75 4 speed speedometer problem
02-14-2007, 10:01 AM
#1
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Member Since: Feb 2007
Location: Yardley PA
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75 4 speed speedometer problem
Hello,
I'am new to this forum, I have recently bought a 75 4spd corvette.
Car is in ny state storage until, winter thaws and I can get the car out (this is killing me, I want to work on this during the winter, so ready for spring cruis'n, oh well). Seller has said the speedo doesn't work (both odometer and MPH) and he gave me a corvette speedo head unit to replace it with. But he is not clear on how he determined that the speedo head unit is at fault....hopefully it is the speedo drive gear in the trans, as I would think this is easier to replace.
4 questions:
1) Can I do a test by turning/feeling the speedo cable (disconnected from dash) to determine if head, cable or drive gear is a fault?
2) If speedo head unit is bad, how hard is to to replace out of dash?
3) If drive gear bad, do I have to drop the trans cross member to get to the drive gear?
4) If sppedo cable bad, is this a togh job to do?
Also what shop manual is good for describing these procedures?
I need to purchase a good one...he gave me the chevrolet 1975 service and overhaul manual....which is not detailed at all.....
sorry about long post, thnx for any info.......
I'am new to this forum, I have recently bought a 75 4spd corvette.
Car is in ny state storage until, winter thaws and I can get the car out (this is killing me, I want to work on this during the winter, so ready for spring cruis'n, oh well). Seller has said the speedo doesn't work (both odometer and MPH) and he gave me a corvette speedo head unit to replace it with. But he is not clear on how he determined that the speedo head unit is at fault....hopefully it is the speedo drive gear in the trans, as I would think this is easier to replace.
4 questions:
1) Can I do a test by turning/feeling the speedo cable (disconnected from dash) to determine if head, cable or drive gear is a fault?
2) If speedo head unit is bad, how hard is to to replace out of dash?
3) If drive gear bad, do I have to drop the trans cross member to get to the drive gear?
4) If sppedo cable bad, is this a togh job to do?
Also what shop manual is good for describing these procedures?
I need to purchase a good one...he gave me the chevrolet 1975 service and overhaul manual....which is not detailed at all.....
sorry about long post, thnx for any info.......
02-14-2007, 12:24 PM
#2
Le Mans Master
Take the speedometer cable loose from teh transmission, then chuck it up in a drill (I believe in reverse if I remember right) and see if that makes the speedo work. If it does then you know the problem is in the transmission and everything beyond that point is ok. If the speedo still doesnt' work, I'd disconnect from the back of the speedo and then spin it again with the drill, and you can watch the actual cable and see if it is spinning. If the cable is spinning, then the problem has to be with the speedo itself.
02-14-2007, 12:29 PM
#3
Drifting
Welcome to the insanity of Corvette ownership!
C3 beat me to it, I was just about to say the same thing. If you do have to replace the cable, you can get at the back of the dash and unhook it. Keep your cool though, it's a tight area. If need be you can pull the dash back just a little to give you some room.
Access to the cable on the transmission is pretty easy, it's right in the open.
C3 beat me to it, I was just about to say the same thing. If you do have to replace the cable, you can get at the back of the dash and unhook it. Keep your cool though, it's a tight area. If need be you can pull the dash back just a little to give you some room.
Access to the cable on the transmission is pretty easy, it's right in the open.