One of my next modifications to my truck will be gears. From what Ive read 4.10 gears seem like a good way to go if you do a good bit of road driving with some off-road. I dont even know what my gears are now, Im guessing stock.

Here my info:
318 magnum
auto tranny
35'' tires
Mostly road driving with some offroad

I want to get lower gears to have more "get-up-and-go." My truck seems to lag on acceleration. But I want to be able to cruise as highway speeds without too high RPMs. I dont have a tachometer either

 

Do you want our opinions on a gear ratio for you? Play with this to find out anything you ever wanted to know. http://www.grimmjeeper.com/gears.html

As for my opinion, 4.10s would be great for that combo.

 

Id like opinions and thank you for yours.

The calculator looks great but I dont know anything to put in any of the fields

 

For both columns:
-select dodge 46re as your transmission.
-select any transfer case (just use nv241 if you want to be safe. thats for a 2nd gen ram, but it won't matter for these pusposes)
-Leave underdrive as "none"
-select two axle ratios you want to compare (one on each side)
-enter 35 inch as tire diameter
-press calculate on each side

If you scroll down to the 3rd and 4th chart, it shows your speed at a given rpm, and your rpm at a given speed. For comparisons sake, you can set one side to have stock size tires with stock gears, and set the other side to have 35 inch tires and see what you'd have to make the gear ratio to compensate for the change in tire size.

 

Pretty neat. I check i out. Will play around with more too.

Do you know what the stock gear ration is?

 

It could have been one of several ratios. Either find your build sheet, or go to your dealer for one, or jack up your truck, and spin a rear tire 360 degrees. Count the number of rotations of the drive shaft. That number, as a decimal, is your approximate gear ratio. For example, if it spins 3.5 times, you probably have 3.55s. 4.11s would show a little more than 4 rotations.

 

Ok thanks.

That brings up a question though. I may not understand this right but.. I thought the point of lowering your gear ratio was to have fewer turns from the engine to make the wheel go around therefore more torque/power upfront. But if you do this then the more turns of the axle, wouldnt that be the opposite?

 

No. Your engine makes it's power by moving through its range of RPM's as quickly as possible. The lower (higher numerically) the gears, the faster it can do this. So the trick is to find gears that give enough bottom end pull, but don't rev out too much at higher (constant) speeds. Larger tires require less rotation of the axles for a given speed, thus lowering the required rpms for that speed. Upgrading to deeper gears can put your power band back to stock, or alter it however you'd like.

With a 46re and 35" tires, go with 4.56's.

 

ok i understand now.

4.56s do you have those?

Whats your opinion on 4.88s? I hear those are pretty popular on jeeps with 35s

 

I have the stock 3.55's in my '95, and 4.10's in my '72. I will be upgrading to 4.88's in my '95 in the future, as it will be my work truck/tow rig on 35's. So I am willing to trade a bit of top end for a bit more low end torque.

Jeeps, with smaller motors, tend to need to rev a bit more to make their power than our v8's. 4.56's will be more comfortable at freeway speeds, but 4.88's will give a bit more edge off road, and torque at lower speeds. So it really comes down to what you want more. Either way, I am sure you will be happy with the upgrade.