Toyota Prius Electric Power Steering Conversion
20 May 2022 - mdr
I drove around for almost a year with manual steering. While not… terrible… it is slightly less enjoyable especially when parking and tight spots.
The plan was always to have electric power steering, but I couldn’t figure out how to fit it all in. There’s an excellent post here that describes the details and wiring of the Prius electric steering module, check it out if you’d like to do the same.
I’ve seen also an old Falcon (that’s similar to the Rambler) conversion here.
The main issue is that I 1000% wanted to keep the column steering and bench seat. I felt like it would lose something important with buckets and a floor shifter. The problem is that you can’t lop off the steering column like others have if you have a column shifter.
What I ended up doing was shortening the entire column/shifter as much as I could. This gave me just enough room to add the Prius electric steering unit in the engine bay.
Cutting the column
The steering column started life as a 3-on-the-tree column. The shifter would move not only up and down, but forwards and backwards too in order to shift the 3 speed transmission. I welded the end together so that the shifter only moves up and down, similar to a typical automatic column.
The column is comprised of 3 main parts: The outer tube (the main column), the inner tube (for shifting), and the steering shaft that connects to the steering box/rack.
I needed to move the shifter back towards the firewall as far as possible. I ended up cutting 3” out of the outer column, then cutting the middle section out of the inner-tube shifter the same amount. I used a sleeve on the shifter tube to get the position on the column where I wanted it, then welded it all together.
Modifying the shafts. Each shaft is welded and contains multiple 3/16” pins for strength. The steering shaft has been cut down, and added an adapter that mates up to the Toyota steering shaft. On the other end, I welded an adapter to the toyota universal joint that converts it to a 3/4” DD shaft. This allows me to keep the Toyota ujoint while being able to adapt to the ujoint on the steering rack.
Mounting the Prius steering motor
I used a 2” steel exhaust pipe that slid nicely into the Rambler steering column to mount the Prius motor. The exhaust slides up about 6” into the Rambler column, and is secured with screws. The exhaust tube is then bolted to the Prius motor.
Here is a shot of the Prius motor in the engine bay. It extends about 10” past the steering column and is pretty snug against… pretty much everything. There’s another mount on this side of the Prius motor that extends down to the cross member and is bolted there for rigidity. I’m going to drive around a bit to make sure everything is hunky dory before pulling the mount off to grind/paint it.
Cleaning up
I ended up denting the column so I decided to throw some bondo and paint on it while it was out. Comically, I dinged it in a different place mounting it… such is life.
Steering and horn button
I swapped out the steering wheel because even though I love the original, it’s just too damn big. I’m a pretty small guy and I still had to squirrel around it. This one is an inch smaller and a much better feel.
I wanted to keep it looking… Rambler-ish so I purchased a Rambler American horn button off of Ebay. The horn mount of course didn’t mate up to the button, so I had to adapt it a bit. I took the horn button mount apart, and rivoted the base to the steering wheel. I then purchased some nylon bolts and used them to space the upper mount to where it would be a good fit for the Rambler button. I soldered a wire to the upper mount, and it worked pretty well. The horn button isn’t as secure as I’d like, but you still have to yank on it pretty good before it would come off.
Here’s the wheel and horn all mounted up, ready for the road test.
Conclusion
There’s a short delay in the Prius motor when starting up, so if I start it and quickly zoom off, I have manual steering for 30-45 seconds. I almost always wait that long before leaving, so it’s really not an issue.
The Prius steering, I gotta say, is really nice compared to the manual steering. It makes driving around and parking much more enjoyable. I pickedup the Prius motor, ecu, and steering shafts for right around $250 on Ebay. I’d say for the money it was a great improvement, and I don’t have all the hoses and complications of hydraulic power steering.