why does my speedo bounce
Joined: Aug 1999
Posts: 19,282
Likes: 103
From: Lawrence, KS
Car: Met. Silver 85 IROC/Sold
Engine: 350 HO Deluxe (350ci/330hp)
Transmission: T-5 (Non-WC)
Axle/Gears: Limited Slip 3.23's
Re: why does my speedo bounce
More than likely, you need to clean the cable and housing:
https://www.thirdgen.org/forums/inte...eedo-woes.html
JamesC
https://www.thirdgen.org/forums/inte...eedo-woes.html
JamesC
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Joined: Aug 2007
Posts: 1,525
Likes: 1
From: Milwaukee, Wisconsin
Car: 1987 IROC-Z
Engine: 383 with Edelbrock ProFlow EFI
Transmission: TH350
Axle/Gears: 12 bolt 3.73 Eaton posi
Re: why does my speedo bounce
It bounces because it wants to go club hopping. 
JK... I have the same issue with mine. After I hit about 30mph I have no idea what my speed is. One time I got going ~90mph down the highway and the thing just kept swaying between ~75-110mph.
JK... I have the same issue with mine. After I hit about 30mph I have no idea what my speed is. One time I got going ~90mph down the highway and the thing just kept swaying between ~75-110mph.
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Senior Member
iTrader: (2)
Joined: Dec 2008
Posts: 990
Likes: 1
From: Peoria, IL
Car: 1988 Camaro Sport Coupe
Engine: 5.0 305 Carb'd
Transmission: 700R4
Axle/Gears: 3.23
Re: why does my speedo bounce
yeah a new cable would help but it wont help if the cable connectors are dirty. take the cable off your tranny and clean the hell out of it. take the cable out of your speedo and clean it to. check your cable, if its not a straight rectangular bar than you need a new cable.
Joined: Aug 1999
Posts: 19,282
Likes: 103
From: Lawrence, KS
Car: Met. Silver 85 IROC/Sold
Engine: 350 HO Deluxe (350ci/330hp)
Transmission: T-5 (Non-WC)
Axle/Gears: Limited Slip 3.23's
Re: why does my speedo bounce
Cleaning and lubing instructions are provided in the link I provide above.
JamesC
JamesC
Supreme Member
Joined: Sep 2005
Posts: 2,151
Likes: 0
From: Osceola Indiana
Car: 92 RS(sold) 1989 IROC-Z
Engine: 350 TPI
Transmission: 700R4
Axle/Gears: ones that turn
Re: why does my speedo bounce
I have the same problem when I reach like 80 it starts floating, but then when i hit like 95 it goes back to normal it always does it exactly the same too. I'll have to try giving it a nice cleaning, and lube thanks james c for the great write up
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Joined: Aug 1999
Posts: 19,282
Likes: 103
From: Lawrence, KS
Car: Met. Silver 85 IROC/Sold
Engine: 350 HO Deluxe (350ci/330hp)
Transmission: T-5 (Non-WC)
Axle/Gears: Limited Slip 3.23's
Re: why does my speedo bounce
JamesC
Member
Joined: May 2006
Posts: 319
Likes: 2
From: Grand Junction, Co
Car: '83 WS6 T/A 65,000 miles
Engine: 5.0L vin H stock, 406SBC right now
Transmission: T-5
Axle/Gears: Corp. 3.73
Re: why does my speedo bounce
Mine bounces a little too...I'm pretty sure it's been pegged out to hard, too many times!
Joined: Aug 1999
Posts: 19,282
Likes: 103
From: Lawrence, KS
Car: Met. Silver 85 IROC/Sold
Engine: 350 HO Deluxe (350ci/330hp)
Transmission: T-5 (Non-WC)
Axle/Gears: Limited Slip 3.23's
Joined: Jun 2000
Posts: 5,364
Likes: 51
From: Enschede, Netherlands
Car: 82 TA 87 IZ L98 88 IZ LB9 88 IZ L98
Engine: 5.7TBI 5,7TPI 5.0TPI, 5,7TPI
Transmission: T5, 700R4, T5, 700R4
Axle/Gears: 3.08, 3.27, 3.45, 3.27
Re: why does my speedo bounce
Clean the cable and lightly spray the steel drive cable with some moly spray. Do not use grease as the way the carble turns the grease is forced up into the speedo and this will deteriorate the speedo head plastic over time. A very common problem on older cars w/ cable driven speedos. The plastics don't go well with the grease.
Supreme Member
Joined: Sep 2005
Posts: 2,151
Likes: 0
From: Osceola Indiana
Car: 92 RS(sold) 1989 IROC-Z
Engine: 350 TPI
Transmission: 700R4
Axle/Gears: ones that turn
Senior Member
Joined: Oct 2007
Posts: 590
Likes: 1
From: Winnipeg, Manitoba
Car: 86 Camaro IROC-Z
Engine: 565ci 900 hp
Transmission: T56 Magnum by RPM Transmissions
Axle/Gears: Moser 9" w/4:56 Detroit Locker
Re: why does my speedo bounce
I believe it could also be the speedo drive in the tranny, my was cable drive and did this, I changed to a Covan dash which came with a Autometer electric speedo and it still does it and it now does not have a manual cable
Junior Member
Joined: Jan 2017
Posts: 57
Likes: 13
From: Rhode Island
Car: 1989 Pontiac Firebird Formula
Engine: 305 TBI (stock)
Transmission: T5 (Converted May 2025)
Axle/Gears: 2.73, non-posi drum
Re: why does my speedo bounce
My 89 Firebird with a T5 has a gear-driven VSS:
The VSS unit I bought during my 5-speed swap came equipped with a 22-tooth gear, but after the swap my speedo was reading 10% low, so I was able to source a 19-tooth gear to account for some speedo inaccuracy (although now it reads 5% fast)
Now I get some minor speedo wiggle above 50 mph - think: +/- 1 or 2 mph, with more variation the faster I go.
I know the drive gear on the output shaft is a red 7-tooth and that the 7-tooth drive / 19-tooth driven gear combo is one that is commercially available for cable-driven speedo setups. Any ideas on cause?
The VSS unit I bought during my 5-speed swap came equipped with a 22-tooth gear, but after the swap my speedo was reading 10% low, so I was able to source a 19-tooth gear to account for some speedo inaccuracy (although now it reads 5% fast)
Now I get some minor speedo wiggle above 50 mph - think: +/- 1 or 2 mph, with more variation the faster I go.
I know the drive gear on the output shaft is a red 7-tooth and that the 7-tooth drive / 19-tooth driven gear combo is one that is commercially available for cable-driven speedo setups. Any ideas on cause?
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