see the drive gear through the hole for the driven gear if you use a mirror and a flashlight. Gears of the same color usually have the same number of teeth.

 

[84ZZ4]

That doesn't do any good... the gears in there are for the stock 2.41s, and I'm ditching those. In fact, both my car and the donor car had 2.41s.