Question: I purchased my first Jeep Wrangler about three months ago-a '00 TJ with six-cylinder and auto trans. I've been searching Web forums and looking through back issues for ideas to modify my Jeep. The more I read, the more disappointed I become about the Dana 30 and 35 axles. This will be a daily driver and will see hardtop about 95 percent of the time, but I also want capable off-pavement performance, no matter what the ride, gas mileage, and so on. The Jeep had 33x12.50s and a Superlift kit when I bought it. I'm not sure how much lift I have, though. I have about 6 inches from the bottom of the fender flare to the top of the tires. I plan on staying with the 33s and going with 4.10:1 gears (running 3.07:1s right now), maybe going to 35s plus a body lift sometime in the future.
What would you recommend for the D30 and D35-a Superior upgrade, or swap 'em out? I'm trying to decide between the Superior upgrade or a Ford 8.8 in place of the Dana 35. I honestly have no ideas for the front.
Mickey Sturgill
via fourwheeler.com
Answer: Yep, you're right about the stock Dana 30/35 axle combination really not being the way to go with 33-inch-tall tires. It's hard to believe that you can even drive it on the highway, let alone on trails with the 3.07:1 gearing. The 4.10:1 gearset would be just about right in the fact that you don't have an overdrive in your transmission and you see a lot of highway driving.
The Dana 30 has proven itself a pretty strong unit. The weak link is the axle U-joints. I definitely would, however, upgrade the axleshafts and U-joints to some stronger aftermarket units, and even consider going with some locking hubs. While the 30 is still not as strong as a 44, it will be a whole lot stronger and most likely capable.
For the rear, it's kind of a toss-up as to going with the Superior axle kit or the Ford 8.8 swap. The latter will be a lot more work, but will gain you a stronger ring-and-pinion combination as well as some stronger axletubes. You will lose some ground clearance under the differential, but not enough to worry about. Keeping the Dana 35 will be a lot less work, but the axletubes are not as strong, and you will still have the rather smallish ring and pinion. My choice would be the 8.8 conversion.
If you're positive you're going to put on some 35s in the future, maybe it's time to go for the 44s front and rear; 4.56:1 gearing may be a better choice for the taller tires if you plan on some serious four wheeling, but your highway speed will require a lot more engine rpm.
Question: I'm about to buy an '89 Ford F-150 4x4 with the I-6 and five-speed transmission, but I don't know about the transfer case. The truck has got a 3-inch body lift and 33-inch Buckshots. The owner says it has 4.11:1 gears and I'd like to know what size of tire best suits the 4.11:1 for highway use and still have some power to turn off-pavement?
I also want to know about some performance modifications for it. I've got some 37-inch Wrangler MTs. Will they fit the 4.11:1 gears better than the 33s? What are the best upgrades for fuel mileage?
Larry Lee
via fourwheeler.com
Answer: The 4.11 gears and 33-inch tire combination are just about the right compromise of good fuel mileage and overall performance, especially with your five-speed transmission. When you put on those 37s, your truck is going to lose both fuel mileage and performance. Swapping gears into the 4.56:1 to 4.89:1 range will surely help the performance, but my guess is that fuel mileage is still going to-well, to put it bluntly-suck. While the 37-inch tires may fit with just the body lift, with any twisting of the suspension there is going to be some body contact. You're going to need about another 3 inches of suspension lift to make sure everything clears like it should.
One of the problems with lifted trucks is they sit high up off the ground, letting lots of air travel under the truck instead of over and around the body. The body is smooth and slippery, while the underside has all sorts of things that disturb the airflow-like axlehousings, shock mounts, driveshafts, transmission, and transfer case. Plus, the taller tires are also wider and heavier, so it takes more power (and fuel) to move them.
Your six-cylinder engine will respond to modifications just like a V-8 will. Bolt-ons such as headers and a good free-flowing exhaust system will help somewhat.