This is a tough question as there are many variables that go into this. The best place to look is your specific drivetrain.
In general, changing out the entire drivetrain on a JK Wrangler with 3.8s will cost around $700-1200 at most shops, but if you’re looking for something to last and want to stay with the original manufacturer (which can be hard) it will cost up to $2000 depending on shop rates.
The cost of regearing depends on what type of gearing you have, whether or not you want an aftermarket install kit and if the gear ratio change requires changes in axles and/or ring & pinion gears.
What is Regearing a Jeep?
In simple terms, regearing is short for changing the gear ratio of your vehicle.
the only general rules are that if you move the ring and pinion closer together (smaller number), you get the same effect as moving the output shaft and wheel farther apart (larger number.)
In other words, a higher number in the ring and pinion or shorter gears will give you higher top speed. A smaller number in the ring and pinion or longer gears will give you more low-end torque.
What is Regearing used for?
Changing your gear ratio can improve acceleration, reduce engine revs at a given speed, decrease engine wear when going up hills or off-roading, increase top speed, etc. Since gears change the balance of torque and speed, any one of these can be achieved by changing the gears.
A very common misconception is that gearing effects your top speed. Theoretically, gearing only affect acceleration and how much power your wheels produce.
These have no direct effect on your speed whatsoever (top speed will always depend on engine power.) For example, a 5.9L Cummins engine with a 4spd manual transmission has a theoretical top speed of 65mph in first gear (theoretically, you could go faster due to wind resistance but there’s no way to prove this as it would require you to drive around in an enclosed space and measure wind resistance.)
When should you re-gear your Jk?
You should think about gearing changes whenever you want to:
1) increase your acceleration from a stop while reducing engine RPM or gas guzzling at cruising speed (when you’re just going to work)
2) move up from a smaller tire size with less traction in off road situations (Jeep Wranglers are notorious for spinning the rear tires, which is why you’ll hear that “Jeepers Creepers” is a phrase used often when people say they have problems with their JK)
3) improve gas mileage at cruising speed
4) improve acceleration when driving around town or in a more urban setting
5) go faster in “leisure” situations
6) improve off-road performance
7) Improve wheel stability
How long does it take to Regear a Jeep?
This depends on if you’re doing a full install or just getting an axle and new ring & pinion. In general, you can expect a full install to take 3-5 days. However, most shops will try to get the vehicle out in 1-2 days (some try even harder but this usually isn’t realistic.) This is usually based on how busy they are and how difficult the install is.
Factors that determine the regearing price?
1) what class of gear ratio (1.5, 2.5, 3.0, 4.0 etc.) you want – this depends on what your budget is and how much power you’re looking for
2) your specific drivetrain (i always recommend the best ratio for your application)
3) if you have to change out axles and/or ring and pinion gears to fit the new ratios
4) the shop’s experience (more experienced shops will charge more, but there are many times they’re just charging more because they can track their costs better or they have higher overhead costs. Also keep in mind that some shops with high overhead will charge lower then a shop with low overhead.
Can I Regear my Jeep myself?
The short answer: Sure, you can but it requires specialized tools that most people don’t have right at home. It also requires a lot of knowledge (and for some, it takes a lot of courage, which is almost scarier.) On top of that, there are many different steps that one has to take in order to complete the job. If you’re familiar with the process because you’ve done it before, then yes you can do it yourself. However, I recommend that you get someone experienced to help you through the process. that way you can cut down some of the costs and ensure that you are not ruining your jeep.
Do I need to Regear 35s JK?
This is a very tricky question. In principle, you don’t need to regear your Jeep if you install 35s with no lift, no bumpers and no other modifications as 35 tires have the same circumference as 32 tires. However, because 35s have a much stiffer sidewall than 32s they will wear your tires out faster and sometimes cause alignment issues.