4r100 trans shifting to o/d too soon
 

2001 f350 with 4r100 trans shifts into o/d drive too soon.otherwise trans operation ok.could going to a 305 tire cause this?

what is too soon? is the tire size the only change you made and now this is happening? what did you go from? i believe a 305 is like a 33? its very possible that it is causing it the shift diffrently.

can't say that it started right after the swap to the larger tires.use to shift into o/d at 80kph[50mph] or so under light throttle.know 65kph[apx.40mph]doesn't seem like much of a difference but it is noticeable.almost seems to lug but not quite.what could be done to fix this driveabilty issue?

Reset your ABS module to the correct tire size will help.

How do you reset the module?

4r100 trans shifting into o/d too soon
 

checked speedo reading against my gps reading and the two are within a mile an hour .i know propably not the most accurate but all i got.so if thats the case then would the tire size chance really have an effect on the tranny shifting.surely there are more people out there with larger tires swapped on their trucks than what i put on.what are these guys experiencing?

The "problem" is that the transmission is commanded to shift at 45-50 MPH under light acceleration :argh: .

These trucks make no torque at 1300-1400 RPM which is when you are at 45 MPH in 4th gear.

Either accelerate more aggressively or use the TCS (OD off) button to hold third gear longer.

tuning o/d off is a option .but i was looking for a cause to this problem.so as you see it the change to the larger tire{effectively changing the overall gear ratio}is the cause?didn't have this issue before.a 305 tire is not that much different in size from stock to even affect the speedo reading.anyone know if there are shift kits or reprogrammers availabe to recalibrate for a higher shift available.

are the tires wider? on the same rims? WEIGHT will make a diffrence with rolling mass as it takes MORE power to turn a bigger tire than a stock weight tire.

Auto enginuity software lets you ajust for tire size changes up to 42" tires... Works great, you can do anyones truck you want (Ford 7.3) and as many times as you want...

Plus it comes with some of the best diognostic software you can buy...:tu:


Talk to Power Hungry Performance about it, they sell it!:tu:

The thing about it is......

The tires are only going to change the relationship between what the PCM thinks the vehicle speed is/was and how fast the truck is actually moving.

As long as nothing else changed when you put on the larger tires (they're barely larger than stock as far as revolutions per mile goes anyway), then your truck will shift to 4th at exactly the same speed (as indicated on your speedometer) as before. With the slightly larger tires, your truck is going at a slightly slower speed than it was with the original tires at any given speedometer reading.

As far as comparing your speedometer to a GPS reading, you're not going to get too much more accurate than that.