HOW TO: 4000 suspension [very long]

[shields@tembel.org (Michael Shields)]

AUDI 4000 SUSPENSION FOR DUMMIES
--------------------------------

("If Shields can fix it, so can you")


Here's what I learned as a not-too-experienced mechanic replacing
suspension components on my '86 Coupe GT.  I'm writing this all up as a
thank-you to the list for all the time and money I've saved.  (Of course,
the list has probably coerced me into being much more discriminating
about my car's maintainence, so I've probably done enough extra work to
even out the savings -- but hey, I don't regret it.)

Anyway, here's how it's done.  All the tricks in one place.


1. General observations

Firstly, having the proper tools *counts*.  I'll comment as I go through
the procedure about what tools you need.  Don't skimp, or you'll be
very sorry.  Start by making sure you have a good stock of sockets,
ratchets, and torque wrenches over a full range (torques involved vary
between 20 and 230 Nm).  Also, you will definitely get your money's
worth from a mallet.

If your suspension isn't regularly dismantled (mine went a full decade
and 112k before getting any major work), it will not come apart cleanly.
You will need to pull, push, oil, and use that mallet many times.
This implies that (a) you have a good assortment of tools for applying
force so that you can avoid spending hours on single components (yes,
really), and (b) you have a good understanding of how things fit together
so you know where and how force should be applied.

One good bit of advice is to spray all the nuts involved with your
favorite penetrating oil once a day for a week before you do the work.

Finally, it's not a bad idea to replace everything you can.  I ended up
replacing not just the strut cartridge, but also *every* nut and bolt I
removed from the suspension components, as well as the strut bearings,
outer tie rod ends, bump stops, dust sleeves, and wheel bearings.
You might also consider the control arm bushings (mine had only 30k on
them); and if necessary, subframe bushings or ball joint.  The hardware
should be replaced because it is almost all nylon-locking, and the rubber
components you should replace as a matter of course.

I bought Boge Turbo Gas dampers from RD Enterprises and everything else
from Linda, except for tie rod ends which I bought locally (wrong part
from Carlsen, 811 419 812 vs. 811 419 812 A).

Dampers are supposed to be pumped a few times through their full range
to release any bubbles (or something) from horizontal storage.  I don't
know if this is necessary, but it's easy.


2. Front suspension

This is about the front suspension in my Coupe, but the 4000Q's rear is
apparently very similar.

2.1. Getting started

Spend some time studying the assembly before you take it apart.  This is
easiest with the non-suspension components removed, so let's do that
first.  Choose a side, then loosen the lug bolts and the axle nut.
The axle nut is 30mm and you will want a breaker bar and 1.5 m pipe
to take it off.  Do this *on the ground*; you need the torque applied
by the tire, and you also don't want there to be any chance of the car
falling off the jackstands when you apply all that force.

Now jack up both sides (of course using jackstands, wheel chocks, &c.).
Remove the wheel.  Remove the brake caliper (two bolts on the back)
and hang it out of the way with a coathanger or cable tie.  If the rotor
hasn't fallen off already, tap it on the back with the mallet.

You should now be able to see how everything works.  The driveshaft
carries power from the transmission to the hub, which rotates in the
wheel bearing.  The wheel is held at a fixed angle about the vertical
axis by the tie rod, and is prevented from moving along the longitudinal
axis by the control arm.  Weight is supported by the spring and movement
along the vertical axis is regulated by the strut.  After seeing this
on the car, suspension theory made much more sense to me.

2.2. Removing the strut assembly

But the goal here isn't to theorize, it's to take it apart.

First remove the nut underneath the control arm that holds on the
roll bar or its link rod (depending on vintage).  This is needed to
let the control arm swing freely, which of course is exactly what the
bar prevents.  If you didn't jack up both sides it will pull itself out
as you loosen the nut.

Next you will need to press out the tie rod end.  Remove the nut and
tap it with the mallet; it might just pop out.  If not I recommend you
use one of those tie rod presses JC Whitney has for $10.  I didn't have
one; I used a pickle fork on one side, destroying the rubber boot.  I was
going to replace the tie rod end anyway, but still, I recommend you *not*
buy a pickle fork.  On the other side I improvised with the gear puller,
but it was awkward.

Now the ball joint.  Use a 17mm wrench and socket to remove the bolt.
Then pry apart the clamp joint as best as you can, and pull down the
control arm by whatever means necessary until the ball joint pops out
of the strut assembly.

Press out the driveshaft.  The right tool for this is a Sears gear
puller; you hook the three jaws onto the hub and turn the shaft with
a 16mm socket, pushing the driveshaft in and the strut assembly out.
(It's not actually 16mm, but some oddball nonmetric size.  Close enough
if you have good six-point sockets.)  Thanks to Dave Lawton for this --
it went very smoothly.  Again, tools count.

The only thing holding in the strut assembly now is the nut at the very
top, under the hood.  Support the hub so the whole assembly doesn't fall
when you remove that nut.  A floor jack is good for this.

The way you have to remove that nut is to hold the strut shaft in place
with its 7mm allen-head recess while turning the nut.  The right tool
for this is a 3078, pictured in the Bentley.  An alternative suggestion
I tried was to turn a 22mm socket with a pipe wrench while holding an
allen key through the square drive hole.  This did not work at all; a pipe
wrench on a socket couldn't hold enough torque.  Another suggestion was
to mill the sides so you could hold it with an open-end wrench.  I ended
up making my own 3078 by cutting 60 degrees out of a 22mm deep socket.
So the tool *can* be fabricated, but it's probably easier to buy it.

My passenger side took a huge amount of torque for some reason --
I ended up blocking the allen key against the fender with a piece of
wood and using the pipe on the ratchet.  I wasn't happy about it, but
it worked and since I was discarding both strut and nut, I didn't worry
about damage to their thread.

Congratulations, you now have the strut assembly off the car!

2.3. Dismantling the strut assembly

First, you need to compress the spring.  This is of course a little
dangerous; use common sense and go slowly.  Beware of the two halves of
the compressor walking towards each other; if that happens back them off
and start over.  You can prevent it by cross-torquing a little at a time
(I alternated giving each side one full turn).

Once you have that done, you need to remove the slotted nut.  The nut is
actually not a hex nut, but a round steel sleeve with thread in the center
and two notches at the top.  To torque it you need to engage the notches.

Let me tell you, you need tools here.  I'll spare you my story, but
suffice it to say that I did not buy the tool, I regretted it, and that
modifying a socket is *not* the way to go.

Fortunately I *did* find an alternative to the official tool.  To make
the Shields Slotted Nut Remover Tool, start with the nut you removed
from the top of the strut.  Lay the new replacement slotted nut on
top of it, centered, slots against the round locking ring, and scribe
where the slots fall.  Then hold the nuts side-by-side and observe
how deep the slots are.  Use these marks to cut away two crescents,
so you essentially have a shorter nut with two small projections 180
degrees apart.  Now grind out all the thread from the center.  I did
all this with a Dremel and patience.

You can now slip the nut over the top of the strut, seat the projections
into the slots, and torque away.  Neat, eh?

I didn't have a problem keeping it seated, but if you do, you could put
another strut nut (this one with threads) on after it, and torque them
both together, since they're the same size.  That is advantage #1 of the
modified-nut tool.  Advantage #2 is that if you have a problem with the
strut rotating in its housing for some reason (I did!), you have the
top end unobstructed and can just put the 7mm allen key back on it.

It basically just slides apart from here.  Spring retainer, dished washer,
bump stop with dust sleeve, and the compressed spring.  Careful with
that spring; carry it gently and don't put it where someone might trip
over it or kids might play with it.

The strut is held on with a threaded cap.  The cap has a *large*
hex-shaped opening in the center which matches yet another special tool.
You don't need that tool at all, because this is, for once, exactly the
application pipe wrenches are designed for.

At this point my old strut disassembled internally and left a puddle of
oil on the driveway.  Kitty litter cleans it up.

If the strut doesn't slide out of its tube, put a 14mm box-end on the
top, follow with a nut, and bang that with a mallet.  This proceduce
is Bentley-approved.

Ok, that's it!  Now is the perfect time to have a new wheel bearing
installed; take the bearing and the hub assembly to any decent garage
and they'll take care of it for you.  Then put it all back together.
You remembered to use new strut bearings, right?

2.4. Reassembly

Here is the part where I scream at my car in the pouring rain.  The car
must have powerful friends because it only rained harder...

If your car isn't cursed like mine, it will just slide back together.
The driveshaft is no problem (mallet, with patience); thread on the axle
nut a few threads so it doesn't fall completely off later, but torque
it very gently.  The tie rod just pushes in once you get it lined up,
which is easy.  The upper mount and the roll bar just go right on the
same way they came off.

Now, for *no good reason*, it took me hours to get the passenger side
ball joint lined up.  After a while I realized I should loosen the
adjusting nuts, but then it took a while (and much WD-40 and coaxing)
to get it to slide out.  It still wasn't vertical.  It's raining now,
mind you, and I am *very* late for work.  After some more cursing and
pleading I finally did get it aligned.  Slip it back in with a mallet
or floor jack and install the new clamp bolt.

Oh, if you're replacing the tie rod end, it's easy.  Slip the vertical
rod into the strut assembly to stop it from turning, and loosen the
nearest nut a few turns.  Give the locking collar one tap with a mallet
on a screwdriver.  Pull the tie rod back out from the strut assembly
and unscrew it.  Installation is the reverse of removal.

FYI, those two settings -- moving the ball joint, adjusting camber, and
moving the tie rod end, adjusting toe -- are the two main adjustments
in an alignment, which is why your car now needs to be realigned.

Doublecheck that everything is torqued to spec and lower the car.


3. Rear suspension

This applies only to the FWD models.  On a quattro, the rear is very
much like the front, so you already know what to do.

The rear is *way* easy and doesn't require any special tools.  This is
because the rear wheels are neither driven nor steered; they just provide
traction and absorb bumps.  It's a self-evident design.

The upper mounting points for the rear suspension are at the very back
of the trunk.  You could do the job entirely from that side, but if you
pull the rear seat (no fasteners -- it's all a clever system of clips
and locating wire!), Audi has thoughtfully installed access portals for
the suspension mounts.  Good design there.

With the weight on the wheels, pull off the black dust cap and loosen
the 17 mm nut.  You will need to hold the shock tube with an adjustable
wrench (I would actually have preferred a hex socket).  The best tool
is an offset box-end ratchet; a nonratcheting box-end will be tedious,
because the nut is locking and does not spin off with finger pressure.
You need to wrench it the whole way.

Now jack up the car on that side (only do one side at a time).  As you
raise the car the spring will lose all tension and the strut will just
fall out of the upper mount.  Isn't that cool?

I recommend you remove the wheel at this point; it makes access a bit
easier and more importantly you have less unsprung weight to move around.

At this point you should take out and set aside the rubber upper mount
and the large washer above this.  Otherwise you will bump them when you
try to insert the new shock from below, and the washer will fall behind
the gas tank, where you will never, ever retrieve it.  Uh, not that I
would do that.

The strut is held at the bottom by a long bolt in double shear.  This is a
critical part with 10.9 hardness and you should replace the bolt and nut.
If your old bolts are rusted as badly as mine were you'll be glad you
have new hardware.

That's really all there is to disassembly.  Pull the washers, bump
stops, &c.  off the old shock and assemble parts onto the new shock.
Orient the lower spring retainer; it adjusts by knocking it up with
a mallet and then back down.  Install the lower bolt and nut (60 Nm;
bolt head away from wheel).  Push the thread of the shock into the upper
mounting hole and prop the wheel up there with a jackstand.  Slide the
rubber mount and washer on and get the new nut started so it won't fall
out of the hole.  Lower the car.  Torque the upper nut and the lugs.
You're done.


4. Driving pleasure

First you need to take it down to the alignment shop.  Drive carefully
and don't go very far or you'll ruin the tires.  It is possible to align
the car yourself (the procedure involves constructing parallel lines with
jackstands and plumb bobs, so you have a reference to measure against),
but I decided I had used up my karma budget.

And second, you need to drive it around for a while, at speed and on
corners, and enjoy the way that when you brake, it confidently glides to
a stop instead of pitching forward, and when you accelerate it doesn't
pitch all the traction away from the front wheels, and when you corner it
doesn't roll like a boat.  The old suspension was great for understanding
weight transfer but not much for driving.

When it works, it's all worth it.  Happy motoring.
-- 
Shields.