So let's talk gears

[kas83]

4.30 or lower, since there's already some worry about lugging it. You can't go with comparable rpm of smaller tires and higher gears. 37s are heavier, wider, and have more flex to them, all of which takes more power to turn. I actually believe you'd do better mpg wise with a lower ratio and turning 100-150 rpm more, with the larger tire and aerodynamic drag.

Sent from my XT1060 using Tapatalk

 

[tanman_2006]

If you have a turbo then 4.10s will be just fine with good tranny cooler. If NA I would go to 4.56 or turbo.

source unknown

 

[kuskoal]

Another problem I need to address. A BIG trans cooler with a fan for low-speed driving

 

[dizdak]

so was a verdict ever made? i am looking into gear swap soon myself, plan on running a 37" tire, have a turbo and 5spd... in looking at posts and gearing charts on the web... the web seems to show 4.11s = 2426rpm at 60, 4.56s = 2692 at 60, and 4.88s=2881 at 60... but that is empty i assume..my truck more often than not has about 10k hooked to it.. i currently have 3.55s and my current tires measure out to 30".. getting off the line right now sucks!! thats at best.. am leaning toward 4.56s when i regear to allow for bigger tires and tow weight... anyone running anything higher than 4.56s for towing?

 

[kuskoal]

What gear calculator are you using? 4.10 (staying with them) and 37" tires are about 2100 rpm in overdrive.

I decided to keep stock gears and add an OX in front and a Grizzly in the rear.

 

[dizdak]

http://www.offroaders.com/tech/gear-ratio-chart.htm
that is the chart i was looking at for an idea...

 

[kuskoal]

http://www.novak-adapt.com/knowledge/gearing.htm

Use that one. You can put in whatever you want. You forgot the OD ratio

 

[dizdak]

ok... will have to look up my 5th gear ratio now so i can plug it in.. thanks..

 

[riotwarrior]

.76 is OD for us, so if chart is only for 1:1 then multiply the rpm by .76 and you get your RPM at said speed.

Don't forget it's a choice to tow heavy in OD and not always a good one!

 

[War Wagon]

I have a 5-speed and 4.10's in my '94 F350. I fully intend to in the near future swap for a ZF 6-speed and 3.55's. I run a 285 tire right now witch is approximately a 33" tire and am loaded all the time(tools, parts, equipment for work). I've hauled a couple crew cab diesel pickups on my trailer, let's say laded trailer weight is about 9000#, down the road since completing the current upgrades for my recent engine build. My problem with this pickup has not ever power but gears that are too low even when it was bone stock. Even loaded with service body full of tools and equip and a trailer loaded with another pickup, I never have to leave 5th gear. I am really looking forward to a ZF6 and some 3.55 gears. I should mention that the first gear these transmissions are different. My current ZF5 42 has a higher ratio in 1st than the 6. I don't think I would desire my current 1st gear with 3.55's, but I believe it would be just right if trading the ZF5 42/4.10 for the ZF6/3.55. A pickup with a ZF6/4.10 combo makes the 1st gear almost useless unless you are trailered or starting out uphill or something. I am familiar with this because at home on the ranch we have 3 gas powered Super Duty's with the ZF6/4.10 combo. I've driven plenty of 7.3L/ZF6 pickups also and there's not often a need for the 1st gear. Now I know comparing auto to manual driving is different, but humor me. Let's say I pulling a heavy trailer with a ZF6/3.55 combo and I can't quite maintain at the lower highway speed RPM I have in OD. I can just pull in 5th gear(DD) and this way am not sacrificing having a nice highway gear for when I'm not loaded. If your running your 4.10's and don't have enough power, I would strongly suggest going the direction of making performance upgrades and not gearing down the rear end, this being said from my observations of my own situation with my own pickup. My biggest and one of my only complaints about it is slow ass 4.10 gears. I know it's not quite the same as your situation but I hope that helps put some perspective on it.

 

[GOOSE]

It will be a sacrifice, highway drive vs. towing grunt. I am contemplating 315-75-16's with either 4;56 or 4;88's and a Gear Vendors. I pretty much do not think 4:10's and 35's go together well for towing heavy. These engines were designed and built to run on the governor, not to be lugged around all day.

 

[fields_mj]

With 4.10 gears and a turbo charger, I think you will be fine. My truck is NA. It had 4.10 gears (ZF5) when I got it, and I've always run tires in the 32"~33" range. It would run 70mph fine, and hit 2500 rpm doing it. Plenty of torque, but sucked fuel. I dropped down to 3.55 gears when I had to replace the center chunk on the D50 front end. Helped a lot with daily driving. Now I haul a 5K travel trailer once in a while and wish I had the 4.10 gears back. With your taller tires and a turbo charger, I think you'll be fine. Like War Wagon said, if you don't like it, I would look at performance upgrades instead of different gears. If I were to build a truck to fit all my needs, it would have a lot of the features that War Wagon has described. Since my funds are limited and the truck doesn't really "make" me money, I live with what I have.

 

[laserjock]

I'm with War Wagon here. I am swapping my 4.10s for 3.55's. That will let me run just shy of 2k unloaded on the highway and if I need more grunt, 4th would put me around 3k at highway speed which is also doable but it will suck fuel I'm sure. I'm also turboing and adding a cam and pump. You have to pay somewhere and to be honest, I figure I'm going to be light a lot more than heavy.

 

[kuskoal]

Why not 3.73? Good medium on ratios. If I were towing I wouldn't do more than 65 mph. Something about a big load going that fast in a light duty truck kinda scares me. It would be 2500 rpm with 1:1 and 1800 with a .76 od.

 

[GOOSE]

I believe its more than just a ratio and how many rpm's you are turning at a certain mph. The higher the axle ratio, the more work your engine will have to do in each gear it pulls. Diesels in general have a narrow efficiency range, that's why over the road tractors have so many gears, the inline 6 cylinders have about a 500rpm range where peak efficiency maintained so they make 500 rpm shifts for all the gears.

Personally, I would run 3:55 gears only if I expected to run empty most of the time and tow up to a maximum of 5,000lbs. Living in mountainous terrain would negate 3:55's as well. Steep grades can bring these trucks right down to 1st gear, I have had it happen on trips.

With 4:10 gears and 285/75-16 tires, I gross 22,500lbs on frequent occasion. I have towed across 4 states with that weight and was able to maintain 60-65mph on the interstates. The truck works HARD from 1st gear on. There is not a doubt in my mind that a Gearvendors or a Brownie would take a huge strain off of the engine towing heavy like this. With a double OD setup like this, I could go to 4:56 gears and keep my overall drive gear about the same. The truck would pull BETTER from the moment I dropped the clutch all the way up to highway speeds. Just as a note, I live in an area that is flat, mountainous terrain would only doubly assert the need for steeper gears and a double OD.