6.4 Hemi Gear Swap

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Phil21502

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No towing yet and as far as hills go it actually goes up hills now with out wanting to downshift all the time. When getting on it good it just flat out runs. Idk how else to explain it. Lol. I know the evic mileage doesn't really count but I was getting 12.5 before and it's staying right around 14 now. I never expected that. Keep in mind I have 35's and a hemifever tune with mds turned off.
 

Ratket

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If u turn on mds I bet u would get awesome mileage on long trips-
 

kry226

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No towing yet and as far as hills go it actually goes up hills now with out wanting to downshift all the time. When getting on it good it just flat out runs. Idk how else to explain it. Lol. I know the evic mileage doesn't really count but I was getting 12.5 before and it's staying right around 14 now. I never expected that. Keep in mind I have 35's and a hemifever tune with mds turned off.

Alright, thanks. Keep us posted on future experiences.
 

LDBagger17

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Hopefully rear diff gets new gears today-tomorrow, got a friend who is off and going to help do swap
 

LDBagger17

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So got rear diff gear swap done, will do front asap. Installed genuine AAM 4.44 gear set, no pinion depth markings anywhere, was told by someone at AAM to use original pinion shim. Installed original shim as a base line and had horrible pattern, put together checked pattern and tore back down and changed shim 4 times. Finally wound up with an great pattern on drive side, coast side is a little toward toe side of gear but has full contact, did final assembly and filled with oil. Drove several short drives 6,13 and 30 miles with breaks in between and check for leaks and recheck oil level yesterday. Today drove 26 miles then almost 100 miles, can tell a real difference in the truck and mpg's are definently better .5-1 mpg. Absolutely no gear noise, mds is a lot more active, and holds in higher gear much better, had to accelerate pretty quick once and could tell a big difference. I will know a lot more after towing later this week, need to break in a little more first. All in all very happy with job and gear choice, also installed AAM finned aluminum cover, case temp this afternoon after driving almost 100 miles, was 126 ambient was 82.
 

15BlueStreak

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Bagger what were your original gears. And what is your tire size? I am really looking into doing 4.56 gears from the 4.10s that I have now. Its a big gamble. But I really think it will put my truck in its sweet spot for towing. Even though rpm difference is not all that much between the two its not all about rpms as more of the mechanical advantage the gears would give.
 

LDBagger17

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was 4.10 and stock tires 235 80 17 I'll post an update end of week will be towing 36' travel trailer 110 miles north through mountains to Williamsport Pa. I went with oem gear sets and they were cheaper than good aftermarket gear sets
 

Ratket

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Ram really neeeds to toss out anything under 4:10 and offer up to 4:88"s. 373 gears are only a viable option under perfect conditions that are rarely replicated " For a gas motor"I bet your mds will activate a lot more and stay active even more yielding better fuel mileage. Plus now when towing I bet you could prolly hold 3rd gear instead of 2nd on the steepest of grades. 3:73"s are fine for a diesel motor that produces all of its tq/hp under 3k Rpms which is how our trannies are designed. I envy you!!
 

LDBagger17

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Ram really neeeds to toss out anything under 4:10 and offer up to 4:88"s. 373 gears are only a viable option under perfect conditions that are rarely replicated " For a gas motor"I bet your mds will activate a lot more and stay active even more yielding better fuel mileage. Plus now when towing I bet you could prolly hold 3rd gear instead of 2nd on the steepest of grades. 3:73"s are fine for a diesel motor that produces all of its tq/hp under 3k Rpms which is how our trannies are designed. I envy you!!

I have to agree never drove or towed with a 6.4 3.73 combination, but judging from the difference I notice already going from 4.10 to 4.44, I can image 3.73 gears would be a real disappointment. Don't envy me though your wise for gathering info.
 

RainDesert

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Thanks for the report LDBagger. I couldn't agree more that Ram should be offering at least their already available 4.44 to the entire 6.4 lineup.
 

LDBagger17

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320 miles so far since gear swap, all seems good, very quite, absolutley love it so far, it's like a completely different truck.
 

14RAM4X4

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Hey Phil, it's been a couple months since you did the swap to 4.88s.

How's the drive with the 4.88s and the pedal commander? I got the pedal commander and I'm saving up for a gear swap. How's the gas mileage? I know before you said it jump up to 14 mpg on the evic right after the install.
 

Phil21502

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Mine is still going strong hovering around 13.5-14mpg depending on pedal commander setting. Lol. Sport mode +4 and stomping it will roast the tires damn near through 1st gear. I always get nervous and let off. And again just the effect that it has on the tranny is worth it to me. The truck is so much smoother and flat out just goes. Idk how else to explain. Just ordered my thuren 3" front kit so we will see how the 35's look. Might have to try 37's next time.
 

LDBagger17

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Ok so I hooked up to 36' TT with 489 miles since gear swap, took a break about 15 miles in to check things. Then continued it's a totally different truck now, towing in 5th gear rpms are about 200 higher than before. First 60 miles of trip were interstate hwys. Once truck hit 5th gear it stayed there, the 2nd 60 miles were mainly state hwys (45-55 mph), truck still stayed in 5th, only once on trip did it down shift from 5th to 4th on a pretty good grade at 55mph. With the 4.10's truck would have never hit 5th below 55mph and at 65-70 on interstates wouldn't stay in 5th on much on a grade. Grated I was not railing on it with new gears and first heavy tow. Fuel milage is up about 1.5 mpg from before when towing, you can just tell everything is operating so much freer. This absolutely is the way the truck should work, still no noise what so ever, this morning pulled plug checked fluid level and magnet (nothing at all on magnet). To anyone wanting to do this I say do it I see no negatives only positives.
 
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15BlueStreak

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Ok so I hooked up to 36' TT with 489 miles since gear swap, took a break about 15 miles in to check things. Then continued it's a totally different truck now, towing in 5th gear rpms are about 200 higher than before. First 60 miles of trip were interstate hwys. Once truck hit 5th gear it stayed there, the 2nd 60 miles were mainly state hwys (45-55 mph), truck still stayed in 5th, only once on trip did it down shift from 5th to 4th on a pretty good grade at 55mph. With the 4.10's truck would have never hit 5th below 55mph and at 65-70 on interstates wouldn't stay in 5th on much on a grade. Grated I was not railing on it with new gears and first heavy tow. Fuel milage is up about 1.5 mpg from before when towing, you can just tell everything is operating so much freer. This absolutely is the way the truck should work, still no noise what so ever, this morning pulled plug checked fluid level and magnet (nothing at all on magnet). To anyone wanting to do this I say do it I see no negatives only positives.




Thank you sir for the great report. This only confirms my want and need to go to 4.56 gears as I run the 275/70/18 tires which puts it identical as yours with 4.44 and 235/80/17. Hopefully I can do this swap before next camping season! :favorites13::happy107:
 

wyo2track

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Ok so I hooked up to 36' TT with 489 miles since gear swap, took a break about 15 miles in to check things. Then continued it's a totally different truck now, towing in 5th gear rpms are about 200 higher than before. To anyone wanting to do this I say do it I see no negatives only positives.


Just wanted to also give you a shout out for the great report! :happy107: :happy107: I'll x^2 above with 15Bluestreak; Great stuff guys!
 

15BlueStreak

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I just have to confirm what company makes a complete gear kit install for front and rear. Nitro Gear sells a complete kit for 1300 but they list some confusing info on their website. It lists for 2500/3500 11.5/11.8 Cummins diesel. I shot them an email to see what is up. Drive Train Specialists list gear sets for 350. They are made by SVL which is operated by Dana supposedly. Not sure of the quality of them.
 

LDBagger17

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If you want aftermarket gears I'd go with Nitro or Yukon myself, If you actually call Randy's ring and pinion they will help you and offer you a discount on a complete package if you ask for it.
 

15BlueStreak

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If you want aftermarket gears I'd go with Nitro or Yukon myself, If you actually call Randy's ring and pinion they will help you and offer you a discount on a complete package if you ask for it.


I will try that when I am more serious about it. My local to me 4x4 shop quoted me $450 per axle for labor which seems fair. So it looks like I would be in the 2k to 2500 range all said and done.:buffer:
 

Ratket

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I've looked into it and that's what I came up with for a full gear swap with parts and labor - about $2,500
 
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