I think my 97 has a 3.55 limited slip but I am not sure. Can anyone tell me how to verify this. I need to know so I can cal my speedo to my new tires. Tires are 285/60/16, originals were 235/70/16. Having problems getting correct shiftpoints from my superchip due to errors caused by conflicting data coming from all the different speed sensors used by the computer for shift calc's. Does any one know of a speed shop in the Dallas area who could do the cal?

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97 F150
sc, flairside
"SHOWTRUCKS USA" conversion package
2.5" dual exhaust
Flowmasters
K&N filter
Superchip

 

To answer your question, there will be a metal tag bolted to the rear differential. This tag will have a number then a space then two more numbers (3 55). There will be an "L" in it if you have LS.

For your problem:
Your difference in tire size isn't really enough to mess up your shift points. You went from a 29" tire to a 29.5" tire. I'm not even sure you could find a speedo gear to "fix" the small amount of error in your speedometer.


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1997 4x4 Expedition- 4.6L, true dual exhaust w/glass-packs, K&N air filter, SuperChip, airbox mods, Edelbrock shocks, 285/75R16 BFG ATs, 2000 "XLT" wheels, 4.10 gears, Auburn LS, Clarion In-dash CD player, Smitty Bilt push bars and nerf bars.

2000 4x2 F150 XLT Reg. Cab LWB- 5.4L, Tow Pkg, 3.55LS, CD player,Remote Keyless Entry, Sliding back glass, Special Appearance Pkg., tinted windows, Line-X bedliner, K&N air filter, SuperChip, airbox mods, 285/60R16 Goodyear Eagle GT IIs and Prime #155 wheels.

http://members.visualcities.com/NoMo

 

On the inside of your door on the drivers side, it gives your axle code. 18 is the 3.08, 19 is the 3.55 and the h9 is the limited slip 3.55. That's the easy way to find out. No need to go under the truck, unless someone has changed the gears since you had the truck.

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'97 F150 4X4 Supercab XLT
Rhino Lining
285/75/16 BFG AT/KO
4.6L Triton V8
5 Speed Manual tranny
K&N air filter
Bug deflector
Six disc changer
Power everything

Coming soon:
#1)Set of 4.10 LSD (need $$$ first)
#2) Superchip (I think)
#3) Manik Brush guard
#4) Westin Side Steps

Payment plan in process for getting to my goals...

 

Thanks guys for the information. I am not sure where to go with the shift RPM problem, but have been told by the chips mfgr that the inaccuracy due to tire diameter is the most likely problem. I am not one to argue with Mike because he does seem to know the chip inside out.