TH400 Speedometer gears

[Gary R.]

Hi guys,
As some of you are aware,I've been looking for some info on the TH400 speedo gears. I have found some conflicting info in the books I have here. In this case I'm going to 336 R&P gears from the original 308's. I was under the impression that I would only have to change the driven gear and want to confirm that. I believe the gear housing changed for the 355- 411 gear sets too but I couldn't find that in any of the manuals here.

The book I have goes to '71 and for a base 350 TH400 with 308 the drive is
#8623311 the driven is # 1359271(37 tooth red) the original gear in the TH400 is white - unknown tooth count?

The 336 uses the same drive gear number and #1362195( 41 tooth Yellow)

Does this sound correct?

Thank you

[Joe L.]

Re: TH400 Speedometer gears

Gary-----

Yes, it does.

[Gary R.]

Re: TH400 Speedometer gears

Thank you Joe, I just need to get a driven gear, which I still think are avail from GM. Do you know why there is a different gear set listed for the Hi per 454?

Gary

[Joe L.]

Re: TH400 Speedometer gears

Gary------

There were 2 different sets of speedometer gears used for THM-400 equipped Corvettes with 3.36:1 axle ratio.

The first set was DRIVE gear #8623311. This mated with DRIVEN gear #1362195. The DRIVE gear was a 16 tooth gear of ORANGE color code. The GM #1362195 DRIVEN gear is a 41 tooth gear of YELLOW color code.

The second set was DRIVE gear GM #8623313. This mated with DRIVEN gear GM #9775187. I don't have specs on the 8623313 gear, although I think that it's a 15 tooth gear. The GM #9775187 is a 45 tooth gear color coded LIGHT BLUE.

All of the above referenced gears except the 8623313 are still available from GM. However, there is available a supercessive part for the 8623313 and that gear is GM #8679984.

I do not know the reason for the use of the 2 different gear sets.