Send your Gearhead questions to:
- Off-Road Adventures, Gearhead Dept.
- 610 West Walnut Street
- Compton, CA 90220
or email them to:
And There’s the Rub
Hi ya! I have a ’99 Dodge Durango with the 5.9L engine. My question is about tire rub. I have a 3-inch body lift and mount 33-inch tires. I also had a Superlift speedo calibrator installed. The right front tire rubs in the rear of the well on right turns only.
- Ion Phase
- Somewhere in Massachusetts
- Via e-mail
First, I’d take measurements to see if the Durango is level side to side and front to back on both sides. Most Durangos are a bit low up front. Yours could be a little more low on the right and that may be your problem. Many owners crank their torsion bars up to make their Durangos level. Use the front lower control arm pivot bolts as a reference point to measure from. If you are low on the right, crank the right one up until it matches the left. If low in front, you can adjust both torsion bars up a little. I get conflicting answers as to exactly how much is too much, but everybody agreed that up to an inch was safe. You might want to have the alignment checked afterwards. You can also adjust the steering stops to prevent tire rub up front.
Jeep Axle Info
Could you give me info about the axles under my vehicle. It’s an ’88 Jeep XJ Wagoneer Limited. The front axle is a Dana 30 with Bill of Material Number 610322-7 and the Dana 35 rear is 605387-1. I’m not sure if the rear is a c-clip or not (it has a “35C” in the upper corner of the housing. I also wonder if the rear has a limited slip or not.
- Chris Lee
- West Virginia
Chris, your front D30 is a no-disconnect model, meaning no vacuum operated center axle disconnect, CAD, that was used on rigs with full-time 4wd. The “-7” indicates it was 3.55 ratio. The rear is also a 3.55 ratio, but sorry to say not a Limited slip. The “35C” stands for “35 Custom” because Dana shipped the units incomplete to Chrysler. It’s not a c-clip type, though yours was one of the last of the non c-clips types. C-clips showed up in some ’88s and ’89 XJs and MJs, according to the Dana manuals but the D-35 line was fully converted by 1990.
F-250 Puller
I am in the process of building my F-250 for truck pulling. I want to add power to the 6.9L diesel. In another article you wrote that the injector pumps are easily tunable. What kind of things can I do to the pump for more power? Also, when I add more power, I need something more for traction. The truck is still a daily driver so I need something easy to drive but strong and still good for off-roading. Do you think the front TTB will be able to handle the stress of pulling? Both the front and rear have 3.55 gears and I run 33s
Jason, Via e-mail
I have the same truck, Jason and it’s been a loyal friend for many years. First off, you’ll need a turbo kit. Banks makes a great one, the Sidewinder, which will give you about 220-250 hp and 450-475 lbs-ft. An earlier version of this kit has been on my truck for 18 years, so I can attest that it holds up. The only pump mod you can do at home is to set the fuel rate up to match the turbo. Given the age of your truck, if you want the best performance, I’d recommend replacing the injectors and having the pump rebuilt by a Stanadyne authorized injection shop. They are generally good for about 100,000 miles and start to go downhill from there. As for traction, if you want a totally streetable locker, go with the ARB Air Locker- 100 percent locked when you need it, 100 percent open when you don’t. Unless your truck was one of the rare ’80-86 F-250s that was ordered with the Dana 50 TTB front, you have the rather wimpy Dana 44. I don’t think it will hold up very well to pulling and big tires. You have two options, swap in a Dana 50 TTB from an ’80-85 F-350, ’87-97 F-250HD, or a Dana 60 beam axle from an ’86-up F-350. The latter choice will be more expensive, but stronger. Either way, you’ll want another Air Locker up front for max traction. You’ll need a gearing upgrade as well. For 33s, you should run 4.10s, with 35s, you need 4.56s, for 37-38 inchers 4.88s.
Thirsty Bronco
I’ve got a ’95 Bronco with a 351. It’s got a 6-inch lift and 35s. I’m getting about 8 mpg, partially due to a heavy foot, but that’s what it takes to get going. I’ve been told that upgrading from the stock 3.55 gears to a set of 4.56s would increase my mileage, I was told as much as to 15 mpg. It seems odd that a deeper ratio would increase my mileage that much. Let me know what you think.
Chris Holdorf, Via e-mail
Well, Chris, it’s true. I won’t promise you 15 mpg, but the gear swap will give you some of the lost mileage back. The best way to explain why is to go back to your bike riding days. Imagine having a 10 speed but with the gears locked into 8th. You’re going to work much harder getting moving, staying in motion and climbing hills. You’ll burn a whole lot more calories in that high gear than a lower one. The bigger tires on your Bronco are just like that. Combining 3.55s with 35s is like having 2.94 gears. That’s the automotive equivalent of 8th gear. You need a whole lot more throttle to get moving, stay moving and to climb hills. That uses more gas. Yes, you can go too far the other way too, making the engine scream at a high rpm and eat up fuel that way. Overall, engines are most economical at speeds inside their “torque plateau,” where the engine torque curve (as seen on a torque graph) levels off near the peak torque area. That point is different for every engine, but medium displacement V8s are usually most economical around 2000-2500 rpms. Fours and V6s are usually a bit higher. Big V8s and light truck diesels are a little lower, 1800-2200 rpms.