gear questions

[LS5DodgeRam]

Hey guys, I was just curious to see if upgrading my gear ratio would do much to my truck...

I have the stock 3.55, with tires that are only an inch taller than stock tires.
What affect would changing the gears be?
Faster or slower acceleration?
Faster or Slower top speed?
Better or worse mpgs?
Any stress on the engine?

Anything helps! Thanks guys!

 

[Redtruck-VA]

Rule of thumb is 33" and taller 4:56, shorter tire 4:10. I use 28" tall tire and turn 2150 @ 65mph. Highway I get 18mpg. IMO, everything is better with a the gear change. The engineers clearly got the gear wrong.

 

[moparman]

I was in the same boat running a tire 1 inch taller than stock but with 3.21's. I went with 4.56. I have the g238 6 speed in mine and turn 2500ish at 65. The change in acceleration was incredible but the 3.7 v6 that couldnt struggles and gets around 14-15mpg

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[LS5DodgeRam]

So my rpms on highway will be higher? How does that work with better mpg? I have the 545rfe tranny( I think that is the name- the 545 something) reason I ask this is I'm going up a couple hundred miles to college and i want a nice mpg

 

[moparman]

So my rpms on highway will be higher? How does that work with better mpg? I have the 545rfe tranny( I think that is the name- the 545 something) reason I ask this is I'm going up a couple hundred miles to college and i want a nice mpg

545rfe is correct. If you want the fuel economy, go with the 4.10's. Youll still get decent fuel economy and put a little more pep in its step. I went 4.56 just trying to help out the v6 with the 20's and 305/50 nittos. 4.10's are also cheaper if youre having them installed by a shop, they basically just go right in. 4.56 is a different story.....ill fill you in if you are doing them yourself

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[Redtruck-VA]

So my rpms on highway will be higher? How does that work with better mpg? I have the 545rfe tranny( I think that is the name- the 545 something) reason I ask this is I'm going up a couple hundred miles to college and i want a nice mpg

This is discussed in many threads, higher rpm alone doesn't equate to using more gas. Fuel usage is determined also by how hard the engine is working at a given rpm. The shorter gear ie 4:10/4:56 has more mechanical advantage then say a 3:55 and it is easier to move the truck from a standing start. Meaning the throttle doesn't have to be leaned on as hard to get up to speed. Also as speed goes up drag increases dramatically, so maintaining speed with the engine working easier will result getting better mileage. The hemi likes 2100-2300 for cruise and very seldom needs to downshift to maintain a constant speed. The engine is at a higher rpm but not working as hard as it would if it was trying to maintain speed at a lower rpm. My wife's stock SUV actually cruises at a higher rpm than my re-geared Ram. Good luck...

 

[moparman]

This is discussed in many threads, higher rpm alone doesn't equate to using more gas. Fuel usage is determined also by how hard the engine is working at a given rpm. The shorter gear ie 4:10/4:56 has more mechanical advantage then say a 3:55 and it is easier to move the truck from a standing start. Meaning the throttle doesn't have to be leaned on as hard to get up to speed. Also as speed goes up drag increases dramatically, so maintaining speed with the engine working easier will result getting better mileage. The hemi likes 2100-2300 for cruise and very seldom needs to downshift to maintain a constant speed. The engine is at a higher rpm but not working as hard as it would if it was trying to maintain speed at a lower rpm. My wife's stock SUV actually cruises at a higher rpm than my re-geared Ram. Good luck...

This is exactly how it works and exactly how it happend with mine.

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[LS5DodgeRam]

Ohh alright I see now I was going to say cuz my truck cruises at 65 with 1850 rpm and I get about 15.5 mpgs

 

[03MopaRamman]

If you go bigger than 33's with any gears your gas mileage will die with the Hemi. I have found that with 285's you have a good balance of power to the wheels and overall Mileage, that is with 17" rims and 4/56's. If you wanna hot rod stick on a set of 265's, 245's for drag racing LOL!

Edit: I owned 35's for 600 Miles and for above and other Reasons Dumped them to go back to the 285's.

 

[LS5DodgeRam]

Do you think as of right now if I put my truck in O/D I would get better gas mileage?

 

[LS5DodgeRam]

If you go bigger than 33's with any gears your gas mileage will die with the Hemi. I have found that with 285's you have a good balance of power to the wheels and overall Mileage, that is with 17" rims and 4/56's. If you wanna hot rod stick on a set of 265's, 245's for drag racing LOL!

Edit: I owned 35's for 600 Miles and for above and other Reasons Dumped them to go back to the 285's.

I have 20x9 deep offset rims with 34x12.50 tires on a stock 3.55 gear ratio
4.7L magnum engine

 

[03MopaRamman]

Nope not unless your towing or want to avoid a downshift if climbing hills or grades under 65 mph.

 

[LS5DodgeRam]

Alright. Hmmm... Debating between an intake or gears if this is the case... (Intake will be untuned) and I'm not sure which way to go!

 

[03MopaRamman]

Yeh seen you had the 4.7, sorry but what I really meant is Gas Engine Ram. Looks like you would want 4.56\s with that set-up. My Opinion only but big honking tires should be put on trucks that do not have to worry about turning them easily (I.E. a diesel with 600 Plus Ft/lbs Torque, and this is by no means a Gasser to Coal Compliment).

 

[Redtruck-VA]

Alright. Hmmm... Debating between an intake or gears if this is the case... (Intake will be untuned) and I'm not sure which way to go!

IMO, gears would benefit you the most. When I am town driving or hot footing the back roads I leave my O/D off.

 

[LS5DodgeRam]

The 4.10 will slip right in? I am against putting my truck in the shop, so this summer I am installing a lift kit myself(I am no stranger to tedious/time consuming work), and if this is possible I would like to do the gears myself then if you believe it would help me out more

 

[Redtruck-VA]

The 4.10 will slip right in? I am against putting my truck in the shop, so this summer I am installing a lift kit myself(I am no stranger to tedious/time consuming work), and if this is possible I would like to do the gears myself then if you believe it would help me out more

I am of like mind, I won't let anyone work on my truck. To do the gear change you will need some speciality tools. I recommend downloading the service manual. Study the procedures and make a tool list. I got my tools from ebay a piece at a time and rebuilt my axle last year.

My Dodge: Dodge Owners Service Manuals - Dodge Cars, Minivans, SUVs

 

[LS5DodgeRam]

alright sweet thanks man I think I'm probably gunna go with the 4.10s so it doesn't involve modding it its going to be a while before though

 

[Redtruck-VA]

alright sweet thanks man I think I'm probably gunna go with the 4.10s so it doesn't involve modding it its going to be a while before though

If you intend to lift the truck, you'll need all the gear you can get. 4:56 would do you better. I believe the modification you are speaking of is to grind the center pin or ring for clearance to install the pin. If you are using the DDT differential this isn't necessary. I would look at at the PowerTrac street locker as it uses the OEM differential and I have heard they are very strong and much cheaper than the complete aftermarket units.
WELCOME TO POWERTRAX® BY RICHMOND GEAR

Just do your reseach and you can make your own informed decision on what you need. Good luck..

 

[LS5DodgeRam]

Thanks man appreciate all the help!