6.4 Hemi Gear Swap

SuperBeeMike · Jul 31, 2018

4:56 Gear Swap Update:

I went out over the weekend with the trailer and I must say, the new gears are really helping the Hemi out. I noticed a few improvements and I wanted to report back.

I went from Reno to Yerington, Nevada, for Night in the Country. Nevada opened a new state route (USA Parkway), and it has some decent grades to pass. I had taken this route before when I had the 3:73's and the truck would struggle on the big pass, down to 35-40mph, bogging 2nd gear. This time, same hill with 4:56's, and I was in 3rd, pushing 50-55 mph, and if I remember right, in the 4k RPM range. I also want to say from a stop, the truck is more motivated to get things rolling now. Another thing to note was my RPM in tow haul mode. Since 6th is locked out, I'm running down the interstate in 5th gear. At 65mph, I'm right round 2500 RPM, and the truck seems to like it. With that, I noticed my gas mileage is up around 1 mpg on this trip, maybe a little more.

Overall I'm am very happy with my truck. It still doesn't pull like a Cummins but it is very competitive now. While going out to Yerington, I got stuck behind some POS VW bus. while going up hill at 40mph. I was able to safely pass the VW, getting up past 70mph before I merged back in. Best part was there was an old 7.3 Superduty Ford behind me, towing a similar sized trailer. We both pulled out to pass and when I merged back in, I had a lot of distance gained between us. Now, not sure if he was maxed out but it was nice to not be holding anyone up out there.

So bottom line, I highly recommend gearing up these truck (Ram, I hope you are listening). 4:56's are the magic combination for stock height, stock tire trucks. Would 4:88's be better, I would say for me, no. highway RPM would be getting up there, more so in Tow/Haul Mode. While being a bit pricey, I find myself much more relaxed, and less stressed, while traveling. That alone is worth the investment to me. I won't ever recoup the cost in fuel mileage but maybe my transmission will last longer, or my engine, or my heart, its hard to say.

Happy Towing - Mike

busterbrown · Jul 31, 2018

SuperBeeMike said:
4:56 Gear Swap Update:

I went out over the weekend with the trailer and I must say, the new gears are really helping the Hemi out. I noticed a few improvements and I wanted to report back.

I went from Reno to Yerington, Nevada, for Night in the Country. Nevada opened a new state route (USA Parkway), and it has some decent grades to pass. I had taken this route before when I had the 3:73's and the truck would struggle on the big pass, down to 35-40mph, bogging 2nd gear. This time, same hill with 4:56's, and I was in 3rd, pushing 50-55 mph, and if I remember right, in the 4k RPM range. I also want to say from a stop, the truck is more motivated to get things rolling now. Another thing to note was my RPM in tow haul mode. Since 6th is locked out, I'm running down the interstate in 5th gear. At 65mph, I'm right round 2500 RPM, and the truck seems to like it. With that, I noticed my gas mileage is up around 1 mpg on this trip, maybe a little more.

Overall I'm am very happy with my truck. It still doesn't pull like a Cummins but it is very competitive now. While going out to Yerington, I got stuck behind some POS VW bus. while going up hill at 40mph. I was able to safely pass the VW, getting up past 70mph before I merged back in. Best part was there was an old 7.3 Superduty Ford behind me, towing a similar sized trailer. We both pulled out to pass and when I merged back in, I had a lot of distance gained between us. Now, not sure if he was maxed out but it was nice to not be holding anyone up out there.

So bottom line, I highly recommend gearing up these truck (Ram, I hope you are listening). 4:56's are the magic combination for stock height, stock tire trucks. Would 4:88's be better, I would say for me, no. highway RPM would be getting up there, more so in Tow/Haul Mode. While being a bit pricey, I find myself much more relaxed, and less stressed, while traveling. That alone is worth the investment to me. I won't ever recoup the cost in fuel mileage but maybe my transmission will last longer, or my engine, or my heart, its hard to say.

Happy Towing - Mike

Thanks for the update. Something I may look to do in the near future.

14RAM4X4 · Jul 31, 2018

So is everyone going with AAM gear sets?
I was looking at Nitro Gears from Just Diffs. They have the front & Rear RP sets with master install kits for $1,325.00 / GPRAM2500. These are the gears I was planning on buying. Labor on the last 2 gear installs was about $900 ~ $1100. So I'm hoping to be in the $2500 range.

found them here: http://www.justdifferentials.com/GPRAM2500-SELECT-p/gpram2500-select.htm

The only note I see on that page states a ring gear spacer is needed for aftermarket locking diffs.

SuperBeeMike · Aug 1, 2018

14RAM4X4 said:
So is everyone going with AAM gear sets?
I was looking at Nitro Gears from Just Diffs. They have the front & Rear RP sets with master install kits for $1,325.00 / GPRAM2500. These are the gears I was planning on buying. Labor on the last 2 gear installs was about $900 ~ $1100. So I'm hoping to be in the $2500 range.

found them here: http://www.justdifferentials.com/GPRAM2500-SELECT-p/gpram2500-select.htm

The only note I see on that page states a ring gear spacer is needed for aftermarket locking diffs.

My shop supplied AAM gears, a new front carrier, and charged me just over $2700. They did reuse some of the bearings since my truck only had 3,500 miles on it. I wanted factory gears as I am pulling quite often and didn't want any issues. Not that Nitro is bad, but I figured AAM would be best. The shop I used recommended the AAM gears too. So far they are trouble free and quiet.

reloaderguy · Aug 1, 2018

14RAM4X4 said:
So is everyone going with AAM gear sets?
I was looking at Nitro Gears from Just Diffs. They have the front & Rear RP sets with master install kits for $1,325.00 / GPRAM2500. These are the gears I was planning on buying. Labor on the last 2 gear installs was about $900 ~ $1100. So I'm hoping to be in the $2500 range.

found them here: http://www.justdifferentials.com/GPRAM2500-SELECT-p/gpram2500-select.htm

The only note I see on that page states a ring gear spacer is needed for aftermarket locking diffs.

That depends on the ratio you select. I am running AAM Chrysler rear gears and Yukon fronts. Since there isn't a AAM Chrsyler 9.25 5.13 option I went with aftermarket. There is a AAM GM factory option but I didn't feel like the added cost was warranted since GM 9.25 gears are not a factory gear in a Ram solid axle.

Some ratios there are only rears available, such as 4.88 (if you can find them). If you can get AAM that is probably best, however, there are plenty of good aftermarket gears too. The priority should be matching the ratio to the tire size you run now or possibly run in the future. Also, the transmission gearing is so high that you can't possibly go too low (within reason). My opinion, based on my own gearing selection, take whatever ratio you're considering and go one size lower.

GsRAM · Aug 2, 2018

Hi Mike,

Good update, thanks. Did you find out in your research if the mopar/aam 4.44 gears could utilize the original front carrier? That would save some cost if possible. Glad you like your new gears!

SuperBeeMike · Aug 2, 2018

GsRAM said:
Hi Mike,

Good update, thanks. Did you find out in your research if the mopar/aam 4.44 gears could utilize the original front carrier? That would save some cost if possible. Glad you like your new gears!

I did not look too far into the 4:44's. After seeing posts about engine RPM's in relation to the different gear ratios, I was actually comparing 4:88's to 4:56's. I knew if I went too far with gears, I could step up to 35" tires to compensate. If I didn't go enough, I would be stuck living with regret. I was nervous on the 4:88's because the pinion gear loses surface area where it contacts the ring gear. I felt the 4:56's would be a bit stronger.

GsRAM · Aug 3, 2018

Ok, sounds good. Thanks!

Don_T · Aug 4, 2018

Does anyone know of a place that can be trusted in northern Vermont to do gear swaps? I am thinking about going to 4.56 or 4.88 in my truck.

theviking · Aug 4, 2018

Don_T said:
Does anyone know of a place that can be trusted in northern Vermont to do gear swaps? I am thinking about going to 4.56 or 4.88 in my truck.

With all the mud bogging and truck pulling up your way you'd think it would be easy to find a shop there.

SuperBeeMike · Aug 6, 2018

Here's how I found my driveline shop. Then I checked Yelp for reviews.

http://www.demandaam.com/locate-a-distributor

Don_T · Aug 6, 2018

SuperBeeMike said:
Here's how I found my driveline shop. Then I checked Yelp for reviews.

http://www.demandaam.com/locate-a-distributor

Thanks Mike, I am looking into this now. I have emailed a couple of shops about it as well. I may have to drive into town where I can use my cell phone and make some calls.

RAM_Designs · Aug 22, 2018

reloaderguy said:
I'm running 5.13s with 37's. If you plan on sticking with 37's then 5.13s feel good. 5.38 would be better for 40's.

What are your rpm's with the 5.13's? I'm running 37's on a 2016 as well, and I can't seem to find reliable info on rpm's, even with calcs. Everything seem to conflict.

U&A · Aug 22, 2018

RAM_Designs said:
What are your rpm's with the 5.13's? I'm running 37's on a 2016 as well, and I can't seem to find reliable info on rpm's, even with calcs. Everything seem to conflict.

http://www.csgnetwork.com/multirpmcalc.html

Have you tried this one. Seems to be very accurate. Use the very bottom calculator....
Input ring gear ratio
Tire hight
MPH
Final trans drive ratio

The picture shows final drive ratios.

Sent from my iPhone using Tapatalk

RAM_Designs · Aug 23, 2018

^^^works great, thanks.

reloaderguy · Aug 23, 2018

RAM_Designs said:
What are your rpm's with the 5.13's? I'm running 37's on a 2016 as well, and I can't seem to find reliable info on rpm's, even with calcs. Everything seem to conflict.

2k RPMs at 70mph. I would never considered 4.56 gears in a 14+ Hemi with 35s or 37s.

reloaderguy · Aug 23, 2018

U&A said:
http://www.csgnetwork.com/multirpmcalc.html

Have you tried this one. Seems to be very accurate. Use the very bottom calculator....
Input ring gear ratio
Tire hight
MPH
Final trans drive ratio

The picture shows final drive ratios.

Sent from my iPhone using Tapatalk

This is a far better calculator.

http://www.grimmjeeper.com/gears.html

U&A · Aug 23, 2018

reloaderguy said:
This is a far better calculator.

http://www.grimmjeeper.com/gears.html

Thanks for the link

The Calculator you linked definitely is a good one. The one I linked and the one you linked come up with identical numbers, I checked.

If you’re looking for more complex calculator that includes under drives and transfer cases than yours is the one to use.

If you’re just looking for simple one for a 4 x 4 or 2 x 4 truck to find RPMs with a given speed the one i linked is simpler.

JMO

Sent from my iPhone using Tapatalk

reloaderguy · Aug 23, 2018

U&A said:
Thanks for the link

The Calculator you linked definitely is a good one. The one I linked and the one you linked come up with identical numbers, I checked.

If you’re looking for more complex calculator that includes under drives and transfer cases than yours is the one to use.

If you’re just looking for simple one for a 4 x 4 or 2 x 4 truck to find RPMs with a given speed the one i linked is simpler.

JMO

Sent from my iPhone using Tapatalk

The math is technically the same but I linked to a page that will auto populate transmission ratios and give you comparative tables for multiple final drive ratios in every gear for user specified speeds.

U&A · Aug 23, 2018

Ok

Sent from my iPhone using Tapatalk

6.4 Hemi Gear Swap

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