6.4L Hemi, 4.56 gearing, stock tires

[sargenthp]

Hey guys,

I am looking to regear my truck to the 4.56 gears since my current 3.73 gearing is underrated for the max GCVW when I am towing my camper and family.

Has anyone done this? Any downsides or problems experienced doing this? Does the MDS kick in more unloaded and have enough power to maintain or even increase speed? See much of a difference in MPG's unloaded on the interstate?

I guess the other question is since my dealership did not know... Do you need to do any reprogramming for the speedometer or even shift points when you regear?

Looking to do this in a few weeks between camping trips.

Thanks!

 

[Sitedrifter]

That is a pretty substantial change in my opinion and I would not recommend it. Your gas mileage will be terrible and MDS will pretty much never kick in.

I see 4.10s are the lowest you can get for the 2500 and I would say that would be sufficiently increase over the 3.73 gears.

 

[KarL45]

Why are you thinking of re gearing. If for towing, having done the re gear, personally, wouldn't waist the money going to the 4.10's. As for the fuel mileage, don't know where you live or elevations, but here in the Rockies, I doubt if I lost anything on mileage but the overall performance of the truck towing and for everyday driving is amazing. To my knowledge, there is not any difference in tuning between the 3.73 and 4.10??? As Ram doesn't offer 4.56 in the 2500, "if there were" would be the best you could hope for unless going to an aftermarket tune. From what all I've read, unless you want to race' I don't" there is nothing out there that would help. Also, as for exhaust and air box mods, personally would have to see the gains in black and white before I would believe it. When pulling our 13k 5'er, and the rpms I am now capable of running after the re gear, I have plenty of power without having to run into the high 4's or 5's. To put in plainly, the jump from 3.73 to 4.56 is like taking 6th gear and putting it on the bottom. that's where this 6.4 engine needs it. I love it and would do it again in a second. MY preference.

 

[loveracing1988]

That is a pretty substantial change in my opinion and I would not recommend it. Your gas mileage will be terrible and MDS will pretty much never kick in.

I see 4.10s are the lowest you can get for the 2500 and I would say that would be sufficiently increase over the 3.73 gears.

How would the gas mileage be terrible? That is what the power wagon came with pre 2014 and they could still get 14 to 15 on the expressway which is about where I am with 3.73 gears and mds. Going 70 mds barely kicks on as it is. If anything mds will kick in more with the higher gears because it will be further up in the rpm's so making more power.

 

[loveracing1988]

Hey guys,

I am looking to regear my truck to the 4.56 gears since my current 3.73 gearing is underrated for the max GCVW when I am towing my camper and family.

Has anyone done this? Any downsides or problems experienced doing this? Does the MDS kick in more unloaded and have enough power to maintain or even increase speed? See much of a difference in MPG's unloaded on the interstate?

I guess the other question is since my dealership did not know... Do you need to do any reprogramming for the speedometer or even shift points when you regear?

Looking to do this in a few weeks between camping trips.

Thanks!

How much are you overweight?

 

[sargenthp]

I am already about 500 lbs over and that was still loading it conservatively. My camper could handle another 3k. I have been looking at the option to replace my 2 ATV's with a SxS, so that would add a bit more weight than I have now.

 

[sargenthp]

That is a pretty substantial change in my opinion and I would not recommend it. Your gas mileage will be terrible and MDS will pretty much never kick in.

I see 4.10s are the lowest you can get for the 2500 and I would say that would be sufficiently increase over the 3.73 gears.

I would actually think MDS would kick in more and longer... The engine would work less than it is now. With these gears it seems I am lugging the engine most of the time.

Yes, my RPMs would be higher figure around 350-400 higher in 6th, so that might eat some more fuel. But if the MDS runs longer I might actually get better unloaded running down the highway.

From Mopar... No. But there are multiple aftermarket gears available. My dealership said they would install Sybrina Gear and Axle? Have not found them on the web yet.

 

[loveracing1988]

I would actually think MDS would kick in more and longer... The engine would work less than it is now. With these gears it seems I am lugging the engine most of the time.

Yes, my RPMs would be higher figure around 350-400 higher in 6th, so that might eat some more fuel. But if the MDS runs longer I might actually get better unloaded running down the highway.

From Mopar... No. But there are multiple aftermarket gears available. My dealership said they would install Sybrina Gear and Axle? Have not found them on the web yet.

I think I would find a different dealer.
http://www.drivetrainamerica.com/p-...-front-456-oe-ring-pinion-gear-set-03-13.aspx
That is the oem part for the front and the rear is the 11.5" axle gearsets in the lower part of the screen.
Karl45 above had it done at a dealer.

 

[sargenthp]

I have been starting to price other shops in the area. Not sure what gears they are quoting me. I know the one shop was asking if I want the noisy aftermarket ones, or more expensive quiet ones. Are these the quiet and strong ones? If so maybe I will just order these up!

Thanks!

 

[sargenthp]

Or not... Looks like the rear gears are sold out and they have the best pricing that I have found with my quick search.

 

[loveracing1988]

I have been starting to price other shops in the area. Not sure what gears they are quoting me. I know the one shop was asking if I want the noisy aftermarket ones, or more expensive quiet ones. Are these the quiet and strong ones? If so maybe I will just order these up!

Thanks!

The ones I posted are the same that come from the factory so the more expensive quiet ones.

 

[KarL45]

Guys, I think you will find that there is no "OEM" 4.56 gear available unless you have the Power Wagon. They are two different carriers and wont interchange. That said, my dealer found the 4.56 through Summit. Probably other mfg's also have them and maybe a little cheaper but spending the money, I would suggest going for the proven quality. Big reason, when you compare the ring to pinion contact area between the 3.73 and the 4.56, you will find that it equates to about a 30% or more loss. If you are just getting it for racing or pulling light to moderate, doubt there would be much longevity difference. Pulling heavy, think that's where the big difference will be. I preferred to error on the side of safety and that's also why I elected to have my dealer install them as well. As for noise, somewhat on the first 1000 miles but now, very slight wine and only on a light cruise which isn't even noticeable to me now. Also, no "Clunks" when stopping or starting. All in all, I'm very pleased and now have close to what I wanted, "A Truck". lol

 

[loveracing1988]

Guys, I think you will find that there is no "OEM" 4.56 gear available unless you have the Power Wagon. They are two different carriers and wont interchange. That said, my dealer found the 4.56 through Summit. Probably other mfg's also have them and maybe a little cheaper but spending the money, I would suggest going for the proven quality. Big reason, when you compare the ring to pinion contact area between the 3.73 and the 4.56, you will find that it equates to about a 30% or more loss. If you are just getting it for racing or pulling light to moderate, doubt there would be much longevity difference. Pulling heavy, think that's where the big difference will be. I preferred to error on the side of safety and that's also why I elected to have my dealer install them as well. As for noise, somewhat on the first 1000 miles but now, very slight wine and only on a light cruise which isn't even noticeable to me now. Also, no "Clunks" when stopping or starting. All in all, I'm very pleased and now have close to what I wanted, "A Truck". lol

Those links I posted are made by aam, which makes the oem gearsets so yes, there are oem gearsets.

 

[KarL45]

Interesting. They weren't ether available or we didn't find them a year ago. Any idea who the mfg. is? Also, what models are they running the 4.56 today?

 

[Ratket]

they offer a 4:88in the 5500 and a 4:44 in the 3500. Now weather or not these are interchangeable, I do not know.

 

[KarL45]

I have a suspicion that the 4.88 is a 11.8" ring. Know that the 2500 and I think even the 3500 with the 66/ 68 RFE trans, run the 11.5 gear. Then, when going to the 3500 Dully with the AISIN trans, run the larger, heavier carrier with the 11.8 ring. At least that's my understanding up to now. Truth, if not for the ring to pinion contact area, knowing what I know now, would elect for a 4.88. Suspect that with that gearing, the 6.4 would run a very close second in towing to the diesel.

 

[loveracing1988]

I have a suspicion that the 4.88 is a 11.8" ring. Know that the 2500 and I think even the 3500 with the 66/ 68 RFE trans, run the 11.5 gear. Then, when going to the 3500 Dully with the AISIN trans, run the larger, heavier carrier with the 11.8 ring. At least that's my understanding up to now. Truth, if not for the ring to pinion contact area, knowing what I know now, would elect for a 4.88. Suspect that with that gearing, the 6.4 would run a very close second in towing to the diesel.

they offer a 4:88in the 5500 and a 4:44 in the 3500. Now weather or not these are interchangeable, I do not know.

The 4500 and 5500 use dana rear axles and a sterling front axle. The 11.8 only comes in 3.73 and 4.10 ratios.

 

[TWILLIAMS9]

Having just switched to the 4.56, I think that it was money well spent! the truck feels "lighter". Pretty close to how it felt stock. I also needed to regear because I recently purchased a travel trailer and needed the power back to lug that thing up the mountain passes. Now I can have my cake and eat it too, having a lifted truck and pulling a trailer!

 

[slim072590]

I've been looking at 4.56 gears and 37 inch tires and it would put my drive ratio slightly over stock with factory 33.3s and 4.10's.... But I don't want to lose or void my warranty as this is my first new truck and I always end up modding everything way past warranty lol

 

[TWILLIAMS9]

You should be fine. My dealership never said anything about my lift and tires. Just that my suspension isn't covered.