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October 2005 4x4 Tech Questions - Techline

Posted in How To: Tech Qa on October 1, 2005
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Question: I own an '82 CJ-7 with a 4-inch BDS lift and I think a 2-inch shackle lift. I run 33-inch tires and have 4.56 gears. My front is a Dana 30 with Warn axles and an ARB locker, and the rear is a Model 20 with Genuine Gear one-piece axles with an Auburn posi-traction. Could I get away with running 35s, or should I stay with the 33s? Most of my four-wheeling is on trails rated 3 to 4.
Les Jones
Lincoln, CA

Answer: There are several people I go four-wheeling with who run 35s with their Dana 30 frontends. Two have stock axles; the other is equipped with Warns. The one went with Warn axles after breaking some stock pieces. They all do some pretty serious four-wheeling. However, all are excellent drivers with a very light foot and they think before they act. And yes, they do run 4-rated trails.

My recommendation is to always use a Dana 44 with 35-inch tires, but even I don't always follow my own recommendation. I have been known to run 33s on an old Dana 25 axle and have it live. Again, it has a lot to do with just how heavy a foot you have, and your driving style.

The rearend should be just fine with your upgrades. The biggest weakness of the AMC rearend is that the lightweight axletubes sometimes bend. But you have to be using the vehicle pretty darn hard for this to happen.

Question: I have a '93 Chevrolet K-30 crew cab with a 350 engine. I would like to build a 383 for better towing performance. In the interest of heavy-duty use and longevity, I would like to use a set of marine-duty heads that I have. They're the late-model Vortec type with insert valve seats for all valves, bronze guides, sodium or inconel exhaust valves (I'm not sure which), and rotators on all valves.

What is your opinion of this setup, and will the rotators have any effect on coil bind in the valve springs? I plan to use the Chevy cam PN 14097395 with 0.431/0.451 intake/exhaust lift.
Ken Bell
Scappoose, OR

Answer: Sounds like a great combination to me. I doubt that is enough cam lift to cause any coil binding. Under hard use such as towing or marine duty, the valve seats and guides are the first to wear out, so your new engine should last a long, long time with those heads.

Question: I have an '01 Cherokee Sport with the 4.0L six and AW4 four-speed automatic transmission. It is a great vehicle, in fact almost perfect, except that the downshift from Second gear to First cannot be controlled with the selector in the First/Second position. Too many times, especially in low-range, Third is too fast and First is too slow.

Jeep offers no fix for this, and I have tried one aftermarket device produced in Oregon that supposedly will prevent downshift into First with the flip of a switch. It did that alright, but it threw the transmission control module into a "limp home" mode; no lockup or no Fourth gear without stopping the vehicle, and shutting off the engine to allow the module to reset. The manufacturer found the unit not to be defective. I was told that perhaps the module programming had changed for 2001, thus causing the incompatibility.

Are you aware of a remedy that works? What about transplanting a transmission from a Wrangler or Grand Cherokee?
Gary Van Heese
Emmett, ID

Answer: You're not the only person who hates the AW4's shifting characteristics and there is not a lot you can do about it other than to swap transmissions, which is going to be a major pain. I'll assume that you want to keep an automatic and a Fourth gear overdrive? How it's all going to be compatible, electronics-wise, is a guess by anyone. But it just may be doable.

As I see it, you have two choices. The first comes from Chrysler, the model 42RE used in the Grand Cherokees from 1993 to 1998 and some '99 models with the 4.0 six-cylinder engine. (The V-8 models have a Chrysler bolt pattern, not the old AMC pattern like your engine does.) Try as hard as I could, I couldn't find any information as to output transmission spline to input transfer-case spline compatibility between the two automatic transmissions, but it's a good guess that they are the same.

Your second choice and perhaps maybe the best, but most likely more expensive, would be to go with a GM Turbo 700R4. It's a stand-alone transmission, so there are no computer controls. It does use a TV cable to control shifts, so you'll have to possibly fabricate a bit on linkage on the throttle assembly. Both Novak Conversions and Advance Adapters have the proper adapter plate between engine and transmission and transmission and transfer case.

The new transmission combination will be a bit longer, so depending on ride height, you may or may not need a slip-joint eliminator kit to solve driveshaft angularity problems. You will also need to either relocate the ignition crank position sensor into the 700R4 bellhousing or swap to a front crankshaft-mounted unit.

The most difficult part of the swap may be in obtaining the proper clearance in the transmission tunnel, as the 700R4 is a bit larger in size.

Best of luck and whichever way you go-let us know how it turns out.

Question: What can I do to hop up my 4.9L 300ci straight-six engine in my '85 Ford Bronco?
Tony Zuniga
San Antonio, TX

Answer: Six-cylinder engines respond to the same treatment as a V-8. That is, more gas in, more exhaust out, and better combustion all make for more power. With that said, the easiest way to make more power as a starting point is with an aftermarket intake manifold and carburetor change, along with a quality set of headers and after-cat exhaust system. Offenhauser ( has a four-barrel intake available; so does Clifford Performance (, as well as camshafts and headers.

Most major cam manufacturers also offer cams for the Ford six. If you want to go all-out with a total rebuild, consider a set of high-compression pistons, a balancing job, and maybe some port work. If this is a trail vehicle, then keep in mind that to maintain some of that good bottom-end torque that the six is famous for, don't go too wild on the camshaft and follow the cam manufacturer's recommendations. Overcamming is a far worse sin than undercamming. Also, you want to keep in mind that the higher compression will require a higher-octane fuel to prevent detonation.

Question: Why does GMC say in the owner's manual not to run chains on my '01 Yukon XL? I called the tire company (BFGoodrich) and they were very nice but couldn't tell me about tire chains. They suggested I call GM, which I did, and a kind young lady checked and said that I couldn't run tire chains because there wasn't enough clearance. She couldn't tell me "clearance from what?"

I called the service department at my GMC dealership, which is 100 miles away, and he said he didn't know why GM recommended no chains.

Help! Sometimes a fellow has to run chains. The highway patrol sometimes requires chains where I live. I'm running the BFG Land-Terrains (sold only by Wal-Mart); they're LT275/75R16s, 31.8 inches in diameter. If the chains may hit the fender liner if loose or at speed, no problem. But, if the chains will tear up a brake or fuel line, that's different. I would want to run them only on the rear wheels.
Mike Dougherty
Baker, CA

Answer: Yep, there are times when the California Highway Patrol does require chains, even on 4x4 vehicles. They have this thing about trying to prevent accidents. Just because you have four-wheel drive doesn't make you a good driver or allow one to drive faster. Their main reason for chains on 4x4 vehicles is that it at least causes the traffic to slow down. And four-wheel drive doesn't really help all that much in stopping distance on ice.

The only reason I could see that GM would say not to run chains is the lack of clearance. Some chains, due to design, take up more room than others. The European V-type, with the ice-biter cleats, most likely takes up the most room, the so called "cable chains" the least.

I believe the body and frame design on your Yukon is similar to the present models and yes, it is a tight fit. In fact, I tried this, and couldn't get my hand between the shock and the tire, it's so close in the back. Take a look at yours and see what you think. There is definitely not enough clearance for any type of chain.

Up front, there seemed to be enough room for chain clearance as long as you remember not to turn too sharply, and even if you forgot, the noise of a chain against the body would quickly remind you. In some situations, it's better to run a single set of chains up front instead of on the rear. However, the vehicle should be in four-wheel drive. Duh! Gee, that stands to reason, right? Even more so because the front will now have more traction, a lot more traction than the rear, and there's a better chance of the rear of the vehicle sliding in a corner, so if this happens, you will have to learn to "drive out of the corner."

As you mentioned, most people run their chains way too loose because they don't want to have to stop and re-adjust them. There is also the factor of one size of chain fitting a variety of tire sizes. Instead of buying the chains at a discount store, I suggest you buy them from a tire store and have the service technician properly size them for your tire and vehicle.

It's nearly impossible to get a perfect fit and eliminate all slop, so this is where chain tensioners come in. Having lived in snow country for 30-some years, I've tried all sorts of tensioners. What I have found works best for me are tarp hold-downs. These are the heavy-duty black rubber units truckers use to hold the tarps covering their loads (kind of like an extra-heavy-duty bungee cord). They come in a variety of lengths. I usually use two on each tire, hooking one end in a chain link, running across about one third of the tire's diameter through a chain loop and back again, hooking the end about one third the distance apart again. I do the same with the other one, in just the opposite direction. They're easy to use and they do the job. If I know I am leaving the chains on for an extended amount of time, I've even resorted to using nylon rope to pull them tight.

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