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Your Jeep Tech Questions Answered

Posted in How To: Tech Qa on May 9, 2015
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FSJ Issues
I recently bought a ’72 J4000. It has an AMC 360ci V-8 in it. On the drive home, I found out it had play in the steering. It took some work to keep it straight on the road. After I got home, I checked the frontend. I discovered that some steering parts needed to be replaced. Since I was under the truck already, I decided to check out the rest of the Jeep. I found that the floors had been patched with really heavy sheetmetal and they need to be fixed right. I also would like to change the steering column that was put in it. It really doesn’t fit right, and it is so close to you, even with the seat all the way back, it’s just too long. And the seats, well, they don’t fit either. Someone took the bench seat out and put in one bucket seat with two bolts holding it in place. I know it’s a lot, but can you please help me? I’ll start with the frontend. Local auto parts stores say they do not carry parts for it and that I have to order them. Who carries parts? Does anyone make new floor panels for this truck? As for the steering column and seats, what vehicles from the salvage yard would work?
Julio Gonzalez Jr
Via email

The good news is that the early J-trucks are easy to work on. However, in most cases, any parts that you need will have to be special-ordered or ordered online. Napa ( and Rock Auto ( both carry all of the J-truck replacement steering components at a reasonable price.

Classic 2 Current Fabrication ( and BJ’s Off-Road ( offer new floor pans for all Jeep J-series trucks as well as other sheetmetal repair panels.

Unfortunately, the J-truck steering columns are long. There really isn’t an easy fix for this. If you want to swap out the steering column or move it up, you’ll have to do a bit of fabrication work. There isn’t a bolt-in swap that I know of. As for the seats, it sounds like someone bolted-in a pair of Wagoneer seats. While they sort of fit in the J-truck, they only allow the use of two mounting bolts. It’s a pretty rickety setup. My ’73 came with similar seats. Ultimately, the cabs are pretty small, so you don’t have a ton of seat options. The factory bench seat might be the best route. Montana Overland ( specializes in FSJs and might have a good, used bench seat or one that can be reupholstered. I ended up installing some PRP Premier suspension seats ( in my truck, but they required custom brackets I welded together and bolted to the floor.

Drive Flange or Locking Hub
Has anyone done actual comparisons between locking hubs and OEM solid drive flanges? Locking hub vendors claim fuel savings and reduced front differential wear. With the transfer case in neutral, just how much horsepower is required to spin an unloaded differential? Considering that differential gears are machined from high-grade hardened steel, how much wear can occur from unloaded gears merely rubbing against each other? If there were measurable wear or measurable fuel savings, wouldn’t using Redline or Royal Purple synthetic gear oil be a simpler solution? From time to time I read about locking hubs breaking on the trail and how to replace them. Since cast iron or machined steel is stronger than cast or forged aluminum, why spend money on locking hubs that can break? Solid drive flanges are essentially zero maintenance. Locking hubs should be periodically serviced. Water can seep into locking hubs and freeze causing them to be difficult to operate. That can’t happen with solid drive flanges. With reliability and maintenance-free being prime design requirements, if locking hubs were a good thing, the military M38 and M38A1 vehicles would have required them. Yes, I replaced the locking hubs on my ’79 CJ-5 with solid drive flanges. Love the magazine. Keep up the good work!
Bill Evans
Via email

In the early days, drive flanges were all that was offered by Jeep from the factory. In 1948, Arthur Warn developed the Warn ( locking hub and advertised that the hubs improved on-road performance and fuel economy. Many other aftermarket companies followed suit. Eventually, locking hubs became standard on all OE 4x4s. Fast forward a couple decades and the OEs switched to unit-bearing disconnect front axles. This eliminated much of the spinning drivetrain that causes parasitic drag, without the complexity and expense of locking hubs. Moving forward, the OEs did away with the disconnecting axle and simply let the entire assembly spin as it did in the ’40s. Today, you’ll see a combination of both disconnecting axles and fully engaged unit-bearing axles without locking hubs on new 4x4s. The OE manufacturers are working to squeeze every mpg out of each vehicle while still keeping costs down. Newer 4x4 systems have far less parasitic drag than the older systems.

On an older Jeep like yours, the fuel mileage is already pretty dismal. Adding locking hubs may not make all that much difference. However, as you mentioned, it’s well known that drive flanges or slugs are generally much more durable. The wear caused by the front axle, driveshaft, and transfer case spinning freely would be pretty minimal in my opinion. I wouldn’t be too concerned about it. The only real downside of using drive flanges or slugs is driveline vibration. After installing lift kits and/or aftermarket axles, the front driveshaft angles can get out of whack. This can happen in some stock applications too. Driving with the frontend engaged at speed on the highway may rattle your teeth if this is the case. A pair of manually locking hubs come in handy and go a long way in smoothing out that vibration. If it was an issue, you could always remove the drive flanges for road use. In the end, the locking hubs are simply more convenient for some people.

I think the main issue with the ’72-’86 CJ hubs is the retention method. The ’72-’80 CJs use six locking hub bolts, and the later ’81-’86 CJs used the weaker five-bolt design. Neither design is ideal since the bolts often come loose, causing failure, even with drive flanges. I always recommend the use of studs over bolts in this application. Warn offers a stud kit (PN 34696) that works on both the six and five-bolt locking hubs. They should be installed using red or blue thread-locking compound to keep them from coming loose.

Grilling Bumper Basher
First off, I love Jp magazine. I bought the first one I saw, and I’ve been a subscriber ever since. Anyway, I see so many ads for replacement front bumpers and so many on your projects and featured Jeeps that I wonder about front collision air bags and if their function is compromised. The Jeep I hope to build one day will be pre-air bag, but what about the others? Second, if I am one of those odd folks who think real Jeeps should have round headlights and leaf springs and don’t want a Wrangler older than a ’93, how tough is it to graft a front grill from a TJ to a YJ?
Mark Arnell
Via email

Jeep spends several years and millions of dollars developing the bodies, frames, and other components of each new Jeep to pass U.S. crash requirements. Even changing something as simple and seemingly innocuous as a motor mount or engine location could cause a vehicle to fail the stringent standards. So yes, aftermarket bumpers significantly alter the crash characteristics and airbag deployment of a Jeep involved in a major wreck or minor fender bender. The good news is that if it is a concern, there are some companies that specialize in developing front bumpers that retain the airbag crush cans. These allow the bumper to hit something at a slow speed without the fear of setting off the airbags. In my experience, Jeep did a good job with the electronics in these systems to start with. They are not overly sensitive. You rarely ever see a Jeep Wrangler airbag inadvertently go off, even during abusive maneuvers off-road. Other vehicle manufacturers have not done as good of a job. I’ve personally had a Nissan Xterra blow a side curtain airbag on me on the trail. It happens pretty quickly and can cause an injury in some cases.

Now, for the grille swap. Unfortunately, the YJ and TJ grilles are not even close to the same shape. They will not interchange without significant modifications. Even swapping the whole front clip would be a quite a body metal-molding task. Interestingly enough, Omix ( at one time offered a bolt-in YJ conversion grille with round headlights under PN DMC-888000K for steel and DMC-777000K for fiberglass. It was a full kit that came with the headlights, marker lights, and all the necessary trim bits, but it’s been discontinued. You might be able to find new old stock hiding in a dusty warehouse somewhere, though.

I get that you like the leaf springs, but the TJ really is a much better Jeep than the YJ overall. You should at least consider going with the round-spring Jeep. I have seen some people swap out the factory rear four-link and coils of a TJ to install leaf springs. This modification provides much more predictable handling in articulating off-camber conditions, and when done properly, it makes the TJ more stable and less prone to rollover in these situations. While a front TJ leaf spring swap is possible, it will require a bit more thought and custom fabrication.

Grand Replacement
I own a ’99 WJ. I’ve owned it for a few years, but now it is totally crapping out on me. The heater core is leaking coolant, the engine is burning oil, the passenger door lock won’t work, the climate control flaps broke, blah, blah, blah. Now it is time for me to look for a new (used) vehicle. What I really want is another WJ. The problem is that I am almost too scared to buy one. When I look on Craigslist, people are selling WJs with busted heater cores and electrical problems! Plus, the local Jeep specialist hates them. What should I do? The WJ is everything that I need in a vehicle! Plus, I will have only about $5,000 or so to spend.
Josh Henley

That’s the rub here. We all fell in love with the last of the solid-axle steel-top Jeep SUVs, which included the XJ, ZJ, and WJ. They get old and no longer work as reliable sources of transportation. You’ll find that most well-used WJ Jeeps will have problems similar to what you are experiencing. It’s not unusual.

I theorize that discontinuing those vehicles inadvertently set Jeep up for the success of the four-door Wrangler Unlimited introduced in 2007. The company originally thought the two-door JK would sell better than the four-door. Just the opposite happened. Many Jeep owners that loved their ZJ, XJ, and WJ Jeeps wanted a robust and capable SUV with four doors, and about the time that their Jeeps started getting long in the tooth, the JK four-door hit the dealer lots. The problem is, you likely will not find a ’07-current Wrangler Unlimited for $5,000. My best advice is to save your money and keep an eye out for an affordable JK Unlimited. Mechanically speaking, that’s about as close as you’re going to get to at least somewhat match the characteristics of a WJ, unless you have access to a time machine.

Boxing Frame
Regarding “Garage Project GPW” (Feb. ’15), I heard there was some theory about not welding the entire boxing plate to the frame but to make long stitches as you have done here. When I plated mine, I did the whole thing in stitches but filled it in after the welds cooled, then ground it down. What is the logic behind not welding it all the way?
Mike Kunz

I’ve done it both ways in the past. Fully welding the plate all at once can cause the frame to warp and twist. I’ve had it happen. Fully welding small sections at a time like you mention would eliminate that problem. Ultimately, fully welding the boxing plate is kind of overkill. One advantage to using an intermittent fillet weld is that if a crack does start for some reason, it will typically stop after only taking out one weld. In theory, the crack would continue on in a fully welded application.

I also like to stagger the intermittent welds top to bottom so they are not on the same plane. I measure them out and mark where to weld with a paint pen. In this case each section of weld is about 11⁄2 inches long. The non-welded areas are about 4 inches long. Sometimes you have to alter the frequency if there is some structural component in the way though.

Frame Drain
I noticed that you completely boxed the frame of your GPW (“Garage Project GPW,” Feb. ’15). For those of us in the northern climates, would leaving some spaces make it easier to clean out the frame or do you want to seal it completely up?
Tim Fox

There really is no way to completely seal the frame, and you don’t want to try. You’ll eventually get water and dirt in there, causing it to rust from the inside out. If you live in a wet climate and plan to use your Jeep in the mud a lot, it would be a good idea to use a hole saw or other method to cut some large holes along the middle of the frame boxing plate. However, you’ll still want to use an intermittent fillet weld to attach it to the frame. Since you can’t seal water and dirt out of a frame, you are better off making it easier for it to drain and escape. You might even want to use a pressure washer to clean it out occasionally.

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