Changing Gears & Correcting the Speedometer

I'm not sure of which year they switched to electronic. I think it was 98. If so, you have to do one of the following:

Speedcal
chip
reflash stock computer

There is no "drive gear on the cable in the tail shaft" to swap out. I just had my stock computer reflashed for $100 for my 4.10's. He just plugged his laptop in under the dash and did his magic. The guy I went to (Panhandle Performance) uses EFI Solutions software.

Arent the 99+ cars the only ones that require a chip or speedcal? I think from 98 back you can get away with a different toothed speedo gear

'94-up have an electric speedo but '99-up PCM controls the speedo so you can have your PCM re-flashed to correct the speedo. The only ways to do it on a 96-98 car is a Speedcal or a speedo gear and the speedo isn't as accurate and they tend to get eaten up becasue I belive you have to use a Jeep speedo gear which isnt a perfect fit but works ok for a little while. You're best bet is the Speedcal. I got mine from DMP for $100 and it works great. Easy to install too.

Panhandle Performance in Panama City?

The white speedo gear will be fine...and ususally $15.00 bucks anywhere, 3 minute install. Your speedo will be off by 5-6 MPH but I'm sure you can live with that...as far as durability, I've had mine since 1998 and it's never had to be replaced (not that it doesn't happen) 98's and below use a gear driven speedo...

tjm73 said:

I'm a bit confused. I bought a 98 GT 5 speed and I have read that if you change the gears out back you need a Speedcal to correct it. I've also read that you might be able to simply swap the drive gear on the cable in the tail shaft.

So which is it? Anyone done this? Someone must have. Absolute accuracy isn't my concern. As long as it's reasonably close (+/- a little bit is ok), I'll be happy.

Click to expand...

The answer is, . . . It depends.

http://www.ffcobra.com/FAQ/speedo.html
http://www.gatineaumustang.com/FTspeedogears.htm
Depends on what gear you put in your car, you can change gears to 3.73 or less and just changing the gears in the tranny are sufficient in giving an accurate reading.

at 4.10 or more (i recommend 4.10 if you don't plan on using a power adder)
the tranny gears start to be less accurate. in my 98 by changing just the driven outer spedo gear I would have been off 7% high by changing both drive and driven speedo gears in tranny I would have been 3% low. I like my speedo to be dead nuts on so i know exacty how fast i'm going when mr. police man is parked on the side of the road and i really don't want to stop cruising at 70mph in a 65.

So i use the speedcal, it is dead balls accrate and cost me 50 bucks used.

If you don't want to buy a speedcal, and you said you would deal with it being reasonablely close just swap the tranny gears then, your call.