Increasing Mileage?

[wmoguy]

I had nice a 7 hour drive this weekend to go sledding, any my ADHD and OCD'ness was in full force the whole time....

I've been thinking about ways to increase fuel mileage on my IDI. I have 4.10's which I think most say are much better for towing, which I do, and live in Colorado so they certainly have their upside. HOwever I hate turning 2400 @ interstate speed, and I'm not interested in oversized tires. For my own sanity, slowing down to 60 when interstate speeds are 75 is not an option.

SInce these things make all their torque below 2k and quite a bit of it, why are we trying to wrap this thing out, where it's always going to be anemic in the HP department? I know down low, with a stock turbo setup, EGT's and smoke become an issue... Assuming one could tame the low boost issues w/ a different turbo, and enough air down low, why couldn't we drag around a bunch of weight (or empty) @ 2k or less RPM's without EGT and smoke issues?

From what I understand, the Gear Vendors units don't do to well with heavier loads, so I'm thinking moving down to some 3.55's are about my best option right?

 

[6.9man]

yep 3.55s are good for milage and with your good torque out put i would say be able to haul good yet with 3.55s just probably not make as good mpg pulling is all. i run 3.55s and can haul 10,000 pounds no problem in fifth anything over that it struggles a little more going up hill. im not sticking out the torque you are either

 

[Simp5782]

It depends on how wild you want to get. You can add a brownie to it or find a SAE 2 adapter, and bolt a Allison MD3060 to the back of it.

Allison has a ratio of 5th is .75 and 6th is .65. .65 @ 75 is right around 2100 and @ 70 is just under 2k.

Install the allison, add a NP 205 transfer case for durability so you can use a divorced transfer case, lengthen your front drive shaft and there you have it. The MD3060 is rated at 300hp and 800ft lbs. I think they are rated at 55k gvw as well. They can be 29" to 33" long depending on if it has a PTO or not.It is electronic however and has a 3.50 first gear which is a little high but still enough to pull decent off the line with a set of 4.10s. Or run L on the transfer case till it shifts to direct on the allison then kick out into H and then back into drive.

I have one I would sell ya , MD3060 with the computer and harness with a divorced NP205 shipped to your nearest freight terminal for $2300

 

[wmoguy]

It depends on how wild you want to get. You can add a brownie to it or find a SAE 2 adapter, and bolt a Allison MD3060 to the back of it.

Allison has a ratio of 5th is .75 and 6th is .65. .65 @ 75 is right around 2100 and @ 70 is just under 2k.

Install the allison, add a NP 205 transfer case for durability so you can use a divorced transfer case, lengthen your front drive shaft and there you have it. The MD3060 is rated at 300hp and 800ft lbs. I think they are rated at 55k gvw as well. They can be 29" to 33" long depending on if it has a PTO or not.It is electronic however and has a 3.50 first gear which is a little high but still enough to pull decent off the line with a set of 4.10s. Or run L on the transfer case till it shifts to direct on the allison then kick out into H and then back into drive.

I have one I would sell ya , MD3060 with the computer and harness with a divorced NP205 shipped to your nearest freight terminal for $2300

Your hardcore man!

I'm just thinking about 3.55's. According to http://www.ringpinion.com/Calculators/Calc_RPM.aspx I should be just under 2k @ 75, and 1712 @ 65 mph

I'm fairly confident my turbo will provide plenty of air down low to accomplish what I'm thinking. The unknown will be drive pressures, but I"m sure I'll find that out soon enough.

 

[Diesel_brad]

3:55 is a tall gear for towing anything remotely heavy.

My PSD w 4:10s and 35s tows well grossing out at 18-20k but I dont go over 65mph. And that is about 275hp at the crank

Empty I wish I had 3:55s but The trucks job is to tow, not cruise, so 4:10s it is

 

[Simp5782]

Yeah my 94 with turbo and some mods with 3.55s pulling my 8k GN empty has a HARD time on hills. Like 25/30 on 4/5 mile 6% grades. I run around 60 on flat lands with it. but the 3.55s REALLY bog on hills. I have the best mileage with my 94turbo @ 68mph getting 24 or so driving here to TN a few times. My 85 has 4.56s and a 4spd it is strictly for towing and it will pull on hills loaded or not.

 

[DragRag]

Based on all things mentioned you need to install a gearvendors overdrive. It really is the only way you are going to get the rpms down and get the mpg's up. I have towed plenty heavy with my gearvendors, and have no trouble with them at all. As a matter of fact, I think they ar pretty stout. If you are trying to achieve good mpg's while unloaded then for the gearvendors. If you area trying to get good mpg's while towing heavy, it is never going to happen anyway, you are better off with the higher rims that the 4.10 gears offer for the torque factor. You can turn off the gearvendors and tow without it anyway, and only use it while unloaded if that works best for you. You have the best of both worlds that way. Towing with 3.55 with any kind of load is a joke IMO if you are trying to get anywhere with any kind of speed.

 

[Black dawg]

I would do the gear vendor also.

 

[Shadetreemechanic]

I routinely tow 10k+ with my 3.55s and a factory turbo, and so do you because a 4.10 with a .86 OD gives a final drive ratio of 3.55. If I am real heavy I just leave it in 4th gear.
If it were me I would change out the 4.10s for 3.55s. If you like the way it tows now just plan on towing in D instead of OD. It should work out the same.

 

[GOOSE]

Go with the gear vendors or a brownie. Gary has the gearvendors and trusts it to haul a hundred thousand dollars worth of livestock around. RLDSL has the brownie and 4:10's. He has some of the best fuel economy numbers that I have seen.

The extra gears keep the engine in its sweet spot, thats where the major increase in fuel economy comes from. I'd stick with 4:10's. its easier to put a double od in rather than underdrive 3:55's when you become unhappy with them. Unless you stumble upon a set of axles, the gearvendors is pretty competitive with a gear swap cost wise.

 

[ocnorb]

I must agree with the above... especially because we know you are towing a 5er in Rocky Mountain territory.

My truck has the 3.55s and I was considering going to 4.56 because my truck is used to tow 80%+ of the time. A good GV set up will work well with these trucks as long as you take the time to maintain them- check and change the oil frequently!

 

[Simp5782]

My truck with 4.56s grossing 34,340lbs. They pull with the 4spd.

http://www.youtube.com/watch?v=udSfWWAr_do


http://www.youtube.com/watch?v=0z31DmUmTUY&feature=related

 

[GOOSE]

My truck with 4.56s grossing 34,340lbs. They pull with the 4spd.

http://www.youtube.com/watch?v=udSfWWAr_do


http://www.youtube.com/watch?v=0z31DmUmTUY&feature=related

How about 5:13's, zf 5 speed and a brownie? What you do with that truck is awesome.

 

[Simp5782]

thanks, If I do anything else very drastic for it and it includes towing it will be an Allison MD3560P with the divorced NP205. I am hoping to get my 6x6 up and going with the DT466 and allison and leave it to towing the Gooseneck trailer with heavy loads. 800lbs of torque with 6.44s will pull pretty hard.

I DO have a 16speed spicer for sale though.... its a 4speed main box with the 4 speed aux brownie hooked to it, but its only a single stick with the air switch for the brownie. Video below.

http://www.youtube.com/watch?v=BJC47912E_4

I would be willing to part with it for a LOW LOW price.

 

[ocnorb]

How about 5:13's, zf 5 speed and a brownie?

Top speed in double overdrive would still be 97MPH @ 3500 RPM on that combo!!

Simp- I showed my wife a picture of your 5th wheel and tow rig.

She said "Thats AWESOME!"


I do believe she is a keeper.

Or batshit crazy...