Differential ?

Sorry, I posted this in the tech section first. Lesson learned!
Anyhow,
2014 RAM 2500 ST 4x4 HD 5.7 HEMI
Current set up:
Conv Diffr Front & Rear Axles
6,000# Front Axle
11.50 Rear Axle
3.73 Axle Ratio
6-Spd Auto 66RFE Trans
Elec SOTF Transfer Case
35"x12.50"x18" A/T Tires
I'm wanting to go up to 38"x13.50"x18" A/T Tires. Here's my questions/worries. Do I need to change the ring/pinion? I'd like to do 70mph @ 2,000rpm or under. I come up with a ratio of 3.77, but I'm currently at 3.73 and this runs ok with a small strain, and bigger tires are gonna only add to that. Also please know I'm gonna put a Detroit Locker, or something similar in at this time too. Don't know if that needs to be taken into consideration on final ratio selection?
If their are any steps, choices, suggestions, do's & don'ts, anyone has to offer please let me know. I'm stuck/confused and appreciate all!
Thanks,
OUFF1968



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If you decide to go with a lower gear ratio, be prepared to spend 2 grand, if not more.

Edit=after you put the 38s on, your gear ratio is way higher than 3.73

I have a 2500 with the 6.4 and a few members have gone to 4:56 and one recently went to 4:30"s. Since I have mds if I ever go 35"s or larger I would definitely go 4:56 or maybe even 4:88"s. In the end it's up to you but with out a doubt you would be happy with 4:56 gears.

go 4.56. that will put you close to the final drive ratio you had with the stock 33" tires.

Try this thread:

http://www.ramforum.com/f158/6_4_hemi_gear_swap-77499/

it may answer some of your questions. It's a lot to read through, but there is a link in there on page 4 to the right gear kit. You can start on page 3.

14RAM4X4 said:

Try this thread:

http://www.ramforum.com/f158/6_4_hemi_gear_swap-77499/

it may answer some of your questions. It's a lot to read through, but there is a link in there on page 4 to the right gear kit. You can start on page 3.

Click to expand...

Thanks, that helps and has me set on the 4:56, now I need to choose a locker or slip unit. Should be able to get it all done over a weekend, but It will probably be a month or so until I get room in my garage, but I'll yell out when I get it done.
Thanks again for all your help and time!


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ouff1968 said:

Thanks, that helps and has me set on the 4:56, now I need to choose a locker or slip unit. Should be able to get it all done over a weekend, but It will probably be a month or so until I get room in my garage, but I'll yell out when I get it done.
Thanks again for all your help and time!


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Click to expand...

unless you do a lot of off-roading, you'll probably get more out of a limited slip unit.

I have 37's and the 3.73's definitely do not cut it. Going 4.56's as soon as I can...should give me 2k rpm right at 75mph. Right now I don't hit 2k rpm until 90-92 mph.