3.55s in a dually rear end?

[NapaBavarian]

Hey-

I'd like to swap the gears in my 1985 truck from the 4.11s it has to a set of 3.55s for economy reasons, I will use it unloaded most of the time, but I'd like to keep my 4.11 axle complete incase I decide to swap back, I've been looking for a complete axle wondering 3.55s were an option since they all seem to have 4.11/4.10...

 

[kblackav8or]

Which axle? You may be looking at changing not only the ring and pinion but also the carrier in some cases. You may actually be able to find someone looking to trade for lower so you may have the upper hand on the trade.

 

[rancherman84]

dont know if they offered 3.55's in duallys,but they did offer them.probably more likely to find 3.55's in a 3/4 ton and end up swaping gears into your dually rearend
i think dually rear ends and single rear ends are different widths

 

[NapaBavarian]

If I need to get a new diff from the junkyard I will, I will likley use an LSD but may use a drop in, if I can find a dually 3.55 then I may drop it in with new slave cylinders, but I doubt that will happen.

 

[RKOCH]

Are you crazy? Leave the 4.10's in. Hell my duelly has 4.88's in it on 33 inch tires. it will not pull as well if you do use the 3.55's.

 

[tuckerd1]

Leave em in and add a Gearvendors or US Gear OD auxiallary transmission.

That's what Im going to do eventually.

Not sure which transmission you are running, but go Here and compare with and without aux. trans. gear ratrios for the different gear sets and transmissions.

You will get a better final drive ratio with the OD aux.

Don

 

[NapaBavarian]

I've been looking hard at that, but it seems so hard to find a used unit. I'm swaping to a zf5, but finding a used gear vendors unit with all the proper parts and at a reasonable price seems to be almost impossible.

 

[darksword]

I swaped from 4.11 to 3.54s I have not had any problems lower RPMs and such...... go for it


Darksword

 

[Agnem]

I've been looking hard at that, but it seems so hard to find a used unit. I'm swaping to a zf5, but finding a used gear vendors unit with all the proper parts and at a reasonable price seems to be almost impossible.

I see one over on TDS in the for sale section.

 

[NapaBavarian]

I see one over on TDS in the for sale section.

Sent an email to find out what input it uses, thanks.

 

[RKOCH]

I swaped from 4.11 to 3.54s I have not had any problems lower RPMs and such...... go for it


Darksword

Sure if you want to go down the road at 90 mph and have less power.... RPM=Power 3000rpm is the magic number. I cruise in my duelly 71 mph flat to the floor and can pull a house with me. My buddies with the 3.55 gears cant pull as much as me and actually get worse MPG because they are lugging the engine instead of turning it where it was meant to be run. If you run unloaded all the time and want a billion mpg go for it. But I thought we were driving trucks here??? Who the hell cares about fuel millage in a truck I bought a truck to work it if I wanted milage I would buy a yugo.

 

[NapaBavarian]

This thing has plenty of power, and there is no reason to turn it at 3k unless you want to see how fast you can wear it out, right now I'm turning 3600rpm at 65mph and I'd like to be able to run 70-75. If I am towing heavy there is always one gear lower...

 

[RKOCH]

The engine was designed to be run at 3k that ain't wearing it out. My duelly has 475k on it now and I have driven it only one way flat to the floor like a diesel was meant to run.

 

[Pacific]

My old truck has 5:13s sure the engine screams at highway speeds but I can pull most hills in OD. My truck weighs about 7800lbs with me and full tank the old truck can pull the 10% grades at 60-80km/h (37-50 mph) in OD with a empty truck. Right now I'am getting around 12.5 mpg which is pretty good in my books.

If I'am carrying a load I use 4th gear and let her go at 3 grand pulling a 10% grade. When I'am on flats trying to do 100km/h (62mph) the old IDI revs about 3000.

Its nice to pull most hills and travel 90% of the time in over drive is sure saves the shifting if I didn't have OD the truck wouldn't go any faster than 50mph.

I would have to agree with the others I would stick with 4:10s if you had a low revving 5.9 cummins that pulls better at lower rpms then go with 3:55s.

 

[NapaBavarian]

RPM=Power 3000rpm is the magic number.

Can you please explain exactly what RPM=Power means? Are you trying to say you get more power at a higher RPM? And as far as luging the engine, a couple years ago there was a really inovative invention, the transmission, you can change the ratio of engine speed to road speed If all you ever do is drag 10,000# then 3k may be fine, but I do most of my towing with the other truck.