4.10 to 3.55 Power loss?

[Tristan]

I think I have found complete front and rear ends with 3.55s. Those of you that have swapped out your 4.10s how much of a power loss did you notice? I am tired of the engine running at 3000 RPM on the freeway. On the other hand I don't want to loose too much power going up the mountain passes around here with my 11' camper on the back. I wish I could afford a Gear Vendors....
Thanks for opinions.
Tristan

 

[MIDNIGHT RIDER]

The power loss, pulling a trailer of any size, will be comparable to the difference between lifting a fifty pound sack and a hundred pound sack.

If you are plenty strong, the difference is negligible; whereas, if you are not so strong, the difference is astronomical.

Does that help??

 

[stiesel]

would i be correct to say approximately a 13% reduction of torque at the tire?

i did this same gear change on old grey. other than the obvious lower rpm at crusing speed i can't tell a difference. but i never tow anything with my f-350

i do however haul a 100 galons of diesel in the transfer tank. i didn't feel that when i changed gearing. but that is probably around 800 pounds. your hauling a lot more. so for what ever that's worth. that's my experience.

 

[tonkadoctor]

There is always some kind of compromise in the automotive world. You just have to decide what you want more, better fuel economy or stump pulling power.

I swapped a 3.08 in place of the 4.10 on my dually for the economy and it made a difference of 2.5 mpg in the city. Bear in mind that 99% of my driving is flat land and just hauling myself around so it was the right choice for me.

If you're getting them at a good price and running a near stock tire size I'd say go for it and try it, worst case is that you won't like them and can swap the 4.10s back in.

I don't know how much that 11' camper weighs but I would'nt think it was much for that F250 to handle especially with a turbo. Just keep an eye on the pyrometer pulling a grade and drop a gear when neccesary.

 

[69oiler]

wait for CarlF350 to chime in, i rode in his truck after he did this swap and we both liked it. my truck has 3.55s and i like em.

 

[sle2115]

I did the opposite and can tell a huge difference for my uses. I pull quite a bit and live in a hilly area. I can usually shift into 4th and never look back as long as I run 35 or so with the 4.10's, where with the 3.55's, I was often in 2nd to pull the same hills. Starting at the same speed, there is no comparison, but then again, as others have said, do what fits your driving. I pull, therefore I wanted 4.10's, but would like the GV for the minimal highway driving, but would never drop that kind of money for one. A ZF5 sounds like what I need and maybe someday I will do that.

 

[Tristan]

According to the tag on the camper it weighs about 2300 pounds. Often I also have a trailer on the back for the motorcycles that would add some more. It is light, I can move it around by had easily.
Often I am driving empty to work and back or with just my dirt bike in the loaded. That is when it is really a drag running on the freeway at 65mph and 3000 rpm.
Being in Western Washington there is usually at least one mountain pass we go over when camping. That is the worry, getting up the hills without too much trouble. I don't mind slowing down a bit, she already does that. It would be worth the drop in RPM while cruising. After running a RPM calculator the drop would be about 375 RPM at 65MPH. Oh yeah and the guy wants $275 for both front and rear complete units. Good deal?

 

[sle2115]

When I had the 3.55's, I only ran out of power once. I literally could not proceed forward! It was a pretty easy fix, stop and pull into 4WD/LO and just keep going. This his was with a full load of firewood in the back of the truck, 7X9 flat bed and a 5X8 foot trailer full of firewood in tow. I had to make a 90 degree turn at the bottom at low speed, so I did not have any chance of a good rolling start and I did not make it. Other than that, it really loaded my engine when pulling the back hoe or big ditch witch that we rented to build my uncle's house. Highway was nice, but I don't do highway much, so the trade was obvious and I already had the F350 with D60/10.25 in the 4.10 flavor, no regrets.

 

[MIDNIGHT RIDER]

One way to look at this, if you are doing the swap with the idea of saving fuel.

It is altogether possible that your mileage could actually drop; then again, it may increase by anywhere from one to three MPG.

There is a real good probability that you could screw up a ring and pinion, carrier, etc.; as, not all gear swaps turn out for the best, probably less than two thirds last over a year in highway usage.

I am not doing the math; but, figure the cost of the gears and all the odds and ends needed to do the swap; figure the realistic increase in mileage and savings in fuel dollars and decide if the dollar savings will pay off.

I have an old Chevy gas-burner that I removed 3.07 gears and installed 4.10 gears; the fuel mileage actually went up a little--believe it or not.

 

[gabbyr100rs]

My truck turns about 2000 RPM at 65 MPH in 5th gear. I have hauled a 14' tandem axle camper with a loaded bed thru hills in North Georgia with no problems what so ever.

I don't know what size wheel/tire combo you are running. My BFG's are 33" tall, so I may be getting additional final drive reduction versus stock.

From what I have read so far, you do not seem to haul or tow heavy enough loads for the truck to have any problems with 3:55 gears. You will, though, slow the motor way down at cruising speeds--your main goal.

Good luck! ;p

 

[Tristan]

It would be a complete axle swap, not just the gears. So I don't think I could screw anything up.
I have a C6 auto, so no overdrive. I am running 28575R16 tires, so they are just about 33" tall.
You are correct, slowing the motor down at cruise speeds is the main goal, improving fuel mileage would be a plus. I just want to make sure the drop in power won't be to much with the camper loaded on the hills and such.

 

[tonkadoctor]

$275 for both!!!

It cost me $320 just for the rear gears, I'd definatly go for it and give it a shot. Worst case is that you put the 4.10s back in because you didn't like it and sell the 3.55s for what you had into them.

a 1 MPG increase in fuel economy would pay for that gear swap very quickly at $3.00 a gallon.

Dropping from the 4.10 to the 3.08 gave me a 2.5 MPG increase just running around town. I do have to use all 5 gears now instead of just using 2nd, 4th and 5th.

Another thing to consider would be a swap to an E4OD. The overdrive would drop your RPMs to 2250 - 2300 @ 65mph with the 4.10 rears giving you the best of both worlds, no loss of pulling power and a serious drop in RPMs while cruising.

 

[Full Monte]

One of my trucks is 3.55 and the other is 4.10. I think the 3.55's are a good choice. I would choose it over the 4.10 for general driving, which is what most of us do most of the time.

 

[Mojave Red]

I say "go for it!" Sure, your going to feel some power loss on the grades with your camper in back. But your still going to make it over anything in WA - just a bit slower... Be sure to watch your EGTs. Your going to enjoy your day to day unloaded driving much more with the lower RPMs. I was going to do an axle swap but ended up going the GV route instead (think I have a final drive ratio of around 3.20). Even with my 10.5 foot camper and boat, I come out of overdrive only on the more serious grades - that's when I'm thankful for my 4.10s.

 

[Full Monte]

Good points, Brian. We camper guys have some unique needs. I love the combination of the 3.55 and Gear Vendors on my 250 utility truck. I think the US Gear on my 350 camper truck is a better choice for really heavy hauling up to 30,000 lbs, though it's not as easy to use as the GV. If you have an 11 ft. camper on a 250, you are heavy and pushing the limits of drivetrain, suspension and gearing choices.