Removing 4WS on my '92 R/T TT
Disclaimer: Before continuing, I suggest you study the "4-Wheel Steering (4WS) System" entry in the Technical Information Manual published by Jeff Lucius. Removal is not easy and can result in very serious safety risks if not done properly. I disclaim all liability for direct, indirect, incidental, or consequential damages that may result from any use of the information or instructions on this web page. Please make an informed and educated decision before proceeding.
Note that all twin turbo 3S cars exported to North America have 4WS except the 1995 & 1996 R/T TTs. While the 3S 4WS is state of the art in cornering technology, I sometimes found it uncomforting when cornering hard in my '92 R/T TT and passing through the 31 mph (50 km/h) activation speed. Because I own a '96 R/T TT, I knew what the car would feel like after removing the 4WS and I liked it. So my decision to remove it was based on the fact that I didn't care for the 4WS handling characteristics, wanted to lose a little weight, eliminate the "power robbing" rear steering pump, and reduce the cars complexity (i.e. reduce the number of gimmicks, I mean gadgets).
To get started, here is a pic of the components that make-up the 4WS system. As you can see many parts are removed entirely and some are replaced with 2WS equivalents. There are really two ways to go about removing the 4WS system, find a 2WS donor car ('95 or '96 R/T TT) or modify what you have to make it work (I did the later since donor cars are hard to come by and can get expensive).
While a donor car would certainly make the job easier, it isn't necessary. The most valuable part you could get from a donor car would be the rear crossmember and assist links (this will become more clear as you read on). You could also make use of the power steering reservoir and the front steering rack but modifying your 4WS front rack would likely be easier. If you have a six speed car, you could also swap the rear differential (instead of plugging where the rear pump resides).
If you don't go the donor car route, the power steering reservoir could be had from any NA 3S (easy to find in salvage yards) and you can keep your 4WS front steering rack and just cap the two lines leading to the 4WS control valve (more on this below).
Here are a couple pics of the heart of our 4WS system removed from my '92. First pic shows it still installed on the rear cross member (upper and lower arms still attached) and the second pic shows it removed entirely.
Now more detailed information.
Front Steering Rack
I initially intended on putting a steering rack from a '92 NA 3S into my car but quickly realized that wouldn't be the best approach (all things considered). The 4WS front rack has two additional lines running to the 4WS control valve. These two lines do nothing more than tell the control valve whether the left or right pressure chambers of the front rack are being pressurized. These lines do not flow oil, just communicate the presence or absence of pressure. Capping them off at the front rack does not change function of the front steering rack. Also, our 4WS racks have a quicker ratio of 2.52 turns lock to lock vs 2.80 for the NA 3S cars. So, for the following three reasons, I'd suggest keeping the 4WS front rack and just plug the left and right pressure chamber lines as illustrated.
Reasons to keep the 4WS front rack (vs NA 2WS front rack):
1) Quicker ratio steering box - While both 4WS and 2WS racks turn the wheels the same amount, the 4WS rack has a quicker ratio; 2.52 vs 2.80 revolutions lock to lock (the quicker ratio 4WS rack is desirable in a sports car).
2) Save money - You'll spend at least a couple hundred dollars to purchase a used or rebuilt front rack from a 2WS car (NA car or '95 & '96 R/T TT).
3) Easier - Much easier to plug two lines than swap racks (unfortunately I realized this after removing the 4WS rack from my car).
Power Steering Oil Pump (engine mounted)
Easy, keep what you have, it is the same on 2WS cars.
Power Steering Reservoir
Replace with 2WS unit, it will have two less lines to contend with, the reservoir is physically smaller, and you lose the filter and low oil level sensor. The 2WS reservoir will also help maximize your weight savings and can be purchased cheaply from a salvage yard.
Items to Ditch / Delete / Remove
As the first illustration indicates above, you can get rid of the hydraulic lines running to and from the rear rack and control valve, the power cylinder (rear rack), the control valve itself, and the rear wheel steering oil pump. This is where the weight savings comes from. You can also grind off the mounting brackets no longer needed on the rear cross member (some shown below).
New Items Required to Complete the Job
1) Rear Differential Plug (custom fabrication)
2a) Assist Links (not carried in US, must purchase from Japan*)
2b) Nuts & Washers (any Mitsu dealer, ask for 4 nuts, MF430123 and 4 washers MF450407)
3) Assist Link Brackets welded to the cross member to mount the assist links (custom fabrication**)
4) Front Rack Plugs to plug the two lines running to the control valve (custom fabrication***)
* I'm sure there are other sources, but I used Costa Mesa Mitsubishi in California since they routinely import items not available in the US. Ask for Mitsubishi PN MB809115. Or you could also try finding a '95 or '96 R/T TT donor car.
** Custom fabrication unless you found a '95 or '96 R/T TT donor car.
*** Again, if you have a '95 or '96 R/T TT donor car, you could swap the whole rack and not need the plugs. But I bet most would rather make the plugs and modify their 4WS front rack.
The following pics give you a good idea of the custom work required. The first pic doesn't show the O-rings on the rear diff plug or the front rack plugs. On the rear diff plug, I simply re-used the oil pump O-ring.
The last graphic simply shows the installation of the assist links and recommended torque.
how much weight does this save? How about 29.5
lbs, much less than most
expect. But you now also free up the horsepower the old rear steer pump
consumed. I also like how my Stealth handles without it and now there are
fewer gadgets to fail on my car.
since August 7th, 2002
Last Updated: 01/02/03 07:25 PM