Engine/Transmission (1998.5 - 2002) gear ratio

[JeffHays]

My truck has a 4. 10 ring and pinon gear and I would like to change to the 3. 54 gear. I'm sure the speedo will have to be reclibrated but is there anything else I need to do? What are the pluses and minuses, I'm sure the fuel milage will improve.



2001 SLT Laramie 2500 6 speed no mods

 

[Silver_Ram]

3 months ago, I changed from 3. 54 to 4. 10. I didn't like the power loss of bigger tires & my transmission was acting up alot. I wanted to go with 3. 73, but for warranty purposes I went with 4. 10. The transmission quit acting up.



I checked the truck with a MAC scanner & radar before and after the gear swap. The speedometer/computer seems to have re-calibrated or re-learned on its own. No explantion for that.



I am moving up from 295/75/16 to 315/75/16 shortly to drop the rpm's a little.

My last tank averaged 18. 4 around town. I hope to improve it a little more.



If your change the gears, the differential split on the Dana 80 will require a case change.



Try bigger tires. I love my 4. 10's

 

[Wooter]

I have a reverse situation - 3:54 gears (4wd) and was thinking a'h, 3:73 or 4:10 would be better. We pull a 10800 lb (empty wt) 5th wheel and needed some more hp to ground. With the current gear ratio, I have never have seen more than 17 mpg

empty, cruise on or off, 55,60, or 65 mph. Before ya spend the money to go for it, get some more opinions. For what its worth.

 

[rubberneck]

I don't know, I love my 3. 54's. I would only consider 4. 10s if all i did was tow. I find that i dont have a problem pulling 6th gear. I guess the fact that i run a few power mods helps. Heck i was just thinking the other day i would like to get a gear vendors OD so i could run double over empty. I bet that 5th over would be a sweet trailer hauling gear though. Have you looked in to the cost of an OD unit vs rear end swap? what is the cost difference? I bet you would be real happy with the OD unit.

 

[JeffHays]

No I have not considered a gear vendors OD don't know about it, I thought there had to be a alternative to gear swap, were can I get info. I would hate to loss that torque up to 2300 rpm but would like to gain top end speed with better fuel milage. I tow part time 5k trailer and spend a lot of time on the road unloaded would love to cruise at 80 plus with better than 13 mpg.

 

[y-knot]

Know matter what you do, gear swap or under drive unit, if you only goal is better fuel mileage, the cost of either change Will never be recovered. Both are very expensive conversions and the improved mileage if any will not cover the cost. I have switched gears several times and all have been on 4x4's, in an attempt to regain power after larger tires were installed. My Chevy I went from 3:73 to 4:56, and on my Ford I went from 3:73 to 5:12. Both cost about $1,800. 00 to do. It improved power by handfuls and in my case I also saw a slight mileage improvement, which was not a concern. I think a diesel with 3:54 or 3:73 gears would be strictly a commuters truck, something to get to and from work every day. It is severely handicapped when forced to two anything over 6,000lbs, and far cry from the big tough truck image it possesses. Almost like the guy that get a full size truck with a 6 cylinder, he probably should have gotten a Ranger or S-10.

 

[2broke2smoke]

i know how you can do the swap for free

we'll just swap axles out



i'll take that big ole' heavy slow dana 80



and give you a nice lite, sleek dana 70



the lower weight will give you better mileage and more ground clearance





yeah that 80 would look great under my truck :-laf

 

[Loren]

Jeff,



Robert finally told me that he intends to publish the article I submitted quite some time ago on selecting an overdrive/underdrive transmission. It sounds like you are a perfect candidate for an overdrive.



I don't have the numbers with me (I'm not home) but I'm pretty sure that a US Gear overdrive will give you the equivalent of about a 3. 28 rear drive ratio. I haven't researched the cost of an axle ratio swap, but I bet an overdrive wouldn't cost you much more.



The two brands I researched are US Gear and Gear Vendors. Both seem to be good units. Both work better with a manual transmission, but for automatics, the Gear Vendors may be a better choice.



One of the biggest advantages to an overdrive versus an axle swap is the ability to split gears. This may not be so significant with an automatic, but it's wonderful with a stick. Both overdrives will allow you to tow with your truck's transmission in 3rd (direct) while still getting the benefits of the overdrive auxiliary transmission.



Wait a couple of months for the next issue of TDR and I hope all your questions will be answered. If not, send me a PM.



Loren

 

[JFinke]

My truck tows 8000-14000lb trailers 75% of the time and I have never wanted 4. 10 gears. I tow so I got the 6 speed and have all the gears I need. Just add a little more HP and set the cruise. Dad's truck with 4. 10's and the same tire/trailer size has to go to fifth on the steep hills to keep egt in check also, but turns an extra couple hundred rpm and gets about 1-1. 5mpg less than mine towing and empty.

 

[Big A]

y-knot,

I have to disagree with you huge. Look at my signature, I have no problems whatsoever pulling a 14k lb double in the Rocky Mountains. As a matter of fact, my 5er alone which weighs 11. 5k, is very little strain on my truck. The only time, that I have felt that I need a 4. 10 gear on my truck, is when I take off at a very steep hill, and have to shift from 3rd to 4th. And even then that's only if I'm loaded with both trailers. If you have ever pulled in the Rocky Mountains in Colorado, you would know what I mean.

Another point, when I pull my 5er on the highway, and want to run 65, or 70, I don't have to put up with that motor screaming at a high rpm.

Big A

 

[2ndgen2500]

yeah i have a 4. 10 gear and personally id like to have a lil more top speed, if anyone knows someone that would like to swap 3. 55 with a 4. 10, id be more than happy to meet up and do it.