Gear Ratio
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Junior User
Joined: Jan 2001
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From: Virginia Beach Good ol' U
Gear Ratio
I recently purchased a gently used '02 F-250 SD,CC,SB 4X4 with the V-10. 
The truck was already lifted 4 in front and 2 in back and running 35's. The door tag says it had 3.73's with LS in stock form. I looked at some gear calulators and according to the ones I used, my truck is running 4.10's. When I'm running 65 MPH in OD the truck is at about 1775 to 1800 RPM or if I take it out of OD and drop back into 3RD gear it then jumps up to about 2650 to 2675 RPM's. My question is, are the RPM's I've indicated the correct RPM for a 4.10 gearset with a 35" tire? Does it seem as if the other owner regeared when he did the lift and tires? 
Thanks in advance.
Later,
Cleve
The truck was already lifted 4 in front and 2 in back and running 35's. The door tag says it had 3.73's with LS in stock form. I looked at some gear calulators and according to the ones I used, my truck is running 4.10's. When I'm running 65 MPH in OD the truck is at about 1775 to 1800 RPM or if I take it out of OD and drop back into 3RD gear it then jumps up to about 2650 to 2675 RPM's. My question is, are the RPM's I've indicated the correct RPM for a 4.10 gearset with a 35" tire? Does it seem as if the other owner regeared when he did the lift and tires? Thanks in advance.Later,
Cleve
Senior User
Joined: Jun 2003
Posts: 475
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From: La Habra, CA
Has the computer been calibrated for the new gears? If not, it sounds like you have 3.73's. The best way to find out is jack up the back end, put the truck in neutral and cound how many times the driveshaft spins for 1 revolution of a tire. If it's LS the tires should spin together when both off the ground. Make sure the tires rotate together.
The superduty's have the 4r100 tranny, which is an E4OD with a wide ratio gear set.
Eric
The superduty's have the 4r100 tranny, which is an E4OD with a wide ratio gear set.
Eric
Last edited by etcetera; Jan 15, 2005 at 03:15 PM. Reason: spelling
Thread Starter
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Junior User
Joined: Jan 2001
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From: Virginia Beach Good ol' U
Thanks guys, I don't know if the computer was calibrated for the gears, tire size or what. This is how I bought the truck. I'll have to do the tire rotation check. Thanks.
Later,
Cleve
Later,
Cleve
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Joined: Dec 2002
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From: USA
No need to recalibrate the speedo for the gearchange, but a change in tire size will throw off the speedo. Only SURE way to know what gear ratio you have, if the speedo is not known to be correct, isi to pop off a diff cover and count the number of teeth on the ring gear and divide by the number of teeth on the pinion gear. The driveshaft spin test can get you close, but it's hard to tell the difference between 3.73 and 4.10 with that test because of drivetrain slop and the closeness of the two ratios.
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Joined: Jun 2003
Posts: 475
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From: La Habra, CA
Originally Posted by Casey
The E4OD and 4R100 have exactly the same gear ratios.
Eric
