Tire Size

[Jackpine]

Originally Posted by BigSur

According to my GPS, I'm over on my odometer approximately 4 miles over a 140 mile ride.....and the speed on the GPS was consistently 1 to 2 mph fast on the Gryphon compared to the GPS. HOWEVER, the mile markers on the interstate made it seems like I was a little under on the odometer!!! I'm going to trust my GPS on this one and scale the TS back I think.

BTW Jack...regarding my shifting issue we spoke about in the other thread, I've confirmed that it's only when there is load on the truck. I had to come up some hills to get to my parents house tonight. On an incline, every shift from 1 to 2 was rough and there was a physical "bump" present from the rear end. I'm not sure if I want to play with the settings on the Gryphon to fix or let my mechanic feel it. Appreciate your write-up though in case I decide to play with it myself.

4 miles in 140 miles is a 2.9% error. Multiply your current TS by 0.971 to correct to the GPS reading.

You shouldn't be in any danger playing with the part throttle shifting yourself. I think I'd REDUCE the 1-2 upshift and downshift by the max (-2) and then maybe add to the Torque Converter unlock/lock speeds by the max for both 1st and 2nd gear. (I'm trying to keep the TC from locking right away so I think values of +2 in 1st and +3 in 2nd might work. Anyway, it's worth a try.

- Jack

[Longshot270]

4 miles over at 140 miles? I'd say that is really close. Personally I would leave it. I'm currently in the process of dialing my tire size in aswell. Just got a set of cooper discoverer atrs and I'm loving them.

[BigSur]

Originally Posted by JackandJanet

4 miles in 140 miles is a 2.9% error. Multiply your current TS by 0.971 to correct to the GPS reading.

You shouldn't be in any danger playing with the part throttle shifting yourself. I think I'd REDUCE the 1-2 upshift and downshift by the max (-2) and then maybe add to the Torque Converter unlock/lock speeds by the max for both 1st and 2nd gear. (I'm trying to keep the TC from locking right away so I think values of +2 in 1st and +3 in 2nd might work. Anyway, it's worth a try.

- Jack

Thanks I might just do that. I'll let you know how it works out.

[agood1]

Hey Guys,
I had to buy a new set of tires so I have to reset my TS in the Gryphon. I went back to the stock tire size of 275/65/18.
Right now with the Gryphon set at 2560, My GPS is showing 2-3 MPH slower than the Speedo. The Gryphon is showing in between the GPS and the Speedo.
Should I increase the MM size and how much?

[Jackpine]

Originally Posted by agood1

Hey Guys,
I had to buy a new set of tires so I have to reset my TS in the Gryphon. I went back to the stock tire size of 275/65/18.
Right now with the Gryphon set at 2560, My GPS is showing 2-3 MPH slower than the Speedo. The Gryphon is showing in between the GPS and the Speedo.
Should I increase the MM size and how much?

Actually, I'd say you are almost dead on if you see no more than about 1-1.5 mph difference between your GPS and the Gryphon. But, to get them to agree, you need to decrease your TS, not increase it. Assuming the difference you see is at 70 mph, you have a 1.4-2% error. Try reducing your TS to 2524mm.

And remember, the dash speedo is always going to read a bit faster than you're traveling, because Ford builds them that way.

- Jack