TJ Tech II

By: Tim Mulverhill

Thanks to everyone who said they enjoyed the first part. Like I said before, there was plenty left out and Part II covers some of it.

Terraflex 'Belly Up' Skidplate Review:

TJ owners choosing to stick with the NP231 transfer case have an off-the-shelf alternative to the factory crossmember/skidplate. The Terraflex kit provides a tremendous amount of ground clearance over the stock setup, though a number of assemblies require modification.

Needed mods include the NP231 tailshaft conversion, a longer rear driveshaft, a 1" body lift, and the use of either 1" motor mounts or the provided spacers. Adjustable rear control arms are needed for TJ's fitted with a 3-4" lift to enable the rear pinion to be rotated for correct driveline angle. That is a lot of work and expense. The tailshaft conversion is a good idea on any NP231, eliminating several weak links and allowing for a longer drive shaft and improved driveline angle. The heavy-duty rear driveshaft is also extra, and a body lift will run under a hundred bucks.

The body lift is a snap to install, taking less than two hours for one person to complete. With the body lift, the radiator spacer won't need to be used since the motor mount lift will keep everything lined up. I replaced the factory motor mounts outright with a set from M.O.R.E. The shift linkage extension won't be needed either since the driveline is also moving up a few inches. Only the spacer pucks and new hardware need to be used.

The new skidplate is smooth on the outside to allow the Jeep to slide over rocks and other obstacles. The factory plate has folds and ridges to catch and hang up. The factory plate is also made of milder steel, and will need to be replaced after a few years on the rocks. Mine was so deformed that it couldn't be replaced after 3 years of trails.

Other parts that needed help were the tranny mount and the skidplate bolts. The tranny mount rubber was squashed and torn with a broken bolt thrown in. Some of the bolts holding the whole driveline up had stripped nutserts. These had to be drilled completely through the frame and replaced with longer bolts. Make sure you use quality hardware grade 5 or higher - it costs more at first but will pay off in the end.

My transfer case was re-worked before re-installing it - the tailshaft housing was changed and the Terra Low gears installed at the same time. It was topped off with a Tom Woods shaft and the Terra plate bolted up. The rear pinion had to be rotated up to help with the driveline angle and 4" lift, facilitated by the adjustable rear control arms. My Tomken engine skidplate bolted right up after drilling two mounting holes in the new plate.

Going from the factory skidplate with a 1.5" spacer to the new Terra plate was a huge change. I gained almost 4 inches of clearance, which is like going from 33" tires to 35's. The plate is not flat on the frame, and some custom fabricators have managed to install flat plates. If you have the resources and experience to make one of these plates the results will be even more dramatic, otherwise the Terra plate is a good option.

On the trail the difference is amazing. Climbing ledges is much easier without hanging up on the skidplate. There is a lot of room to work with now. If I could tuck the damn gas tank up into the frame as well I'd be even happier since that still hangs up on steep descents while dropping off of an obstacle.

Downsides: The famous 'TJ Steer' is very noticeable now. Any rapid changes in throttle application will 'steer' the vehicle to one side or the other, depending on acceleration or deceleration. This won't be as noticeable on TJ's with lower or no lift at all. Center of gravity is also a few inches higher than before and drivers need to keep this in mind, though it would still be lower than adding another 2" of spring lift.

A TJ with a 1-2" coil spacer lift and the 1" body lift could conceivably run 32-33" tires with this setup and have relatively minor changes in driveline symptoms. Adjustable control arms might not be needed. Clearance would be the equivalent of putting 35" tires on.

For those with the cash and haven't installed their lift yet, Rubicon Express makes a long-arm suspension which replaces the skidplate with a similar unit. The long control arms help eliminate the 'TJ steer' and smooth out the ride. If you are starting from scratch it isn't that much more expensive than the traditional method and probably the way I'd have gone if I didn't already have a lift.

TJ Problems:

TJ's have had some manufacturing problems you should be aware of; I'll try to mention some of the more common ones here:

Cracked Exhaust Manifold Welds - I had mine replaced under warranty. It is a common problem that the dealers are well aware of. This part is required to be repaired under warranty for 7 years from date of manufacture, purchased new or used. This is under Federal emissions warranty regs, Jeep cannot dispute this. Some dealers may try to weasel out on this but they are required to cover this part. Symptoms are a slightly louder exhaust note. Weld cracks are visible on inspection. If you own a 2000 TJ, the manifold is covered until 2007 - it is even written in the owner's manual.

Squeaky Front Driveshaft - Eventually the non-serviceable CV joint in the front driveshaft loses lubrication. It makes an intermittent squeak when the vehicle is rolling. Since the TJ driveshaft is always turning it will squeak so long as a front wheel is turning. For the longest time I thought I was losing a front wheel bearing. Until I replaced the front driveshaft with serviceable joints I'd spray the CV joint with silicone grease. It would stop the squeak until it rained or I drove through water. Now I keep it as a spare.

There are other issues owners have faced, these two happened to me. I also had the 'grind into reverse' AX15 problems Jim Lambert had. Jeep told me they 'could not duplicate'. I guess they didn't try reverse. They didn't want to try much after seeing the 33" tires. Revenge was mine when leaving the dealership and I heard one guy say to his salesman, "I want one like that". Ha!

Things to Add to a TJ Spare Parts List:

Control Arm(s) - Not much of a trail cure for one of these. Some rear and front arms look extremely similar, enough so that I think a spare could pull double duty for front or rear - especially the adjustable types. Check around, there are plenty left after lift kits are installed. You only need half of the set for spares.

Tie Rod - These tend to wad up easily. The factory ones are very light weight. I bent mine, replaced it with a HD Rubicon Express unit, and keep the straightened factory rod taped to my rollbar as a spare. All you need to do is try turning the wheel with power steering with a tire wedged against something solid. The tie rod will be the likely loser. If you do carry a spare rod make sure you have the tools to remove the broken one.

Torx Bits - Half of the bolts on a TJ are Torx. If you don't replace them make sure you have the bits to do repairs. The CJ and the YJ guys aren't going to have them to help you out. I've found that many of these bolts to be of poor quality and strip easily, especially those holding body parts together - windshield frame, tailgate hinges, etc. Get a good set and be careful, or replace some of them with regular hardware.

Deep Water:

Some of the trails we run have sections with water crossings - Florida Road, Nor-Hatch, Hedgehog, etc. TJ's are better prepped for this than some other models. The axles, tranny, and transfer case all have extended vent lines with breather valves. These run up to the top of the radiator in front or to the gas tank filler in back. I discovered this when I went to install extended lines to find they were already there. Sometimes the valve will clog causing a component to puke fluids from excessive pressure buildup - this happened to my transfer case.

TJ's come with drain plugs in front of the seats, under the carpet. If you keep the carpet on a daily driver it can (and should) be removed for trail rides easily - it snaps in and out and should take five minutes either way.

If you do take on water, pull the plugs and let it drain. The depressions in the floorpan behind the seats trap water and are a good candidate for a hole-saw and a set of drain plugs. Extras may be needed in front if you use the M.O.R.E. front cage kit, which mount through the existing plug holes.

Using one of the aftermarket tub liners eliminates the need for carpeting and waterproofs the interior. Jim Lambert Rhino-Lined his TJ and recommends removing the rollbar and any hardware prior to application.

TJ's use a fan clutch, which allows the fan to stop turning when faced with resistance from deep water. Earlier models had to have the fan removed or disconnected to prevent having the radiator sucked into the fan. The air intake on TJ's is higher than YJ's and less prone to aspirating water. They can be made even higher by installing a K&N canister air filter on a cut-down intake tube on top of the engine. This is one of the simplest mods to make and eliminates the airbox.

The one item that really needs to stay above water is the computer. It is mounted under the dash on the tranny well hump in front of the console. While it is probably marginally water resistant, submerging this item will probably produce negative results.

This is on top of all of the other precautions to take in deep water, which have been covered in other articles.

Hope some of this helps, and I'll see everyone at the BBQ.

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