Welcome to my descent into madness! (UpFixin Der GT3)
01-24-2014, 11:55 PM
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Welcome to my descent into madness! (UpFixin Der GT3)
Or what happens when you give an engineer to many tools…
In June of 2012 I picked a ‘new to me’ 2004 GT3. This was my 1st 911 based (I.E motor waaaay back there) track car, but my 3rd track Porsche – the 1st two were a 914 and a 944TurboS. My track toy for the last 9 or so years was a Subaru STi - a really great, fast car that was so far outside its design envelope that it was both funny and sad at the same time, and very, very different from the GT3. So we have gone from mid engine to front to AWD to rear – to quote a smart man ‘long strange trip…’
The acquisition of this car provided a number of ‘character building’ experiences – the most significant being learning a bit more about characters – see https://rennlist.com/forums/996-gt2-...and-story.html for more info…
When I got the car there were several issues that I wanted to address immediately – the most significant being the transmission needed to be rebuilt. I got some estimates and decided that the only way that made sense was for me to trade some sweat equity to offset the costs.
I would like to say that I sat down and planned my little ordeal out, but what really happened was I started to remove the transmission and pretty soon one thing led to another. At this point I really did sit down and start to think through things, and talking to people, and thinking….
What I ended up deciding to do was:
I will try and write this little adventure with the hopes that it may provide information to others.
I would like to thank folks at Orbit Racing, DeMan Motorsports, Flying Lizzard, and TRG for parts and information.
In June of 2012 I picked a ‘new to me’ 2004 GT3. This was my 1st 911 based (I.E motor waaaay back there) track car, but my 3rd track Porsche – the 1st two were a 914 and a 944TurboS. My track toy for the last 9 or so years was a Subaru STi - a really great, fast car that was so far outside its design envelope that it was both funny and sad at the same time, and very, very different from the GT3. So we have gone from mid engine to front to AWD to rear – to quote a smart man ‘long strange trip…’
The acquisition of this car provided a number of ‘character building’ experiences – the most significant being learning a bit more about characters – see https://rennlist.com/forums/996-gt2-...and-story.html for more info…
When I got the car there were several issues that I wanted to address immediately – the most significant being the transmission needed to be rebuilt. I got some estimates and decided that the only way that made sense was for me to trade some sweat equity to offset the costs.
I would like to say that I sat down and planned my little ordeal out, but what really happened was I started to remove the transmission and pretty soon one thing led to another. At this point I really did sit down and start to think through things, and talking to people, and thinking….
What I ended up deciding to do was:
- Get all the manuals I could find, talk to people, and read everything
- Remove the transmission and rebuild it
- Remove the motor and pin the water lines
- Replace the suspension with the better part of a 996 RSR suspension
- Clean up anything I found to be problematic
I will try and write this little adventure with the hopes that it may provide information to others.
I would like to thank folks at Orbit Racing, DeMan Motorsports, Flying Lizzard, and TRG for parts and information.
Last edited by rbahr; 05-14-2020 at 11:29 PM.
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Nickshu (05-14-2020)
01-25-2014, 12:08 AM
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Suspension first...
My obsession with the GT3 suspension started with a conversation about the European only GT3 RS which, as I understand it, was the homologation vehicle (so to speak) for the 996 RSR.
As I read about these cars, what became obvious was that the GT3 handles pretty well out of the box at the OEM ride height. Trouble is 1st thing we do is lower these things when we put them on a track. This does not work well with the GT3 suspension – roll centers, bump steer, camber curves – anything important handling wise has a nervous breakdown. This is where the RSR comes in, as it has a suspension that is designed to operate lower.
In my reading, I decided that this car was a GREAT design, I could unbolt parts and bolt in new suspension points, and new suspension bits.
Onto the transformation of the suspension…
A caveat: I am assuming that if you do this, you have access to tools, lots of tools – presses, mills, wrenches, sockets, (air tools are nice) really big hammers, and your wife’s oven…
An inventory of my car (it was new to me and I needed some detail)
- Moton Club Sports with 1000/1100 lb springs - Needed rebuilding $225 per corner
- 2 piece lower control arms with monobolls – front & rear (Monoball holder or ‘fixed bearing assembly’ RSR P/N 996.331.441.90 - Monobolls worn out, replaced with Fluro FLR-GXSW18.35MS: Spherical Plain Bearing GXSW 18.35 MS Motor Sport Series. Got them from Hoerr for $59.00 each
- Front shock mounts – OEM GT3 – worn bearings. - I was unable to find a replacement, tried about 12 different manufacturers. Went with Porsche Motorsports and used the RSR/Cup car part – same! 9R1.331.779.00, Cost $160 per @ Suncoast
- Rear shock mounts – These were manufactured buy MODE Inc – www.modeinc.com sold by a number of folks, and you guessed it – the monoballs were worn - $55 each.
- Motorsports Centerlocks… - Not much to wear out here – just a big nut…
- Solid rear motor mounts
There were other goodies, but a lot was OEM GT3!!!
01-25-2014, 12:34 AM
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The List
RSR List – prices are combination of used and new
- Front Uprights - $950 ea (See note below!) - RSR P/N 996.341.157.9E (L) 996.341.158.9E (R), RS P/N 996.341.157.92 (L), 996.341.158.92 (R)
- Front Cross member - $400 used - RSR P/N 996.341.081.9B
- Front wheel bearings ~$100 new - RSR P/N 999.053.042.10
- Front blade type sway bar - I decided against using these – what I had was ‘good enough’
- Front & rear wishbone brace AKA caster adjuster $320 - Aftermarket – lots of good/equivalent choices
- Brakes – Can’t afford them right now! - changes a number of things
- Rear uprights - $800 ea - RSR P/N 996.331.111.9E (R), 996.331.112.9E (L)
- Rear Wheel bearings – yep – RSR gets you bigger / better $110.00 ea - RSR P/N 999.053.050.00
- Rear axle side-carrier - $750 - RSR P/N 996.331.051.9E & 996.331.052.9E
- Rear blade type sway bar - I decided against using these – what I had was ‘good enough’
- Rear upper wish bones - $400 - Instead of using the RSR parts, I used some good aftermarket ones – many good choices out there
- Rear toe link (track rod) $450 - Instead of using the RSR parts, I used some good aftermarket ones – many good choices out there
- I am not doing steering racks, air jacks, RSR rims, and probably a number of other things
RS Prices & P/Ns: Missing a few things…
- 996-331-052-92 AS SIDE PANEL 1 1318.63
- 996-331-051-92 AS SIDE PANEL 1 1318.63
- 997-341-661-90 LID 1 49.48
- 996-331-112-90 AS WHEEL CARR 1 968.21
- 996-331-111-90 AS WHEEL CARR 1 968.21
- 997-341-158-93 AS WHEEL CARR 1 1336.44
- 997-341-157-93 AS WHEEL CARR 1 1336.44
Really, Really important notes here:
- The ‘wishbones’ front and rear are the same as the OEM GT3 Save money here
- The RSR uprights are different from the cup uprights – different part numbers
- The front RSR uprights use a brake caliper with very different bolt spacing than the OEM GT3 caliper. Use the GT3 RS part – same as RSR EXCEPT you can use your OEM caliper. I have Pet V7.3. To find the GT3RS parts you need to look for the designation M004 in the Model column for the 2005 GT3. You can still buy these parts from you dealer even if the car was never imported here. GT3 RS P/N 996.341.157.92 (L), 996.341.158.92 (R)
- The 996 RSR parts still use the old (pre 997 GT3) ABS sensors
- The 997 RS/RSR use a different mechanism for the ABS sensor, and although retrofitting this is possible, it will NOT be easy
- The rear RSR uprights do NOT come with E-brake support – more on that later
- The rear RSR uses a 355mm disk rotor, the 996 uses a 330 mm rotor, the 997 uses a 350mm rotor – more on that later.
- The 997 RSR front cross member is very slick in that you can actually adjust the roll center, I went with the fixed (lowered) roll center of the 996 RSR to save money as I won’t probably be adjusting that very much
- Part numbers are not always part numbers – As Rick DeMan pointed out to me – they are really casting numbers – my rear axle side-carrier have a ‘normal’ part number, but is very different – see my pictures
Last edited by rbahr; 05-14-2020 at 11:35 PM.
01-25-2014, 12:44 AM
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‘Where’s the beef?’
With pictures being worth lots of words here goes many word equivalents
These are the old caster adjustments and new ones – not so much give on the new ones…
Rear axle carriers: Note the differences in height ~12mm!
Rear Upright – New and old – Notice the lack of E-Brake fixins…
Rear mockup
Rear toe link
Motorsport centerlocks – now these are fun to remove
Front RS upright being test fitted
Front cross members: Also note the change of the mounting points ~6mm.
These are the old caster adjustments and new ones – not so much give on the new ones…
Rear axle carriers: Note the differences in height ~12mm!
Rear Upright – New and old – Notice the lack of E-Brake fixins…
Rear mockup
Rear toe link
Motorsport centerlocks – now these are fun to remove
Front RS upright being test fitted
Front cross members: Also note the change of the mounting points ~6mm.
Last edited by rbahr; 05-14-2020 at 11:37 PM.
01-25-2014, 12:59 AM
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Installation
Front Uprights:
Start by removing the big nut holding down the ABS wheel, remove calipers – tie them off, remove rotor, remove tie rod, wish bone, ball joint – the correct tools make all the difference
This tool is indispensable, I needed to open it up a bit to be able to use it...
Front Cross member – After you remove the old suspension, simply unbolt old one, bolt in new one – oh yea – don’t forget to support the gas tank since the straps that hold it in place are in turn held by the cross member, use torque wrench, check/use the RSR torque values, paint nuts, yada, yada, yada
Lower control arms: There is only so much you can do with these – replace the caster adjustments and replace the monoballs
(and you thought I was kidding about the oven)
These are the new LCA monoballs, get inserted into the holders (cooking in the oven).
The above is the tool I made to extract the caster 'pucks' from the LCA. When I figured out the sizes, it was easier than using a press...
Shock mounts:
MODE shock mounts: I sent these back – cost $55 per mount, they have special tooling, I broke stuff, and decided it was just easier before it got really expensive…
Rear uprights
Start by removing everything in somewhat this order:
Brake pads, Brake caliper – tie it off somewhere that won’t be moving, Brake rotor, disconnect wishbone, tie rod, ball joint, E-brake, ABS sensor, brake sensors, E-brake, rear axles, remove wheel carrier – leave the E-brake on the carrier, since this will help later when you forget why you are here.
Once everything is disconnected, just remove the axle side-carrier and bolt in the new one.
Start by removing the big nut holding down the ABS wheel, remove calipers – tie them off, remove rotor, remove tie rod, wish bone, ball joint – the correct tools make all the difference
This tool is indispensable, I needed to open it up a bit to be able to use it...
Front Cross member – After you remove the old suspension, simply unbolt old one, bolt in new one – oh yea – don’t forget to support the gas tank since the straps that hold it in place are in turn held by the cross member, use torque wrench, check/use the RSR torque values, paint nuts, yada, yada, yada
Lower control arms: There is only so much you can do with these – replace the caster adjustments and replace the monoballs
(and you thought I was kidding about the oven)
These are the new LCA monoballs, get inserted into the holders (cooking in the oven).
The above is the tool I made to extract the caster 'pucks' from the LCA. When I figured out the sizes, it was easier than using a press...
Shock mounts:
MODE shock mounts: I sent these back – cost $55 per mount, they have special tooling, I broke stuff, and decided it was just easier before it got really expensive…
Rear uprights
Start by removing everything in somewhat this order:
Brake pads, Brake caliper – tie it off somewhere that won’t be moving, Brake rotor, disconnect wishbone, tie rod, ball joint, E-brake, ABS sensor, brake sensors, E-brake, rear axles, remove wheel carrier – leave the E-brake on the carrier, since this will help later when you forget why you are here.
Once everything is disconnected, just remove the axle side-carrier and bolt in the new one.
Last edited by rbahr; 05-14-2020 at 11:39 PM.
01-25-2014, 01:12 AM
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Fun & Games with the rear RSR uprights
Now we need to take that expensive RSR upright and reduce it to a large pile of metal shavings. I chose to install the E-brake since I want to be able to drive this thing on the street. This is actually not so difficult to do:
Need to make a metal tab and bolt it down, drill a hole for the cable, drill a couple of small holes for the retaining springs, install all the parts and done… That was easy…
The casting marks are there for the cable hole, the recess is there for the actuator, and the rest you wing it, so to speak
First drill a 12mm hole for the brake cable
Now machine and locate a small tab that will the default non-loaded position for the E-brake pads - I used measurements from the tab of the standard 996 GT3 upright.
Lastly, 2 small holes will need to be drilled for the spring ends - not critical, but still requires some care...
Here comes the fun part:
We have E-brakes and now we would like the real brakes to work (picky, picky, picky). This turns out to be both a bit terrifying and easy all at the same time…
As mentioned above, the 6GT3 uses 330mm rotors, the 7.1GT3 uses 350mm rotors (cup part numbers 997-352-405-91 & 997-351-406-91), and the RSR uses 355mm – I can get the number, but I won’t be using these anyway.
Turns out that the formula to make all this work without completely mucking up you brake bias is simple – Machine 9mm off the two pads where the calipers mate, use the 997 rotors and your calipers. Although if you do this, I would strongly suggest doing your own mock up to verify the numbers – but it worked for me. You will also need to cut down the studs for the brake calipers ~ 5mm, otherwise they bottom out.
This was terrifying for me because I was doing my best to keep the hub positioned so that I had <.002in (.05mm) of error across outside corners of each of the 2 pads, spanning the distance front to back and right to left. I had adjusted my mill before starting but the first one still took ~8 hours to figure out how to shim and bolt this thing down and to convince myself that I would not need to buy more uprights. A real machinist with a real machine shop could probably do it a lot quicker and As I pointed out to my ever understanding wife – ‘If I knew what I was doing, I would be nervous’
Now you are basically there – just need to point out that this was actually the easy part – you need to adjust everything (front and rear caster, toe, camber, track, shocks, ride height, etc) so that this car actually behaves nicely – more on that when I solve that problem, but I will probably start with the RSR settings and hopefully convince a smart person or 2 to help. (One tip I got from Orbit, is to keep the axle inclination below 9 deg – which drives ride height)
Need to make a metal tab and bolt it down, drill a hole for the cable, drill a couple of small holes for the retaining springs, install all the parts and done… That was easy…
The casting marks are there for the cable hole, the recess is there for the actuator, and the rest you wing it, so to speak
First drill a 12mm hole for the brake cable
Now machine and locate a small tab that will the default non-loaded position for the E-brake pads - I used measurements from the tab of the standard 996 GT3 upright.
Lastly, 2 small holes will need to be drilled for the spring ends - not critical, but still requires some care...
Here comes the fun part:
We have E-brakes and now we would like the real brakes to work (picky, picky, picky). This turns out to be both a bit terrifying and easy all at the same time…
As mentioned above, the 6GT3 uses 330mm rotors, the 7.1GT3 uses 350mm rotors (cup part numbers 997-352-405-91 & 997-351-406-91), and the RSR uses 355mm – I can get the number, but I won’t be using these anyway.
Turns out that the formula to make all this work without completely mucking up you brake bias is simple – Machine 9mm off the two pads where the calipers mate, use the 997 rotors and your calipers. Although if you do this, I would strongly suggest doing your own mock up to verify the numbers – but it worked for me. You will also need to cut down the studs for the brake calipers ~ 5mm, otherwise they bottom out.
This was terrifying for me because I was doing my best to keep the hub positioned so that I had <.002in (.05mm) of error across outside corners of each of the 2 pads, spanning the distance front to back and right to left. I had adjusted my mill before starting but the first one still took ~8 hours to figure out how to shim and bolt this thing down and to convince myself that I would not need to buy more uprights. A real machinist with a real machine shop could probably do it a lot quicker and As I pointed out to my ever understanding wife – ‘If I knew what I was doing, I would be nervous’
Now you are basically there – just need to point out that this was actually the easy part – you need to adjust everything (front and rear caster, toe, camber, track, shocks, ride height, etc) so that this car actually behaves nicely – more on that when I solve that problem, but I will probably start with the RSR settings and hopefully convince a smart person or 2 to help. (One tip I got from Orbit, is to keep the axle inclination below 9 deg – which drives ride height)
Last edited by rbahr; 05-14-2020 at 11:42 PM.
01-25-2014, 01:13 AM
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I will write up my tranny rebuild and to a lesser extant the water line pinning (yep - I pinned and did not weld)
Last edited by rbahr; 05-14-2020 at 11:43 PM.
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01-25-2014, 01:36 AM
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can't beat technical hands-on threads, awesome! thanks for posting
01-25-2014, 09:57 AM
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Excellent !
I had started posting a few tech info on the 996GT3 suspension differences back in 2011, but never finished it.
https://rennlist.com/forums/porsche-...96-gt3-rs.html
I think that I will copy this thread there.
I had started posting a few tech info on the 996GT3 suspension differences back in 2011, but never finished it.
https://rennlist.com/forums/porsche-...96-gt3-rs.html
I think that I will copy this thread there.
01-25-2014, 10:44 PM
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You're the Man! Pretty brave too. Keep it up, we all can learn a lot.