Do I really need 4:10 axles?

[riverfarmer]

Hey I've been driving my new rig around for three months now. It's a cc lb 350 4x4. 5spd turbo idi
She got stock tires and 4:10 gearing. I've turned up the fuel and the turbo a bit. Just for reference.

I towed a 10k travel trailer over the pass, snoqualamie pass in washington 3022 feet and covered in snow, and had 0 problems doing it. Mostly we move people and a smaller loads. But the occasional tractor or bigger piece of equipment.

I have a hard time going 55 or 60mph. And an even harder time getting 13 mpg.
Honest question. Could I tow 10,000 lbs with 3:55 gears?

Thanks Eric

 

[fordf350man]

i dont see why you couldnt, you have the 5 speed for gearing, and you wouldnt have to go down to 3:55 could go with a 3:73 or something like that, i have a c6 3 speed with a 7.3 non turbo and 3:55 in the axles and pulled around 8 to 9 thousand with no problems, i am in michigan i dont have that kind of elevation to deal with

 

[GOOSE]

I have a very similar set up and would not consider ditching the 4:10's, unless it was for 4:56's. I would have to do about 75% of my driving empty on the freeway to consider 3:55's. Go with a gearvendors or a brownie, that will help you all the way around, better mpg empty and better gears for towing.

 

[The Warden]

Do you know the history of your pump and injectors?

I'm a bit surprised by your mileage...unless you have a lead foot, I have a suspicion that your fuel system could stand to be renewed, especially if there are over 100K miles on the pump and injectors. I'm an F250 extended-cab, but otherwise pretty similar to your truck (IDI turbo 4x4, ZF5, 4.10's), and I average between 16 and 17 mpg. I only get below 15 mpg if I'm hauling heavy or driving exclusively in-town, and if I baby the throttle, I can break 20 mpg on a flat freeway run.

An OD unit would be the ideal, although it isn't cheap...3.73 gears would work well, but I don't think I'd go all the way to 3.55 gears with an IDI unless you're empty most of the time. At the same time, I had 3.54 gears on my old E-350 van and was very happy with them...but, that van was predominately a freeway cruiser that didn't see a load very often (although, when it did, I didn't have any problems)...

Just my $.02

 

[bike-maker]

You can always change your gearing the redneck way like I did...buy bigger tires.

 

['94IDITurbo7.3]

so you are saying that your truck struggles to do 55-60mph? if so that is injector/ip issues. nothing to do with gearing.

 

[gatorman21218]

check your throttle cable. make sure you are getting full travel out of it.

 

[riverfarmer]

It's the original fuel system. 189k.

My rig will do 80 but I'm at 2000 rpm at 60.
What's the intervals for injectors and pump?
I was looking at the baby moose pump and balanced BB injectors. I won't have $1000 extra until July or August.

Sorry to sound stupid but what's a browny? I know what a overdrive is. There's one on Craigslist for $500 today in Seattle.

The truck runs great. Starts easy. Pulls great. I was told by the PO that he got way better mileage. I don't know the guy.

What about more air? Timing? It has a 3" straight exhaust and a new down pipe. A big filter and 3 inch intake tube would help probably.
Thanks for all the input. This is my first idi I had a cummins before. Damn dodge for not making a p pumped crewcab.

 

[IDIDieselJohn]

Give 'er a tune up and go from there!!


My 7000lbs '85 E350 extended cargo van 6.9L C6 with 4.10's got me 16.4mpg on a trip at 60mph. Shes revving around 3k at that speed! New pump and injectors! And still haven't had it timed yet either.

 

[RLDSL]

' I dont see why you couldnt switch to 3.55's' says the guy from MICHIGAN , heck, you could tow a house with 3.55's there, but not out where the OP lives, he lives in the HOME of auxilliary transmissions .

That truck with 189k needs new ip and injectors and properly timed first off. The rear end should be good, if anything I would go to a 4.56, but not the other way if you plan on towing 10k trailers on those mountains.

A brownie is a 3 or 4 speed auxilliary transmission that originally came out of an old semi truck or dump with twin stick setup, and like with the one I have, which is a 3 speed, gives a deep reduction range below first, then the ability to split each subsequent gear with a direct and overdrive range. so I end up with a double OD in 5th and just the right gear when pulling hills( or driving around empty, i can just leave it in OD range and it basically acts like I have a higher rear end ratio )

 

[The Warden]

It's the original fuel system. 189k.

My rig will do 80 but I'm at 2000 rpm at 60.
What's the intervals for injectors and pump?
I was looking at the baby moose pump and balanced BB injectors. I won't have $1000 extra until July or August.

The general rule of thumb is that, if you have over 100K miles on the pump and injectors, you're living on borrowed time. Actually, IMHO 189K on a stock IP is pretty impressive, but it's a fair bet that it's pretty well worn out and probably not at the correct timing by now. I'll bet money that replacing the injectors, the injector pump, and setting the pump timing properly will do you wonders for power and for fuel economy

Damn dodge for not making a p pumped crewcab.

I'm going to get flamed by some for this, but you could always make a P-pumped crewcab

 

[DragRag]

Run the gearvendor as suggested. Or install 255/85r16 tires at 33.5" tall, but skinny still.

 

[dizdak]

if you weren't across the country i would trade you my 3.55 geard axles for your 4.10s.. i have same exact truck and usually tow around 9-10k, and its a slug with the 3.55s..

 

[GOOSE]

It's the original fuel system. 189k.

My rig will do 80 but I'm at 2000 rpm at 60.
What's the intervals for injectors and pump?
I was looking at the baby moose pump and balanced BB injectors. I won't have $1000 extra until July or August.

Sorry to sound stupid but what's a browny? I know what a overdrive is. There's one on Craigslist for $500 today in Seattle.

The truck runs great. Starts easy. Pulls great. I was told by the PO that he got way better mileage. I don't know the guy.

What about more air? Timing? It has a 3" straight exhaust and a new down pipe. A big filter and 3 inch intake tube would help probably.
Thanks for all the input. This is my first idi I had a cummins before. Damn dodge for not making a p pumped crewcab.

You are definitely due for a new fuel system and timing. There is power and fuel economy hiding right there. 100,000 miles is usually considered the norn, 150,000 if well taken care of, filter changes and additive used regularly.

2000rpm's at 60mph doesn't seem too bad. Most 4:10 trucks turn 2500 at about 75mph. Less gear will cause more lugging which isn't good for mileage either.

If there was a Brownie for $500 near me, I'd already be on my way to get it.

 

[92F350CC]

With your mountains, I would want a bull moose over the baby moose.