Needs some help, I've done some searching but having found the answer yet. I have a 2001 F150 Supercrew w/ 4.6L 4R70W trans and a 3.55 non-ls rear end. I'm towing a TT that weighs in around 5800lbs.

If I replace the 3.55 with 4.10. Will it improve towing performance and does it put more stress (or too much stress) on the transmission? Not to concerned about gas mileage, just looking for better towing performance.

Thanks
Rob

 

Yes, changing the gears to 4:10 will help performance a lot. However, that may put you higher than you'd like to run the engine on the hghway for hours on end. What is the negine turning with overdrive locked out at your crusing speed now?

 

On the highway without overdrive the RPM's are about 3200 to 3500. I tried towing with overdrive but it ends up doing a lot of hunting around so I haven't been using overdrive. I'm in South Florida so everything is flat luckly. I think if I hit a mountain the truck might explode. I guess my main problem is driving at highway speeds. I've been reading more about the rear end gearing and it seems that a 4:10 gives you more low end power but not much on the top end? Not sure if there is much I can do to get better performance without buying a SD truck.

 

If you switch to 4.10 gears, your truck might be able to run interstate speeds in OD w/out constantly shifting.

 

What about 3.73 gears instead of the 4:10's? Doesn't look like there is a lot I can do to get better performace. Besides the rear end gear. I've talked to some others that have added shift kits, exhaust mods & chips. None of it seemed to help them.

Does anyone know about how much it would cost to have a shop or dealer change them out?

Thanks

 

What size of tires do you have???
I had a 2000 F150 ext cab 4x4,with 3.55 gears and 265/70/17 tires and the 5.4L.I pulled a 5000lb trailer with it but it was not pretty.It was into 2nd gear alot,sometimes up to 4500RPM which is not where I want to be pulling anything,a couple of times I thought the truck was gonna explode!!!
I now have a 2001 F150 ext cab 4x4 with the 7700lb package(3.73 gears and 245/75/16 tires) and there is no comparison between how these 2 trucks pull.
I still do not pull in O/D but in 3rd it has the gearing now to lug up alot of hills where the 2000 would shift down to 2nd and scream!!!
I can't even imagine trying to pull my trailer with the 4.6L(I've owned one and there is no comparison to the 5.4L).
The 5.4L is adequate but no rocket,but I pull into the mountains all the time,usually with a wind so it's different pulling than what you do.
On the flats the truck just purrs along,I could pull in O/D there but as soon as it gets to a hill it's gonna shift so I don't bother.
So if ya don't want to change gears,maybe tires,or upgrade to the 5.4L.On the flats it should be more than adequate.Grab a friends truck with the 5.4L and pull with it for a while I'm sure you will notice a big difference over the 4.6L.

 

You can "test" the effects of 4.10's by getting some smaller tires. To figure the right size, check out the RPM calculator on at Randy's Ring and Pinion. Click Here. Select RPM from the list on the left.

Put in your stock configuration: For me it is
Ratio: 3.55
Tire: 30.05 (from the Tire Height calc. - 255/70/16)
MPH: 65
--> RPM=1803 in OD

Then change Ratio to 4.10 and see the new RPM (2082 for me).

Now set ratio back to 3.55 and vary tire size until you find the same RPM as the 4.10. For me 26" tires will duplicate the effects of a 4:10 rear end. The tire height calculator will help you identify the tire size - for me, 255/50/16.

Finally, find one of those used tire places to pick up a set of smaller tires for dirt cheap prices.

TADA! Hopefully for a fraction of the cost of a new gears, you can try 'em out. See if 4.10's are too much or not enough....

 

You say, "RPM's are about 3200 to 3500"....

How fast you going???? When I'm towing my #4500 TT in third and going 60 mph, my rpm's are around 2300. I've got the 3.55 gears and 31" tall tires too. It'll go to about 2500 at 65, but all it seems to do is suck more gas...... Don't really get there that much faster, so 60 works well for me.

I start approaching 3000 at 70, but don't feel I need to travel that fast in most cases.

I've tried OD, but it bogs down too much, and I end up having to press the gas pedal more and the trans temp actually goes up. If I stay at 70 in OD, it's better, but I don't need to be going 70 anyway!

Good luck! I like the suggestion of 'testing' it out with smaller dia tires....... Something to think about. I'd need to go to 3.73's in order to get back to the stock effective gear ratio I had when I had the puny 235/70/15 tires........ (29" tall).