Changing Gears & Correcting the Speedometer

[tjm73]

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.

 

[StngStr]

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.

 

[tjm73]

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.

From the BBK website ( http://brothersperformance.com/shop/mustang/brospeedcal.html ) for their speedometer corrector...

"A must for all gear swaps on 1999-2002 Mustangs Allows Correct Calibration of your speedometer. When changing to diff gear ratio. Comes with complete instructions and setting for all gear ratios. Simple Plug In installation.

Can also use on 94-98 mustangs instead of using speedo drive gear for a more accurate speedometer calibration."

This is the source of my question. Is it possible to make the speedo reasonably close with a change to the speedo drive gear?

 

[StangLou]

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

 

[SLOW 97]

'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.

 

[Kevin2811]

Panhandle Performance in Panama City?

 

[Red mustang Gt 46]

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...

 

[Joel's98GT]

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.

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.

 

[COramprat]

I just installed a Speed Cal yesterday. I had the white speedo gear in since I had my 4.10's installed last July. When I removed it to put the old one back in it was all chewed to hell. My speedo also was about 10% off so I was reading 80 and going 72 mph. And, being off 10%, I've got about 2000 ghost miles on my car. My opinion is just to go with the speedcal. That way you can adjust for different tire combos too.

As far as what cars can use the speedcal it is 96-04 5 speeds and 96-98 autos. The 99+ autos have to have a computer flash.

 

[killervette]

98 used gears to adjust....i had a 98 with 3.73s. 99+ is electronic

 

[mac9898]

99 needs speedcal

 

[HIGDON]

I put a white(23 tooth) gear in my buddy's 98 on Sunday when I did his 3.73's. I used a speedcal when I did my gears (4.10). Use the speedcal, no matter what ratio, the 23 toth gear is at it's maximun range on 3.73's. You could change the drive gear but it's a MPITA. Speedcal for 90 bucks at Texas Mustang.