PSC Motorsports 621MR Steering Box

[BigDaveZJ]

I just got off the phone with Karl over at PSC Motorsports and I've got one of their 621MR Steering Boxes on the way for my ZJ.

For those unfamiliar with the 621MR from PSC Motorsports, it is a 4-bolt box as opposed to the stock 3 bolt box. What this means is that you have an additional mounting point so that it is harder to break an ear off of the box. MANY people, myself included, have replaced steering boxes and had bad days on the trail because of this.

Here are the specs on the 621MR from PSC Motorsports:

13-16:1 variable ratio
3/4"x30 input shaft
Large 3.125" piston diameter
Metric o-ring type ports
Modified for hydro assist

This box is capable of running a hydro assist setup, as it has already been tapped for the hydraulic lines. However, I will not be taking advantage of this quite yet as I doubt my Dana 30 is up for hydro assist! But once the 30 is out, and a 60 goes in, I will be taking FULL advantage of what this box can do!

While I'm in there adding the new steering box, I will also be adding a steering box brace. I have not decided yet if I will go with a pre-fab one, or fabricate one myself, but one way or another I will have a steering brace.




Update 3/26/06

Finally had some time today to tear out the old box and get started on getting the 621MR in. It was pretty easy getting the old one out. The 621MR is in place right now, but not completely mounted.

I'm working on getting the 4th bolt mounting figured out now. I found what I think is a steel sleeve that goes inside a shock bushing and found it to be about the right length. Since it was originally a flat piece and then rolled to make the sleeve, similar to HREW, but not welded, I decided to weld it to give it some strength. After some careful grinding I got it down to size to fit in between the steering box and the unibody. Tuesday I'm going to come up with a way to figure out the best way to drill the 4th hole and finish getting the box mounted. Then I'm going to clear the pump of the old power steering fluid and get all of the lines hooked up. If I have time I'm going to get some steel to start work on the steering brace. I'll post up some details on how I'm going to fab up the steering brace once I get it all figured out myself.

I should be able to at least take the ZJ for a spin with the new box on Tuesday, so I'll post up how things go. I'll have some pics up as well of the stock box vs the 621MR as well as the spacer I made too.

UPDATE Sunday April 2nd

The box is in! I still haven't made the steering box brace yet, but will be doing that possibly next weekend.

Here's some pics of everything.

The reason this whole thing started. Notice the crack starting on the mounting ear? It's in the one spot not covered in PS fluid.


Here's some comparison pics of the stock box vs the PSC 621MR. Outside of the 4th mounting hole, the bling billet caps, and the ports for hydro assist, they're about identical on the outside.






Here's what I used for the spacer for the 4th bolt. I found a sleeve for a shock bushing laying around the garage and welded it up to make it basically HREW (but not really).


Next I tackled how to figure out where to drill for my 4th hole. I took some very crude measurements off the PSC box seen in this picture:


And then marked off on the Jeep where the 4th hole should be based on the measurements from my piece of cardboard


Once I had the hole drilled, I slipped the bolt through the spacer and tightened up the steering box and sprayed a little primer in there to cover up any bare metal






This was definitely one of the easiest modifications I've done so far. Without the proper tools though (pitman arm puller, welder, drills, cardboard and sharpies) I can imagine it would be a much more daunting task.

I took it to work the next day to get a feel for the way the Jeep drove with the new box. I had heard a couple people say that it was almost too easy to turn the wheel with the PSC 621MR. I didn't find this to be the case at all. Driving at highway speeds there was still a good amount of road feel in the wheel, but maneuvering through parking lots and such was MUCH easier with the increased power of the PSC 621MR. In situations where it used to feel like I had no power steering at all, I'm now able to put one finger on the wheel and can turn it just fine.

I'll post up more as soon as I get the Jeep offroad again!

ROAD TEST UPDATE

Spent some time driving the ZJ on the road over the last couple weeks. About 200 miles of city and highway driving. So far I am LOVING this box! I can't wait to get it on the trail and really take full advantage of it. Tonight we were playing Shriner's Circus moving rigs around and I got in Pam's with the stock box and 245's right after driving mine with 33x12.50's and the PSC box, and there was a very significant difference in ease of turning. So far this has certainly been a worthy upgrade. I also built a steering box brace today that I'll post up some pics of soon. We'll be making another one for Pam's ZJ, and another for Tom's (Z) this weekend, so we'll have some build pics of those.


MOAB UPDATE

So now that I've some time with this box on the trail I can give a little more feedback about it. It certainly is easier to turn than the stock box. It's not a HUGE difference, but enough to where my arms and shoulders weren't sore after a day of wheeling. And the added comfort of knowing there's a 4 bolt holding it in (and the brace that I made for it) really put me at ease.

I may add a power steering fluid cooler at some point too. After a long day on the trail the box became harder to turn for a little bit. Then once the fluid cooled down, it was back to normal.

Now I just need to set up some hydro assist!!!!


LONG TERM UPDATE

Had the box in for a little less than 2 years now. There is significant movement of the sector shaft. Ease of turning is still about the same, and the 4th bolt with the brace definitely has eased my concerns of the box snapping off the mounts, but now my concern lies with the sector shaft. The box hasn't seen a TON of wheeling as my Jeep was down most of this summer, and we didn't get out as much as we wanted to in 06. I really had hoped the box wouldn't be showing such significant signs of wear this early. It's definitely an upgrade as far as ease of steering and additional mounting strength, but several other people I've talked to have developed slack in the sector shaft as well. Looks like I'll just slap a Waggy box in there when this one goes out and just drill and tap it for hydro assist when the time comes.


FINAL UPDATE
I now have a a very heavy, and rather expensive paperweight. The PSC box is out, Waggy box is in, and the dead spot seems to be gone. I'll keep the PSC box with me as a trail spare, but that's about the only good use for it at this point. Obviously YMMV, but my experience with this box has not been the greatest.

[Cue-Ball]

Those things are pretty cool, AW put one on Chase's awhile back and it turned out AWESOME.

[nate]

Yup I run one on mine, have had it for about a year.

Ordered one for my truck a few days ago as well. 841MX

[BigDaveZJ]

The guy in the brown truck dropped off a really heavy box yesterday!

Gonna be putting this thing in soon, since the ZJ is kinda DOA without it. Lots of pics and thoughts on the box to come!

[Cue-Ball]

Awesome.

[nate]

I put the 841MX in my truck Thursday. I haven't driven the truck since it needs a few other parts night, but I have power steering and brakes now, so that's a plus. Replaced the pump, hydroboost, few lines and then the box. Of course it ended up being the box that was giving me problems.

Decent customer service from PSC, but it wasn't spectacular like the first time when I ordered my box from Tom. When it was just him and his wife running the place.
The first box then sent for my truck got shipped an old address in Alaska. I'm not sure who messed up, but I gave them my Idaho address. They ended up having to build another box and sent it to the proper address.


The workmanship was better IMO though. So whoever is building the boxes is taking pride in their work.


You know what's messed up? The Dodge box is bascially the same as the stock ZJ box. Only 3 1/2" bolts hold it on. 7000lb truck empty.

[BigDaveZJ]

Updated the original post.

[nate]

Dave, what I did to mount that 4th hole is I guesstimated where I needed to make my hole, took a hole saw and cut though the sheetmetal. Slide a piece of tubing in there, welded it and done... Bascially that's how the factory mounts are.

[Z]

Dave, what I did to mount that 4th hole is I guesstimated where I needed to make my hole, took a hole saw and cut though the sheetmetal. Slide a piece of tubing in there, welded it and done... Bascially that's how the factory mounts are.

Now THAT's a smart way of doing it. Hmmm, I think I need to retrofit that to my PSC.

[BigDaveZJ]

nate, that's basically what I'll be doing. The factory holes are a little bigger than the bolts already, bolts are 3/8" and the holes are 1/2" from what I remember, so I was just going to drill it with a 1/2" and hope I get it right!

[nate]

I used I think a 1 1/4" hole saw, 1" OD tube I believe.

[BigDaveZJ]

Finished up getting the box in today. Outside of missing my drill mark by about 3/16" of an inch it went VERY smoothly. I took the ZJ out for a spin around the neighborhood once I get the steering fluid topped off and holy crap does it steer easy now! Definitely digging the new box in a major way. I've got a bunch of pics too of how I did things and will get them posted up here soon along with a full writeup on the installation and a review of the product. I'll also be building a steering box brace and will post up a writeup on that too.

[BigDaveZJ]

Updated to include pics and a review of the test drive.

[zjrick]

Did the same on mine late last year.

Sooo much better than the stock even without the hydro assist connected. Eventally I also hooked up the hydro assist and the PSC pump with remote reserv. Best Mod I've done.

Point and Shoot steering!

[chadjans]

You might want to shim up the gap between your spacer and the top of the frame rail and weld it all in. Mine only took an 1/8" shim to fill the gap between the spacer and the frame rail.

Chad

[JHKolb]

Anyone know how similiar (or not) the ZJ box is to the WJ? I know mine is going and don't really want to put an OEM box in.

[canadian_driver]

how does the hydro assist steering work? do you just need a resvior and cylinder or a pump aswell?

[nate]

Just a cylinder and lines to the box AFAIK.

[BigDaveZJ]

bump for the moab update

[OHIOZJ]

first off nice write up. i plan on ordering mine here soon.

my question is do you think temporarily that you could get away with not installing the 4th bolt? if i get it i am going to have to put it in and then drive it somewhere to get the sleeve welded in. im sure it will be ok since the stock box only uses the 3 bolts. i know the 4th makes it much stronger. i just dont want it to ruin anything.....

[nate]

Sure, the 4th bolt is just an extra.

[canadian_driver]

i just stuck mine in today, and i love it, its a great choice, i didnt put the 4th bolt in yet, but i plan too, however it doesnt seem to be loose or anything, it is a big diffrence from stock

[Sandy R]

Curious if anybody has any updates on their experience? Mine has now been in for about 10 months but for only about 3,000 miles. I have a lot of play that has developed. I ordered a steering brace from Kevin but I don't believe that will prevent or cure the slop IN the box. While I enjoy the power I'm not finding this an extreme unit. How about you guys? Am I missing something?

[BigDaveZJ]

Sandy,
I have a lot of slop in mine too, but in looking at it I believe it's slop coming from the steering column itself. Could be wrong though.

[Sandy R]

Sandy,
I have a lot of slop in mine too, but in looking at it I believe it's slop coming from the steering column itself. Could be wrong though.

Hmm, OK, I hadn't considered that as the cause. Thanks for the feedback.