4×4 Conversion

Converting a 4×4 SUV to the Ultimate Track/Street Car

Eastern Vice President/Track Chairman
First Settlers Region – PCA


Upon purchasing my 1991 Grand Prix White 964, I thought what many other 964
owners did, “Why does this thing look like a 4X4??”

So, my recent purchase soon found me on a mission with two goals in mind:

  1. lower the car for appearance and better handling
  2. complete “stage I” of a transition to the ultimate street/track car

Researching the various products ranging from just lowering springs to a
Stage III Racing shock/spring setup yielded a decision to purchase what I refer
to as a “middle of the road” setup. After all, I wanted to have a car that could
survive on the street, driving it to work and back, running errands, etc. – and
still be great a great handling machine at the 10 plus track events I attend
each year.

I ordered a set of Bilstein HD (Heavy Duty) shocks and H&R sport/lowering
springs for a 965 (Turbo). Mind you, I had plenty of discussion on the Rennlist
boards in regards to why Bilstein didn’t make a “sport” shock, but instead, an
“HD” version, which basically is a “sport” version without the proper title. The
decision to use 965 sport/lowering springs from H&R was purely mathematics, I
wanted a little more stiffness than the 964 springs would provide, which is
about 25-35 pounds more per corner…and I had heard from a buddy of mine in
California that this would work, and had been done – on HIS 964. Also, the
“progressive rate” springs offered by H&R provide a less harsh ride on the
street than some of the other products offered on the market. So, there you have
it, what I thought was the ultimate “middle of the road” setup for a 964.

What follows is a DIY procedure for the installation of my new Bilstein HD
shocks and H&R progressive rate 965 “Turbo” sport/lowering springs. While I made
an attempt to list pertinent details in the installation process…I also
assumed that anyone attempting this procedure will be fairly mechanically
inclined, so I’ll make an attempt to be moderately detailed.

Please note that many steps in this procedure are dangerous, due to the
nature of preloaded springs and the fact that you will be working under a 3000
pound vehicle for part of this procedure. Please make any and all attempts to
maintain a safe working condition and utilize what any mechanically savvy person
would label as ?common sense?.

List of Materials, (hopefully I have included everything)

bullet Your new shocks, springs and a good attitude
bullet if you?re like me, a box full of latex gloves!
bullet TWO floor jacks, and at least a pair of jack stands
bullet several blocks of wood, I use 6″ pieces of 2X4
bullet your basic 3/8″/1/2″ ratchet/socket assortment
bullet a set of metric wrenches/assortment of screwdrivers
bullet your favorite pry bar, or “attitude adjuster” as I refer to it

Special Tools

bullet a 1/2″ drive, 10mm allen socket, trust me, you WILL need this…as SEARS
doesn’t carry them in stock, you may have to chase down your local MAC/SnapOn
tools dealer, you can own one to the tune of about $20-25…this was needed to
remove the large allen bolts that secure the front shocks to the wheel
carrier…these are normally a bi#$% to remove! You may want to order this
particular tool well in advance of performing the install.
bullet A 1/2″ drive, 150lb+ torque wrench – this, you will use with the 10mm
allen socket to remove the large allen bolts on the front shocks, ***please do NOT attempt to use your new 1/2″ drive 10mm allen socket with
the following tool, this tool was not intended to be used on an impact wrench,
while tempting (believe me), it will likely get you nowhere, and has the
distinct possibility of ruining your new socket***
bullet Impact Wrench, while this is not required, it helped out on removing the
lower bolts that secure the rear shocks to the trailing arms -and- bolting down the “hats” via the shock shaft that is otherwise difficult to
secure while tightening the large “nylock nut”
bullet a spring compressor, it doesn’t have to be an “ultra-special” Porsche
spring compressor, the one available for rental/loan from your local Pep Boys/Autozone will do just great – after all, that’s what I used!
bullet a couple of nice OLD comforters/blankets that you have secretly recovered
from the “to be scuttled” pile that your wife, girlfriend, lover, whatever, had been compiling – don’t sneak the one off the guest room bed,
you will be busted, and consequently punished via a lowered “cap” on the P-Car

Ensure you warn your friends, neighbors, and loved ones, including the dog –
that you don’t want to be bothered, for a WHOLE day, and that you will have
LARGE tools on hand in case this warning is not heeded! Save the beer for your
post install celebration dance, you’ll need 100% of your wits about you! Zoloft
and Paxil tablets MIGHT be a consideration as you may possibly endure bouts of
disappointment that grow into deep depression…just kidding…as you learn that
those 10mm allen bolts WONT budge. (Are you getting the idea I had a little
trouble with these??)

One thing, while you may be able to scoot that floor jack of yours under the
car prior to lowering…keep in mind that you have to retrieve that jack once
you’re finished! Suggestion: Make a set of four 1ft. long 2? x 8? pieces, 45deg.
bevel one end. Once you?re finished with the front install, before lowering the
vehicle, place one of these pieces under each tire?same for when you are
finished with the rear! This my friend, is a valuable hint learned from
experience…don’t ask! (Thank God I have a sense of humor – and TWO floor

One more thing: this procedure was written from memory, basically “off the
cuff” as one would say, so, while some steps may not be the ideal way, they were
done MY way. Some steps or details may be omitted due to lack of memory -or-
things I just DIDN’T want to remember!

Please enjoy my attempt at helping you, the “Do it Yourselfer” perform this

Let’s begin!

Installation Procedure for front shocks/springs:

  1. Jack vehicle up, via jack pads located directly behind front wheels. You
    can jack one side, or both up, it won’t matter…after all, you can only do
    one side at a time! -secure vehicle with jack stands, NOT on any suspension
    point, for obvious reasons.
  2. Disconnect brake line retainers, the encapsulated speed sensor for your
    ABS and anything else that “borrow” the shock housing for a mounting point.
    You will have to separate the fittings for your brake lines where the rigid
    line meets the flexible rubber one.
    Tip: This is a good time to upgrade to SS braided brake hoses. Assemble
    the brake lines for the meantime, for the purpose of not draining your master
    cylinder and consequently leaving brake fluid all over the floor…you will
    STILL have to bleed your brakes when installation of the front struts/springs
    is complete.

  3. Here’s where you grab your biggest 1/2″ drive torque wrench and 10mm allen
    socket I told you to purchase, WELL before you attempt this procedure.
    removal of 10mm allen bolts that secure front struts to the wheel carrier.
    Don’t remove bolts all the way, just break them loose at this point.

  4. Note: these two bolts are responsible for your CAMBER adjustment
    for front-end alignment, this is a good thing to know. As you loosen them,
    your wheel carrier will likely adjust itself to the most positive camber side
    of the adjustment…this is okay. Again, DO NOT use an impact on these! Are
    you starting to get the idea that this is where I went wrong?? While it didn’t
    appear to damage my socket, it did wear out the allen bolt hole where the
    allen socket went…this caused LOTS of trouble being that no other attempt at
    using an allen-type tool was productive from that point on…requiring the use
    of a drill, a punch, a chisel and LOTS of four letter words. Too bad I didn’t
    have the camera at the ready for this segment of my ordeal. As you can see,
    the “School of Hard Knocks” is multi-faceted.
    Support the wheel carrier, I used a floor jack with a block of wood atop the
    saddle and placed it under the “hat” of the brake rotor, preload the carrier,
    just a little. The next step will require this, as you will be releasing the
    top support mechanism for the strut/spring assembly…and you don’t want it to
    fall, causing potential damage to your wheel carrier assembly and fender well.
  5. Enter front compartment and pull back/unsnap the carpeting in the vicinity
    of the shock you are removing. See the four nuts surrounding the large one?
    You are going to undo the four smaller nuts using a 13mm socket – remove them
    completely, washers too. Leave the larger nut alone for the meantime.
  6. Slowly release the preload you have on the strut/wheel carrier assembly,
    being attentive to the fact that the upper part of the strut assembly is not
    connected to the vehicle anymore. You should be able to lower the carrier
    assembly all the way down to full extension without any consequences…use
    good judgment here as I can’t remember anything that would cause a problem.
    You may have to remove your swaybar link?
    Tip: Your strut spring assembly may release from its upper attachment
    while lowering the wheel carrier, if not, kindly assist it with a
    rubber/plastic mallet BEFORE lowering wheel carrier to full extension. There
    should be a seal installed that provides quite a bit of “stiction” holding the
    strut assembly to the upper body mount/shock tower.
  7. Once the strut assembly is completely released from the shock tower and
    wheel carrier is at full extension – remove the 10mm allen bolts completely,
    being sure to catch the nuts/washers (were there washers?) off the end of them
    and having one hand on the strut assembly…guess why?
    Notice that I have my front rotors removed in some pics, I was changing
    out my rotors at the time and though some of the pics would show more if I
    left them off.
  8. Carefully guide strut/spring assembly out of it’s position, place unit on
    one of those old blankets, stand up and do your best “celebration/touch-down
    dance”…at this point, in my opinion, you have just completed one of the most
    difficult parts of the procedure, well maybe, don’t get too excited just yet.
  9. Now, this is your first chance to use that handy-dandy impact wrench of
    yours. Use it to remove the nut that retains the hat assembly…you will NOT
    need a spring compressor for the front shocks, although please use one on the
    Tip: If you do not have the use of an impact wrench, you can always opt
    for a piece of leather, a pair of vise grips and a socket/ratchet. The
    provision for an allen wrench at the top of your strut shaft will be basically
    useless as the nut is on there pretty good and the concave shape of the hat
    makes it fairly difficult to get a good grip with a combination wrench, either
    end. Use the leather to prevent damage to the shaft from using vise grips.
  10. Once the hat is removed from your original shock/strut assembly, set aside
    the various washers/spacers, rubber bumper, etc. in correct order or removal.
  11. Remove spring and unscrew spring perch from body of shock, transfer spring
    perch over to new shock assembly – unless you already have spring perches for
    your new shocks, some shocks do not come with these…my Bilsteins did not.
    ***Your originals will be completely reusable and likely compatible with your
    new shock.
    If you are using lowering springs from H&R, you should have a note inside the
    box describing how you need to obtain the proper bumpers -or- trim yours down,
    I just followed the guidelines for trimming my originals, nice and simple. For
    a Porsche C2/C4 you will need to trim off ¾?. Also, unless you have ordered
    new boots, you will be reusing those as well.
    Assemble the new strut/spring assembly just how your factory unit was, ensure
    spring perch is installed correctly, flat part down, offset facing upwards,
    orient spring per instructions provided, this is especially important with
    progressive rate springs. *Tip: Again, you should not need the assistance of a
    spring compressor to assemble the front units and this is where your impact
    wrench comes in handy again, tighten nuts that retain the hat until good and
    snug, I don’t recall a torque value, nor did I use one.

    This is a good time to stand your new assembly on end, step back and admire
    your new creation, beat your chest and do your best Tim Allen impersonation!


  12. Navigate your new shock/strut/spring assembly into the wheel well,
    inserting top end first and install the four 10mm nuts that secure the
    assembly to the top strut mount, finger tighten only at this point.
  13. Using your floor jack, position the wheel carrier to where the holes line
    up for the two large allen bolts that secure the bottom of the strut assembly
    to the carrier,
    lower allen bolt with corresponding nut, finger tighten only. Then, by the
    procedure I was using, I placed one lug nut on the lug closest to the 12 ?o
    clock position, then took a 19mm deep socket and a ½? ratchet, basically using
    it as a lever, I muscled the wheel carrier up until the second allen bolt hole
    lined up and placed the other allen bolt through, finger tightening with
    corresponding nut on the end.

  14. Tighten the four 10mm nuts at the top of the assembly to 27ft lbs.
  15. At the bottom of the assembly, notice that the upper allen
    provides camber adjustability, the lower just holds everything together.
    Adjust the wheel carrier assembly, via floor jack, so that the upper allen
    bolt is pretty much in the middle of its adjustment range and torque both
    allen bolts to 100 ft lbs. I use my car on the track quite a bit, so I put 150
    ft. lbs of torque to the allen bolts once I had my car aligned on a machine?so
    far, so good. (fingers crossed)
    Again, do NOT use an impact on these bolts!!


  16. Once again, separate the brake line and place in applicable support tab
    mounted on strut assembly, then install speed sensor/ABS sensor harness/wiring
    into their proper locations.
    Tip: The plastic retainers that connect the speed/ABS sensor wiring to
    the strut assembly have a removable “apple core” of sort. With “core” pushed
    out -or- removed from plastic retainer, press retainer into position, once
    into position, press “core” in to hold retainer in place. IMPORTANT
    Remember, because you had to separate the brake lines to properly install the
    front strut assemblies…you will have to bleed your braking system!! While
    installation of the rear shocks do not require separating of any brake lines,
    it is a good idea to bleed them as well. Once I was finished installing the
    front strut assemblies, I hooked my pressure bleeder up and bled the front
    lines only. I then put the front wheels back on the car and prepared to
    install the rear assemblies, bleeding the rear lines after completion.



Rear Shock/Spring Removal and Installation

Alrighty then, by now you’ve apparently made it out alive with the
installation of your front strut assemblies – was that hard?

Relax, in my opinion, the rear shock assembly removal and
installation is NOT as difficult, but it is several times as dangerous!! This is
where you will need the assistance of a spring compressor.


  1. Raise rear of vehicle and place securely on jack stands. I placed the jack
    stands under the jacking pads, forward of rear wheel well and directly behind
    the door. Careful, as you tend to turn your 964 into a “teeter-totter” in this
    situation, so if you have a set of four jack stands, this is where they become
    helpful as it would be ideal to leave the front end on jack stands.
    Tip: Use discretion when raising the rear of the vehicle if your front
    is still on jack stands. I used my big floor jack and a piece of 2×4 under the
    engine to jack up the rear of the vehicle all at once, vice one side at a
    time…besides, how would you place your jack stands under the jacking pads if
    your floor jack was there?? If you figure that one out…let me know.
  2. Remove: airbox lid/filter element on right hand side of engine
    compartment, heater blower motor/down tube on left hand side. The procedure I
    used said to remove the rest of the air box?I did NOT find this necessary?but
    then I have average hands.
  3. Place a jack under the trailing arm, with very little or no preload, just
    so when you release the top of the shock from the vehicle, there?s not a
    sudden release of tension.
  4. Using a 13mm socket, 3/8? ratchet, and an extension, or assortment
    of?remove the three nuts holding the shock to the vehicle, being careful to
    keep track of the washers and nuts. NOW is the part that pretty much required
    the use of an impact wrench in my case?remember this bolt is in there at a 147
    ft. lb torque value?plus all the corrosion that helps it stay there!
  5. Set your impact wrench on reverse, place a 26mm impact socket on it and
    remove the bolt that attaches the lower shock mount to the trailing arm. Be
    , be sure to have one hand on the shock as it may fall upon
    removing the bolt form the trailing arm?mine were still held firmly in place
    by the plastic hats that retain the spring.
  6. Wrestle rear shock/spring assembly from body of vehicle??once again, do
    your best ?ARGH ARGH ARGH? as you place the assembly on the floor. I figure it
    best to remove both shock assemblies at the same time.
  7. USING A SPRING COMPRESSOR <hint hint> attach spring compressor to spring
    in a matter that allows you to compress the spring. Adjust tensioner on spring
    compressor so spring obviously has NO tension on retaining hat.
  8. Again, this is a good time to use the impact?remove the nut securing the
    hat to the shock assembly, remove hat assembly making sure to set any washers
    aside for proper reinstallation. You will only need the retaining hats off of
    your original factory shocks! Unless you have purchased new ones?in that case,
    well aren?t we just loaded!? At least you?ll save some time being that you
    won?t have to disassemble your original rear shock/spring assembly to scavenge
    the retaining hat. Again, YOU may need to reuse the spring perch/adjuster off
    your old shocks, my new Bilsteins came with them.
  9. Remove spring compressor from old spring and compress new spring as
    necessary and place onto new shock, ensure you have spring properly oriented
    as to top/bottom.
  10. Place retaining hat atop spring and screw on nut ? by hand! My Bilsteins
    came a new nylock nut as I?m sure your choice of shock will, due to the fact
    that you?re only supposed to use a nylock nut once?you did know that?didn?t
  11. Tighten nut, I found a torque value that stated 43lbs?but that value was
    out the window being that I used my impact on this. Go ahead, YOU figure out
    how to tighten that nut to spec, without the shaft rotating excessively!
  12. The factory manual says to lubricate the upper strut mount/retaining hat
    with tire assembly compound?you tell me, WHO has some of THAT laying around? I
    sprayed mine with some soapy water, as did the person who wrote the procedure
    that I used had.
  13. Install new rear shock/spring assembly into upper mount/receiver in
    vehicle?this is where it gets a bit tricky as you have to align the studs
    properly, before inserting the assembly because the plastic retaining
    hat/mount fits snugly inside the receiver in the vehicle, so once you push it
    up in there, you pretty much aren?t able to rotate it as to line up the studs
    with their corresponding holes?so patience is a virtue!!
  14. If you left your jack under the corresponding trailing arm, then you
    should be in the ballpark for placing the lower mounting bolt and threading it
    in by hand?you will likely have to incorporate a little adjustment via floor
    jack to get the hole lined up good as to be able to thread the bolt in
    properly?do NOT cross thread! Your trailing arm is aluminum?and costly! Finger
    tighten bolt as far in as possible at this point.

  15. Place washers/nuts on upper shock mount studs?tighten to 15 ft. lbs <91,
    27 ft. lbs on 1991 and later models.
    Tip: Use a long flat tipped screwdriver, place the washer/nut on the
    screwdriver shaft, properly oriented, holding washer/nut in place with
    fingers, place tip of screwdriver blade on top of shock mount stud and release
    washer/nut as to ?slide? them into place?leaving screwdriver in place, attempt
    to start the threading of the nut onto the stud, repeat for remaining
    washers/nuts. This may save you a few bouts with four-letter words and
    such?keep a magnet handy.
  16. Tighten lower shock mount bolts to 147 ft. lbs. ? it might be a good idea
    to use anti-seize on these bolts, so they?re not as hard to get out next
  17. Perform your best mental check list:
    -Brakes bled?
    -Brake lines snug?
    -Retained properly?
    -Flexible brake lines oriented correctly as to not snag ?or- bind with front
    wheel movement?
    -All speed/ABS sensors in place?
    -All nuts/bolts torqued correctly?
  18. Lower vehicle, ensuring you have all jackstands, wood blocks, etc. clear
    of the vehicle.
  19. Assemble heater blower motor assembly on left hand side of engine
    compartment ?and- airbox/filter assembly on right hand side.
  21. PRIOR to starting vehicle, manually pump brake pedal until firm?this
    ensures there are no surprises when you back out of the driveway!!

Now that you have successfully completed this procedure, and have experienced
a successful test drive, give yourself a pat on the back with one hand, with the
other ? dial your local P-Car alignment facility to schedule a four wheel
alignment/corner balance.

Oh yeah, give your dog, wife, kids, whatever, a big hug?not necessarily in
that order ? well, you gotta hug the dog first! ?and of course, go for that beer
you?ve needed ALL DAY LONG!


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