ZJ Power steering box for better on-road manners?

[seanyb505]

I read over in the junkyard thread that someone said some ZJ years steering boxes were direct bolt-in and provided better feel and handling. I have never read anything in the last four years about this, has anyone heard about this or tried it? It seems like most upgrades have been known since before time began and have been covered enough times to annoy the long time members.

 

[ehall]

The only factory difference I have been able to find for ZJ versus XJ is a slightly shorter lock-to-lock turning arc, meaning slightly faster gearing. But since the XJ and ZJ boxes use progressive gears you're only going to notice it in the parking lot when you're doing a full turn, and they will be indistinguishable in a straight line. Also worth noting that many/most of the aftermarket boxes are the exact same part for XJ and ZJ.

To me it seems unlikely to produce a major benefit, but simply using a newer box with less miles in conjunction with slightly faster turning will probably make it feel better. If your box is broken already sure get a ZJ box. Otherwise spend the coin on something else

 

[seanyb505]

My steering is getting super sloppy so i went down there and made sure everything was torqued properly...still sloppy so Im looking at my options.

 

[ehall]

Here are your options

YJ, TJ, and Durango w/ plow have fixed-rate gearing that is more predictable (easier to visualize tires relative to steering wheel) but has longer turning arc. XJ, ZJ, and Durango w/out plow have progressive-rate gearing that is faster at the edges than the center, which produces shorter arc that makes three-point turns simple, but makes it less precise.

XJ, ZJ, YJ and TJ all have the same piston bore and will work the same with your pump, or work equally better with a bigger pump. Durango boxes have a larger piston and therefore require more fluid pressure to produce the same head pressure, so you need a bigger pump to realize the potential of the bigger piston (IE, its actually harder to push the jeep off a rock with the stock pump since the head pressure is distributed across a larger surface area). Highway driving probably won't notice and many people don't complain at all.

The YJ box has four mounting holes, all of the others have three.

There are also some aftermarket providers like PSC that will probably make a box to spec for you

 

[seanyb505]

So no real upgrades to make it tighter at speed? It doesnt see off-road at all, so things like larger tires and rocks dont really play into my needs

 

[ehall]

The ZJ and Durango boxes both have faster gearing which will be noticeable just not a tremendous difference in straight line. You'll feel it turning off side streets though, the car will be noticeably more responsive. If you get a newer box the slop will also be gone and you'll notice that too.

98 XJ 3-3/8 turns NSP 88278133

98 ZJ 3-1/16 turns NSP 88278121

98 Durange w/out plow 2-15/16 turns NSP 88278139

The Durango box is almost 1/2 full turn shorter travel, so the wheels are going to be traveling through their arc much faster. If you will never leave the street then your stock pump will probably put out enough pressure to turn the wheels without any drag (vehicle is much lighter, after all). If you are worried about it the ZJ box will give you a slight improvement but most of the gains will be from newer box

 

[hubs97xj]

Not sure if it's relevant, but something I noticed when I replaced mine- NSP 88278133 is listed only for 96-98 Jeeps- no other applications when I checked. For prior and later XJs, NAPA lists NSP 88278076. They're physically identical to the Jeep-only box, are also on a variety of GM platforms, and the turns-to-lock varies between 3-1/16th and 3-3/8. They're also 200 bucks cheaper. I never got a specific answer as to why, but they're all 3 CarDone rebuilts, according to my local NAPA. I didn't feel like paying $400 for a stock box for mine, so I got one for an 01 instead.

I'm not sure how many ttl mine is, but it cured my wandering and sloppy steering.

 

[88 Wagonman]

I swapped to the ZJ box and I like it. I wouldn't recommend it for offroading, but for street it works well. As stated, it will not feel different in a straight line, but short and quick turns are faster. Also, it is a bit "stiffer" when turning at low speeds which I like, but my wife does not, just a matter of preference I guess.

 

[DieselSJ]

The ZJ and Durango boxes both have faster gearing which will be noticeable just not a tremendous difference in straight line. You'll feel it turning off side streets though, the car will be noticeably more responsive. If you get a newer box the slop will also be gone and you'll notice that too.



The Durango box is almost 1/2 full turn shorter travel, so the wheels are going to be traveling through their arc much faster. If you will never leave the street then your stock pump will probably put out enough pressure to turn the wheels without any drag (vehicle is much lighter, after all). If you are worried about it the ZJ box will give you a slight improvement but most of the gains will be from newer box

From reading other posts on here, it sounds like the Durango box has some internal stops that limit the movement. So the 1/2 turn less would translate into not turning as sharp. In fact, someone just posted an article on how to remove those stops so that the box has the correct travel.

 

[ehall]

I know the gear box for the Durango w/ plow has the same 3-3/8 radius as the YJ and TJ boxes, but I don't know if they are the same because of internal or external limits. I find it hard to believe that the street gear box would have stricter turning limits than the plow gear box.