140 MPH speedometer swap question
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Joined: Dec 2002
Posts: 1,592
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From: IL
Car: 1988 Formula
Engine: 421 Little M block
Transmission: TH400 w/brake
Axle/Gears: 9" 4.30s, Wilwood discs, 28X10.5-15
140 MPH speedometer swap question
I have a general question / observation about the Firebird with electronic speedometers:
Do the 140 speedos use a different pulse signal than the 120? I ask because if it does then you will also need the VSS buffer box for the 140 speedometer, or is it basicly the same gage with a higher top speed?
In my case I have a dakota digital VSS box so I can adjust the pulse signal for any electronic speedometer but if I need to change it from the current setting this means a trip to the chassis dyno to recalibrate the speedometer
I am doing this swap to also have the 8000 rpm tach. I assume the tach nothing special needs to be done.
Do the 140 speedos use a different pulse signal than the 120? I ask because if it does then you will also need the VSS buffer box for the 140 speedometer, or is it basicly the same gage with a higher top speed?
In my case I have a dakota digital VSS box so I can adjust the pulse signal for any electronic speedometer but if I need to change it from the current setting this means a trip to the chassis dyno to recalibrate the speedometer
I am doing this swap to also have the 8000 rpm tach. I assume the tach nothing special needs to be done.
Thread Starter
Supreme Member
Joined: Dec 2002
Posts: 1,592
Likes: 31
From: IL
Car: 1988 Formula
Engine: 421 Little M block
Transmission: TH400 w/brake
Axle/Gears: 9" 4.30s, Wilwood discs, 28X10.5-15
Re: 140 MPH speedometer swap question
I did not think this was too difficult of a question.
Thread Starter
Supreme Member
Joined: Dec 2002
Posts: 1,592
Likes: 31
From: IL
Car: 1988 Formula
Engine: 421 Little M block
Transmission: TH400 w/brake
Axle/Gears: 9" 4.30s, Wilwood discs, 28X10.5-15
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Car: 85 Trans Am
Engine: 98 Vortec 350 LT1 Cam w/ TPI
Transmission: T56
Axle/Gears: 9 bolt 3:27
Re: 140 MPH speedometer swap question
Yes the 120 to 140 is as simple as swapping the cluster. Swapping the mechanical 85 mph to a 120 or 140 is obviously more involved.
Thread Starter
Supreme Member
Joined: Dec 2002
Posts: 1,592
Likes: 31
From: IL
Car: 1988 Formula
Engine: 421 Little M block
Transmission: TH400 w/brake
Axle/Gears: 9" 4.30s, Wilwood discs, 28X10.5-15
Re: 140 MPH speedometer swap question
I thought so but wanted to be sure before a take it apart and realize I need another part to finish the swap.
Thanks,
Thanks,
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