6.4 Hemi Gear Swap

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brandonjansen

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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:

I can't fit 40's on my current setup unfortunately. The 37's already required some trimming on the 12 wides. However the dream is for bigger tires in the future which is part of the reason I did go to 4.56's. I'll just need to add some more lift to make that happen ;)
 

Campertruck

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I bought a 2016 3500 chassis cab with 4:44 gears and the Aisin.
It is a SRW 4x4 truck and I wrote a small review of the truck in another thread here. This truck gas the 11.5 rear diff and I'm wondering if those looking to swap gears wouldn't try the 4:44. From the first time I learned about the 6.4 and what gearing they were putting with it I was concerned it would force the engine to be at a very low rpm which would make it always be below its power band. Having my truck for a few months now and having towed approximately 9,000 lbs through the mountains in NH, I have to say the 4:44 ratio is properly matched for the truck. It has the factory 18" wheels and tires and an aluminum flatbed. In local driving this winter I'm getting about 12 mpg , on the highway it goes right into mid 14 mpg range. When it was towing it was getting 11 mpg. At 70 mph the tach is at 2050 rpm. Ironically when I'm driving 50 mph on side roads the evic reads high teens.
I hope this helps with your thoughts on gear changes.
I've owned 5 trucks with the Cummins and I'm not regretting the 6.4 Hemi at all. Bonus points... I get heat on those cold morning in just a few minutes...
 

Ratket

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^^^ So I'm not crazy for thinking maybe 4:88"s with 35" tires... and if you got that from the factory then I should be able to have at least those same gears installed and warrantied from ram- I have a 14 ram 2500 6.4
 

Campertruck

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I think Ram should offer the Aisin in the 2500 trucks. I prefer the mapping or shift logic they use. With the 4:44 it seems to be in the right gear at the right time.
 

DannyMK2

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I bought a 2016 3500 chassis cab with 4:44 gears and the Aisin.
It is a SRW 4x4 truck and I wrote a small review of the truck in another thread here. This truck gas the 11.5 rear diff and I'm wondering if those looking to swap gears wouldn't try the 4:44. From the first time I learned about the 6.4 and what gearing they were putting with it I was concerned it would force the engine to be at a very low rpm which would make it always be below its power band. Having my truck for a few months now and having towed approximately 9,000 lbs through the mountains in NH, I have to say the 4:44 ratio is properly matched for the truck. It has the factory 18" wheels and tires and an aluminum flatbed. In local driving this winter I'm getting about 12 mpg , on the highway it goes right into mid 14 mpg range. When it was towing it was getting 11 mpg. At 70 mph the tach is at 2050 rpm. Ironically when I'm driving 50 mph on side roads the evic reads high teens.
I hope this helps with your thoughts on gear changes.
I've owned 5 trucks with the Cummins and I'm not regretting the 6.4 Hemi at all. Bonus points... I get heat on those cold morning in just a few minutes...

the difference between 4.44 and 4.56 is minimal, and i dont see any aftermarket 4.44 gear sets available for the front (unless im missing them). would be a lot cheaper to go 4.56.
 

loveracing1988

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the difference between 4.44 and 4.56 is minimal, and i dont see any aftermarket 4.44 gear sets available for the front (unless im missing them). would be a lot cheaper to go 4.56.
He is saying there are oem 4.44 gearsets vs going aftermarket with 4.56's.

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theviking

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He is saying there are oem 4.44 gearsets vs going aftermarket with 4.56's.

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Who makes the OEM gears? And do the chassis cabs model use the same front/rear axles as the 2500's?
 

DannyMK2

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He is saying there are oem 4.44 gearsets vs going aftermarket with 4.56's.

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hes suggesting another gear ratio that hasnt been discussed in this thread, which is great. im saying the difference in performance between the two is minimal, but there is a significant difference in cost being that the only supplier for the front is OEM, which could be a reason why its not being considered as an option.
 

loveracing1988

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hes suggesting another gear ratio that hasnt been discussed in this thread, which is great. im saying the difference in performance between the two is minimal, but there is a significant difference in cost being that the only supplier for the front is OEM, which could be a reason why its not being considered as an option.
I said that because if you read the post above mine he wanted them installed at a dealer and be covered under warranty. I know if I re-gear I will go OEM just because of noise issues I've seen pop up with aftermarket gears like Yukon.

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loveracing1988

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Who makes the OEM gears? And do the chassis cabs model use the same front/rear axles as the 2500's?
AAM makes the axles and gears. The front will be the same but the rear could be a 11.8 vs the 11.5 in the 2500 and 3500 srw. The 11.8 doesn't come in a 4.44 or 4.56 though.

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Campertruck

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Just to be clear:
My truck is a 2016 3500 Single Rear Wheel chassis cab with the 11.5 rear axle.
When you spec the Aisin , it only comes with the 4:44 ratio, you can't order it differently unless you order the 4500 or 5500 and then you can get 4:88 gears but I think the axle changes also.
The only reason I posted was I saw people were going for the 4:56 gears and I thought the 4:44 might be available and possibly more common.
Regardless of which one you get, it's really noticeable how much better the 6.4 performs when it is paired with the lower ratios.
I was trying to spec my truck with 4:10 but the Aisin option won't let it happen. It turns out the RPMs are not an issue at 70 mph.
 
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mtofell

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I'm starting to think seriously of having this done soon. After re-reading this thread (which is great and thank you for all the info everyone) I'm thinking the 4.30s are perfect for my situation. Stock tires with no plans to change due to 5th wheel clearance concerns and daily driver mostly under 70 but every once in a while I get out of town a bit and want to cruise at 75-80. I just fear the 4.56s could be a bit too tall with my stock 33" tires.

I am curious though about all the aftermarket talk. Are there any opinions on which brand or supplier is best to go through? Of course cost is a concern but I'm more worried about getting the right parts and getting something quality.
 

reloaderguy

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I'm starting to think seriously of having this done soon. After re-reading this thread (which is great and thank you for all the info everyone) I'm thinking the 4.30s are perfect for my situation. Stock tires with no plans to change due to 5th wheel clearance concerns and daily driver mostly under 70 but every once in a while I get out of town a bit and want to cruise at 75-80. I just fear the 4.56s could be a bit too tall with my stock 33" tires.

I am curious though about all the aftermarket talk. Are there any opinions on which brand or supplier is best to go through? Of course cost is a concern but I'm more worried about getting the right parts and getting something quality.

I would not buy any rear gears except for AAM. Aftermarket gears whine, if you read through CF you will see that comment come up frequently. On the other hand, AAM makes OE gears and are known to be the highest quality for this application.
 

KarL45

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For those of you thinking the 4.56 is to low on the hi way, I run the stock 33" tires and tack 2200 rpm at 80. That's where the 6.4 is just beginning to be happy on rpm's. Especially in the mountains. For example, going over the mountain between Grand Junction and Denver. If the traffic is running fast, generally run 5th and 6th. If it does shift to 4th, still not in the true power band of 4 to 6k. My only objection to going 4.88 is the size of the pinion and the reduced ring to pinion gear contact area. I'm sure, towing 13-14K like I do that I will have to get the rear re-set at some point. Current mileage is just over 44k and towing mileage, approx. 30k. Other than a fluid change, is doing very well. As for the 4.44 gears, if you can get them as a oem gear, the difference would hardly be noticeable.
 
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mtofell

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Thanks guys - are the 4.56s available as OEM? My dealer didn't think so but they didn't seem to be trying too hard to find out.
 

drittal

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4.44 is available on chassis cab SRW 3500 with 6.4 and aisin options. I think 4.56 used to be available in PW, but the axles may have changed since then.


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jaflowers

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4.44 is available on chassis cab SRW 3500 with 6.4 and aisin options. I think 4.56 used to be available in PW, but the axles may have changed since then.


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If 4.44 is available OEM on the SRW 3500....isn't the rear end on the 2500 the same size?? If so I would think if you want to lay out the coin the dealer would be able to put the 4.44 in our trucks no issue.... but I don't pretend to know what all this type of swap entails other than change the front and rear gears for the 4x4 version. I'd personally only look at the OEM dealer swap to keep my lifetime warranty but not everyone buys that.

The 4.56 PW is gone now and the diffs. did change.
 
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mtofell

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I'd personally only look at the OEM dealer swap to keep my lifetime warranty but not everyone buys that.

I was leaning this way but the cost is just outrageous and my ******* dealer says the best they can do it 4.10s.

I found a great local shop today with an owner that's been doing gears for 35 years. I could tell from talking to the guy that he's the one I want doing this. He says he can get OEM but they are just stupid expensive. He likes Yukon gears and admits there were problems 10-15 years ago but that lately their stuff is good. He also said there was some kind of a lifetime warranty but I didn't get all the details.

I have the MaxCare lifetime warranty but I guess now it won't cover the differentials. For cost estimate he said 2200-2500 part and labor but could be more or less. A lot depends on what kits are needed and how things go when opening it up.
 

reloaderguy

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I was leaning this way but the cost is just outrageous and my ******* dealer says the best they can do it 4.10s.

I found a great local shop today with an owner that's been doing gears for 35 years. I could tell from talking to the guy that he's the one I want doing this. He says he can get OEM but they are just stupid expensive. He likes Yukon gears and admits there were problems 10-15 years ago but that lately their stuff is good. He also said there was some kind of a lifetime warranty but I didn't get all the details.

I have the MaxCare lifetime warranty but I guess now it won't cover the differentials. For cost estimate he said 2200-2500 part and labor but could be more or less. A lot depends on what kits are needed and how things go when opening it up.

OE gears run about $225 more retail. You don't necessarily need OE front. I'd spend the extra money.

https://www.ringpinion.com/b2c/ProductDetails.aspx?ProdID=12337&Source=DiffWizard&ShowAA=true
 
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mtofell

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