6.4 Hemi Gear Swap

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mtofell

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I didn't know there was a 4.30 gear that fit into these trucks. I thought the 4.30 was a Ford setup.
 

wrtaylo

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Howdy,

Sorry for the delay in response.

For the parts, I do not have the individual items...I dropped the package off from just differentials to the shop and told them everything should be there (I did leave the business card from the guy I worked with at just diff in case). Sorry!

After driving for several days, I could infer that the 4.30 is perfect for the 33-34 tire, 4.56 would be great with a 35+.

For the noise I hear, basically when you let off the gas and coast. Noticeable, but not more than you know something is different in the tone. I have the mufflex exhaust, so there is a base rumble anyway.

I plan to,change diff fluid after 500 miles, per the nitro gear recommendation.

Mileage has stayed the same so far, I do think the speedo is a bit off now.

Hope this helps!
 

snapper23

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After reviewing All of these comments on gear change over and the opinion, I think you should just find an old military transport truck, lol. Once you guys go ultra high in gears these drinks now become more limited in the use on road, especially the highways. This is a lot of money to limit your trucks true intended potential. If your going to play on the mid all the time and on the farm and around d town only . Have fun !!!

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loveracing1988

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After reviewing All of these comments on gear change over and the opinion, I think you should just find an old military transport truck, lol. Once you guys go ultra high in gears these drinks now become more limited in the use on road, especially the highways. This is a lot of money to limit your trucks true intended potential. If your going to play on the mid all the time and on the farm and around d town only . Have fun !!!

Sent from my XT1585 using Tapatalk
Why? These trucks have 2 overdrive gears. My truck with 35's and 3.73's runs around 1500 rpm's at 70 mph, about 2000 rpm's going 82 mph. If I jump up to 4.88 gears I still would be able to cruise just as fast and would make the drive ability of the truck a lot better.

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Ratket

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i bet your mds activates a lot more now. God I can't wait to do this. Do us a favor- Post ur rpm for 65 and 75 so the people who say " it's not street able" will understand that it is completely feasible.
If I lived at sea lvl and it was flat.. 373"s would be fine with a stock 33" tire. I live at 6k feet and drove to 8.5k feet all the time and I want to run 35"s or even 37"s.
 
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RAM_Designs

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According to the online calcs, with 37's and 4.56's my 2k rpm on the highway would be at 75ish instead of 80ish with the stock tires and 3.73's. Sounds good to me.
 

RAM_Designs

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Even with 4.88's and these 36.6" Terra Grapplers, I wouldn't hit 2k rpm until 70-71mph.
 

brandonjansen

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According to the online calcs, with 37's and 4.56's my 2k rpm on the highway would be at 75ish instead of 80ish with the stock tires and 3.73's. Sounds good to me.

I can confirm that. With my 4.56's and 37's I turn 2000 rpm at almost exactly 75 mph. And that's in a Cummins... a hemi most certainly won't have an issue with that as you have far more rpm to play with.
If I was going to do it over again I'd probably run 4.10's or 4.30's with my 37's because of the fact that I have a Cummins and a more limited rpm range. For a hemi running 37's 4.56's would be a great choice
 

RAM_Designs

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I can confirm that. With my 4.56's and 37's I turn 2000 rpm at almost exactly 75 mph. And that's in a Cummins... a hemi most certainly won't have an issue with that as you have far more rpm to play with.
If I was going to do it over again I'd probably run 4.10's or 4.30's with my 37's because of the fact that I have a Cummins and a more limited rpm range. For a hemi running 37's 4.56's would be a great choice

Yeah I thought the sweet spot for the 6.7 was around 1600-1700? Not sure, I don't follow the CTD stuff very closely. 2k rpm at 75mph sounds perfect to me with the 6.4 like you suggested. That's right around where I usually have my cruise set at, and it's a hell of a lot easier getting up a little hill with the rpm's at 2k versus 1600-1800.
 

brandonjansen

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Yeah I thought the sweet spot for the 6.7 was around 1600-1700? Not sure, I don't follow the CTD stuff very closely. 2k rpm at 75mph sounds perfect to me with the 6.4 like you suggested. That's right around where I usually have my cruise set at, and it's a hell of a lot easier getting up a little hill with the rpm's at 2k versus 1600-1800.

With the stock turbo unloaded yes 1600-1700 is about where you want it. That's typically where I am for the highway driving I do daily which is part of the reason I went for the 4.56's. I don't typically get much higher than 65 mph daily. But when I do get out on the open highway where I could get up higher that's where 4.10's would be a nicer option to bring the rpm down a bit.
However for towing it's perfect because it loves being up around 2000 rpm with weight behind it. That keeps the boost up a bit more, EGT's down, the transmission happy, and it pulls like you wouldn't believe. It's definitely a beast when it comes to towing with this setup.
 

wrtaylo

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HI all
So with the 6.4 and 4.30 setup, I have been setting the cruise at 70 and staying at the approx 1900 rpm range, that is with 33's

I think some one asked the cost. 1325 from just diff, and 1000 for the install. Still a bit pricey, but saved me the cost of trading and losing depreciation plus the cost of the diesel. I am gonna run this setup for a year, and then do the keep or trade evaluation. Right now, it is def on the keep side.
 

Ratket

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Have u noticed - Does the mds seem to activate easier-
I looked on their site and they do offer 456& 488- I really really want to do this
 

Ratket

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Well how u liking it so far?
 

wrtaylo

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So far so good. Just about to hit 500 miles. In the back of my mind I still think 4.56 would have been ok. I was worried about fuel mileage and it has not been impacted. The mds kicks in all of the time now, which is kind of an odd sensation, since it was basically inert with the 3.73.

Would I do it again....absolutely. Would I go 4.56..... Only if I wanted to run bigger tires, bigger than 33.

I have not towed yet, but from the way things feel now, I am sure that I will notice an improvement.
 

15BlueStreak

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I like this. I have factory 4.10 gears. My MDS rarely kicks in. Pretty much have to be 65 and under and no head wind at all if anything a tail wind. I think 4.56 gears would be awesome in this truck. Definitely be an even better tow machine. I pull a 9k bumper pull camper. What do you pull with yours?
 

Boudreaux

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I am assuming by these prices the carrier does not need changing with the 4.30 or 4.56 gears? Surely they use a ring spaced or something. Also when considering going to a lower gear it is important to remember that 6th is .625 vs the .7ish that has been the norm for years. That means low cruise rpms even with low gears.
 

brandonjansen

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I am assuming by these prices the carrier does not need changing with the 4.30 or 4.56 gears? Surely they use a ring spaced or something. Also when considering going to a lower gear it is important to remember that 6th is .625 vs the .7ish that has been the norm for years. That means low cruise rpms even with low gears.

That's correct. No need to change the carrier at all. It's simply a ring and pinion change and at a minimum, pinion install kits. However pinion bearings are often required due to damage getting it off the stock pinion. If the truck has higher miles then I would change all the bearings anyway as that's the time to do it.
 

14RAM4X4

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With the stock turbo unloaded yes 1600-1700 is about where you want it. That's typically where I am for the highway driving I do daily which is part of the reason I went for the 4.56's. I don't typically get much higher than 65 mph daily. But when I do get out on the open highway where I could get up higher that's where 4.10's would be a nicer option to bring the rpm down a bit.
However for towing it's perfect because it loves being up around 2000 rpm with weight behind it. That keeps the boost up a bit more, EGT's down, the transmission happy, and it pulls like you wouldn't believe. It's definitely a beast when it comes to towing with this setup.

You could always move up in tire size :happy107: From your pics, it looks like you can go a size up to 40's!!!!!

That would bring your RPM's down a bit and should work out nicely for 4.56's. AEV uses 4.30's for 40's, so the 4.56's should work perfectly for you :naughty:
 
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