"In theory, theory and practice are the same in practice they're different". - some smart quotey guy I know
On paper it's a nut up top and a bolt down below. In practice, it is removing some stuff that is not all that simple to remove or to replace. On the plus side you don't screw up your ride height on these later cars and you don't screw up your alignment. You don't even have to bleed the brakes!
Ride height - apparently on the older cars changing the shock type can change the rear ride height and Porsche published different spring arm angles for gas shocks. With this later G50 coupe, that was no longer an issue* - Porsche published a single spring arm angle. And now I have perhaps? verified that this seems to work just fine. Both sets of measurements are close to a full tank of gas, same spot in the garage after a nice drive but slightly different air pressures. Euro height gets quoted as 25-1/2" front, 25" rear from the ground up through the center of the wheel to the first painted surface. This is the method I used here to get the measurements. My ride height looks good, but measures almost the inverse, although even correcting for the floor, I am still seeing a rear to front rake of about 1 degree which is correct.
When we change the front struts, and do the alignment and corner weighting we'll see what's really up.
Ride height before (air pressure 32/34, full tank) forgot to change pressure after an auto-x!
Drivers side Front | 25" |
Driver's Side Rear | 25" |
Passenger's Side Front | 25-3/8" |
Passenger's Side Rear | 25-1/4" |
Ride Height after (air pressure 29/34, Full tank) *updated with full tank of gas
Driver's Side Front | 25" |
Driver's Side Rear | 25-1/2" |
Passenger's Side Front | 25-1/4" |
Passenger's Side Rear | 25-1/2" |
* After a few hundred miles they seem to have brought the rear up about 1/2", old P-car people tell me it's because the gas shocks have a bit of a spring to them. So it's not drastic but it seems to be a thing at least anecdotally.
Parts choices - were easy for this aging boy racer. A season of auto-x, some test and tune, some DE and some time on the big track but I also need a car I can live with day to day on real roads. Taking mrs P to dinner, grabbing ice cream cones. So I will sacrifice ultimate grip for not shaking my fillings loose. Predictable and tight, but not too tight.
The air cleaner on the 3.2 is a functional design that works well but is in the way of literally everything. Not happy to stop there, they also made it hard to remove and replace. I think the guy who put the A/C stuff in also did this, because they have clearly never done service work, ;) In a perfect world I'd replace the stock air box with something a lot smaller that does not block access to the plugs, valves and rear shock mount. But that may be up to me to design. Or maybe I will hit the lotto and go to ITBs? The best basic compromise I see around is a stock box with the front cut off, which you can buy pre-cut for north of $200. For a square ring of plastic. Maybe I can find one at a junkers? At the least I would replace the clamp on the crankcase vent with something a bit simpler to manage since it is around the rear of the housing.
Tools:
Stubby 17mm ratcheting box wrench - for the top nut on the shocks
10mm nut driver - for the bolts that hold the air box on to the MAF.
10mm small socket wrench - for the locknut holding the rear of the airbox down to the intake manifold
12mm socket - for the big bolt (on the rubber shock mount) in front of the airbox
short blunt pliers - for the wire clip on the crankcase vent in the back of the airbox (I used long pliers (pictured below) to get it out originally. We called them "three stooges pliers" at my old garage)
Phillips head - for the 2 screws holding on the hose clamp at the rear of the airbox
Painters Tape - to tape off the inlet to the MAF so you cannot drop anything into the intake.
Vice Grips - for the tops of the Boge shocks (to keep them from spinning). A crescent wrench also works.
5mm Hex wrench - for the Bilsteins - to stop them from turning
22mm socket - for the shock lower bolt
Big impact gun or 30"+ breaker bar to get the lower shock bolt off.
Quick jack (or equiv) to get car in the air. Jackstands are fine too, you just need a free jack for the trailing arm once the car is in the air.
Hydraulic jack - to lift the rear trailing arm when installing the new shock.
Torque wrench - bottom bolt needs to be tightened to 92 ft/lbs. Bilstein has a sleeve on the upper shaft so you just snug the nut down until it stops. Really nice. :)
Materials/Parts:
Shocks: I went with Bilstein Sport shocks based on reams of internet results that seemed to point to sports (yellow) in the rear, green (heavy duty) in the front.
My auto-x superiors advised me to do the rears since they have all the weight on them, the fronts "never go". IDK about never, but their point was certainly made. I'll do the fronts when I am ready to do a full alignment and corner balance. Shocks come with new bushings, washer and top lock nut.
Shock Bottom bolt: I always buy new hardware just in case the old stuff is damaged. It is cheap insurance at a minimum, and looks better anyhow. "while you're there..."
Bottom Bolt rear shock (2) 900-082-054-01-OEM
Bottom Bolt Washer (2) 999-025-062-02-OEM
Penetrating oil - spray those bottom bolts liberally the night before.
And some kind of general purpose cleaner and towels, because you will find all kinds of grime back there.
Ok, here we go. The high level is:
Lift the car
Get yourself some room to work,
Do the top,
Then remove the bottom bolt, and the shock
Next put the new shock up into position until the shaft goes into the engine compartment
Raise the trailing arm on the free jack until it is high enough to screw the bottom bolt in loosely to hold the top of the shock in place.
Go up top and tighten it up,
Then go below and finish up there.
Then do the other side.
Put car back together
Airbox cover is off. The hole on the back of the airbox is where the crankcase vent connects. (the fabric covered hose)
A wider view with the whole airbox gone. You have great access to the plugs, valves and hood strut. The little fabric covered hose coming at you in the back is the crankcase vent with it's awful clamp. I put painter's tape over the MAF to ensure we don't get dirt in there or drop a nut down it.
Driver's side has plenty of access. You don't need to remove the aux heater duct unless you want to. Those 3 electrical connectors are the head temp (white, top) and the two crank sensors. Try not to move them around.
The old Boge shock. It is covered in the shipping coating, so this is an original. 120,000+ miles. The car still rides ok, but is a bit of a spongecake in turns.
Helpful tools: Bosch LED work light is really great. Magnetic base with a built in carabiner so you can also hang it. Pivots on all different angles. 10 & 12mm sockets for the airbox. Stubby phillips head for the hose clamp behind the airbox, 10mm nutdriver for the bolts holding the air box to the MAF, stubby 17mm ratcheting box wrench for the top of the shocks, vice grips for tops of Boge, Allen key for tops of Bilstein shocks.
it's a tight fit but the stubby box wrench makes short work of the top nut while the vice grip prevents the shock body from rotating.
Nut #1 is gone! Time to drop the shock out. Go below and remove the 22mm bolt, just make sure you don't drop it on your head. I was able to get the passenger side off with an electric impact gun. I was not as lucky with the driver's side.
The one challenge working alone on this is you have to get the top of the shock up through the hole and then get the bushing, washer and lock nut on it to hold it in place while you hold it from below. So we use a spare jack to lift the trailing arm. I pushed the shock up through the hole, and then raised the trailing arm with the jack (using my leg) until I could use my free hand to put in the bottom bolt. Then I could go up top and tighten the shock.
A closer look at that. Yes it looks very precarious but it is only holding up the trailing arm. Not much weight and maybe 1-2" total to fall. The quick jack is locked in position so even if the hydraulics completely failed the car would not budge.
Same drill on the driver's side, but a lot more room to work.
The bottom bolt was not interested in coming out, so I grabbed a 30" breaker bar. "I'm not asking" The Spitfire is waiting patiently for a new head gasket.
The old shocks, covered in the factory anti-corrosion coating. You can see the yellow paint on the bolts from the assembly process as well. I think they painted fasteners to confirm that they had been torqued to spec but I am not sure. Not everything got a mark.
All done! Time to re-assemble and go for a drive.
The airbox can be a little bit tricky to do.
* There are blind bolts holding it on to the MAF
* The crankcase vent is a pain to get back on to the nipple (try stubby pliers or changing the clamp to a standard screw on) A mirror could help here as well.
* The air cleaner cover latches in back are legendary for their ability to frustrate.
The right side in this picture is the rear (this is looking from passenger side to drivers side into the MAF) you can see where the stud comes up from beneath the housing, you can see the 2 screw holes to hold the hose clamp, the nipple for the crankcase breather and the coup de grace - those 2 bolt holes going into the MAF on the blind side You can use a mirror or just feel for them. Just be careful not to drop the bolts or washers. I was able to start them by hand and then use the nut driver. I spent a few minutes while it was out getting a feel for it, making sure my hand would fit.
For the latches on the cover, I just practiced a bit while it was all out of the car just to get the feel of the thing. That helped a lot when I had to figure out what was what on the far side. All in all, not as bad as I was expecting.
References / Thanks:
My favorite 911 YouTube guru! He is as funny & sarcastic as he is skilled at working on these cars. (English subtitles) https://youtu.be/elEiK_fX5oE
My Favorite Bosch Work Light: https://www.boschtools.com/us/en/boschtools-ocs/12v-max-lights-fl12-121246-p/
The good car folks of the Pelican Parts, Rennline, & Impact Bumpers bulletin boards <take a bow>
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