MrPack91

Speedometer is off know what could be causing it?

Tony71502

Can't really calibrate them. Ask him what the gear ratio is in the rear end. That's the leading cause of this problem. Tire size affects it as well, but not this much.

If he has different gears in the rear end then the fix is a different speedometer cable gear, a cheap plastic part.

MrPack91

But for my own knowledge since i'm new to this what do you mean gear ratio in rear end?

Tony71502

The final drive gears are in the rear end(axle housing). You can change the ratio as you see fit. 3.55:1, 3.73:1, and 4.10:1 are common ratios used instead of the stock ratio.

Basically that means the driveshaft turns 3.55 times, for example, for every 1 turn of the axles.

MrPack91

Not sure what the gear ratio is

Tony71502

Stock is 2.73:1. If he's is seriously trying to sell the car... tell him to jack it up and put a mark on the driveshaft and inside of the tire with whiteout. Tell him to put the car in neutral and spin the driveshaft and count how many times the driveshaft spins to rotate the wheel one full time. If it is ~2 3/4 turns then its 2.73. Etc

The gears I am talking about are in my avatar picture, didn't even realize it.

MrPack91

You sir, have a lot of car knowledge.

AdderMk2

You obviously haven't met ME yet...

If you know nothing about cars, you should avoid buying a mustang.

prangy

Why should he avoid a Mustang, I literally know jack crap compared to any of you and I am getting along just fine with the help of you guys, and local wisconsin guys that have been doing mustangs forever. What would you suggest to start with, a geo metro?

83glx5.0

Yes, stay away from something that has an abundance of parts available for it and is easy to work on.