Speedometer jumping and lagging
Thread Starter
Instructor
Joined: Jul 2005
Posts: 246
Likes: 0
Speedometer jumping and lagging
Gentlemen, I replaced my speedometer cable then it ended up melting on the headers and not allowing the cable to move. So I bought a new cable installed it and now the speedometer jumps and is lagging. Can the gear inside the tranny be stripped? Is this hard to fix? Would a poorly routed cable cause this?
Any thoughts?
Thanks
Mike
Any thoughts?
Thanks
Mike
Racer
Joined: Mar 2005
Posts: 487
Likes: 0
From: Jacksonville FL
it's a piece of cake. i just changed my gear to compensate for a diferential change that a previous owner did with out bothering to recalibrate the speedo.
there is just one bolt holding the sleeve in place. remove it, pull out the sleeve and the gear should come out with it or be sitting loosley in the hole.
the gears are cheap and most of the usuall suppliers will have them.
there is just one bolt holding the sleeve in place. remove it, pull out the sleeve and the gear should come out with it or be sitting loosley in the hole.
the gears are cheap and most of the usuall suppliers will have them.
Thread Starter
Instructor
Joined: Jul 2005
Posts: 246
Likes: 0
Well, I checked the speedometer gear. Its a "natural" color 19 tooth gear and appears to be in good shape. I took the car out for a spin and the needle doesn't jump anymore but its reading the wrong speed.
I have a 1980 corvette with the turbo 350 tranny and as far as I know the stock rear end. Also, I am running 255 60R15 tires.
Should I be using the 19 tooth gear?
Mike
PS I also check the cable to the speedometer with a drill and got 40KPH, then check the other cable through the cruise transducer and got 40kph again. So, im pretty sure my cables are ok, I used the old speedometer gear at an adapter to check the cables.
Also, I noticed that clip that holds the speedometer gear and housing in place is allow it to kinda move, not a lot but there is alittle movement there.
I have a 1980 corvette with the turbo 350 tranny and as far as I know the stock rear end. Also, I am running 255 60R15 tires.
Should I be using the 19 tooth gear?
Mike
PS I also check the cable to the speedometer with a drill and got 40KPH, then check the other cable through the cruise transducer and got 40kph again. So, im pretty sure my cables are ok, I used the old speedometer gear at an adapter to check the cables.
Also, I noticed that clip that holds the speedometer gear and housing in place is allow it to kinda move, not a lot but there is alittle movement there.
Last edited by celeryman22; Apr 28, 2006 at 11:12 PM.
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Racer
Joined: Mar 2005
Posts: 487
Likes: 0
From: Jacksonville FL
What is the ratio on your rear end?
do you have the AIM for your year vette? it will tell you how many teeth are on your speedo drive gear.
with the tire size, rear end ratio, and number of teeth on your speedo drive gear, you can find out what size speedo driven gear you need at this site:
http://www.tciauto.com/tech_info/speedo_gears.htm
good luck and i hope this helps.
Mike.
do you have the AIM for your year vette? it will tell you how many teeth are on your speedo drive gear.
with the tire size, rear end ratio, and number of teeth on your speedo drive gear, you can find out what size speedo driven gear you need at this site:
http://www.tciauto.com/tech_info/speedo_gears.htm
good luck and i hope this helps.
Mike.
Thread Starter
Instructor
Joined: Jul 2005
Posts: 246
Likes: 0
As far as I know the rear end is 3.07. Also, I do have the assembly manual but I cannot find where it tells me the drive gear. On the page that details teh drive gear it refers me to drawing 14020821. Which I do not have.
Racer
Joined: Mar 2005
Posts: 487
Likes: 0
From: Jacksonville FL
it shoud be there on a page with a table on it. the table lists every possible transmition and rear end combination allong with the drive and driven gears used for each combination.
the only other thing you can do is to look into the hole in the transmission and count the teeth on the gear. you will need to mark one tooth and spin the drive shaft slowly so you can count the teath on the gear as it goes around.
it's much easier to look this kind of stuff up in a book, so i would look a little harder before i climbed back under your car again.
the table is there. it has to be. how else would the GM assembly guys know what gear to put on the car?
what year is your vette anyway? i don't suppose it's a 73?
good luck and i hope this helps.....
Mike.
the only other thing you can do is to look into the hole in the transmission and count the teeth on the gear. you will need to mark one tooth and spin the drive shaft slowly so you can count the teath on the gear as it goes around.
it's much easier to look this kind of stuff up in a book, so i would look a little harder before i climbed back under your car again.
the table is there. it has to be. how else would the GM assembly guys know what gear to put on the car?
what year is your vette anyway? i don't suppose it's a 73?
good luck and i hope this helps.....
Mike.
Thread Starter
Instructor
Joined: Jul 2005
Posts: 246
Likes: 0
My vette is an 1980. And its an 8 spline drive gear. From what I can tell it appears everything down below and the cables are ok. I have had the speedometer gauge out of my car for a year. Could I have messed the gauge up by touching the needle or something like that?
Mike
Mike
Thread Starter
Instructor
Joined: Jul 2005
Posts: 246
Likes: 0
There is one 90 degree bend where it leaves the transmission. Then there is another almost 90 degree bend where it goes into the cruise transducer. I will see if I can get rid on the second bend.
Mike
Mike
Burning Brakes
Joined: Feb 2002
Posts: 752
Likes: 31
From: Melbourne Australia
one possibility
On a 77 i had, with a binding speedo that would "stick" at varoius speeds, the new speedo cable inner was just a fraction long and it seems, any force onto the end of the speedometer causes it to bind. You can check this by unscrewing the cable from the transmissision a few turns to provide a bit of free play on the inner cable. If that fixes it then remove the inner cable, grind 1/8" of an inch off one end and reinstall.
Just something to check...might not be your problem however.
Good luck,
Joe
Just something to check...might not be your problem however.
Good luck,
Joe
