Just replaced a steering rack so decided to crack open the failing one and see what is going on. The car would not self center after left turn and the problem is likely a loosened pinion shaft lock nut. Here was the original thread. Chapman's post #2 provided the necessary understanding. Looking to buy a Gen1 Prius with Steering, oil consumption, and P0420 code | PriusChat Here is the picture of the 22mm adjustment nut and 19mm lock nut (both are loosened so not riding lower like they should be on the shaft) Here is the "nutty" design, adjustment nut can't be all that tight as it needs to give the gear/bearing assembly room to turn. Even though the lock nut is locked tight against the adjustment nut, that "lock" doesn't prevent both nut from turning and loosening as 1 unit. The lock nut basically has to grab onto the greased threaded pinion shaft ends by itself. From Toyota'srecall directions, sounds like lock nut has some sacrificial metal which deforms and grabs on as it is tightened. Now imagine if the person doing to recall tightened it incorrectly and had to redo. Whatever locking mechanism is weakened. Its a one time use and the installer better get it right. A friend suggest locktite would probably work as well as a sacrificial nut grabbing onto these greased threads. Anyhow, no vehicle to try our theory on now since the original car has a good working rack in it now. Also tightened the adjustment on a CRV rack/pinion recently. The adjustment nut is also the end cap, locking mechanism is really a bolt that grabs onto something internal (presumably the pinion shaft) and against the adjustment nut/endcap to provide a much more secure locking mechanism.
Well, thats the joke from a friend. Just noting the locking mechanism isn't very robust. Curious what is the difference between original factory assembly and the recall rework. Probably either tighter torque or better locking nut to get a better bite on the threaded pinion shaft.
Much more highly deformed locking nut, so much so that it munches the pinion shaft as it is tightened. You have one chance to get it right; if you say oops, you recover by replacing the entire rack. (Another PC member recently reported getting a new rack that way ... took it in for the nut recall, drove home with a brand new rack.) That and a mystery green threadlocking agent preapplied on the nuts (none of the normal colors of Loctite), and a recall procedure warning six ways from Sunday to have the pinion threads absolutely clean of grease before the nuts go on. (Threads cleaned with brake cleaner, but without contaminating the bearing or the gear grease, talk about walking a tightrope.) -Chap
Wow interesting. Make sense it has to munch down on the pinion shaft. As you said, 1 shot and quite a tight rope given the cleanliness required for thread locking compound. I'll take a closer look at my rack. Didn't any residual evidence of green thread locker but maybe covered under the grease. I was noodling if there was a simple way to set a key to prevent rotation at arbitrary angles. Say a castle nut + cotter pin design like the outer tie rods. But no way to drill that cotter pin through hole in the pinion shaft without pulling it out. Maybe a tack or JB wield? since the pinion only allows 1x attempt for lock nut install anyways. Anyhow... just curious. Been "fixing parts" on the last couple of car repairs (door lock actuator motors, weak/broken solder on early 2000 lead free solder transition, rebuilding bushing for dogbone style mounts, even resizing the complex PCV hoses on turbo cars) so was wonder how I could repair this rack. Probably a lost cause
Since I didn't have the symptom, I did not have the recall done. I feel better about skipping this one. Bob Wilson
Howard, thanks for the thread and the photo. Thank you Chapman for the more detailed explanation of what the steering recall takes. This makes me even more grateful Toyota took care of this repair for free on my 2001. I've been working on cars for over 20 years, but I can appreciate a second chance at tightening a nut correctly. Anyone have any reliability data on the new OE or aftermarket rebuilt 1st gen racks?
Awesome pic, Howardc64. Did you do the steering rack replacement yourself, or have Toyota do it? I'm guessing that since you have the failed part, you did the job...
Following up on an old thread. Just encountered green locktite on a power wheelchair motor to gear box assembly. Lots of people break the bolt on these on removal and reassembly as its super tight. Found out green locktite require heat for removal. Probably why Toyota used it on this design. Wonder how much sacrificial nut and green locktite each contributes on holding the lock.
