Swapping from 3.73 to 3.42 Gears

[AKaiser]

Dave, thanks for the info.

 

[DHerbeck]

My supplier in Tulsa is telling me the same thing about availability as Morse has posted. AAM is saying mid-May for availability. I am wondering if they are just now beginning to make the 3. 42 gears for the current 11. 5 inch rear end we have.



I am still excited!

 

[therabbittree]

I think this is a great swap and a good Idea. . I run 3. 07 gears in my 92 w350 srw with a 5sp getrag . . and it out pulls my friends 2001 6spd 5600 3500 with 4. 10's. the 3. 07s are great. . I normally drive around in 4th ie 1 to 1 ratio . . unless out on the freeway... . low speed and backing trailer I use lowrange... lowrange for my snowplowing . . heck in lowrange I can hit almost 50mph... any how. I think the 3. 42 will work great in a g56 truck. . even a older 5600 early 3rd gen. remember most of us don't leave then engine sstock power wise. in fact my friend with the 2001 is UPSET because he has 410's he wishes he had the 355's. My dads 02 had 410's and we swapped 355 in and its much better. . and mpg did go up a little.

Just my opinion . . and experiece. .

Later

Deo

 

[DBusch]

did anyone ever find out about the overdrive gears in the G56 that comes in the 4500/5500 trucks???

 

[SAndreasen]

#ad
i have 3. 54 gears and run 285/75/16 tires this gives me 80 mph at 2000 rpm i tow from 26,000 to 37,000 and i love the gears i wouldnt mind if they were a little lower . i can see no reason for these trucks to be geared lower than 3. 73 i get hand calculated 11mpg even haulin the big loads

 

[DHerbeck]

i love the gears i wouldnt mind if they were a little lower .



i can see no reason for these trucks to be geared lower than 3. 73 i get hand calculated 11mpg even haulin the big loads [/QUOTE]



You are running 3. 54 gears and state that you wouldn't mind if they were a little lower. Then you state you see no reason for these trucks to be geared lower than 3. 73... ..... I am confused with your statement.

 

[AKaiser]

You don't suppose he meant "lower speed" as opposed to "lower numerically?"

 

[JACummins2500]

Cummins has a computer program on their website to calculate the proper gearing for trucks equipped with their engines. They caution against any gearing that takes the vehicle below peak torque at 55mph. The rational being that you should not lug the vehicle when hauling a load and 55 mph being the likely speed when on a 2 lane road. Of course, they must assume you will always be loaded when making a recommendation like that.



The G56 was to get a faster 6th gear once the 07. 5 were out. Has this happened? I agree that the "old" G56 with a 3. 73 was to slow.

 

[AKaiser]

Cummins has a computer program on their website to calculate the proper gearing for trucks equipped with their engines. They caution against any gearing that takes the vehicle below peak torque at 55mph. The rational being that you should not lug the vehicle when hauling a load and 55 mph being the likely speed when on a 2 lane road. Of course, they must assume you will always be loaded when making a recommendation like that.



The G56 was to get a faster 6th gear once the 07. 5 were out. Has this happened? I agree that the "old" G56 with a 3. 73 was to slow.

I'm going to guess they are, based on a discussion I had online with a Dodge rep. She did some research and concluded that you could now get 4. 10s with a G56. Apparently the website vehicle configurator is incorrect. We shall see.



Based on the Klenger gear caluculator, I figure, with 3. 42 gears, I could tow anything I needed at 55 in 5th with the stock 265-70R17s. Any daily driving I could run the 33s I'm using now, and gain a 300 RPM decrease (over stock tires/3. 73s) at interstate speeds (70 in IN). It would be nice to have taller 5th and 6th gears and 3. 73s, though.

 

[Vaughn MacKenzie]

I think BSFC has more bearing than RPM when pulling a load (having the engine heavily loaded). The graph I saw for a 24-valve engine put the best BSFC at 1950 - 2000 RPM, but I don't know how it compares to a HPCR motor (don't have that one in front of me). BSFC at 1650 RPM is about the same as 2150 RPM, but for the sake of the engine and drivetrain it's better to run at the higher RPM.

Vaughn

 

[AKaiser]

Bsfc

I think BSFC has more bearing than RPM when pulling a load (having the engine heavily loaded). The graph I saw for a 24-valve engine put the best BSFC at 1950 - 2000 RPM, but I don't know how it compares to a HPCR motor (don't have that one in front of me). BSFC at 1650 RPM is about the same as 2150 RPM, but for the sake of the engine and drivetrain it's better to run at the higher RPM.



Vaughn

#@$%!



Brake Specific Fuel Consumption



I had to look this up, and only found three posts with the #@$%! acronym in the last 3 months (default search setting). There are about 3 pages in the history of TDR, FWIW. Couldn't spell it out in plain english?

 

[Vaughn MacKenzie]

Sorry, almost spelled it out for ya AKaiser, but I was in a hurry

 

[AKaiser]

Sorry, almost spelled it out for ya AKaiser, but I was in a hurry

It was late, and I was (still am) tired, hence the #@$%! (< Aint' he cute :-laf )

 

[MAlexander]

Hey D - I have a 06 Mega 3500 with a 4:10 and I am trying to do a gear change to either a 3:73 or 3:42 and the Dodge dealer here told me that niether gear will fit in my housing. Thanks for the part number and I will research the size problem.

 

[DGoyer]

For people changing tire size, this may be helpfull. When you re-flash the computer for rev. per mile, it also asks for teeth on ring gear. I contacted American axle, Bob Dunn got back to me with 120 for the 11. 5. So have the dealer or who ever doing this imput it with the rev's per mile to get the exact spedo read.

 

[Cummins Cowboy]

first of all who wants to only drive 60-65?? I don't, out here I usually set my cruise at about 83mph, on the interstate, on my '06 it really sucks the fuel at this speed I am about 14mpg or so, to help with this I bought a smarty, I have not quite run a full tank with it yet but it appears that my mileage is up 2mpg, with a mix of half towing and half city/highway across the board. IMO the problem with our trucks is the timing is set too far back especially when you get to and above 2k RPM, this is where the smarty kicks in, on my truck you really can feel the truck run better when it gets to this point. you can also see that CRUISING EGT's are nearly 200degrees cooler than without the smarty, this tells me the diesel is burning and makeing power rather than heating up the damn cat and wasting fuel for emissions!!!! if this proves to be true which it looks like it will the smarty will well pay for itself within a year, being able to puff a little smoke when I want, and having a truck that is a hill pulling beast now, are great side benfits

 

[y-knot]

Man I love guys like you, your willing to take that chance and separate yourself from the herd. Way to many people on this site and in general only talk about what they would like to do or have done, you are a doer and not a talker, that is refreshing. Don't listen to the nay sayers, if it was up to those people we would still be living in caves and using torches to see. Weather or not the gear change gives you your 2 MPG increase you want, your still a winner, good luck with the swap and keep us posted.

 

[Lightman]

For people changing tire size, this may be helpfull. When you re-flash the computer for rev. per mile, it also asks for teeth on ring gear. I contacted American axle, Bob Dunn got back to me with 120 for the 11. 5. So have the dealer or who ever doing this imput it with the rev's per mile to get the exact spedo read.

I think some one is feeding you the wrong numbers to get 120 teeth on the ring gear you would need a housing 3 times as big as we have. pull the cover and count them there will be a difference from 4. 10 to 3. 73 but not any where close to 120 teeth more like in the 30-40 something range just a guess on the number

 

[bighammer]

... . I bought a smarty, I have not quite run a full tank with it yet but it appears that my mileage is up 2mpg, ... .

Is that verified by your overhead display, needle position, or seat of the pants?

 

[DGoyer]

Sorry for the mis-info it is the speed senser ring that bolts on to the ring gear.