4.56 or 4.88 gears for towing with 6.4 Hemi?

[RoadRamblerNJ]

(Axle Ratio x Vehicle Speed x Transmission Ratio x 336.13) / Tire Diameter in inches = RPM

(5.13 x 75 mph x .625 x 336.13) / 34 inch tire = 2,377 rpm

That IS the sweet spot.
Me, I prefer running about 2800 - 3000 RPM's but I'm a little nuts.
Point is, dif btwn 4.56 & 4.88 ia probably to small to feel. Same with 4.88 to 5.13.
But, 4.56 to 5.13 you will def. know you changed something.
3.73 to 5.13 and you'll think your engine grew a few more cylinders.
I hung in & worked in speed shops for years & never ever heard anybody complain about going to too short a gear.
Now, go buy them 5.13's and start grinin'!

 

[RoadRamblerNJ]

I’m thinking about a aftermarket muffler and to hide the noise.

With the radio off it would drive you nuts.

You could always just make believe that whine was coming from a blower! THAT'LL make you grin too.
Both will make you quicker out of the hole.

 

[GsRAM]

Agree 100% on keeping the RPM's up!

You should maybe talk to a counselor about all that cursing you're doing. LOL.
Sorry, I had to.

LOL!

 

[bootucker10]

Ideally in the future I would like to get a 3500 SRW Cummins, but that won’t be for about 4 more years so I am looking for the best options to hold me over until that time.

 

[bootucker10]

I have the new Cummins that came out in 2019 and it pulls 32,000 with a 3.73 gear ratio .. get's about 16 mpg .

 

[MetalGrand]

I ended up going with 4.56’s. The owner of the shop did not recommend 4.88’s for my truck. He would install them if I wanted but he would only warranty 4.56’s or lower, so I went with 4.56

 

[Bldrinker]

I ended up going with 4.56’s. The owner of the shop did not recommend 4.88’s for my truck. He would install them if I wanted but he would only warranty 4.56’s or lower, so I went with 4.56

What was his reasoning?

 

[Tunaman]

How is 5.13’s going to affect my daily driving?

They'll think you are very wealthy..

 

[sandawilliams]

I have the new Cummins that came out in 2019 and it pulls 32,000 with a 3.73 gear ratio .. get's about 16 mpg .

16 towing?

 

[David F]

16 towing?

I have the same truck, 2500 with Cummins, get 13 MPG when towing.... flat. about 10.5 in mountains. 10,000 lb 5th wheel.

 

[Lucy Girl]

Your truck still has stock trans programming so it will just get to 6th faster. Its not like you will run higher rpm in each gear it just goes through them faster.

You will be a bit over 2000RPM at 70. Probably around 2200-2300. That is perfect for cruising. My MPG went UP when i went to 4.88. Less effort for the truck to get 7,000 moving. Les effort = less fuel. Just dont drive like a race car.

5.13 will just five you way more torque at the wheel.

Good luck on your endeavors sir. [emoji41][emoji1303]


Sent while firmly grasping my redline lubed RAM [emoji231]

Love torque. Best thing ever.

 

[sandawilliams]

I have the same truck, 2500 with Cummins, get 13 MPG when towing.... flat. about 10.5 in mountains. 10,000 lb 5th wheel.

Evic or real mileage?

 

[68PowerWagon]

I ended up going with 4.56’s. The owner of the shop did not recommend 4.88’s for my truck. He would install them if I wanted but he would only warranty 4.56’s or lower, so I went with 4.56

All those shop owners freak out cause they think the ratio is too low but they don't realize how weird out trannies are geared. I went with 4.56 with stock tires & am completely satisfied. I pull a 13k pound 5th wheel a couple times a month & it made a huge difference. Actually made a big difference just driving around town. If I had larger tires I would definitely go with the 4.88's or 5.13's. I am turning about 2k @ 65mph & only lost about a 1/2mpg. I think you need to do a little more homework on this site to figure out what you really need or you are going to be unhappy. With those size tires & 4.56's, you are going to basically be back to the way it was with stock tires & 3.73's.

 

[dhay13]

My daughter bought a brand new 2016 Wrangler Unlimited and had a 4" lift and 35's installed. I told her to go with 4.56's but the shop talked her into 4.88's. She wishes she had listened to me. She had to buy a car to commute to work cause the Jeep cranked too many RPMs. She said she would probably go with 37's next time to offset the higher ratio

 

[62Blazer]

My daughter bought a brand new 2016 Wrangler Unlimited and had a 4" lift and 35's installed. I told her to go with 4.56's but the shop talked her into 4.88's. She wishes she had listened to me. She had to buy a car to commute to work cause the Jeep cranked too many RPMs. She said she would probably go with 37's next time to offset the higher ratio

Interesting comment. There is around an 180 rpm difference between 4.56 and 4.88 gears at 70 mph, which is a pretty small difference. In any case paying to replace the 4.88 gears with 4.56 gears would have been cheaper than buying a car. Not saying anything is wrong with having a commuter car as I do the same thing versus driving my PW on 35's everyday, but it's hard for me to think that the small difference between 4.56 and 4.88 gears caused the vehicle to not be acceptable as a commuter.....and not the simple fact that it's a lifted Jeep on 35's.

 

[dhay13]

Interesting comment. There is around an 180 rpm difference between 4.56 and 4.88 gears at 70 mph, which is a pretty small difference. In any case paying to replace the 4.88 gears with 4.56 gears would have been cheaper than buying a car. Not saying anything is wrong with having a commuter car as I do the same thing versus driving my PW on 35's everyday, but it's hard for me to think that the small difference between 4.56 and 4.88 gears caused the vehicle to not be acceptable as a commuter.....and not the simple fact that it's a lifted Jeep on 35's.

The 4.56's may have been too much too. Her office moved to further away and the Jeep just wasn't feasible to drive that far. She gets about 8 MPG IIRC. It was costing her a few hundred a week for gas. Probably wouldn't have been much better with the 4.56's but my point was she listened to the shop and regretted it

 

[RamminMopar]

Just had 4.56 gears installed on a 3rd gen with a 545rfe. Been taking it real easy on it so its hard to really tell but shifts are quicker,feels lighter and just kinda chugs along with less throttle.

 

[Bldrinker]

Just pulled my trailer for the first time with my 4:88’s.
Love it. 5th gear with tow haul off is good for about 65-70mph around 2500rpm with 34’s.

from Apple valley ca to mesquite nv got 7mpg. Had some large hills. Was getting almost 8 until I hit the hills.

trailer is a bumper pull toy hauler 37’ tip to tip. 32’ of box.
Just over 10,000 empty. I’m running a light load so I’m probably around 11,000-11,500

 

[U&A]

My daughter bought a brand new 2016 Wrangler Unlimited and had a 4" lift and 35's installed. I told her to go with 4.56's but the shop talked her into 4.88's. She wishes she had listened to me. She had to buy a car to commute to work cause the Jeep cranked too many RPMs. She said she would probably go with 37's next time to offset the higher ratio

What RPM at 70


Sent while firmly grasping my redline lubed RAM [emoji231]

 

[dhay13]

What RPM at 70


Sent while firmly grasping my redline lubed RAM [emoji231]

Not sure. I haven't driven it for awhile but what I remember it was over 3000 at about 55 but again, that was several years ago. I have never driven it on the highway but we do have a 4 lane near our house and I drove on that. She rarely drives it anymore. Sits in the garage about 90% of the time