Speedometer issues
Thread Starter
Joined: Apr 2017
Posts: 2
From: PA
Speedometer issues
Hello,
I have a 1991 Mustang LX 5.0 Vert automatic that I am rebuilding. The speedometer is off by 15 MPH at lower speeds and at higher speeds can go up to a 20-25MPH difference (clocked with GPS).
Now, as far as I am aware everything is stock... However, I believe it is possible my rear end has 3.50 or 3.73 in it. I have no pulled the pumpkin apart to find out for sure. I have put in a brand new speed sensor and it made no difference at all.
I have plenty of time before I put the car back on the road, but I am ordering parts and figured if I can find out what I need I will at it to my shopping cart (providing Summit offers said needed part).
Any help would be greatly appreciated.
I have a 1991 Mustang LX 5.0 Vert automatic that I am rebuilding. The speedometer is off by 15 MPH at lower speeds and at higher speeds can go up to a 20-25MPH difference (clocked with GPS).
Now, as far as I am aware everything is stock... However, I believe it is possible my rear end has 3.50 or 3.73 in it. I have no pulled the pumpkin apart to find out for sure. I have put in a brand new speed sensor and it made no difference at all.
I have plenty of time before I put the car back on the road, but I am ordering parts and figured if I can find out what I need I will at it to my shopping cart (providing Summit offers said needed part).
Any help would be greatly appreciated.
5th Gear Member
Joined: Jul 2012
Posts: 3,628
From: ohio
Put the rear end up in the air and rotate the wheels 1 full turn, count the number of rotaions of the drive shaft, that is your gear ratio. A 3.55 gear ratio will be 3 1/2 turns, a 3.73 will be 3 3/4 turns. Once you know your gear ratio ,, order the correct gear for the speed ometer.
5th Gear Member
Joined: Jul 2012
Posts: 3,628
From: ohio