Question: I'm in possession of an '86 Jeep Cherokee Laredo with the 2.8L and three-speed auto. My questions are concerning a possible engine swap. Other than the 4.0L, knowing it will probably mean swapping out the entire front end, what other options might I have? Maybe an engine from another vehicle besides a Jeep, and which ones?
My local used parts suppliers all offer the 4.0 but with an extensive list of items that I would have to gather from various other vehicles. No engine would be complete. And the used sales lots want about as much as it would take me to transform my machine.
My intentions for this machine are a daily driver and some light 'wheeling in the foothills around Las Vegas, with an occasional trip to Moab or the like to explore some of the beginner trails. I'm looking at a 3.5- to 4.5-inch lift with slip-yoke eliminator, shafts, and 31- or 32-inch tires.
Answer: Let me tell you right off the start that selling the Jeep and buying one with a 4.0 in it will place you money ahead. My guess is that you didn't factor in the time involved. Also, don't forget you're going to have to swap out the wiring harness as well as the computer. I also would never consider buying a motor that was not complete. It's a crap shoot as to just how well the motor ran before the accident that placed it in the salvage yard. It would be very frustrating to make the swap and then find that the motor had a terrible knock or smoked badly. By trading up, at least you know what you're getting because you can drive the vehicle and actually check the motor out.
As far as an engine from another vehicle, I have seen some Chevy 4.3L V-6s installed that came out quite nicely. These incorporated the trans as well as the transfer case from the donor vehicle. Again, remember you're going to need the wiring harness and computer to match the new engine.
Question: I own a '00 Ford F-250 Super Duty 4x4 with a 7.3 Power Stroke. Its main job is to pull a 25-foot travel trailer on trips, or an '01 Jeep Wrangler to destinations like Colorado. The owner's manual said, "Never tow in overdrive."
The Jeep weighs 3,500 pounds and the trailer (loaded) weighs a total of 6,000 pounds. That's half or less what it's rated to tow. Towing out of overdrive doesn't seem to load the engine at all, and the turbo can be heard unloading. When in mountains, I would never use overdrive, but on long, straight, flat stretches of interstate, would I hurt anything towing in overdrive? My goal is to use less fuel and have the truck outlast me.
Answer: I would suggest that you go ahead and tow in overdrive. The transmission, if an automatic, will shift down when needed. Keep it in Drive when in the mountains, or whenever it wants to hunt between Drive and overdrive. I would suggest that you invest in a transmission temperature gauge and try to keep the temperature between 180 and 200 degrees. Never let it exceed 220, and if you do, change the transmission fluid at the first opportunity.
If it's a manual six-speed, I also suggest towing in overdrive. I have a similar ZF transmission in my own truck, and I tow in overdrive all the time. While in overdrive, my diesel can pull most small grades, even with a total load of 20,000 pounds, because it makes a considerable amount of horsepower due to aftermarket accessories and modifications. However, under a heavy pull up a grade, I often slow down and shift to Fifth gear (direct) to lessen the load on the clutch and rather smallish overdrive gear. Like you, I want the maximum in fuel mileage and life out of my truck.
Question: Is there any advantage to running a slightly smaller-diameter tire in the front of a fullsize rig? Seems that most of the weight of that kind of rig is at the front, so would it benefit from having the front tires turning slightly faster? Seems rear tire traction would be somewhat slower, which would provide a more balanced application of power.
Off in space with too much time on my hands.
Daniel G. Johnson
Answer: Yep, you are off in space with this one. But I like people who think. New ideas get tried-some work, some don't.
Unless it is a full-time system with some sort of viscous coupling or a differential within the transfer case, the front and rear axle are locked together and must turn at the same speed. What is going to happen if there is good traction and the tires can't slip? Something is bound to break, be it the U-joints, driveshaft, or gears.
Now if the front tires can slip, that means rubber is going to be worn off a lot faster than if the tires didn't slip. This wear will even take place on dirt.
A tire only generates a given amount of traction, be it forward or sideways motion. If the tire is slipping while going forward-let's say 30 percent-then there will only be 70 percent of the traction left for steering input. Now with that said, some mud racers do exactly that; let the front tires turn faster than the rears, but keep in mind that they are in a very low-traction situation, and some think that there is some stability to be gained. Just as a note: Some full-time 4x4 systems actually split the power unequally front to rear for better handling on the street.