Anybody already rebuilt a 7852 serie ZF power steering rack on its S4/RS4 !?

[RC200]

Seems there's no rebuild tutorial about a ZF 7852 type steering rack for Audi whereas there're so many for BMW, Porsche, VW ...
Audi owners don't rebuild temselves their steering rack !?

[Luvshok]

Ive got a spare rack and a rebuild kit sitting in the garage right now... Im sure the concept is pretty straight forward to any other rack out there.

[RC200]

Ive got a spare rack and a rebuild kit sitting in the garage right now... Im sure the concept is pretty straight forward to any other rack out there.

I did a Nissan 300zx rack in the past, it was straightforward, even the workshop manuel described how to do it.
ZF racks are far more complicated and over engineered, many people have leaky racks after their rebuild, seems there's some seals that require special attention when fit, deeply inserted in the rack and prone to fail easily ....

[Luvshok]

Good to know before I attempt mine once it warms up a bit

[RC200]

So, I rebuilt the ZF rack last we, and this is pretty straightforward for the S4 (ZF rack # 7852 974 609 / 8D1 422 052 LX):
_no special tool needed as a special ZF wrench to unscrew the rack tube, in fact there's only a snap ring to remove to get the sleeve out and get access to the rack shaft
_one pinion housing seal and one rack body seal are a PITA to remove b/c they're fitted really deep, but can be done

I found something interesting about my original trouble that pushed me to rebuild it (http://www.audizine.com/forum/showth...#post9375325):
There's a major problem of conception in the (ZF) racks made of 100% aluminum including the bolts and the the yoke (In my Nissan rack, the yoke and the adjustment bolt are made of steel !)
Probably due to moisture over the years, the yoke and the adjustement bolt were literally welded to the rack body and so, applied stress on the rack shaft.
This one of th reasons why some people don't manage to adjust this bolt when the rack is still in the car.
I screwed up the adjustment bolt (hex 18mm), so I drilled it out to access the yoke.
The yoke was impossible to remove from the top, so I waited to remove the rack shaft to be able to push it inside, moving it sideways and then, I managed to pop it out.
To my mind, the yoke fits too tightly in the rack body, so decided to shave it a bit an I put a lot of grease, don't want it happens again.

I'm now waiting for a replacement of the adj bolt , so the rebuilt rack is not in the car yet, I know the banjo bolts will be a PITA to put back.
I take benefit of this delay to change all the suspension control arms, and obviously the rack is easier to put back when you don't have the upper control arms in front of your eyes.
Pay attention when sliding the rack from the driver side to get it out, you need to rotate it 2 times because 2 things rub against the pipes and banjo bolts fitted on the rack: one brake pipe in the middle of the car and one corner of the heatshield on the driver side.

Will post some pics of the rebuild later.

[jaychen]

interested to hear how you did it, what is the interesting thing you found?

[blmlozz]

I was going to send mine to a place that a lot of C4/C5 people use to rebuild their ZF racks, but seeing as your in France..

[RC200]

The seals kit I used (but paid £22 ...):
http://steeringseals.com/audi-s4.html

Has the exact number of parts needed, not more, not less (all the bushings are included, the new copper seals for the main banjo bolts are not provided, the bearings neither but you rarely need to change them)

[blmlozz]

That's so affordable.

I've never done a rack rebuild, how difficult has it been?

[RC200]