6.4 Hemi Gear Swap

[14RAM4X4]

@ Ram_designs

Brandon is running 37's but he is also rocking the 6.7L Cummins, not the 6.4 like you and me. HUGE difference!

 

[pytbul]

I changed from 3.73 to 4.56 gears on my 2500 with 6.4. totally changed how the truck drives. I live in the mountains and pull a 10000 lb 5th wheel. Mileage changed slightly to the better. I pretty much cruise at 65 mph and can stay in 5th gear instead always being in 4th. The only time I don't like the gears is when we travel empty on I-15 where the speed limit is 80. But still not bad.

 

[mtofell]

God I hate to hear this..... I know I would like my truck so much better with those gears. I'm frustrated that I can't trust the longevity of my truck enough to sink the money into it (tranny blew up at 40K as still doesn't feel right but that's another story).

Did you get it done at the dealer? My dealer told me the only available gears were the 4.10s and it would be around $3500. Of course, they are somewhat lost about things so that well may be inaccurate.

 

[brandonjansen]

The dealer is definitely inaccurate. They're probably looking at just OEM replacement parts which would in fact only be 4.10's. I'd highly recommend having an experienced gear shop do the work. For one, they can get you whatever you want. Two, they'll make sure the gears are set up properly (I wouldn't trust a dealer to do that). And three, they'll be cheaper.

 

[mtofell]

The dealer is definitely inaccurate. They're probably looking at just OEM replacement parts which would in fact only be 4.10's. I'd highly recommend having an experienced gear shop do the work. For one, they can get you whatever you want. Two, they'll make sure the gears are set up properly (I wouldn't trust a dealer to do that). And three, they'll be cheaper.

I'd mainly be going the dealer route to keep my lifetime warranty intact. I suppose the gears wouldn't be that big of a deal to fall out of warranty. I wonder if they'd void the warranty on other parts because of the swap? Are there any outward signs of the swap or would they even know?

 

[loveracing1988]

I'd mainly be going the dealer route to keep my lifetime warranty intact. I suppose the gears wouldn't be that big of a deal to fall out of warranty. I wonder if they'd void the warranty on other parts because of the swap? Are there any outward signs of the swap or would they even know?

Short of opening up the axles they would never know.

Sent from my Nexus 6 using Tapatalk

 

[pytbul]

God I hate to hear this..... I know I would like my truck so much better with those gears. I'm frustrated that I can't trust the longevity of my truck enough to sink the money into it (tranny blew up at 40K as still doesn't feel right but that's another story).

Did you get it done at the dealer? My dealer told me the only available gears were the 4.10s and it would be around $3500. Of course, they are somewhat lost about things so that well may be inaccurate.

I had a local shop do the swap. $1650 front and rear.

 

[pytbul]

God I hate to hear this..... I know I would like my truck so much better with those gears. I'm frustrated that I can't trust the longevity of my truck enough to sink the money into it (tranny blew up at 40K as still doesn't feel right but that's another story).

Did you get it done at the dealer? My dealer told me the only available gears were the 4.10s and it would be around $3500. Of course, they are somewhat lost about things so that well may be inaccurate.

I had a local independent shop do the work. $1650 front and rear with new bearings and seals.

 

[14RAM4X4]

I changed from 3.73 to 4.56 gears on my 2500 with 6.4. totally changed how the truck drives. I live in the mountains and pull a 10000 lb 5th wheel. Mileage changed slightly to the better. I pretty much cruise at 65 mph and can stay in 5th gear instead always being in 4th. The only time I don't like the gears is when we travel empty on I-15 where the speed limit is 80. But still not bad.

A few questions about your gear swap... * first, are you on stock tires or larger than stock (what size)?

Then:

1 - What are your rpms at 65, 70, 75 mph?
2 - Did the gears make a big difference on daily drivability with the trans shift points?
3 - How is it at holding speed on the hwy (65 - 75 mph)?
4 - Any increase / decrease in mpg city / hwy? - from above, I assumed you were talking about towing
5 - Any other observations you've made good or bad about moving to 4.56s? Any regrets about it?

I'm thinking 4.56s would be a pretty good match for mostly unloaded daily driving from 35 - 65 mph with stop & go traffic. Most of my hwy trips are slower than 65 anyways due to traffic.

 

[mtofell]

A few questions about your gear swap... * first, are you on stock tires or larger than stock (what size)?

Then:

1 - What are your rpms at 65, 70, 75 mph?
2 - Did the gears make a big difference on daily drivability with the trans shift points?
3 - How is it at holding speed on the hwy (65 - 75 mph)?
4 - Any increase / decrease in mpg city / hwy? - from above, I assumed you were talking about towing
5 - Any other observations you've made good or bad about moving to 4.56s? Any regrets about it?

I'm thinking 4.56s would be a pretty good match for mostly unloaded daily driving from 35 - 65 mph with stop & go traffic. Most of my hwy trips are slower than 65 anyways due to traffic.

Here's a site with and RPM calculator that is pretty cool:

Differential Gear Ratio Calculator | West Coast Differentials

It's been a few months since I looked into it but I seem to remember on the highway it was like losing 6th gear and having 5th as the top. Maybe a 400 rpm difference. Not too bad until you're going over 75-80ish.

The people I've read about going from 3.73 to 4.56 are super happy with it.

I'm especially interest in hearing about #2 - the shift points.

 

[pytbul]

A few questions about your gear swap... * first, are you on stock tires or larger than stock (what size)? Truck is bone stock except for gears.

Then:

1 - What are your rpms at 65, 70, 75 mph?The following chart lists the RPMs your engine will be turning while driving at a given speed.

Road RPMs at given speed in miles per hour
65 70 75

1 9701
2 5496 5919 6342
3 4235 4560 4886
4 3003 3234 3465
5 2433 2620 2807
6 1862 2005 2149

R 13335 14361 15386
2 - Did the gears make a big difference on daily drivability with the trans shift points? Really helped with the 1 to 2 shift while loaded. tightened the shift points up across the board.
3 - How is it at holding speed on the hwy (65 - 75 mph)? Much nicer holds gears longer
4 - Any increase / decrease in mpg city / hwy? - from above, I assumed you were talking about towing. slight increase when towing. didn't notice any loss in day to day
5 - Any other observations you've made good or bad about moving to 4.56s? Any regrets about it? love the results. only regret is slight gear whine. But you really have to listen for it.

I'm thinking 4.56s would be a pretty good match for mostly unloaded daily driving from 35 - 65 mph with stop & go traffic. Most of my hwy trips are slower than 65 anyways due to traffic.[/QUOTE

Overall i am really happy with the change in performance and driveability when towing the fifth wheel or with just the slide in camper. Only problem I have is when empty. I just can't keep my foot off of the skinny pedal.

 

[14RAM4X4]

Overall i am really happy with the change in performance and driveability when towing the fifth wheel or with just the slide in camper. Only problem I have is when empty. I just can't keep my foot off of the skinny pedal.

Thanks for the info. I was pretty sure this was the direction I wanted to go. And now I will start saving my pennies. Hopefully next summer I can move to 4.56s.

I can live with a little gear whine. I hardly heard anything above the hum/roar of my MTs at hwy speed. Nothing the volume control won't take care of.

 

[wrtaylo]

ECM / Programming Change

Howdy,
I am new to the forum, I have been following this thread. I went to my local 4x4 shop yesterday, and was about to pull the trigger on the 4.56 swap. However, they brought up several questions that spooked me......

Do I need to do any programming change with the gear swap (they were worried about the ECM kicking the truck into limp mode) - I did not think so, but I wanted to hear from others that have done the change to a 2015.

Speedometer calibration - does it throw off your displayed speed (maintaining stock wheels)

I live in SC, so we have rollers for the day to day, and then decent pulls up to the smokey mountains. The 3.73 has caused the truck to lug significantly pulling a 6500# load.

Thanks all for the help / advice. Sorry for the first time post asking tons of questions!

 

[DannyMK2]

Howdy,
I am new to the forum, I have been following this thread. I went to my local 4x4 shop yesterday, and was about to pull the trigger on the 4.56 swap. However, they brought up several questions that spooked me......

Do I need to do any programming change with the gear swap (they were worried about the ECM kicking the truck into limp mode) - I did not think so, but I wanted to hear from others that have done the change to a 2015.

Speedometer calibration - does it throw off your displayed speed (maintaining stock wheels)

I live in SC, so we have rollers for the day to day, and then decent pulls up to the smokey mountains. The 3.73 has caused the truck to lug significantly pulling a 6500# load.

Thanks all for the help / advice. Sorry for the first time post asking tons of questions!

no and no. gear swap requires no programming whatsoever. only thing that is going to affect the speedo is a change in tire size.

 

[brandonjansen]

Exactly what DannyMK2 said above. No need for programming change and it definitely won't go into limp mode and the speedometer won't be affected at all as the newer Ram's read them off the wheel speed sensors, not the transmission output shaft.

 

[wrtaylo]

Thanks

Thanks for the info! I plan to get the gears ordered this week, looks like an approx 2 week back log at the shop. I will post up the results.

Thanks again!

 

[RAM_Designs]

I need some 4.56's myself, these 37's are making me a little too sluggish. Let us know how it goes, I'm sure you'll get yours done before I decide to order anything.

 

[mtofell]

Thanks for the info! I plan to get the gears ordered this week, looks like an approx 2 week back log at the shop. I will post up the results.

Thanks again!

Keep us posted... in particular I'm interested to know how the parts ordering goes. I've read there can be some confusion, especially on the front diff. Where are you ordering from?

 

[wrtaylo]

Will do. Clemson 4x4 is handling everything.

Looking forward to the better drive ability. Riding through the mountains yesterday it was running through the gears, could not find a happy place.

 

[wrtaylo]

Not so good news.....

After the initial quote of 1800....after specing out everything, the quote came in at 2700. The guys at the shop spent all day calling around trying to get the price down. Looks like the gears were not the issue, it was the dress kit ( bearings,set) that were approx 500 an axle.

So I held off. That is getting way too close to trade in territory. I had a less than 2k threshold in my mind.......

They are going to call around some more this week, and see if they can find anything else.

Crap