ABS Control Unit (convert 964 C4 to 993 C2)

[KelvWKK]

Hi Gentleman,

I will share my experience in cloning a 993 3.8 RS, from a 964 C4 (except bodywork).
I’ve researched, but incapable to find 1consolidated thread w all the Part Numbers (bits to connect the dots).
I‘ll document my 993 3.8 RS Clone* works, for the benefit of anyone interested in the superced Part Numbers.

Before I start, I would like to give my heartfelt thanks, to many folks here for advice.


I must first explained that the previous owner badly forward-dated** to 993 3.8 RS.
Many of the parts have either damaged or mismatched, & no speedometer readings!
With endless unexpected damages / meshed-up parts, & my fundings quickly drained (a common problem with cheap fixes and aftermarket Macgyver mixes).

The issues ranged from Fuel Line Leaks, Engine Oil Leaks, Electrical Fires from all the Macgyver Splicing, damaged ABS Parts/Wiring/Booster Pump, no Speedometer readings till date from ABS, damaged G50 6-Speed Transmission, destroyed LSD, warped & worn Clutch Assembly, damaged Bushings & Bearings, damaged Starter, damaged Tachometer, etc (the list goes on… haha.).

So, most of parts replaced are NOS with latest supersede Part Numbers.
But due to limited remaining budget, some “pre-owned parts” are used (hence the older/pre-supersede part number shared below).






I am terrified of mixed-matched & aftermarket parts, as they are just not meant for me.
So I am adamant in keeping everything factory 993 3.8 RS, as a clean 1-make (does not make sense to re-wield the suspensions’ mount and transmission tunnel area, hence only the Shell remain as the 964 3.8 RS widebody. everything else 993 RS.).

I will build this 993 3.8 RS clone with all factory parts & my daughter will manage it as I’ve been in and out of the hospital.
With only a working 993 3.8 RS Varioram engine + 964 chassis, below is my journey.



(1) Handling Portion - Front: Everything else should be similar to standard 993

993.341.017.80 A-Arm /L
993.341.018.80 A arm /R
993.341.049.07 Ball Joint (x2)
999.084.621.01 M12 Lock Nut (x2) A-arm to joint



993.341.157.82 GT2 Wheel Carrier /L
993.341.158.82 GT2 Wheel Carrier /R
- Note: Consider to remove o-ring on the coupling, as the GT2 Wheel Carrier has a smaller fitment area (to bolt the RS/GT2 Wheel Carrier).


999.053.041.04 Bearing (x2)
993.347.031.82 RS/GT2 Steering Tie-Rod (x2)
- Note: Consider your Steering Rack variant due to LHD/RHD.
https://rennlist.com/forums/993-forum/603629-rs-upright-question-do-they-change-the-spindle-height-4.html
993.333.513.80 RS/GT2 Stabiliser Bar Support (x2)
- Note: Consider to adjust the mounting position, of your 964 C4 Side Member (to fit RS/GT2 Tie-Rod).
https://forums.pelicanparts.com/porsche-964-993-technical-forum/693615-random-notes-964-993-suspension.html


https://rennlist.com/forums/964-forum/904951-my-964-c2-transformation-build-thread-12.html
https://rennlist.com/forums/964-forum/722585-inner-993-rs-tie-rod-in-964-steering-rack-2.html



993.343.510.70 GT2 CoilOver (x2)
993.343.156.00 Caged Nuts Shock-Carrier (x2)
999.072.006.01 M14 Bolt Shock-Carrier (x2)
999.067.039.01 M12 Bolt Shock-Carrier Allen-Head (x2)
964.343.042.00 Strut Bar (note that it might not fit some CoilOver’s mounting plate, due to the adjustment bolt’s position).




(2) Handling Portion - Rear Everything else should be similar to standard 993

993.331.041.81 RS/GT2 Wishbone
993.331.042.81 RS/GT2 Wishbone
993.331.045.80 RS/GT2 Wishbone (x2)
993.333.051.70 GT2 CoilOver (x2)
https://rennlist.com/forums/market/1226054


Part 3 of ABS, below.
Thank you and best regards.

[TJ9931]

Did a quick search for the abs Pressure Pump by Ate on sunset porsche parts online
ORDER 993-355-953-02 - Porsche (993-355-953-01)
Replaces 964-355-901-01
Description:
4wd. Without turbo. 911. With all wheel drive.
*****NOTE
there are Two Pumps, the one you need is for all wheel drive aka your C4.
Other cars have optional Limited Slip # 220 / 224 - ABD not necessary
Then sunset shows older part numbers below
Replaces: 964-355-901-00, 964-355-901-01, 993-355-953-00.
Appears you need pump from all wheel drive with hydraulic system from964 or 993C4s

The confusion is that porsche shows parts manual drawings for two different models but does not spell out why schematic drawings are layed out differently.
Two, they do not show old or original part numbers.

The carrera2 or 993 carrera brake system is Vacuum Boost assisted whereas all wheel drive C4 is Hydraulic
Has higher brake pressure, better for sporting use. Wish I knew this earlier, before I bought C2 with LSD ugh
Hope this helps?
Perhaps other long term members can provide more assistance.

[TJ9931]

Did another search and more results and more fitment
ABS Pump Assembly - Porsche part # 993-355-953-01 searched.
Found this # fits your 964 C4 car 89 - 1998
https://www.gaudinporscheparts.com/oem-parts/porsche-abs-pump-assembly-99335595301

[TJ9931]

Found this thread here also:
Garth S states the OLD part # off his car is 993 355 053 50 (pulled from my '96 C4S parts car)

Thread is here
WTB/Needed: 993 C4S ABS Hydraulic Pump
Originally Posted by golfnutintib
Hey guys I thought I would try the power of the RL Board and put this out there...

I am in urgent need of an ABS Hydraulic Pump for a '96 Carrera C4S (wide body non turbo model).

Part # as far as I can tell is 993 355 953 50.

Alternative part number MAY be 993 355 953 01, although some dealers seem to think this part may be for a non wide body 4WD car (but I can't imagine it is a different part...maybe just a different part number).

Anyway, if any RL member has one of these that is working and can be shipped to me in California, I would greatly appreciate it.

Thanks in advance.

Reply Garth S
PM sent .... BTW, the correct p/n is 993 355 053 50 ( pulled from my '96 C4S parts car) ... mine has the mounting bracket attached, which somewhat obscures the p/n.

https://rennlist.com/forums/993-forum/914311-wtb-needed-993-c4s-abs-hydraulic-pump.html

[KelvWKK]

(3) ABS Portion - Seek Advise, as I am still studying the ABS Harness & 993 RS Piping differences, between the Electro-Hydraulic 964 C4 / 993 C4 / 993 RS

ABS Control Unit (Electro-Hydraulic): 964 C4 to 993 RS
964 RS/C4: 964.618.126.01
993 RS/C4: 993.618.127.00
Question 1 (Wire Harness): What 964 / 993 variants, can interchange?
-> Would 964 C4 or 993 C4S harness work.
-> or 993 RS use a C2, due to G50 (maybe not, due to vacuum & hydraulic.).



ABS Booster Pump (Electro-Hydraulic): 964 C4 to 993 RS
964 RS/C4: 964.355.053.52 (964 have power boost ratio: 4.8)
993 RS/C4: 993.355.053.50, 993.355.953.02 (993 have power boost ratio: 3.6)
Note 1 (interchange): Interchangeable for 964 & 993 C4/C4S/TT (supersede).


ABS Hydraulic Pump (4 Channel): 964 C4 to 993 RS
964 RS/C4: 964.355.955.00
993 RS/C4: 993.355.955.50
Question 1 (Wire Harness): What 964 / 993 variants, can interchange?
-> Would 964 C4 or 993 C4S harness work.
-> or 993 RS use a C2, due to G50 (maybe not, due to vacuum & hydraulic.).
Question 2 (Pipings/Brake Lines): Is the 964 C4 the same as 993 C4S and 993 RS (for both the above Part Numbers)?


ABS Master Cylinder (25.4mm): 964 C4 to 993 RS
964 RS/C4: 964.355.025.52 (20.6mm).
993 RS/C4S/TT: 993.355.903.00 (25.4mm).
Question 1 (Wire Harness): Are there any Harness needed (I assume it’s fully mechanical & no Harness needed)?
Question 2 (Pipings/Brake Lines): Could the 993 C4S and 993 RS Piping, be identical (assuming 964 C4 is totally different, in both Pipe Size and Piping Layout)?




Brake Calipers (996 C4/TT): 964 C4 to 993 RS
I’ve temporarily re-used the 996 set (matched bias ratio), that the previous owner installed.
This Axial/Radial mount-type, did not affect the rear parking brakes issues.
I’ll study more on how factory 993 RS works, but I’m guessing it uses a smaller rotor.



*Do note of some differences in supersede part numbers, and variations from early/late 964C4, hence please do your due diligence to check.
I learnt from many expensive mistakes, such as not adjusting my 964 C4’s Side Member, before cutting my GT2 Tie-Rod to fit…
**This 964 rear suspension’s top-mount was modified to 993, by previous owner and works great till date (I’ve read some online research, that many have also done this forward date, from 964 Semi-Trailing Arm, to 993 Multi-Link Design).

Hope to seek your kind advise and apologies on the long posting.
Really hope to seek any advise at all, as I hope to replace to factory 993 RS ABS Harness and 993 RS Pipings (as a 1 make 993 3.8 RS setup).

[KelvWKK]

Originally Posted by TJ9931

Found this thread here also:
Garth S states the OLD part # off his car is 993 355 053 50 (pulled from my '96 C4S parts car)

Thread is here
WTB/Needed: 993 C4S ABS Hydraulic Pump
Originally Posted by golfnutintib
Hey guys I thought I would try the power of the RL Board and put this out there...

I am in urgent need of an ABS Hydraulic Pump for a '96 Carrera C4S (wide body non turbo model).

Part # as far as I can tell is 993 355 953 50.

Alternative part number MAY be 993 355 953 01, although some dealers seem to think this part may be for a non wide body 4WD car (but I can't imagine it is a different part...maybe just a different part number).

Anyway, if any RL member has one of these that is working and can be shipped to me in California, I would greatly appreciate it.

Thanks in advance.

Reply Garth S
PM sent .... BTW, the correct p/n is 993 355 053 50 ( pulled from my '96 C4S parts car) ... mine has the mounting bracket attached, which somewhat obscures the p/n.

https://rennlist.com/forums/993-forum/914311-wtb-needed-993-c4s-abs-hydraulic-pump.html

Thank you for your kind advice.
I’ve read through and very informative to help my re-build.
I’ve started ordering some of the parts from you advice and updated the summary in my initial post.

Regarding ABS Harness & Piping: I tried, but could not find any firm information on this.

ABS / Trunk Harness: Would you know if a 964 C4 Harness fit the above 993 RS Brake Parts?
Logic: Both are 4-Channel Electro-Hydraulics.
Doubts: Theoretically a RS is C2. However 993 C2 is not on a Electro-Hydraulics system.
-> Seek Advice: Hence it points back to 993 C4S Harness (confusing & hope to seek advice)?

Piping: Would you know if the 964 C4 piping, be used to fit the above 993 RS Brake Parts?
Logic: Theoretically both are 4-channels.
Doubts: But I believe the piping design is totally different (size and layout).
-> Seek Advice: Hence does the 993 RS setup, use 993 C4S piping (confusing & hope to seek advice)?

[KelvWKK]

Seek Advice: If anyone knows the Model with its default harness, that successfully fitted the 993RS ABS setup (993 C2 or C4 or TT).

- Could you share if your Air-Cooled’s Model (for me to hunt down the same Model’s ABS Harness).
- Or if you have changed the ABS Harness, could you share the Car Model that you purchased from (I’ll source from same Model).

Much appreciated and apologies to trouble you for advice.

[Cobalt]

So I am trying to digest this and from someone who has done most of this already you have me a bit confused.

The 993 and 964 ABS has no compatibility if it was originally 964 you will need to replace the tone rings and pickups I see since you already have 993 fronts I must assume if they changed to multi link the same goes for the rear.. I don't recall the exact count but I believe the 964 has 52 vs 54 teeth for the 993. Then you will need to plumb a line for the 993 four channel ABS vs the 964's 3 channel system. The 964 RS came with a 25.4mm MC and the C4 a 23.81 At least the one I removed from my 90 C4 was. Replacing with the larger 25.4MC requires adapters and the cost is crazy these days it was $500 a few years back they are over $1000 today.

You will need to rewire your existing harness and you can purchase the correct connectors to use with the 993 ABS unit but it will be work.

These projects are far more complicated than most can imagine.

GL

[KelvWKK]

Originally Posted by Cobalt

So I am trying to digest this and from someone who has done most of this already you have me a bit confused.

The 993 and 964 ABS has no compatibility if it was originally 964 you will need to replace the tone rings and pickups I see since you already have 993 fronts I must assume if they changed to multi link the same goes for the rear.. I don't recall the exact count but I believe the 964 has 52 vs 54 teeth for the 993. Then you will need to plumb a line for the 993 four channel ABS vs the 964's 3 channel system. The 964 RS came with a 25.4mm MC and the C4 a 23.81 At least the one I removed from my 90 C4 was. Replacing with the larger 25.4MC requires adapters and the cost is crazy these days it was $500 a few years back they are over $1000 today.

You will need to rewire your existing harness and you can purchase the correct connectors to use with the 993 ABS unit but it will be work.

These projects are far more complicated than most can imagine.

GL

Hi Cobalt,
Thank you for your advise.
Complete 993 Undercarriage:
Yes. Essentially I’m on a full 993 setup, w the 964 C4 parts removed.
Full 993 undercarriage (front and rear) and on a G50 6-speed w LSD.
So the rear shaft having the 993’s teeth count, but I believe the front is a 964’s teeth count as the front arm were the damaged 964 C4 arms (with modified 964 coupling, since the 964 C4 transmission was removed & swapped with the 993 C2 G50 6-Speed).



Electro-Hydraulic ABS System:
And yes. I believe the 964 C4 is on the hydraulic ABS setup & so is the 993 RS (as opposed to the C2 Vacuum setup).
My entire harness is in very bad shape, and I chanced upon a used 993 C4S harness.
So I’m wondering if anyone has successfully plug-&-play the below “993 RS Setup”, on a 993 C4S, or plug-&-play on the 993 C2.

Hence I intend to change the full ABS setup to 993 RS.
- ABS Control Unit 993.618.127.00: I have purchased that.
- Master Cylinder 993.355.903.00 (25.4mm bore): I am still sourcing, as I’m currently on 964.355.025.52 (20.4mm bore).
- ABS Hydraulic Pump 993.355.955.50: I am still sourcing, as I’m currently on 964.355.955.00 (4 Channel w LSD).

Question: With that, could you share if you successfully fit the RS ABS System, on a 993 C4S or C2 harness?
Sorry to trouble you for advice.

[Cobalt]

I have converted a C4 harness to a C2 brain both 964 but never tried to convert to a 993. You will need to have both tone rings the same teeth to work.

This is a bit involved and I was considering pulling the entire unit and going with a BMW 4 channel race setup in the future.

Since my car was a C4 converted to C2 I had to make a piece to work with later 993 hubs. I cut the front axles to make a 964 RS style front assembly. You will need to verify what you have n the rear first and than make the adjustment for the front to be the same.

[KelvWKK]

Thank you so much for your advise, Cobalt.
Wow! Yours look really professional!
- My Front is on 964 C4 Tone Rings/Coupling (964.349.092.01), as the previous owner convert to a C2, but kept the 964 C4 ABS Brain Control Unit (terrible mess of mix/match).
- The Rear is always on a full 993 undercarriage and drive shaft to the 993 G50 6-Speed.
Question #1: Pertaining the next step, I will follow your route. To swap out the front, into the 993 RS Tone Rings, to pair with the Rears & also to pair with the 993 RS ABS Wheel Speed Sensors “as a set” (for the ABS Brain Control Unit to read).
(1) Regarding Connectors & Harness: Can I learn from you, which 911 Model that you purchase them from (964 C2, 964 C4, 993 C2, 993 C4S, or aftermarket)?

(2) Regarding conversion from your ‘90 C4: Can you advise if you converted to 964 C2 or 964 RS (as I believe both systems are slightly different).
- C2 (964 & 993): I believe are 3-Channels, on Vacuum setup.
- RS, TT, C4S (993): I believe are 4-Channels, on Electro-Hydraulic setup.

(3) Regarding spare 993 C2/RS “used set”: Would you happen to have a spare set, to let go (Tone Ring, etc)?





Question #2: Pertaining the ABS Harness, in the front Trunk of car, that connects the ABS Brain Control Unit, to the ABS Hydraulic Pump, ABS Brake Booster Pump, etc (your 964 is a ‘90 C4, hence you modified the existing, instead of starting from a C2 Harness).

(1) Regarding Electro-Hydraulic connectors: Is it due to RS & C4 being on Electro-Hydraulic, so you started from C4 Harness as a base (which the C2 Harness doesn’t have)?

(2) Regarding 964/993 Wheel Speed Sensors & Connectors: Is it due to Connectors being unable to fit the Toner/Coupling size (are C2 /C4 / RS, slightly different)?


Apologies on my many questions, as I’ve done much online and PET checks but I could not understand it.

-> Essentially Drawing #1, Harness 1 & 2: Affects all the Harnesses & Sensors, in Drawing #2 & #3.
Issues with the PET Catalogue & Drawings, is my lack of understanding between M339AWD vs M224 for Harness: Hence I could not understand if I should use “993 C2 Harness & Connectors” (Vacuum) or use “993 C4S Harness & Connectors” (Electro-Hydraulic)”.
Since I’m building a 993 RS Clone, the ABS is the Electro-Hydraulic system (similarities in C4S & TT’s 4-Channel setup, apart from the M/C).
But my confusion is that it does not make sense to me to use M339AWD, as a RS is a RWD (conflicts the Connector Types, due to a non Electro-Hydraulic Pump despite the same ABS Brain Control Unit & same ABS Brake Booster (same PN: 993.618.127.00).




Thank you again Cobalt and best regards.

[Cobalt]

I like to use what I have and the stock harness was there. So I purchased the correct connector to fit the C2 ABS brain and rewired it. It was a lot of work and unfortunately my old brain doesn't recall the specifics off hand this was 4-5 years ago. The factory manuals will give you the pinouts which need to be converted.

BTW the C4 ABS units are crazy expensive. Mine was toast hence the reasoning to switch over. I have a bunch of C2 units which were much more reasonable.

I cut mine just after the tone ring. It appears they just removed the CV joint and retained the rest. I will check I might have a spare set of 993 tone rings if I do I will get in touch.

[KelvWKK]

Thank you so much again, for your advice, Cobalt.

I initially thought the 993 RS Default ABS Harness is either (if I use all the exact 993 RS ABS Brain, Hydraulic Pump, ABS Booster Pump & M/C):

(1) 993 C4 & TT Harness: Due to the Setup Being “Electro-Hydraulic” (due to connectors).

(2) or 993 C2 Harness: Due to the RWD as opposed to AWD (due to connectors).

->but it seems I am wrong: It sounds like the original 993 RS has its own ABS Harness (a hybrid of Connectors: Connectors for Electro-Hydraulic pumps and Connectors for C2 RWD Vacuum ABS Brain).

[Cobalt]

Kelvin,

My car is a 964 started life as a C4 with electrohydraulic 3 channel ABS braking vs vacuum. I used the harness that came with the car it was just a conduit for running the signal and I did not see the need to change it out. Simple plug and play of the pickups at the uprights the 993 uses the same end connectors as the 964 units the difference is the angle the pickup is mounted to the upright.

I do have a spare set of 993 front tone rings if you need them. They have been dismounted. and are in like new condition.

[KelvWKK]

Originally Posted by Cobalt

Kelvin,

…the difference is the angle the pickup is mounted to the upright.

I do have a spare set of 993 front tone rings if you need them. They have been dismounted. and are in like new condition.

Regarding 993 C2 Tone Rings, Parts & Sensors: Thank you so so much and really appreciate it.
I will PM you, to purchase from you. Really appreciate it.

Regarding other 993 RS Parts and Harness: Should you have any spares to let go, I am very much interested to also purchase from you.

Best regards,
Kelvin

[KelvWKK]

Problem Resolved: It is due to the previous owner’s fabricator raising the height of the front trunk, to clone a 993 position, for front fender and hood (964 chassis with 993-shell sheet metal).

Keeping this info here, should anyone be reverting from 993 to other variants, as the front height is different.



Hi Gentlemen,
Over the past 2years of my build, changed my RSR Build alittle and I’m now working towards a 964 RSR Body, but everything else will be the more modern 993 RSR.
I could not complete a 964 RSR clone as planned, as the rear frame has been cut and modified by the previous owner, to fit the 993 undercarriage (didn’t realise the extent of the cutting till recently).

With that, I hope to reach out for advise as I have an issue with the body work.
It seems that the door does not line up with the front Fender wing.
As you can see, the front of fender lined up with the front trunk lid.
And the gap between the fender & the front wiper panel, is in-line.

- Could I have missed out a shim or a bracket for 964 front fenders?
- Or could the 994 doors be totally different, vs the 993 (since the car was forward dated).

Hoping to reach out to any folks who might have restored their 964 or 993 shell.
Thank you in advance.

[KelvWKK]

Sorry gentlemen, as I have another question to seek advise.

Qn: Would you know if the 964 turbo rear trunk lid, is different from the standard 993?

My builder is in the midst of body work and they informed that it will not line up to the body.
Taking a 964 turbo trunk lid placed side by side with my 993 trunk lid, I could see a 1.5 inch difference in length.
Since my car was fitted with the whale tail, I never got down to fitting the 993 trunk lid.

- Hence could my 993 trunk lid, be mistakenly from a G-body (right of photo)?
- Or indeed the 964 turbo trunk lid (left of photo), is longer than the standard 993 (right of photo)?

Hope to seek kind advise.

[Cobalt]

I am assuming they cut the rear cross member out and repalced it with a 993 version to fit the 993 deck lid. This will also require the use of the 993 tail lights. It sounds like you will need to replace the rear cross member to a 964 unit to use the 911 deck lid. The turbo 3.6 lid you have is the same as the 930 part. It just used spacers to make it work. In fact all the non motorized deck lids on the 964 were from the G-body cars.

[KelvWKK]

Originally Posted by Cobalt

I am assuming they cut the rear cross member out and repalced it with a 993 version to fit the 993 deck lid. This will also require the use of the 993 tail lights. It sounds like you will need to replace the rear cross member to a 964 unit to use the 911 deck lid. The turbo 3.6 lid you have is the same as the 930 part. It just used spacers to make it work. In fact all the non motorized deck lids on the 964 were from the G-body cars.

Thank you so much for the advise.
It makes sense as they line up very differently.

I was just searching the forum and noticed that the 993 lids are indeed shorter than the 964 (similar to the g-body).
I’ll have a word with the builder, as the RSR plan is for the body and shell to clone a 964 RSR (but everything else, to clone a 993 RSR).
So they will probably have to make some adjustments and add spacers.

Rear Engine Deck - Are there different versions?

Thank you again for you kind advise.
I’m working on this, while I continue my search for 993 RSR 4-Channel ABS full system, and the entire car’s harness.

Best regards.