Steering Rack question.

steely · 02-05-2011, 01:23 PM

This is probably a weird question, but I cleaned and lubed the steering rack (bearings were ok) and with the puck in, the action seems a tad snug. (on the bench - not in car)

I don't feel grinding, but it just takes a little more force to get her to budge than I think I recalled needing. Sound normal? I used mobil 1 synth.

I haven't re-assembled everything yet, still waiting on some parts. (new lock washer & lock nut)

KTL · 02-05-2011, 07:48 PM

There's actually a "breakaway" torque that can be used to measure how much you should shim the puck- 5 to 7 INCH pounds is the recommended drag. I posted a few pages from a 914 Clymer manual that detailed the rack assembly pretty good.

Steering Rack "Rebuild" Procedure

steely · 02-05-2011, 09:29 PM

Thanks Kevin for bringing that last paragraph to my attention. I'll setup and measure it, although I wonder if I'd need to change the shim arrangement as I didn't change any of the existing hardware and assumed the depth would be unaffected. The spring seems to dominate here as well. I am wondering if the mobil 1 bearing grease made a difference. It seems thicker, and I may have used more than the recommended .8 oz.

Believe it or not, I had saved your post, and a few others, earlier to work from.
I appreciate the feedback.

RoninLB · 02-05-2011, 09:59 PM

Kevin supplies great feedback

steely · 02-06-2011, 11:14 AM

Yes he does (and so do you).
Once I get done family time, and I think there might be some kind of game on tonight, I will be applying it.

I do the research here and believe it or not, take a slew of notes, but I neglected to get a literal feel for this one before I stripped & cleaned it - bugs me so I will measure it.

KTL · 02-07-2011, 05:39 AM

Dan,

Glad you found that Clymer info helpful. What did your puck look like? Agreed gthere's no reason to re-shim if you're putting it back together with same old parts. Just wondering if wear on the puck would warrant checking preload/breakaway torque? My puck had a significant wear area cut into it

chris_seven · 02-07-2011, 09:40 AM

The type of grease used is interesting and I wonder if changing the viscosity of the grease makes much difference to the initial breakout torque?

The Mobil 1 grease has a quoted viscosity of 220 cSt (40 degC), which doesn't seem too bad compared to some Moly greases.

The early 911 manual specified either LiquiMoly KFZ3 which was a general purpose Moly grease or LM-47 which is still available.

LM-47 has a specified viscocity of 105 cSt (40 degC) which is lower and I guess would feel different off the car.

How much change there would be at the steering wheel is interesting, but I suspect very little, although we do use LM-47

We have been replacing the 'Thrust Piece' with new parts machined from Phosphor Bronze for a few years now as virtually all the racks we check show wear of this part.

steely · 04:42 PM

Kevin / Chris,
My regrets and belated thanks for the input - I had little time this past week to do anything or respond, and you gave me pause.

My puck shows wear. I didn't use any gauges to measure it but I'm confident it is ok to go back in. I read up on cSt ratings and stripped most of the synthetic off. Searched here more and decided to take the advice given by (the late) Warren Hall - like Chris, he recommended a moly base lube, specifically Swepco 101 which I have ordered. It supposedly has a softer texture, but I do not know the cSt rating.

I borrowed an in-lb torque wrench and with the rack semi dry, I was glad/relieved to see that it read at the top end of the rated 5-7 in-lb (for running torque). Initial breaking(?) torque was ~8 or 9. The Clymer does not differentiate between the 2 IIRC. I did not have a chance to measure when I had more grease in there unfortunately.

When I get the Swepco, I will thoroughly clean, re-lube, post my measurements, and live with the results.
Thanks again for the information.

*UPDATE* With Swepco 101 I measured 5 in-lbs - nice - hope it feels this good installed.