Steering Gear Pinion Shaft Lock Nut Design

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.

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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.

 

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

 

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.