DarrinGT

I am swapping the 4:10's and going to 3:55's. My thinking is that the acceleration may actually be quicker because it will let the Cummins motor stay in the lower rpm range longer getting better use of the torque before letting the higher rpm HP take over.

Does this make sense or am I just dreaming,..?

DNRCustoms

Well, depends on your transmission, if your running the 518 non lock up, then it should definatly pull the gears farther which would make it quicker for say.. I think it has to do with a lot of variables.. Tire size, the way your trans shifts, trans model.. But you will most likely pick up some top speed and pull each gear a little farther and pick up some mpg on the highway.. Good Luck!

DarrinGT

Thanks, I have a Ford C6 Automatic that is built, shift kit, and low stall towing RV converter and a Gearvendors Overdrive. I usually shift it manually with a B&M Shifter and it grabs the gears pretty hard. I am definitely doing it for the lower highway rpms but to also bring them down to a better power range while towing my 5th wheel.

RollinCoalSmoke

It "the 3:55s" will let you pull longer in each gear but i'm not sure about the towing part. I have both 3:54s w/5sp. & 4:10s w/gearvenders and an automatic. On flat ground the auto w/4:10s will outpull the other. But after getting up to speed "70+" the ole 5sp w/3:54s will walk away. Fuel economy suffers w/4:10s 13.84 mpg but i'd argue all day it has more to do with the auto trans than the 4:10s. Hope this didn't confuse you it was meant for a comparison only. Maybe it shed a lil light on what your trying to accomplish.

peobryant

4.10's are "better" for towing, but 90% of people that tow, don't tow heavy enough to "need" 4.10's. The switch to 3.54's will get you better fuel mileage, due to lower RPM at highway speeds, and they will be fine for towing.

Thunderhog

Quicker, no. Faster, yes.

92roughstock

You will likely lose some speed off the line, but accelerating from say, 30mph, to highway speeds most likely will be close to the same. If you dont like your power with the 3.54s, turn some screws on the pump to take up the slack.

I've towed in the mid 20K range with 3.54s. I dont think 4.10s are necessary under 95% of towing conditions.

The_Head

^^ You towed 25,000 lbs or was the total weight of the truck and trailer 25,000 lbs?

RollinCoalSmoke

I don't know about him but i've scaled 49,700 with a 24v 6sp w/3:54s. My nephew came down to help out and ran the hotshot rig over to load what he thought was pipe but it was drill collars that instead of weighing 22lbs/ft it weighed 250lbs/ft. Nobody can say the Dodges won't pull with 3:54s, it pulled that load about 100 miles, couldn't stop in a country mile tho. Never ran hot, egts about 900, fuel mileage @ app. 12.5mpg. Total drivetrain workout lol.

92roughstock

The Head- it was a Gross Combined of ~24-25K on a regular basis. Average MPG was in the 13-14 range unless I hit a bad head wind.