Rack befuddlement - engineers in the house?

[brp914]

The purpose of pinion shims to set rack end play. But how does it work? Does the depth of the rack grooves vary top to bottom? Is the pinion axis slightly canted towards the rack?

What is the end state? Does the pressure block pushing on the rack cause wear in the rack bushings, then forcing the rack into the pinion causing it to bind?

I'm surprised our host or that pachyderm place don't sell rebuild kits. I got the bearings, but that doesn't fix what's wrong.

[tperazzo]

I just went through this last week. All documented in the video below. I did discuss the purpose of the shims toward the end. I hope this helps.
https://youtu.be/kjg82Gv_-Go

Keep in mind that the rack bar flexes into the pinion.

There should be no end play in the pinion shaft.

Put it together without the rack bar to check for binding on the pinion shaft stack.

If you watch the video, you will see where I ran into trouble.

[brp914]

Thanks, I'll check that out.

[jjeffries]

Mr. Perazzo's technique is very sensible and how I should have done mine when I serviced it around 2015, as part of a while-in-there refresh on a new-to-me 82 SC acquired as a non-runner; meaning, I didn't have before/after experience to know what the steering SHOULD feel like. The step I didn't consider at the time was to "put it together without the rack bar". I replaced all the bearings and tried a little remedial refacing on the somewhat grooved puck**, then put it all together and in the car.

When I'd reassembled it, using all the shims that were there originally, it felt a stiff but I figured I'd been careful, done the job right and that it would break in. It didn't, and the guy who aligned the car refused to test drive it due to the "sticky rack".

I therefore re-removed the rack, and tried a couple of different of variations with less shims, but it still wasn't right (although, note that I make no mention of a spring scale here, because I didn't obtain one to test preload). Bottom line: with no shims, the rack and I felt happy. Ideally, I would have measured the replacement bearings' external dimensions to understand what role they'd played in this change, but I wasn't about to press them out and risk harming the rack casting. I like the way it feels now and a couple of more experienced 911 guys say it's good.

** re the puck: at the time, there was mention of Chris Flavell at Fenn Lane Motorsport making replacement pucks out of Delrin or something similar; he was supposed to offer them thru Wayne/Pelican. I sent an email asking for details/ offering to place an early order, but no response. I'm not telling this to dump on him (he recently took his own life) but to wonder if those replacement pucks were any good? Some of those in our cars can be quite acutely worn/damaged.

In a nutshell: Do what Tom is suggesting; my story is meant to show that not checking the pinion shaft stack can cause issues. Best of luck, John

[brp914]

JJ, was your rack stiff before you took it apart?

[tperazzo]

If your puck is worn then it's highly likely that more shims are required to take up the distance.

My rack was too tight because the rubber o ring was over compressed
between the new needle bearing and the yoke washer.

I would check that if you are having problems.

[ClickClickBoom]

When I rebuilt my rack, I found the torque spec to rotate the rack somewhere on the interwebz to be 8 LB IN. With the yoke installed fingertip force is all thats needed. I used my LB IN torque dial wrench to confirm. Whatever the puck material how you get that measurement is not important, Delrin, PTFE, brass aluminum, or whatever as long as it's softer Rockwell style than the rack. Shim stock can be purchased on the internet, or possibly shims might be sourced as well. This tech is not terribly complex, so solving is relatively easy.

[jjeffries]

Mine was binding after the installation of new bearings. John

Originally Posted by brp914

JJ, was your rack stiff before you took it apart?

[Harpo]

So was mine. I need to take mine back a part and follow Tom's video. BTW Tom your video was awesome

Harpo

[E Sully]

Couple of threads that may help you. Have you checked the universal joints on the steering column?

Steering stiff after rack rebuild
Steering Rack "Rebuild" Procedure

[tperazzo]

Originally Posted by Harpo

So was mine. I need to take mine back a part and follow Tom's video. BTW Tom your video was awesome

Harpo

Thanks Harpo! Hope you get yours turning smoothly.

[Blackbyrd]

I had taken apart a steering rack for rebuild about 6-8 months ago, I specialty blasted the housing for both strength and finish As well as plating caps and hardware With the same techniques and vendors as I did when I worked for Singer.
I wasn’t happy with the worn puck so A friend and I have made prototypes of the puck.

I purchased a pile of “correct” size bearings from different manufacturers to get the shim situation sorted,
I think if you have a glass table you can carefully shim the bearing, but I haven’t tested this theory, you would also need something to block debris from getting into the bearing.


I noticed everyone calls it a “rebuild” by simply replacing parts with off the shelf bearings as well as the top o-ring
followed by Grease repacking then it’s “rebuilt” This Puzzles me.

But What about the 4 side seals and the “bearing slider Bushings” on each end of the rack ?
The “bearing slider bushings” are Made of same material as the puck btw.

When I first saw Toms Ahh Garage Time video (great stuff, I fully support his channel) I was expecting the side seal/slider bushing to be addressed as well but that wasn’t mentioned.

I pulled apart a second rack After watching toms video since I needed to rebuild two of them. Watching his motivated me to get back on the project and fully investigate How to really fully and completely 100% rebuild a rack from every corner.

The second one I pulled out definitely had signs of wear On the “bearing slider bushings”
for that reason we made prototypes of both the puck and the sliders.
It’s a soft metal so we tried a few metals to see what worked the best.
I’m hoping to test the first rack as soon as I can, I may attach it to a servo motor and see what happens if I leave it over night as my car isn’t ready for the road and I don’t want to hand it to anyone with out testing first.

I found the round rings with 12 teeth that hold the seals and “bearing slider Bushings ” in place On either end.
I had to buy 250 of them in order to get my order processed It was pretty impossible to find and took some detective work. IF ANYONE NEEDS ANY LET ME KNOW

As was the small o-ring for the smaller bearing
it’s as if the steering rack Industry doesn’t want you to find out as no one sells this stuff.

I’m now on the hunt for the correct side grease seals that go onto the “bearing slider bushing”
It takes 4 all the same size

I did a lot of digging and no one seems to replace these

If I can’t find them in the next few days ( as I plan to visit a few seal specialist this week)
I’m going to just make them, I know a guy who is good at making rubber parts and understands compounds

It’s insane that none of this data is easily obtained
The rebuild industry does not want you to know.

My end goal is to put together a true complete inexpensive kit to put this all to rest.
The expensive parts will be the bushings as they are made in small quantities 20-40 pieces at a time in SOCAL (USA) not by the thousands in China.

[Kraftwerk]

Just to continue with a bit more of "rack befuddlement" inside the rack housing you'll find a 17mm nut (the pinion nut- under the rubber yolk) that holds the coupling flange. This nut is 'crimped' at the factory, it has a kind of 'furled texture' on either side of the nut .. looks almost as if someone grabbed w/ a vice grip, looking closely those markings are nice clean lines-it's ALL factory doing... I am guessing they really wanted it it to stay on there so the squeezed the heck out of that nut 'ovalizing' it a bit, hence the 'lock-nut' moniker.