Change gear ratio on rear axle

[tnctx02]

Installed a BDS 4" lift with 35" BFG tires. Factory rear gear is 3.21. Been trying to decide if changing the rear gears to maybe 3.92 would be the way to go now. I have the 3.6L V6 in the truck.
Appreciate any and all help with this.

 

[Jbp19classic]

Is it 2wd or 4wd?

 

[tnctx02]

4 wheel drive. This is also my first truck without a live axle in the front.

 

[WY-Dave]

With vehicles now-days that are so computer controlled you will affect many systems, ABS, trans control for a start.


Here is a re-gear calculator. http://www.4lo.com/calc/geartire.php This will put the RPMs close to back to were they were. It will come up with a number that probably does not exist. But use one that is close and the above mentioned systems should be close enough to no need reprogramming.

BUT with bigger tires there is more weight. So "performance" will be slightly affected. This why some people will go up(numerically) a step or two. With my Jeep that had 3.73s I skipped 4.10 and went with 4.56.

Then the flipside, now you have more weight to stop, braking can/will suffer. If a drastic change, bigger brakes are in order.

When modifying now days, it's a domino effect. I want bigger tires, so gotta get a lift and regear. For the Jeep that one "lil" thing cost me $8000 to do it right.

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[Jbp19classic]

I don’t have any first hand experience with this, but I’ve heard others quoted upwards of $2000 to have a shop swap gears because the front diff isn’t an easy gear swap like the rear. If you’re going to do it, have you considered going to aftermarket gears even lower than 3.92? Something like a 4.10 or 4.56? Just out of curiosity what has your experience been so far with the 35’s/V6/3.21 combo? I have the same set up but with 34’s and have no real complaints.

 

[CincyCuda68]

I don’t have any first hand experience with this, but I’ve heard others quoted upwards of $2000 to have a shop swap gears because the front diff isn’t an easy gear swap like the rear. If you’re going to do it, have you considered going to aftermarket gears even lower than 3.92? Something like a 4.10 or 4.56? Just out of curiosity what has your experience been so far with the 35’s/V6/3.21 combo? I have the same set up but with 34’s and have no real complaints.

More in the 3k to 3.5k range, it’s not an inexpensive upgrade.

 

[tnctx02]

I don’t have any first hand experience with this, but I’ve heard others quoted upwards of $2000 to have a shop swap gears because the front diff isn’t an easy gear swap like the rear. If you’re going to do it, have you considered going to aftermarket gears even lower than 3.92? Something like a 4.10 or 4.56? Just out of curiosity what has your experience been so far with the 35’s/V6/3.21 combo? I have the same set up but with 34’s and have no real complaints.

It doesn't have the same get up and go is the main problem.
I expected the mpg to drop and it did from 24mpg to about 17.5mpg average now.
I do love the way the stance and how it rides, so no going back. Looking for ways to improve it a little more and changing the gear ratio seemed like a good place to look to start.

 

[ram1500rsm]

You’ll have to change front and rear gears. I haven't spent much research time on the topic since the change is way more expensive than I thought and more involved as well cause for the back I’ll need parts from a 2011 truck. I think the front is prob the same thing.

Knowing a thing about regearing from my previous Jeep Wrangler unlimited I bought the truck with 3.92’s already. I went from 3.21 to 4.56’s in the Jeep for $1k otd and I thought it was going to be as cheap with the RAM

I’m running 37’s with the 3.92’s and the 6 speed trans. Little more sluggish acceleration wise but fine otherwise. I’m running very light 37’s at 69lbs each and I have no regrets. My truck is about 600 or so lbs heavier than stock as well and I’m not into drag racing lol, so she manages the weight just fine. I did a calculation with the tire size and effective gearing and she’s behaving pretty much like a truck on stock tires with 3.55’s and 6 speed not optimal but I won’t spend the money to regear in my case. Best mpg fwy so far is 18Mpg with the 37’s and the extra weight, fwy only at 68-70mph. Tires calibrated with GPS and I have my own tune with HPTuners.

Untitled by RAM RSM, on Flickr

If you have the 8 speed trans, you have better gearing with 3.21's than my truck with 3.92's so you should move 35's just fine. Just make sure you keep your tires weight as light as possible. it'll take more effort to move Nitto MT tires in 35x12.5x17 at 80lbs each than Cooper STT Pro 315/70/17 at 67lbs. Visually they'll appear very similar in height.

 

[tnctx02]

You’ll have to change front and rear gears. I haven't spent much research time on the topic since the change is way more expensive than I thought and more involved as well cause for the back I’ll need parts from a 2011 truck. I think the front is prob the same thing.

Knowing a thing about regearing from my previous Jeep Wrangler unlimited I bought the truck with 3.92’s already. I went from 3.21 to 4.56’s in the Jeep for $1k otd and I thought it was going to be as cheap with the RAM

I’m running 37’s with the 3.92’s and the 6 speed trans. Little more sluggish acceleration wise but fine otherwise. I’m running very light 37’s at 69lbs each and I have no regrets. My truck is about 600 or so lbs heavier than stock as well and I’m not into drag racing lol, so she manages the weight just fine. I did a calculation with the tire size and effective gearing and she’s behaving pretty much like a truck on stock tires with 3.55’s and 6 speed not optimal but I won’t spend the money to regear in my case. Best mpg fwy so far is 18Mpg with the 37’s and the extra weight, fwy only at 68-70mph. Tires calibrated with GPS and I have my own tune with HPTuners.

Untitled by RAM RSM, on Flickr

If you have the 8 speed trans, you have better gearing with 3.21's than my truck with 3.92's so you should move 35's just fine. Just make sure you keep your tires weight as light as possible. it'll take more effort to move Nitto MT tires in 35x12.5x17 at 80lbs each than Cooper STT Pro 315/70/17 at 67lbs. Visually they'll appear very similar in height.

I have the 8 speed trans and am running around 45ish in the 35x12.5R17 BFGs. Main issue I would say is it feels kinda sluggish now compared to the stock tires. Trans hardly stays in 8th gear when going down the highway at 70 mph.