I can squawk the 35s from a dead stop without the brake torque and squeal them with it. 4.10s might be ok but not 4.56s, the last thing I want to do is shorten it up and burn the tires (and fuel) even more.
I can squawk the 35s from a dead stop without the brake torque and squeal them with it. 4.10s might be ok but not 4.56s, the last thing I want to do is shorten it up and burn the tires (and fuel) even more.
I'm new to this site but not new to the off road world. I ordered my 392 last month and can’t wait to do a monster build on it. I've seen quite a few nice rigs on this site and really like some of the ideas people have. I like to look around at you all's rigs to get ideas of do's and don'ts for when my time comes but occasionally someone says something that just makes me feel I need to help out.
@JC, my reply is by no means meant to dog you but maybe open your eyes and help others in their Jeep builds. It’s great that you can "squawk" your tires from a dead stop, XR or non-XR, these are some pretty bad ass Jeeps but there is way more factors involved in having a dialed in Jeep. The correct gearing for your vehicle is super important for the performance and engine/tranny life. These drive trains, especially new vehicles, are so engineered and tuned in for fuel economy, emissions and power. The engine is engineered and tuned to run its best during what’s called a "standard day" condition, meaning that the engine preforms better at set veritable’s during standard day conditions and those are sea level, barometric pressure @ 29.92 and temperature @52F.
Now, match that engineering (the 392 was engineered by the old Viper crew) with the rest of the drive train and configure the vehicle (gears and tire size) to operate at its optimum range, usually @ 65mph or 70mph and the correct engine RPM’s. This will ensure the engine is operating at its correct operating temperature, power range, fuel delivery and emissions output and the easiest way is through the gear set. There are several graphs out there that show what your gearing should be using your tire size and RPM range. The graph will show you what gearing is best for you, if you want better mileage, more power or a balance of power and fuel economy. The best gearing choice is one that’s close to your stock configuration. Having an engine powerful enough to light up 37” tires while running 3.73 gears is awesome but is NOT optimal and putting massive stress on the power train which will catch up with you sooner or later. Now 3.73 gears with 33” tires would put your RPM’s around 2207 to 2470, that gearing is more for fuel economy/balanced power but not near high power range setting and is great for the engine and tranny. But go even further with the same gears running a 37” tire and you’re looking for trouble.
So someone ordering a 392 with the XR package (4.56 gears) and going to run a 37” tire is right one the money. Personally, I feel its well worth the extra $4k just for the gear set alone. Swapping gears usually runs the average person $2k per axle anyway and they don’t have the added cost of buying a different Carrier to go from 3.73’s to 4.56 ring and pinions. But if someone is NOT going to run a tire larger then 33”, the non-XR is the way to go.
Sorry for the long reply but your Jeep is going to treat you the way you set it up.
