Gears inquiry

[Nickx86]

So i am going to bite the bullet on some new gears for the truck. I have a 6.4 hemi 4wd 3.73 and I’m upgrading to 4:56 since I hate the constant downshifting on rolling hills here in NJ. My question is anyone in the area of NJ, NY, PA area know of any good reputable places to do gear swaps.

 

[U&A]

I know this is not the response you are looking for but can i ask,

What size tire do you plan to run?

Stock hight of 33” ?


Sent while firmly grasping my redline lubed RAM [emoji231]

 

[U&A]

I recommend contacting a gear manufacturer of your choice and seeing who they have as installers in your area. If you do it this way you will get the warranty on the gears whatever it may be.




Sent while firmly grasping my redline lubed RAM [emoji231]

 

[Nickx86]

I know this is not the response you are looking for but can i ask,

What size tire do you plan to run?

Stock hight of 33” ?


Sent while firmly grasping my redline lubed RAM [emoji231]

currently have 285/60r20 which is about 33ish new. Might go up to 285/65r20 which would be 34, nothing bigger since I don’t want the extra rolling resistance

 

[U&A]

With 4.56’s going from 33’s to 34’s you ar going to loose roughly 100rpm.

From experience.

Decide on the TALLEST tires you plan on EVER running and base your gear choice off of that.

Im sure you have been badgered it to death with opinions on this but if you’re considering 34s I would definitely consider 4.88 gears


Sent while firmly grasping my redline lubed RAM [emoji231]

 

[G. Mcpherson]

Chester County Transmissions. Coatesville PA

 

[Nickx86]

With 4.56’s going from 33’s to 34’s you ar going to loose roughly 100rpm.

From experience.

Decide on the TALLEST tires you plan on EVER running and base your gear choice off of that.

Im sure you have been badgered it to death with opinions on this but if you’re considering 34s I would definitely consider 4.88 gears


Sent while firmly grasping my redline lubed RAM [emoji231]

I actually didn’t think about going down the route of 4.88 gears to be honest.

When I regeared my Jeep and my old ford I went up two gear sizes, each one of them had the same issue as this truck up hill. They both got the one inch bigger tires.

I’d have to do a bit more research on the 4.56 vs 4.88 debate. What size tires are you running on your rig?

 

[U&A]

I actually didn’t think about going down the route of 4.88 gears to be honest.

When I regeared my Jeep and my old ford I went up two gear sizes, each one of them had the same issue as this truck up hill. They both got the one inch bigger tires.

I’d have to do a bit more research on the 4.56 vs 4.88 debate. What size tires are you running on your rig?

Use a calculator, no guessing required.

Select the 68 RFE in the drop-down menu for your transmission. It’s the same exact gear ratios as our 66 RFE

Then all you have to do is put in your desired gear ratio and tire size and then you can mess with the calculations at the bottom and see your exact speed and rpm.
Add about 50-75 rpm for wind resistance

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

I have 4.88’s and I’m running 35s. I kinda wish I went to 5.13’s.

IMO

33”tires need 4.56
34”tires need 4.88
35” or large need 5.13

Again... JMO


My next set of tires I’m going to go a tiny bit shorter but a little wider. I’d like to get a tad more RPM.

Sent while firmly grasping my redline lubed RAM [emoji231]

 

[Ratket]

Use a calculator, no guessing required.

Select the 68 RFE in the drop-down menu for your transmission. It’s the same exact gear ratios as our 66 RFE

Then all you have to do is put in your desired gear ratio and tire size and then you can mess with the calculations at the bottom and see your exact speed and rpm.
Add about 50-75 rpm for wind resistance

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

I have 4.88’s and I’m running 35s. I kinda wish I went to 5.13’s.

IMO

33”tires need 4.56
34”tires need 4.88
35” or large need 5.13

Again... JMO


My next set of tires I’m going to go a tiny bit shorter but a little wider. I’d like to get a tad more RPM.

Sent while firmly grasping my redline lubed RAM [emoji231]

Even if you stay at a 33” tire.. 4:56 wont make you happy, I whole heartedly agree with the above post. Minimum should be 4.88 or 5.13.

check a gear calculator and drive ur truck around at those RPM”s and make sure it’s “ Good for you”

“ They said gears would make this truck drive better, the shop recommended to go from 373 to 456... but I feel it could even go a little more” <—- you don’t want to utter these words, check and triple check to make sure you are getting what you want.

 

[U&A]

Don’t let the gear ratio number scare you. Back in the day transmission gearing was different than what these trucks have. A lot of shops might hear you say the words 488 or 513s and think you’re insane but they did not understand what the final drive gear ratios that are in your transmission.

The 66RFE that is in the gasser HD trucks has the SAME EXACT gear ratios in the trans at the 68RFE that comes with the cummins.

FCA ****** up big time on that one.

Back 20-30 years ago final drive rations were close to 1:1.

Our 4th gear is 1:1. Times have change. Thank you EPA.



Sent while firmly grasping my redline lubed RAM [emoji231]

 

[FlatbedHemi]

4.88s for sure. I was hesitant as well, but dont regret a thing. Love the way it holds gear, loaded, unloaded, or towing.

 

[Nickx86]

4.88s for sure. I was hesitant as well, but dont regret a thing. Love the way it holds gear, loaded, unloaded, or towing.

what kinds of speeds are you running and fuel economy are you noticing w the 4.88 vs stock, I remember you getting those gears done a while back. I’m not afraid of gears, this would be my third vehicle getting gears lol.

My first truck needed all the help it could get, it was a 04 f150 extended w the 4.6 V8, 4 speed auto and ****** 3.55 switched to 4.10 and it was happier. My second was 99 Cherokee, I6 w 5 speed, bigger tires slowed that thing down on highway hills 3.08 didn’t help so 3.73 and it was a blast to drive after that

 

[FlatbedHemi]

what kinds of speeds are you running and fuel economy are you noticing w the 4.88 vs stock, I remember you getting those gears done a while back. I’m not afraid of gears, this would be my third vehicle getting gears lol.

My first truck needed all the help it could get, it was a 04 f150 extended w the 4.6 V8, 4 speed auto and ****** 3.55 switched to 4.10 and it was happier. My second was 99 Cherokee, I6 w 5 speed, bigger tires slowed that thing down on highway hills 3.08 didn’t help so 3.73 and it was a blast to drive after that

I was told that y fuel economy might go up with the gear swap, but Im thinking that the people that told me that do more in-town driving than highway. I drive 25 miles to work at 75 on a rolling farm to market road. Running on that road I get about 12.5 according to the dash. I got anywhere from 14-16 on that same road before the swap, but that was on summer blend gasoline. My job changed in June, which changed my commute, so I dont know if my mileage is due to the road, the fuel, or the gears. All of those variables changed within a few months of one another.

I did get it out on the interstate, and running 80 to keep up with traffic I got about 15mpg. Not sure what factor increased the mileage at that speed, but it did. Thats all on 34" tires.

 

[Mountaineer83]

I know my truck drops 1-2 mpg seems like when they switch to the winter blend gasoline. I hope that may be your case as well.

That happened to me when I got my new tires. I thought the tires were causing the drop but come to find out, it went back up when the summer blend came back.

 

[FlatbedHemi]

I know my truck drops 1-2 mpg seems like when they switch to the winter blend gasoline. I hope that may be your case as well.

That happened to me when I got my new tires. I thought the tires were causing the drop but come to find out, it went back up when the summer blend came back.

Well, I changed my commute in June, went from 13 to 15. Then I ditched the flatbed in July, went up to 16. I regeared in August and didnt get out of the breakin period good and had a trailer hooked up at least once every tank and they started changing fuel about October I think.

who the hell knows what my fuel mileage will be in 6 months.

 

[Thorbeast]

33”tires need 4.56
34”tires need 4.88
35” or large need 5.13

Damn, well that is way more extreme than I've read. It was suggested to me that I do 4:56 or maybe 4:88 with 37s.

With your suggestions there, how would that impact fuel economy on the highway around 70-75mph? Using 4.88s or 5.13s?

 

[68PowerWagon]

Do gears mess with your speedometer? Shop doing my gears said it might be affected. I thought only changes in tire size would mess with the speedo

 

[FlatbedHemi]

Do gears mess with your speedometer? Shop doing my gears said it might be affected. I thought only changes in tire size would mess with the speedo

No. Speed sensors are in the wheels, not the transmission so you are correct that only the tire size changes will change your speedometer. However, I did use my AlpahOBD tuner to change my gear ratio when I had my swap done just in case it affected any of the shift characteristics. A lot of guys don’t though, and dont seem to have any issues.

 

[FlatbedHemi]

Damn, well that is way more extreme than I've read. It was suggested to me that I do 4:56 or maybe 4:88 with 37s.

With your suggestions there, how would that impact fuel economy on the highway around 70-75mph? Using 4.88s or 5.13s?

I cant vouch for 5.13 or 37s, but on 4.88s and 34s I get anywhere from 12.5 on my daily commute to 15+ on the interstate doing 75-80. Towing 8k lbs it only dropped to 8.5, which is way better than the factory 3.73s did towing.

 

[sandawilliams]

I tow 8800# with another 1500 in the bed. 3.73's average mpg is 9.3 hand calculated. I've been pondering 4.56 as I only tow at 65 mph. I know it will tow easier but I don't really have problems now. Any thoughts? What kind of money am I looking at for both axles with rear lsd?