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Answers to all your Jeep questions

Posted in How To: Tech Qa on April 6, 2017 Comment (0)
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True Tale

I look forward to every Jp magazine sent to me, and I read it from cover to cover when I receive it. I’ve been reading it for many years. I see you have lots of tires mounted at Discount Tire. I live in Chelan, Washington, and have checked with Discount Tire in Wenatchee, as they're the closest Discount Tire store to me. They do not mount tires on beadlock wheels and tell me that no Discount Tire in their system will mount tires on beadlock wheels. I have not been able to find a tire store willing to mount them.

Also, I have been looking to find some 37x12.50-15 Dick Cepek Mud Country or Extreme Country tires. Again, no luck. I thought for sure that was a size that was offered. I’m looking for good mud and snow tires to replace my 36x13.50-15 tires that are worn out now. Any thoughts on a tire that will measure a true 35 inches when mounted on 15x10 wheels?

The Jeep I want the tires for is a ’79 CJ-7 with a built 401ci V-8 engine, T-18 transmission, Dana 20 transfer case, Dana 44 front and rear axles, 4.27:1 ratio axle gears, ARB Air Lockers front and rear, a full cage, on-board air, a Warn winch, a 3 1/2-inch Rancho lift, a 1-inch Daystar body lift, and much more!

I would appreciate your ideas on what to do in my dilemma.

Vance Myers
Chelan, WA

Thanks for reading! Unfortunately, beadlocks are not commonly found at most tire stores. In some cases, they are considered race or off-road–only wheels. Most traditional tire stores will want to steer clear of beadlock wheels because there is probably some liability that they can’t take on, especially if you want them to actually install the tires and wheels on the vehicle and send you down the road. Not all beadlock designs are DOT compliant, so just letting you drive out of the parking lot is a huge risk for a large company. You could try locating an automotive race shop that specializes in racecar parts or a small off-road shop to help you with the mounting. You might have to make a short drive, but I’m sure you could find a race shop associated with the Wenatchee Valley super oval track, which is only about 40 miles from you.

On the plus side, you don’t necessarily need a tire shop or even a tire machine to mount or dismount tires on true beadlock wheels, although it does make the task at hand a little easier. The real key to mounting and dismounting tires on beadlock wheels at home is to make sure the tires are warm and to use plenty of soapy water on the bead and mounting surfaces. It’s a lot of work, but totally possible to use a Hi-Lift (hi-lift.com) jack or other method to break down the inner tire bead. The wheel can then be pried out of the tire once the locking ring is removed. Companies like Extreme Outback Products (extremeoutback.com) offer tools like Tyrepliers and the Beadbuster to help break down the tire beads. The company also has large tire irons available that will simplify wheel removal. You could even get your hands on an inexpensive manual tire machine (PN 69686) from Harbor Freight (harborfreight.com). A clever individual would make a party out of it and invite a few knowledgeable 4x4 buddies over to help.

Modern brake advancements on newer 4x4s have led to larger diameter brake rotors, which have all but killed off the 15-inch wheel. The 15-inch wheels just don’t provide enough brake clearance. There isn’t a single new U.S. 4x4 worth modifying that is available with 15-inch wheels. I’m with you, though. I’m still a huge fan of big tires on 15-inch wheels for older 4x4s. Regardless, 15-inch 4x4 wheel and tire sales have dropped off significantly, leading most tire companies to discontinue the less popular tire sizes for 15-inch wheels, including the 37x12.50-15. However, if you don’t mind using bias-ply tires, you still have lots of options, although most of them are very aggressive mud tires that will not work well on slick icy surfaces. Maxxis (maxxis.com) and Interco Tire (intercotire.com) both offer bias-ply 37-inch tires that fit 15-inch wheels. Interco also has a 37x12.50R15 Super Swamper IROK radial tire that might work for your application.

You could also look into the 35-inch tire market. Many companies offer streetable 35x12.50R15 radial tires and not all of them are the same exact diameter. Of these, the Goodyear (goodyear.com) Wrangler MT/R is among the tallest of the 35-inch mud tires available.

When you look at the bigger picture, a tire that measures a true 35 inches tall isn’t providing a significant enough amount of ground clearance over a typical 35-inch tire that measures in at around 34.5 inches. You’re only losing 1/4-inch of ground clearance. This small height difference will hardly keep you from conquering a trail, but it has put significant limitations on the tires that are available to you. The Dick Cepek (dickcepek.com) Extreme Country 35x12.50R15 specs out to 34.7 inches tall on a 10-inch-wide wheel. If you truly like the looks and performance of the Dick Cepek Extreme Country, that’s probably the tire you should go with, instead of compromising on the tread pattern for a marginally bigger tire diameter. The Dick Cepek Mud Country is no longer offered.

4.0L Swap

I have acquired a complete 4.0L engine out of a ’97 Jeep Grand Cherokee, minus the wiring harness. I was thinking of dropping in my ’86 CJ-7 project. Are there any products on the market that can be used to control the fuel injection for this engine? I have seen products like the Fast E-Z EFI, but those are for throttle body injection. Is there anything out there at a reasonable cost to control the hardware I already have?

Also, do you think it would be worth the effort to take the 4.0L head and fuel injection and put it on the stock 4.2L block?

Ken Gaito
Fredericksburg, VA

Sounds like a solid plan. The fuel-injected 4.0L will be a great addition to your CJ-7. In fact, Mopar (mopar.com) created a complete MPI kit for the 4.2L using many of the 4.0L injection parts. Unfortunately, it’s not as simple as bolting the 4.0L head to the 4.2L block. There are several water jacket passages in the 4.0L head that don’t match up to the 4.2L block. Of course, there are people who have plugged these passages with epoxy and successfully installed the 4.0L head onto the 4.2L, but I wouldn’t recommend this.

I think your best bet is to keep the 4.0L complete and swap it in place of your 4.2L. You will need a wiring harness and computer. Hesco (hesco.us) offers many 4.0L swap components that may help with your conversion. However, the company only offers an engine wiring harness for the ’91-’96 4.0L. Painless Performance (painlessperformance.com) offers a complete wiring harness and computer, which can be used to swap the ’91-’98 4.0L into nearly anything. You could also get a modified harness for your ’97 4.0L from Hotwire Auto (hotwireauto.com). The company will require a stock harness to build the new one for you. You should be able to find a stock ’97 4.0L engine harness and computer at the wrecking yard or on eBay (ebay.com).

Overdrive XJ

I’m going to start a new project once I find my donor Cherokee. The plan is to stroke the 4.0L to a 4.6L. I was pondering what to do with the drivetrain, then I had seen the article on using the 8.8-inch Ford rearend. So now I’m thinking of using a pre-’79 Ford F-150 9-inch rearend and the Ford Dana 44 front axle (I’m a diehard Ford person). My brother is the Jeep person in the family, and with all the aftermarket parts available for the Cherokee, it works for me. What is the best non-electronic overdrive transmission and transfer case that bolts to the 4.0L block? I’m looking for dependability. I’d like to avoid adapting anything if at all possible. If I’m going to adapt anything, I’ll look at Ford C4 or AOD since I’m quite familiar with them. Thanks for any insight on this.

Bill Starnes
Via email

It sounds like you have a cool project in the works. If you are looking for a full-width Ford 9-inch from a fullsize truck, you can use the 9-inch out of a ’74-’86 F-150 or ’78-’86 Bronco. Some of the early two-wheel-drive trucks will have the less desirable 28-spline axleshafts and small-bearing carrier. Look for the 31-spline ’shafts, and if you can find it, the factory nodular iron third-member found in some ’70s Camper Special pickups. This third member is identified by the letter “N” cast into it. Avoid the Ford van 9-inch axles. They are slightly wider than the truck rearends and will not match the 4x4 front axle width.

You don’t have a lot of options if you want an overdrive automatic transmission with no electronics. The factory AW4 four-speed automatic that came in many XJ Cherokees bolts directly to the 4.0L block, is incredibly durable, and has an overdrive gear. However, it has some electronics. I would not recommend the three-speed C4 or the AOD. The Ford transmissions just don’t seem to work or hold up as well off-road as some of the other options available. Plus, there are other transmissions that will give you better transfer case options without the use of an adapter. Perhaps your best transmission choice is the GM 700R4. It can be inexpensively adapted to the 4.0L with a simple 5/8-inch-thick adapter plate and a new flexplate, both of which are available from Advance Adapters (advanceadapters.com). If you wanted to strip down the 700R4 even further and make it more bare bones, you could install a manual valve body.

As for the transfer case, I think an NV231 will hold up fine. You should be able to find a 700R4 factory-mated to an NV231 in some midsize Chevy SUVs and pickups. You might also consider a Chevy NV241 transfer case. These can be easily mated to the 700R4 as well. Adapters are available to clock the transfer case for extra underbody or ground clearance.

Exhausting Y-Pipe

I have a ’79 J10 with an AMC 360 V-8 and a T-18 four-speed manual transmission. I want to remove the rusty aftermarket headers and replace them with the stock cast-iron manifolds and Y-pipe. It seems the ’79 Y-pipes are unavailable. I can find a ’80s Y-pipe, but the web says it won't fit. Is it something to do with the switch to the driver side differential and TorqueFlite transmission?

Have you had any experience with this problem? Are the ’79 and ’80 J-trucks all that different?

David Gibson
Via email

Well, this is kinda how it goes with older model Jeeps. Off-the-shelf parts slowly dry up because fewer and fewer of these Jeeps are on the road every year. I was unable to find a Y-pipe for your ’79, but Walker (walkerexhaust.com) does offer factory-like Y-pipes and other exhaust components for many Jeep applications.

Unfortunately, the ’80-and-newer Y-pipe will not fit your application. Part of the reason is because of the driver side front differential. The differential, front driveshaft, and transfer case will want to exist in the same space that the ’80-and-newer Y-pipe does.

If you are willing to experiment, you could try the Y-pipe from an AMC V-8–powered CJ-7. This Jeep has the differential on the same side as yours. Walker offers a Y-pipe for this application under PN 40376. It may not be a direct fit, but it might be a good starting point for you if you are able to modify it to work.

You do have another option. The good news is that your Jeep truck is not a complex vehicle. Most competent exhaust shops can build you a Y-pipe from scratch and then route your exhaust to the rear of the Jeep.

Limited Slipped

I bought my ’13 Wrangler Unlimited used, so I wasn't able to get it with a Trac-Lok rear differential, which I enjoyed on my CJ-7 and Cherokee. Which aftermarket limited-slip differential do you think would come closest to the Trac-Lok performance? I live in Michigan's beautiful, albeit snowy, Upper Peninsula and spend most of my time on-road.

John Barnhart
Via email

The factory Trac-Lok is a mild clutch-type limited-slip differential made by Spicer (spicerparts.com). It’s a great choice for the rear of Jeeps that spend most of their time on-road, yet also need to traverse snowy and icy conditions or mild off-road trails. It’s one of the most seamless full-time traction-adding differentials available. There are many aftermarket limited-slip differentials. However, most of them are more aggressive than the Trac-Lok. The great news is that Spicer offers the Trac-Lok rear differential for your Jeep as an aftermarket part. It’s essentially the same limited-slip differential that comes from the factory in a Wrangler, but you don’t have to purchase it from the dealer. Also, Omix-ADA (omix-ada.com) offers an aftermarket version of the JK Dana 44 Trac-Lok, which will perform similarly to the original.

Regardless of which manufacturer you choose, always make sure you use a friction modifier in the gear oil of an axle with a clutch-type limited-slip. The friction modifier will keep the differential from chattering when turning corners. It’s available from several different companies, but Spicer offers a friction modifier under PN 43161.

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