Are 4.56 Gears Enough?

[Winston]

Still working the deal! I'm actually the one who spec'd it for the buyer, as we work together. Twenty years later, I've got the opportunity to buy it! But, it's currently in the shop.....can't get the CEL to not come on. The coolant temp sensor thinks the coolant is well below zero, even though it's been very warm this winter.....it was 50 degrees on the day I was looking at it, and we were indoors. When they hook it up to the computer, I can see the graph, and it starts out in the -25, -17, -40 degree range, depending on the day, even though it's nowhere near that cold. Once the coolant starts to warm up, you can see the reading "jump" in the graph to somewhere in the -11 to +17 degree range, which is when the CEL goes on. From there, it jumps again to around 100 degrees, and from there, it will no longer jump, rather it will steadily climb to operating temp. When you turn the vehicle off, it will read below zero again, even though it's already at operating temp. Since the vehicle is already warm, it takes 6 mintues (I tested it three times) for the temp gauge to jump from being bottomed out to halfway between the lowest position and the 210 marker (about quarter tank if it was a gas gauge), and then about 3 or 4 minutes to settle at operating temp. It's got the shop stumped....they've replaced the coolant temp sensor several times, tried different ECMs, etc.

Not my skill set at all, but I’ll offer the advice that has saved me hours, days, and weeks of troubleshooting. Check the simple things first. Check the wires, make sure their sheathing is all good. Check the things you can see.

 

[POTTERJLUR]

Looking to join the fold at some point in 2026, and if it were up to me, I would have ordered a Final Edition with the 4.88 gears. However, it is not an option on the Moab edition, and it's not that obvious without clicking on each individual vehicle to see if any of the leftover FEs were ordered with the 4.88 ratio. I plan on running 37s, leaving the T-Case alone, and when problems arise, Atlas. Keep in mind that I live at 7,400 feet. I'm thinking the 4.56 wouldn't be ideal, but good enough considering the cost of a gear change. There are those that tell me I'm crazy for wanting the 4.88s, but I'm not going to lie, I think the 4.88s should be an option, with 5.13s being the "should I" ratio. Any thoughts?

I don't think you could have ever ordered a 392 with 4.88's that I remember?

 

[Agar426]

I don't think you could have ever ordered a 392 with 4.88's that I remember?

I was able to build one on the site. Of course, I wasn't in a position to buy at the time, so I never pushed it further, so I suppose it could have been otherwise.

 

[Agar426]

Not my skill set at all, but I’ll offer the advice that has saved me hours, days, and weeks of troubleshooting. Check the simple things first. Check the wires, make sure their sheathing is all good. Check the things you can see.

They've checked it all. Disconnected every sensor, traced all the wiring, replaced the sensors, etc. Hoping it gets sorted out soon!

 

[Agar426]

I hope you are able to get it sorted and the purchase done. Wish I could help with the diagnosis, but not my skillset by a longshot.

Much appreciated! Yeah, the shop is kind of stumped, as is AEV. I'm hoping it's not a wiring harness type of thing, as AEV doesn't have any TJ components any longer. There are other companies that offer harnesses, but that doesn't mean it would be the solution. I'm hoping it's something simple they are somehow overlooking.....

 

[Agar426]

Apologies on the late responses.....I didn't get any notifications over the weekend. I was getting them last week......hmmmmm.

 

[Earl 392]

Like you said it has so much torque it doesn't care....I have a '21 non-xr, been running 37's for almost 5 years. If I switch to rear wheel drive, via tazer, it will lay a patch of rubber....

That’s with 3.73 gears?

 

[prodriquez]

That’s with 3.73 gears?

My wife’s 392 is still on 3:73’s. It’s a mall crawler, but I’d bet she’s around 6,000 lbs with all my takeoffs + her bumper and winch.

 

[Agar426]

Not my skill set at all, but I’ll offer the advice that has saved me hours, days, and weeks of troubleshooting. Check the simple things first. Check the wires, make sure their sheathing is all good. Check the things you can see.

Update: It was a short in the wiring going to the coolant temp sensor connector. Replaced it with the Mopar kit, and all is well now, and the owner is letting me drive it for a couple of weeks, as he wants me to be sure I want to buy it, and it's been running great!