Speedometer issues??

[Y2KSVT]

So a buddy of mine is looking into a 91 Mustang GT Convertible. It's lightly modded, and with 3:73's. He said that as soon as you would take off, or start to accelerate, the speedo would jump to 60-80mph and just constantly jump back and forth betweent 60 and 80. This is a 5 speed transmission. Does anyone know what this could be? He doesn't want to buy the car if it's something too expensive to fix. Any ideas? Anyone ever seen this? Thanks!

Mark

 

[Ryan]

first thing I'd look at is the speedo cable and also to make sure the right gear was used when they swapped in the shorter gears.

 

[Y2KSVT]

I was kind of thinking along those lines, but I don't really have any experience with Mustangs, or with gear changes. I've seen people just disconnect the cable, and you don't have a speedo, but never heard of the needle just going straight to 60-80 and jumping back and forth.

Mark

 

[Ryan]

I don't either, but that should be the only culprt since I believe they are cable driven. Could be bound somewhere or loose at either end. With something like that, makes you wonder about the accuracy of the odometer too.

 

[Y2KSVT]

With something like that, makes you wonder about the accuracy of the odometer too.

Which I'm sure is another one of his worries. From the pictures, it looks like a pretty clean car. The current owner has only had the car for 3 months. Says he is looking now, for his 4th Mustang in less than 3 years.

Mark

 

[91hatch]

Change the speedo gear and that should solve the problem. they probably just never changed it when they changed the gears

 

[Y2KSVT]

Change the speedo gear and that should solve the problem. they probably just never changed it when they changed the gears

Well the guy owes $6900 on the car, and my buddy isn't giving him a dime over $6000 for it. But as for the issue at hand, I've seen cars that never changed the speedo gear. Doesn't the speedo just read off? Not act funny like this?

Mark

 

[Silverstangs]

Well the guy owes $6900 on the car, and my buddy isn't giving him a dime over $6000 for it. But as for the issue at hand, I've seen cars that never changed the speedo gear. Doesn't the speedo just read off? Not act funny like this?

Mark

Yeah normally the speedo will be off.. typically read higher than what they are going.