This is a bit long and I apologize.

I have a 2000, F150, 4.6L, 4R70W, 3.55LS, Super Cab XLT with bed liner tool box and headache rack. Normal passenger, tool, and cargo load is about 800 pounds. The truck has 43000 miles on it and runs flawlessly, almost.

My problem occurs while driving highway speeds in OD using Cruise Control in the 65/70 mph range.

When an incline is encountered, the computer controlled transmission begins to react. First, the torque converter unlocks and rpm increase by about 400. If the incline steepens, the next step is a downshift from OD or 4th to 3rd and the rpm increase another 400. At least, this is how it should work. My truck, sometimes, once the downshift to 3rd is complete will downshift again to 2nd which jumps the rpm by close to another 2500 when driving at 70 mph which amounts to an rpm change from 1900 rpm to about 4600 rpm. Immediately upon completing the shift to second, it returns to 3rd and will then work its way up in the normal way. This procedure is very smooth but I cannot imagine that it is good for the transmission. This does not happen if I am not using cruise control or if I am using cruise control and driving at speeds in excess of 2000 rpm. My conclusion is that the shift points while in cruise control are erratic under 2000 rpm because the computer may have a shift rev limiter that somehow stimulates the downshift to second while in cruise. I believe that driving in access of 2000 rpm probably exceeds the shift rev limiter setting thereby not allowing the to second gear downshift.

I am wondering if changing the 3.55s to 4.10s will rectify this situation. It should lower the shifter speed limiter to under 65. If so, this will help and I believe that the 4.6L would become more drivable as well.

Can anyone here offer an experienced comment on this?

Thank you in advance.



George

 

George,

I have the same setup as you only in a 98. I did that gear change about 3 months ago and I have no issues with shifting. I did it mainly for towing purposes but its an all around improvement over the stock 3.55. Your only issue will be reprogramming the computer for the gear change since your truck is a 99+ model. If you don't you will have an incorrect speedometer and probably some shifting issues. Ford can't do it for you because they didn't offer 4.10 for the 4.6 F150 so its not an option in the software. There are aftermarket programmers available that will do it though.

 

tmc0747,

Thank you for the reply and the input about the speedometer synchronization. That thought had not crossed my mind.

If I am not mistaken 4:30s were a standard offer on the 2000 4.6. This is only another 5% which should help rather than hurt and Ford should have a program to synchronize that ratio.

It is easy enough to check through a dealership. I would rather not buy a programmer for the sole purpose of synchronizing the speedometer. I have close to four years of bumper to bumper extended warranty remaining to cover breakdowns.

Thanks again!



George

 

George,
Came across a 2000 owners manual. 3.55 was the lowest ratio listed for the 4.6 and 3.73 was the lowest for the 5.4. Although it may have been possible to go lower via special order???

Good luck

 

tmc0747,

You are exactly right, but I did not know this before your post.

Because of your post, I revisited a couple of Ford dealership service departments. Both confirmed the accuracy of your information. One told me that what I am experiencing is not unusual for the 2000 4.6 V8 but not to worry because he did not feel that any harm is being done. I sure hope that he is right about that! None the less, I am beginning to enjoy an increased bit of peace of mind after talking to him.

Thanks again for your reply.



George