Drive Train Upgrade, S to S4: Project Thread Blog

[Landseer]

1st a disclaimer.
I'm an amateur mechanic & 928 enthusiast.
This is the first time I've swapped S4 suspension into S car.
Just because I have a trillion posts on two forums doesn't mean I necessarily know****.
Am operating on a great deal of online research as I work through this swap.
Do your own, too, before making your swap.
If you've done it before and have wisdom to impart --- please interject it wherever you can within this thread!!!
Same thing with questions. Interject them.
At the end, we can use MPDano's sticky thread for posting a condensed Cliff Note version.


Patient is 84 Euro car, 200K mi.
Objective is upgrade to later model Borg Warner trans, year 85 or later. (this is the easy part -- far easier than front suspension swap)
Secondary objective is upgrade to bigger brakes. (opportunistic: as donor has them)
Tertiary objective is conversion of current 84 ABS to later ABS (to capture improvement that was made after 1986 VIN# 999)
Basically, the antilock tooth count on later cars is different and the wiring/brain are different and we will address that during the swap.
Its the grey car in this picture at Blue Ridge Pkway, taken fall 2010.




Intial state of Patient:
It has perfectly working S-Brakes (rebuilt fronts:brgs seals pads rotors 2000 miles ago)
(rebuilt during this thread in early 2011 -- Ground Cleaning, 16V Euro)
A bad rear ABS sensor (wire wrapped around axle and pulled out)
Trans is G28-07 5 speed that grinds on 3-2 downshift and when cold on 2-3 upshift.
New Bilstein shocks and strong original sport springs, 3 green stripes.
Sits too high in front, need to free-up the adjustable collars.

Primary donor is 86.5 USA 5 speed car, 150K mi.
It has great shifting 5 speed w/ Borg Warner synchros (like all post-84 models)
It is the midyear S model that the factory upgraded to incorporate most S4 mechanicals, including brake size.
It has big brakes. To swap front, need to swap all suspension due to dimensional changes (except springs & shocks)
To swap rear, we will swap everything at once as a unit --- Torque tube, trans, rear carrier, brakes, emergency brake cable.
Like front, we will leave rear shocks and springs hanging from the body, no swap on these.

Why sacrificing it? It left the road at 60MPH to avoid another car accident.
In some circles, this is known as "involuntary off-roading".
The car slid down an embankment and the driver used the right side to scrub-off speed.
Driver/owner kept it in his garage for 3 years, not knowing what to do with it.
Deep rocker bends, 4 inches of crush beneath door, not fixable by me.

Porsche 928, 86.5, cold start after compression check - YouTube

[Landseer]

Here are some pictures as we perform the trans and rear suspension swap.

[Landseer]

Another shot of both suspensions being removed.

One note --- I won't do it this way again. Too awkard. (btw, tires were added afterward, but it didn't help since the suspension was unpinned where the shock bottom normally connects to the suspension.

It might have been be less awkward if the shocks and the lower shock pins were removed with the rest of the stuff, but we weren't swapping those items.

Next time, I'll revert to my old way, chain-up trans & TT. Remove carrier and suspension as one, including shocks so that the suspension stays pinned. Then remove trans & TT as one. And then put the shocks and springs in whatever car needs them.

[Fixer]

Cool project Landseer. With cheap donor cars out there this is something we all think about. Keep the info and pictures coming when you can.

[AirtekHVAC]

cool thread Chris...keep 'em coming!

[Landseer]

Donor car was from Wisconsin, about 4 hours away.
We saw the ad (thanks to DougM) at 8am, had it in our driveway before midnight.
Car was betrothed to another by the time I'd made contact.
But I moved faster and won it.
Paid $1800 cash. Got there first.

Great 86.5 5-spd for parts - Rennlist Discussion Forums

[Landseer]

So, I need to go out into the garage this morning and remove the Euro front suspension.

I had it all opened up early 2011.

Here is a picture from then. See the teeth on the hub? That represents the tooth count for early antilock brakes. Regular S car antilock. (later antilock has fewer teeth)



To get big brakes on an S car you have 2 choices.

1) keep the S spindles and buy some spacers so the big calipers just fit the S car spindles.

or

2) swap the S spindles for the later S4 spindles. This requires also moving the S4 upper and lower A arms, S4 hubs with integral antilock teeth, also, getting S4 tie rod ends and lower S4 ball joints. The suspension is dimensionally different from S cars, starting for 86.5 year cars and carrying through S4.

I've chosen method 2.

But since my Euro happens to have optional early antilock, and because the tooth count on the S4 hub that accompanies the S4 spindle is much less, using S4 front spindles and hubs with low tooth count will mess up early antilock.
(beginning at 86.5 S car, aka, pre-S4).

To do this right, I need to map the differences between the Euro 84 antilock and the 86.5 antilock, including wiring and brains if needed. This includes rear axles as well, which also have lower tooth count on the later axles. Will describe that later when I repack the CV's with grease.

If your S car getting a big brake conversion doesn't have antilock, its a non issue. You can run antilock hubs on a non-antilock car. Same for rear axles, at least as far as the outer ends are concerned.

(Inners where they attach to trans flanges have some minor mods due to a difference in inner CV joint width, bolt length and grease caps. All simple stuff to work through, though. Basically, the inner joints changed for 85 model year and beyond to thinner CV's, a grease cap that fits into the trans flange, and shorter attachment bolts. None of this has interaction with antilock directly)

[Mrmerlin]

Chris this is a cool, project as you may already know the early ABS hubs are different from the S4 ,
as they are smaller the S4 has larger front hubs and thus different diameter ABS rings with a different tooth count

[Landseer]

Perfect segue, my Colorodoan mentor, for these shots----

Contrasting pictures: S hub versus S4 hub.

I think the S4 A-arms are shorter to compensate for the longer hub, allowing tire to be placed at nearly same place within respective wheel wells.

[Landseer]

A few more pictures.

Upper A Arm contrasting pictures.
S4 (rebuilt) on left; 84 S car on right.
S4 is significantly shorter.






Here are a few of the S hub and spindle, just prior to removal...

[Landseer]

Bilsteins will stay with Euro.
But collars are frozen.
And front stance has been too high.
Need to regain adjustability before installing the front S4 suspension on the Euro.
Much easier to mount the shock & spring during mounting of upper A arm

Had to remove collars, need to replace with new.

[Fixer]

Very informative. Interesting how Porsche changes very little externally but is always improving the things we can't see. Shorter A arm would stiffen the suspension.

[Landseer]

edit: Another enthusiast told me not to use of pipe wrench for removing shock collars.
Spanner wrench only.
Pipe wrench encourages them to bind.



If I'd realized that my donor A Arms had bad ball joints before I started the project, I'd probably have skipped this whole brake conversion.

Jim Bailey made a comment recently that was interesting.
Guys with early model track cars are using the shorter S4 upper A-arms.
But are using the lower S A-arms in combo.
That way, they build-in camber suitable for track.
Stock adjustment is minimal, otherwise.
Probably using adapters to mount their bigger brakes instead of spindle swap.



One more note --- If you are sticking with S suspension, then the S upper ball joints can be replaced using a generic kit. And you need some boots from an Audi because those in the kit suck.

The S-4 upper ball joints are more integral to the S-4 Arms and a kit isn't available.
You have two choices. Get rebuilt A Arms from 928 Intl.
Or, buy replacement tubular A Arms from 928 Motorsports.
I chose the rebuilt units. They cost about $350 each.
Wife will probably use a magic marker to write some reminder on the freezer lid about unauthorized spending.

[Pete R]

I have done this.. You are right about everything so far. Upper and lower a arms are shorter on the s4. You can't mix s4 and other parts, but they all bolt together the same way. Stuff just has different measurments

[Pete R]

Originally Posted by The Fixer

Very informative. Interesting how Porsche changes very little externally but is always improving the things we can't see. Shorter A arm would stiffen the suspension.

Yes, but the hub is longer putting the wheel at the exact same spot so there is no stiffening due to the arms

[whiteNSXs]

Great pictorial, Landseer.
From your pictures, it is now perfectly clear why the later 928s have less negative scrub radius. The A arms are just shorter on the later cars. This translates to less tolerance for a less positive offset front wheel. Will you be using new wheels or remaining stock?
Thanks for the write up.

[Landseer]

Good question, don't know!

My favorites are the Carerra III's.

[Pete R]

Originally Posted by whiteNSXs

Great pictorial, Landseer.
From your pictures, it is now perfectly clear why the later 928s have less negative scrub radius. The A arms are just shorter on the later cars. This translates to less tolerance for a less positive offset front wheel. Will you be using new wheels or remaining stock?
Thanks for the write up.

Again, the a arms are shorter but other components are longer. When I did my swap my wheels were in exactly the same place, to the mm.

[whiteNSXs]

Originally Posted by Pete R

Again, the a arms are shorter but other components are longer. When I did my swap my wheels were in exactly the same place, to the mm.

Pete,
I think we are talking about different subjects here. Although the front track remain the same as you pointed out, the steering geometry has changed due to the steering pivot is now more INWARDS so the axis intercepts the ground more inwards too. The older car can use 50mm offset front wheels as I see that Landseer has Turbo Twists. However, with the suspension swap, his front wheels will need to have 55mm+ offset to maintain the negative scrub radius given stock ride height. The Turbo Twist is ET 50mm so it is not optimal after the swap unless he lowers the car and dial in less negative camber. Anyway, Landseer indicated that he would like CIII wheels which are 57mm ET and would fit just fine on the new set-up regardless of ride heights. 16x7 stock wheels are et 65mm, I believe, so they also work fine.
Cheers.

[whiteNSXs]

Originally Posted by Landseer

Good question, don't know!

My favorites are the Carerra III's.

I am using the Carrera III 18x8 and 18x11 on my S4 currently. I actually much prefer the Carrera Lightweights which I had earlier but sold them as the fronts are et 50mm. The Carrera Lightweights are fine on earlier cars and look mighty good on them.
My car pictured.