Speedometer Gear Question
Thread Starter
Racer
Joined: Nov 2009
Posts: 289
Likes: 0
From: Franksville Wisconsin
Speedometer Gear Question
I have a '81 Vette with auto trans TH350C. I'm replacing the speedometer with rebuilt 140 mph unit. While I'm at it I thought of checking the sppedo cables for freedom and lube them with liquid graphite lube. Unpon inspection I see the speedo drive sleeve fits loose in trans and has been leaking some. So I remove it and plan on new O ring seal at least. Now I see I need a new housing and gear. My question is the gear in it now is very light green in color (I thought it was discolored from white) but I count 20 teeth. The catalogs from corvette america and a few others list 34-45 tooth gears how can this be? I don't think anything much more than 25 tooth will fit in the hole in trans. My speedo was reading 7-10 mph slow. Also does the drive gear on trans mainshaft make a difference? Help!!!!!!! Thanks in advance.
Le Mans Master
Joined: Nov 2008
Posts: 5,691
Likes: 12
From: columbus oh
I have a '81 Vette with auto trans TH350C. I'm replacing the speedometer with rebuilt 140 mph unit. While I'm at it I thought of checking the sppedo cables for freedom and lube them with liquid graphite lube. Unpon inspection I see the speedo drive sleeve fits loose in trans and has been leaking some. So I remove it and plan on new O ring seal at least. Now I see I need a new housing and gear. My question is the gear in it now is very light green in color (I thought it was discolored from white) but I count 20 teeth. The catalogs from corvette america and a few others list 34-45 tooth gears how can this be? I don't think anything much more than 25 tooth will fit in the hole in trans. My speedo was reading 7-10 mph slow. Also does the drive gear on trans mainshaft make a difference? Help!!!!!!! Thanks in advance.
Thread Starter
Racer
Joined: Nov 2009
Posts: 289
Likes: 0
From: Franksville Wisconsin
Well I got a new housing and 19 tooth gear from summit racing. They do not show a 20 tooth for a TH350 only 19 +. I hope the drive gear in trans will work with the 19 tooth speedo driven gear. I also got a 20 tooth 4 spd gear from corvette america. It looks the same except color. If it does not work it did'nt cost much.
Thread Starter
Racer
Joined: Nov 2009
Posts: 289
Likes: 0
From: Franksville Wisconsin
Thanks! Looks like I need 19 tooth driven gear, if I have 9 tooth drive gear as I recall.I will look this morning to verify.
Last edited by WhiteC3; Dec 29, 2009 at 09:20 AM.
Thread Starter
Racer
Joined: Nov 2009
Posts: 289
Likes: 0
From: Franksville Wisconsin
It was green 9 tooth so I'm good to go. For reference: TH350 C drive gears pink 7 tooth,8-black,9,green and 10- purple
Also for info. if using a TH350c in earlier vette or decomputerizing an 81-82 If you use the cruise control speedo cables, the B&M lock-up transducer fits in place or inline with cruise control transducer.
Also for info. if using a TH350c in earlier vette or decomputerizing an 81-82 If you use the cruise control speedo cables, the B&M lock-up transducer fits in place or inline with cruise control transducer.
Last edited by WhiteC3; Dec 29, 2009 at 11:13 PM.
