I am running the size listed on the rear end listed in the title. I know I lost some from the stock 16's on my 97. I do tow a small 5th wheel as well as a boat or a jetski depending if we are going fishing/camping or jetskiing/camping. I make seperate trips for each.

My question, what would a 4:10 rear end do for me both positively and negatively.

While towing the 5th wheel I can do around 55 on the flats and then slow down to around 40-45 on the slight hills here in south central Kansas. I run in drive not OD and am turning around 24-2500 rpms. The truck will drop down to 2nd on a couple of the hills and jump to around 3500 or so rpms. My main issue is that I have to take off at a snails pace and I know I am very close to my weight limits on my towing capacity.

Was thinking the 4:10 would help me out a lot on the low end but I also don't want to torch the tranny with the steeper gears.

Thanks in advance all,
Chris

 

Your current tire height with 255/70/16 is 30.06 inches. You can use the calculator on the link to compare your RPM with different gears at different speeds. Of course this won't tell you whether or not your tranny will grenade due to the change in ratio you are thinking about.....

http://www.ring-pinion.com/content/calculators/RPM.asp

 

Thanks for the link. Here is what it came up with when I input a 4.10 rear end with 30" tall tires at 70 MPH.


Auto RPM=3301
AOD=2250 This is the set up I have. Automatic with Overdrive
Manual= 3214
5 Speed Manual = 2572

With the 4.10 it looks like 2250 at 70 MPH. Does this sound too high for long distance running? How bad will that hurt my fuel economy. I am only getting maybe 13-14 mpg right now with the oversized tires and am running about 4.8% off with the speedo.

How much difference would there be from a 3.08 to a 3.73 versus a 3.08 to a 4.10?

I'm sorry if these sound like idiotic questions I am just looking for the best compromise while getting some increase low end for towing.


Thanks,
Chris

 

Well going from 3.08 to 3.73 is about a 23% change. Going from 3.08 to 4.10 is about a 33% change. So going from 3.73 to 4.10 is about a 10% change.

I have a 4.6 with 3.55 gears and it cruises real nice on the highway so I think if you went to 3.73 it would be fine.

Next time you are driving run without the O/D on and see what its like at different RPMs and then imagine if you would like to drive a long distance at that RPM or not.

I am new to Ford 150's so don't know much yet about the Trannys durability so I can't help there.

 

I do run with the OD off when I am towing and I don't care for it. I am turning around 2500 in 3rd and if it has to down shift to 2nd I go to around 3500. That is even with the 2" taller tires than the stock ones. So you answered my question. Looks like 3.73's for me.

Thanks for the input.

Chris

 

I would not go higher than 3.55's or 3.73's, 4.10's would be good for off the line, but it would kill your gas mileage when cruising (you would be running some high RPMs).

 

2500-3000rpm is great for the either V8 engine to get peak torque. 3.73 gear would put you at 60-72mpg at 2500-300rpm in 3rd gear. That's probably where you want to be. 4.10 would be 55-65mpg which shouldn't be necesaary for relatively flat Kansas.

I used this calculator that let you puts in your own gear ratios.

2nd is 1.55
3rd is 1.00
4th is 0.70