98 GT SPEEDOMETER 20 MPH TOO FAST
01-27-2011, 08:40 PM
#1
Thread Starter
Join Date: Jan 2011
Location: indiana
Posts: 7
98 GT SPEEDOMETER 20 MPH TOO FAST
New to the forums here and I have a 98 gt with the speedo that is registering 20 mph too fast. The rear end is stock but the tire size has been changed to 275/40/18. What is the best fix for this since the car has a speed sensor and a gear. Is there a specific gear tooth to get me in the vicinity of the spped I am actually traveling. It causes me to rack up more miles than I an really driving. I am currently at 60,000. Any help would be appreciated.
01-27-2011, 08:46 PM
#3
wrong, he needs a new speedo gear to correct for the rear end gears. Pre-99 are mechanical speedometer. Sounds like someone had 4.10's and changed back to stock and left the 4.10 speedo gear in there.
Last edited by teej281; 01-27-2011 at 08:50 PM.
01-27-2011, 08:56 PM
#5
Thread Starter
Join Date: Jan 2011
Location: indiana
Posts: 7
I think the gears are the stock ones but I am not sure. I do know in 5th gear @55mph I am turning 2 grand on the tach. I wouldnt have thought the tire size would have made that much of a difference but they are a lower profile than stock... I have checked the speed with a garmin gps.
01-28-2011, 12:43 PM
#8
Underboss
Join Date: Jan 2006
Location: Helaware
Posts: 20,273
Tuner will not work on 96-98's
A mechanical speedo gear change will get you close but you are gonna need a speedcal to be spot on
http://www.dallasmustang.com/mustang...DED-RANGE/7626
A mechanical speedo gear change will get you close but you are gonna need a speedcal to be spot on
http://www.dallasmustang.com/mustang...DED-RANGE/7626
01-28-2011, 02:31 PM
#9
4th Gear Member
Join Date: Sep 2009
Location: NC
Posts: 1,481
First off, welcome to the forum!
He cannot have a speedometer gear for a 4.10 along with a factory ring and pinion ratio, becuase if that were the case, he would be reading way too slow on his speedometer. Also, 2000rpm at 55mph doesn't sound like a stock ring and pinion gear ratio. He needs to confirm which rear gear ratio he has so he knows what speedometer gear he needs for it.
He cannot have a speedometer gear for a 4.10 along with a factory ring and pinion ratio, becuase if that were the case, he would be reading way too slow on his speedometer. Also, 2000rpm at 55mph doesn't sound like a stock ring and pinion gear ratio. He needs to confirm which rear gear ratio he has so he knows what speedometer gear he needs for it.
01-28-2011, 02:35 PM
#10
4th Gear Member
Join Date: Apr 2008
Location: New York
Posts: 1,306
best way to check the ratio is to lift the rear up and turn the wheel over one turn and count the number of turns the driveshaft turns and thats the ratio. Mark the tire and drive shaft with whiteout or a marker to make sure you dont lose track.