I am swapping gears and after several months of research and opinions from everyone, including my janitor at work, I settled on 4.56 as the best option for me as I may go to 37's someday, not soon. This is a running commentary on the thoughts of this swap and why I did it and the actual real world driving of my Jeep.

Why am I re-gearing?

Well, here it is; the Jeep ran fine with BFG AT35's and didn't need a re-gear, but I decided to go a little more aggressive and installed Nitto Trail Grapplers in 35's. Great tire by the way, but huge heavy.

Now my in town driving around is fair and in 1-3rd gears, auto, it runs great, but I have to drive with the cruise as I have a very heavy foot and if I don't set the cruise I will be doing 60 in a 35.........

So, with the cruise set at 45 it now swings +- 5 mph as it comes to a small hill up or down.

When I go up hill, the cruise attempts to stay in the same gear and accelerate, but that won't happen as there is too much weight on my rig.

Then as it hits 39 it downshifts and accelerates to 50 to catch up right as the hill levels out.....

The other drivers around me think I am nuts or racing them and it is getting old.

On the highway at 75 my rpm's are low and the ECO light never comes on and it downshifts all the time trying to stay at speed, RPM's are trying to stay about 2700 in 4th then will drop to 2000 in 5th and back up to 2700 in 4th.

Gas mileage doesn't exist... Really bad, remember, I am heavy and so are the tires.

All of the charts say go with 4.10 as the optimum gears for my style, but when I ask my mechanic he said 4.56 as I wouldn't like the settings of the 4.10 especially if I ever went to 37's.

So I called David at Northridge and asked him what he recommended and it was the 4.56's.

I worry about the RPM's at 80 as that is my speed on the Interstate, but I don't do much of that at all. Mostly under 50 everywhere as I avoid the Interstate driving as it is boring. Plus, I don't think the 3000 rpm others have said they get is that bad for this engine. It likes RPM's as it really kicks in at 4000 all the way to 6500.

So David hooked me up with R&P's in 4.56, master install kits, new carrier loaded for the Dana 30, and a Truetrac for the 44.

They should be here today and tomorrow, hopefully.

My installer will do the swap for $650 and I supply the fluids and he will take 3 days to complete as he does the first 3 heat/cool cycles that he likes to see to break in the gears.

That is what I have for you for now and I will let you know what I think as we get the gears in and after the break in period.

More to come........

 

I was going to say...4.56 with 35s and 80mph are not a great mix.

Just don't keep it there long.

The fact that you are going to 37s eventually make 4.56 the best choice.

I still went 4.10s for mine. I drop it off tomorrow to go under the knife. Oh yeah....I also got a rear OX with electronic actuation!!! Woot!

 

This is good as we can compare actual numbers and driving experiences.

It amazes me that when you ask a question you get several different numbers for the exact same Jeep.

We shouldn't inflate our posts to justify our decisions as it will affect others that do the same thing.

There are several posts about this and the numbers and driving experience is all over the place.

I drove around in 4th on the interstate at 80 and was at about 3000 rpm's and it wasn't that bad. The red-line is 6500.....

We shall see as I will be on 35's for a couple of years.

Still have that nagging feeling I should have gone to 4.10's, but we shall see.

The 4.10 was my choice and was talked out of it.

 

I have Toyo M/T 35x12.50 and went with 4.88 gears! Love it! It seems to work perfect with the tires. I also have a lot of additional weight with bumpers, winch, and additional add ons. But if you are ever towing the 4.88 are amazing. I had the same problem with cruise control on stock gearing... No longer an issue.

 

I also have a 2012 JKU 3.73 gears, auto with 35" Toyo MT 35x12.50 and I am torn between 4.56 and 4.88.. but this info helps!

 

I agree I also have the 3.6 and when I have the ash I am putting in the 4.56 gears I am running 35s and someday going to 37s

 

3000 RPMs is a lot to cruise at. Doesn't matter what redline is. I think you will find if you drive at 75-80 with those gears and 35s your fuel economy will be 12-13.

Interested what the guy above who posted about his 4.88s has auto or stick and what his RPMs are at 70. Not ish.....but really measured at 70.

 

I have driven a couple of cars that cruise at 3000-3200 at 75 on the interstate and although I understand what you say about the extra RPM, I don't know if that will be a big problem for me as I usually avoid the interstate as I like the back roads better.

I am ready to jump to 37's if that is necessary, I'll still do it in a year or two, but I want to see what the real numbers come out too and what kind of performance I get.

No, I don't want a race car or dragster, just better than what I have now.

You are right about the gas mileage and usually I don't care about that but, as the price goes up.......

Hopefully both of us will get something out of this thread.

Oh, BTW I received the parts and will bring them over to the installer today so we can get ready for the change.

Funny though, the Truetrac says it is for a Dana 20... Looked the part number up and it is for the Dana 44 and Northridge says it fits, I checked with them.

We will see.......

 

Okay, what is your RPM at cruise, 75-80?

It seems it would go through the gears really quick.

And yes, I know that the change from 4.56 to 4.88 is only about 7%............ 210 RPM at 3000-3210.

 

I rev at 2200 at 80 mph in 6th. I have to say auto trans and mods is a tricky situation to get perfect.