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Answers to all your Jeep questions

Posted in How To: Tech Qa on January 9, 2019
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Tick-Tock 4.0L

I have a ’99 Jeep Cherokee XJ with a 4.0L engine, 4.5-inch Rubicon Express lift, 33-inch tires, and 4.56 axle gears with Eaton Detroit Truetrac limited-slip differentials. It performs great. The Jeep has roughly 205,000 miles on it and the engine is getting pretty noisy. I’m not sure if it’s a lifter tick or worse. I don’t only go off-road with my Jeep. It’s fully street legal and I used to drive it all over the place on 2- to 3-hour road trips, but lately the engine noise has me wondering how reliable it really is. What are the first steps in diagnosing what the noise is? I’ve had one mechanic say it sounds like a normal 4.0L and another mechanic that I work with is very concerned with the noise. What are your thoughts?
Jesse Chism
Via email

The 4.0L Jeep engines are nearly bulletproof. If properly maintained, they can easily hit 250,000 miles. Unfortunately, sometimes they still have issues. It’s difficult to identify an internal engine noise via email, but there are a few things you can check. The first thing to remember is that the 4.0L engines were never all that quiet to begin with. The 4.0L engine was based on a 50-year-old design. Having said that, it’s also not uncommon for a 4.0L lifter to have issues. I think you should first inspect the oil pressure. The typical oil pressure rule for older engines like your 4.0L is to look for 10 psi for every 1,000 rpm. If it’s dipping below this, you could have a failing oil pump or worn bearings in the engine. Although, some 4.0L engines will run for years on minimal oil pressure. Regardless, excessively worn or damaged engine bearings will be easy to diagnose when inspecting the engine oil. If there are lots of metal flakes in the oil, you likely have a bigger internal issue and a teardown might be required.

I’d recommend getting your hands on a mechanic’s stethoscope. These can be purchased inexpensively through companies such as Harbor Freight (harborfreight.com). Carefully poke around the engine to pinpoint where the noise is coming from. Also, be sure to check carefully around the exhaust manifold and collector. It is not at all uncommon for the tick of an exhaust leak to be mistaken as an internal engine problem. Unfortunately, the 4.0L is well known for having exhaust leaks. There are a number of aftermarket headers available to cure a leaky OE cast-iron exhaust manifold if you do find this is the cause of the ticking.

Flatfender Tech

What did you use for a transmission mount on the Garage Project GPW? I am thinking of swapping an SM465 or SM420 in front of the Spicer 18 in my Willys. I want that low first gear. Also, what does your Jeep feel like with coilovers?
@phillywilly46
Via Instagram @cappaworks

Over the years I’ve tried using the stock flatfender transmission crossmember and mount, and several different custom crossmembers that I’ve fabricated. The result was pretty much always the same: While the transmission and transfer case were securely held in place, I was never happy with the ground clearance or the skidplating that protected the vulnerable Spicer 18 oil pan. I decided to solve these problems on the Garage Project GPW. For this Jeep, I fabricated a one-piece skidplate/crossmember, similar to the stamped-steel skidplate you can find underneath a YJ or TJ, only much of mine is made from 1/4-inch-thick steel plate. A transmission mount pad is built into the skidplate. It utilizes a Daystar (daystarweb.com) urethane GM transmission mount that attaches to the foot of the transfer case adapter. The skidplate attaches to the frame via six 3/8-inch bolts and RuffStuff Specialties (ruffstuffspecialties.com) threaded weld washers. I also raised the transfer case several inches for more ground clearance. The transmission tunnel needed to be cut and modified to accommodate the new raised transfer case location. So far, I’m really happy with it. Eventually, I’ll extend the skidplate forward to protect the engine oil pan too.

The SM465 and SM420 are both great transmissions. The SM465 offers a 6.55:1 ratio First gear and the SM420 offers an ultra-low 7.05:1 ratio First gear. However, both transmissions have their drawbacks. First and foremost is that they are essentially three-speed transmissions when you are driving on the street. You generally will never find much use for the low First gear on the pavement. The gaps between the three gears on both transmissions can make for quirky driving on the street. Something else to consider is that the SM420 is old and it is getting harder to find parts for. Also, with some adapters the front driveshaft clearance can be a problem on the SM420 when used with a Spicer 18. The SM465, while much newer and easier to find parts for, is massive and hangs down several inches below the framerails. You should check the actual dimensions before pulling the trigger on an SM465 swap in a small Jeep. If you are set on a four-speed manual truck transmission, you might want to consider a T-18 transmission. The T-18 is extremely adaptable, readily available, you can find them with a 6.32:1 First gear, and it’s pretty compact for its strength and durability. In some areas a good swappable version of the T-18 can be difficult and expensive to locate, but Herm the Overdrive Guy (hermtheoverdriveguy.com) offers several versions of the T-18 rebuilt with an adapter for a very reasonable price. The company has other low-geared rebuilt truck transmissions available too, if you decide to go a different route.

For years I dealt with the drawbacks of leaf springs on my other flatfenders. I was regularly bending and breaking leaf springs. Axlewrap was also a real issue, to the tune of having destroyed several driveshafts, yokes, and a transmission case. On the GPW, I wanted to eliminate these problems. Adapting the Land Rover radius arms and Fox (ridefox.com) coilover shocks eliminated the problems I had with the leaf springs, but it’s a comparatively complicated suspension design that requires a bit more thinking and fabrication. It’s much easier to hang a set of leaf springs. Not having any axlewrap has been the biggest advantage of my suspension selection, although it does ride very smooth. I’ve since increased the spring rates slightly. I started with 200 in-lb springs all around, but they did not support the weight and ride height I wanted to maintain without excessive coilover preload. I later switched to 200 over 275 coils up front and 200 over 250 coils in the rear. I run about 1 inch of preload.

Solid Steering Conversion

I had a quick question about the power steering mount you fabricated for the Garage project GPW. You said you used DOM boss tubing. Is that tubing a specialty item that you ordered online, or are you able to easily source it from local places? The easy to get to places near my house are not much more than hardware stores, and they don’t seem to have the right diameter or thickness. Any ideas where I can buy boss tubing? I like the idea of building my own mount. On the last conversion I did I used the common prefabbed mount. I had to cut and grind a ton to get around the front crossmember.

I’m running full-width Wagoneer axles. One thing I did that I haven’t seen before is that I cut and replaced all of the crossmembers, widening the frame to match the front axle spring pad widths. This kept me from having to narrow the axles or outboard the spring hangers.
@macdamike
Via Instagram @cappaworks

The DOM boss tubing isn’t anything special. It’s simply heavy-wall DOM tubing. I purchased inexpensive remnants from the local Industrial Metal Supply (industrialmetalsupply.com). The company keeps short sections of various diameters and wall thicknesses on hand. If you can’t find the tubing locally, you can buy it online from companies like Speedy Metals (speedymetals.com). The company sells the heavy-wall DOM tubing in 1-inch increments, or you can purchase pieces in 12-, 18-, 24-, 36-, 48-, and 60-inch lengths. You’ll need around 20-24 inches to fabricate the four boss-style mounts needed for a traditional Saginaw steering box. I used 7/8-inch 0.499-wall for three of the mounts and 1-inch 0.250-wall tube for one of the mounts. I needed a bit more diameter on the upper forward mount to make contact with the frame for welding. This tubing essentially has a 1/2-inch hole and the steering box mounting bolts are 7/16 inch. The bolts are a loose fit, so they don’t corrode and become stuck, and the box will not wobble around in the mounts. The larger bolt hole gives you some room for error and warpage when welding. You could very easily use thinner tubing with something like a 0.120-wall thickness, but you’ll need to fabricate additional brackets to attach the bosses to the frame. I wanted to keep it simple, even if it added a bit more weight.

You can purchase the premade cast steel steering box mount from Advanced Adapters (advanceadapters.com). It simplifies locating the steering box on the frame, but as you noted, it often causes clearance issues with other components. It’s a great bracket to start with, but it often needs to be modified or spaced for proper steering box fitment. The DOM boss mounting method spreads the load across the frame better than the cast bracket. If properly done, the DOM bosses are less likely to cause the frame to crack.

Widening the frame is one way to accommodate the wider spring perch mounts on the Wagoneer axles. It’s certainly a lot more work than outboarding the springs with mounts from companies such as Dave’s Customs Unlimited (davescustomsunlimited.com), M.O.R.E. (mountainoffroad.com), and Poison Spyder (poisonspyder.com). The advantage to going the route you did is that it will provide more room between the framerails. This will be a huge benefit when installing the exhaust system and steering shaft. With a standard-width frame, it’s usually an incredibly tight fit to keep the exhaust inboard for better ground clearance. You should be able to very easily run the exhaust inside the framerails. The wider frame also opens up transfer case options besides the smallish Spicer 18, Dana 20, and Dana 300. Pretty much everything that sits between the framerails will be much easier to locate and mount during your build.

Dos Jeeps

I have two questions. The first is about my ’17 two-door JK. I read an article about an AEV bracket-style lift. It uses brackets, spacers and all stock suspension parts. I like the idea of using stock suspension parts. My Jeep is a daily-driven commuter vehicle so ease of parts availability is key. What are the long-term thoughts on this type of lift?

My second question is about my ’76 CJ-7 with the T-18 transmission. I’ve heard bad things about this particular year T-18. I’m not positive of the year of mine because the Jeep was a conglomeration of parts when I bought it 25 years ago. It has the numbers 13-01-097-901 cast in behind the shifter. On the driver’s side below the shifter is a stamped, riveted tag with T-18-1B on it. Below that tag is a cast in WG DIV. What exactly do I have and what are the shortcomings and positives?
Vinny Eckes
Via facebook.com/JohnCappa4x4

When a JK is lifted with the stock-length control arms, the front axle moves rearward and the steering caster decreases. This causes a slightly rougher ride and poor handling. Most suspension lift companies offer longer lower control arms to correct the caster, but this does little to combat the slightly rougher ride caused by the control arms located at more of an angle. Most of the suspension lift kits from AEV (aev-conversions.com) are bracket lifts. Rather than replace the factory control arms with longer adjustable arms, the control arm mounting points are relocated lower on the frame with drop brackets and the factory control arms are retained. This design has several benefits. The drop brackets correct the caster, retain the factory ride, and reuse many of the OE suspension components. The only real disadvantage is the loss of ground clearance under the lower control arms and their mounts. If you don’t plan on extreme wheeling over rocks and logs, the bracket-style lift is a great way to go. So for a daily driver where ground clearance is less of a concern, this is probably one of the best lift kit options.

As for your CJ, the T-18 is the best manual transmission ever offered in the ’76-’86 CJ model. It’s a heavy-duty truck transmission. Of course, it’s not particularly fast shifting, but it’s incredibly durable, especially when put into a small Jeep. Versions of the T-18 transmission can be found in V-8 powered 1-ton trucks of the same era, so you know it’s overkill in a CJ. Most ’72-’75 CJ T-18 transmissions feature the slightly less desirable 4.02:1 ratio First gear and a front cast-iron adapter plate that mates to the AMC bellhousing. The ’76 model was a crossover year for the Jeep CJ T-18, so your Jeep could have the T-18 with either the 4.02:1 or the more desirable 6.32:1 First gear and no front adapter. All ’77-’79 Jeep CJs with the T-18 came with the wide-ratio version that features the 6.32:1 ratio First gear. No front adapter plate is present on these models. The 13-01-097-901 casting stamp on your T-18 transmission indicates that it originated in a ’76-’78 CJ. It could have the 4.02:1 or the 6.32:1 First gear. Ultimately, if your First gear is already plenty low for the type of off-roading you do, then there is no need make a change. There is absolutely nothing wrong with the T-18 with the 4.02:1 ratio First gear. It’s only undesirable if you need more low-range gearing off-road.

JK Sponge Brake

I bought a ’07 Jeep Wrangler Unlimited Rubicon with 80,000 miles on the odometer in 2014. I got it at/or below wholesale, according to a friend I called before buying, who owns a used auto business. It already had a FabFours Lifestyle front winch bumper with a Warn 9000-pound winch and 17x9 American Eagle wheels with 285/70R17 BFG KM2 tires. On the initial test drive to the shop to have it checked out, I noticed the brakes were spongy. Not knowing when it was last fully serviced, and knowing few people ever change the brake fluid, I had all the fluids changed, figuring (hoping) that new brake fluid and a good bleeding would solve the spongy pedal problem. Unfortunately, this was not the case. After three more bleeding attempts, it was close to right. I took it in for a final try while getting some other minor work done, but I eventually decided to leave it as it was, since it was so close to feeling right. The mechanics wanted to try to get it where we felt it should be, only to make it worse again.

I’ve had everything but the calipers replaced. The Jeep even has a new master cylinder. I later went with a brake upgrade featuring larger rotors and braided stainless steel lines. The lines were my idea. I’ve put more than 250,000 miles on motorcycles. Braided stainless steel lines are always the first thing I change on a bike to eliminate hose expansion. The Jeep still has a spongy brake pedal. In all of the columns I’ve read in Jp regarding this specific year and model JK Unlimited Rubicon, I’ve never seen any mention of this problem with your project vehicles. Most that I’ve talked to say it’s normal for this year Wrangler, even the local dealer.

Do you have any ideas on what the root of the problem may be? I never experienced any vehicle with this problem that couldn’t be fixed in all the years I worked as a mechanic, and I did an extensive amount of brake work.

I’ve wondered what difference there is in the parts between these early JK Unlimiteds and the ’12-’18 models, since the later versions do not appear to have this problem from what I have heard. Any insight or info that might give a solution would be appreciated. My brakes are not confidence inspiring in emergency braking situations.
Gary Grimes
Via email

Unfortunately, none of the ’07-’18 Jeep JK Wrangler models have noteworthy braking performance. This problem is exacerbated with the installation of heavier, larger-diameter tires and wheels. Contrary to your belief, your ’07 JK Unlimited Rubicon uses exactly the same master cylinder part number as every other JK model, all the way up through 2018. In fact, all of the JK models share the same brake calipers, rotors, and pads too.

Fortunately, there are a few companies with easy-to-install upgrade kits. Dynatrac (dynatrac.com) is one of them and offers its Pro-Grip brake system that bolts on to all ’07-’18 Jeep Wrangler JK models. It features larger uniquely vented rotors for the front (13.50-inch) and rear (14.25-inch) as well as performance front and rear brake pad linings. The increased rear braking power provides more balanced braking, reducing nose dive, and it improves the control of the vehicle in mild and hard braking conditions compared to upgrades that only address the front brakes. With the system installed, you’ll instantly notice a more inspiring brake pedal feel and that less brake pedal pressure is required to make stops. Stopping distances are said to improve by up to 30 percent compared to stock brakes on a Jeep JK outfitted with a 4-inch lift and 37-inch-tall tires. Perhaps the biggest advantage of the Dynatrac Pro-Grip brake system is that it does not require the hydraulic system to be cracked open. Messing with the hydraulics is something that often leads to other brake issues for most shade tree mechanics.

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