Topic: speedometer cable replacement
in Forum: C3 Driveline Components
Already a Member?
Click Here to Login
Not yet a Member?
Click Here to Register for Free!
Wasn't sure where to post this sorry if I'm in the wrong place do you have to remove the transmission mounting bracket in a 78 Corvette coupe automatic to replace the lower cable Speedo cable
thank you
SPONSOR AD:: (Our Sponsors help support C3VR)
Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
No 
Joel Adams
C3VR Lifetime Member #56 
My Link 
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
replaced lower speedo cable and driven gear.still no speedometer.Tested upper cable with drill and got reading on speedometer.
disconnected lower speed cable from transducer and put rear up in the air to see if cable would spin. it did not.
any suggestions
Lifetime MemberEquinunk, PA - USA
Joined: 10/31/2007
Posts: 2465
Vette(s): 1972 conv, 4-speed, 350, 200hp, numbers match, rally wheels, war bonnett yellow w/white top. good condition, nice driver.
Sounds to me like the gear drive in the transmission is the culprit. Did you pull the pan and look for pieces?
we pulled out the driven gear.it was in one piece but the gears appeared melted. together. we replaced it along with new cable. still nothing
Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Most obvious culprit at this point is the drive gear on the trans tailshaft. It has most likely "apple cored", meaning worn down so much in the center that it no longer touches or drives the driven gear. Only solution is to remove the driveshaft, and tailhousing, to get to the drive gear to replace it. 
|UPDATED|3/17/2019 4:31:04 PM (AZT)|/UPDATED|
You CAN get the speedo to move if you spin the cable from the bottom, correct?
|UPDATED|3/17/2019 4:31:04 PM (AZT)|/UPDATED|
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
that's pretty much what the driven gear looked like whe we pulled it.
we connected new cable and left it unattached from the transducer. lifted the rear wheels put it in drive but the cable didnt turn.If that is what your asking
thanks for the Input. I was hoping for a more simple solution.
ty
Joel
any chance you have a pic of the drive gear. Ecklers only shows the driven gear sleeve.
maybe a part number
thanks
Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Need to see if the speedo will move if you turn the cable by hand, or with a drill motor. This will let you know if the cable from bottom to top is working.
Part #? Nope...it goes by the colors of the gears. Find out what color the drive gear is(red, green, blue, orange, etc), and we'll know how many teefers it has. Once you know that, getting a replacement(if needed) is fairly easy.
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
in Forum: C3 Driveline Components
SPONSOR AD: (Our Sponsors help support C3VR)