Erratic speedometer
Thread Starter
Cruising
Joined: Apr 2016
Posts: 14
Likes: 1
Erratic speedometer
1993 Corvette
Anyone experience this and have suggestions as to what it may be.
Driving the car and the speedometer seems normal.
After car warms up.. roughly 20 minutes into drive the speedometer gives erratic readings. Will show the speed eg 80km/h but jumps around from 60-90 km/h....
Radio volume also goes up and down when it is set to increase with speed.
And with cruise set... car lurches. (without using cruise, car runs completely normal)
seems to happen pretty consistently wtihin 15-20 minutes of drive but not when cool.
Car runs normal without cruise set
Anyone experience this...Any suggestions?
Anyone experience this and have suggestions as to what it may be.
Driving the car and the speedometer seems normal.
After car warms up.. roughly 20 minutes into drive the speedometer gives erratic readings. Will show the speed eg 80km/h but jumps around from 60-90 km/h....
Radio volume also goes up and down when it is set to increase with speed.
And with cruise set... car lurches. (without using cruise, car runs completely normal)
seems to happen pretty consistently wtihin 15-20 minutes of drive but not when cool.
Car runs normal without cruise set
Anyone experience this...Any suggestions?
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
Are there any codes stored? Vehicle speed sensor mounts on transmission and there are nylon gears that make it work. Its possible they are worn"apple cored )( ". While drive gear is being checked for condition make sure retaining clip is present and not broken.
Team Owner
Joined: Sep 2003
Posts: 25,414
Likes: 2,745
The last fellow I suggested "checking" drive gear to didn't until all else he attempted failed. He looked "again" and the retaining clip on the drive wasn't retaining the gear. I doubt you'll find VSS errors because the VSS is working still UNLESS it's ever dropped all together.
The one thing you might do is note the color of the drive gear and then the tooth count/color of the driven to confirm the VSS is a match to the tooth count. Check the VSS for an 8 digit part # and note the color of the connector for the car harness.
Do you know if the MPH/KPH is correct when it works? Do you know the axle ratio? What size tires?
That information would help tell you "what to expect" when you remove the VSS to check things.
The one thing you might do is note the color of the drive gear and then the tooth count/color of the driven to confirm the VSS is a match to the tooth count. Check the VSS for an 8 digit part # and note the color of the connector for the car harness.
Do you know if the MPH/KPH is correct when it works? Do you know the axle ratio? What size tires?
That information would help tell you "what to expect" when you remove the VSS to check things.
Last edited by WVZR-1; Jul 8, 2016 at 11:19 AM.
Thread Starter
Cruising
Joined: Apr 2016
Posts: 14
Likes: 1
The last fellow I suggested "checking" drive gear to didn't until all else he attempted failed. He looked "again" and the retaining clip on the drive wasn't retaining the gear. I doubt you'll find VSS errors because the VSS is working still UNLESS it's ever dropped all together.
The one thing you might do is note the color of the drive gear and then the tooth count/color of the driven to confirm the VSS is a match to the tooth count. Check the VSS for an 8 digit part # and note the color of the connector for the car harness.
Do you know if the MPH/KPH is correct when it works? Do you know the axle ratio? What size tires?
That information would help tell you "what to expect" when you remove the VSS to check things.
The one thing you might do is note the color of the drive gear and then the tooth count/color of the driven to confirm the VSS is a match to the tooth count. Check the VSS for an 8 digit part # and note the color of the connector for the car harness.
Do you know if the MPH/KPH is correct when it works? Do you know the axle ratio? What size tires?
That information would help tell you "what to expect" when you remove the VSS to check things.
not sure axle ratio. Everything is original equipment.
I the gear a separate component from the VSS. Or does it all come as one pc?
Team Owner
Joined: Sep 2003
Posts: 25,414
Likes: 2,745
Team Owner
Joined: Sep 2003
Posts: 25,414
Likes: 2,745
The drive gear retainer is a bit different for the ZF and I've never looked at the drive gear through the VSS port to see how easily it could be checked. I've been fortunate to have never needed to replace the drive gear with rear axle changes. Everything up to a 3.73 can use the same drive. 3.90 plus requires replacement of the drive gear so those people would have had one in hand.
Where are you located? I noticed you mentioned KPH so you for sure ain't in West Virginia USA. LOL
Where are you located? I noticed you mentioned KPH so you for sure ain't in West Virginia USA. LOL
Thread Starter
Cruising
Joined: Apr 2016
Posts: 14
Likes: 1
The drive gear retainer is a bit different for the ZF and I've never looked at the drive gear through the VSS port to see how easily it could be checked. I've been fortunate to have never needed to replace the drive gear with rear axle changes. Everything up to a 3.73 can use the same drive. 3.90 plus requires replacement of the drive gear so those people would have had one in hand.
Where are you located? I noticed you mentioned KPH so you for sure ain't in West Virginia USA. LOL
Where are you located? I noticed you mentioned KPH so you for sure ain't in West Virginia USA. LOL
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Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
gears are separate parts. If needed: Car should have come with 3.45 rear axle these are what should be there. zfdoc.com is a source for parts
12507670 Gray 15 tooth drive gear
25513049 Green 42 tooth driven gear
10456089 Vehicle speed sensor
12507670 Gray 15 tooth drive gear
25513049 Green 42 tooth driven gear
10456089 Vehicle speed sensor
Team Owner
Joined: Sep 2003
Posts: 25,414
Likes: 2,745
OP - I believe you could inspect the drive gear to see if the retainer has maybe failed. Correcting it might likely require removal of the driveshaft to allow enough movement to add a new retainer or what ever is required. I'd maybe try to get my hands on a new/used drive gear retainer before I started.
The retainer from GM is NLA, # is 12507671. ZF# 0501-310-390.
Maybe with your location you call Rockland Standard Gear using the ZF#
http://www.rsgear.com/
ZF DOC - Arizona USA maybe
http://www.zfdoc.com/
Maybe post a WTB here on the CF and if someone has a trashed ZF they could help you.
The retainer from GM is NLA, # is 12507671. ZF# 0501-310-390.
Maybe with your location you call Rockland Standard Gear using the ZF#
http://www.rsgear.com/
ZF DOC - Arizona USA maybe
http://www.zfdoc.com/
Maybe post a WTB here on the CF and if someone has a trashed ZF they could help you.
Thread Starter
Cruising
Joined: Apr 2016
Posts: 14
Likes: 1
OP - I believe you could inspect the drive gear to see if the retainer has maybe failed. Correcting it might likely require removal of the driveshaft to allow enough movement to add a new retainer or what ever is required. I'd maybe try to get my hands on a new/used drive gear retainer before I started.
The retainer from GM is NLA, # is 12507671. ZF# 0501-310-390.
Maybe with your location you call Rockland Standard Gear using the ZF#
http://www.rsgear.com/
ZF DOC - Arizona USA maybe
http://www.zfdoc.com/
Maybe post a WTB here on the CF and if someone has a trashed ZF they could help you.
The retainer from GM is NLA, # is 12507671. ZF# 0501-310-390.
Maybe with your location you call Rockland Standard Gear using the ZF#
http://www.rsgear.com/
ZF DOC - Arizona USA maybe
http://www.zfdoc.com/
Maybe post a WTB here on the CF and if someone has a trashed ZF they could help you.
It's a good start. It being intermittent I may just leave it until car gets stored but I know where to start now.
Team Owner
Joined: Sep 2003
Posts: 25,414
Likes: 2,745
Use the GM# 10456089 (Kenova mentioned) and try your local auto parts stores for a cross reference to just price. If reasonable enough maybe you just do it. You could likely resell the VSS for a recovery of most of the monies.