Installing universal standalone GCU requires certain modifications to be done to the mechatronics unit inside Getrag GS7d36sg transmission.
To modify it You’ll need:
- Soldering station
- Dremel /w abrasive plate
- Torx
- Side cutters
- 1mm2 and 0,35mm2 Wires (silicone/PTFE wires, oil resistant, 200C rated)
CAUTION: This modification require soldering experience and steady hand due to very tight location of soldering
RECOMMENDATION: please use NOISE SUPPRESION circuit that can be found at HTG e-SHOP to minimize risk of signal noise. Circuit description can be found at WIKI / WIRING / NOISE troubleshooting
Open DCT mechatronics cover by unscrewing T25 TORX bolts around cover. Please keep in mind that remaining transmission fluid may leak while opening the cover.
1. Disconnect main connector from mechatronics unit by pulling plastic lock up, and pulling connector out.
2. Unscrew round connector in gearbox housing. To remove it completely use long tool to unlock and unplug connector from temperature and input shaft speed sensor behind clutches. It is also possible to remove front clutch dust cover to allow easier access to the plug. i. Remove front dust clutch cover. ii. From front of the trans you can clearly see Torx screw that holds ground clip. Unscrew it. Pay attention not to drop the screw. iii. From side pan location where the loom turns i to case connector insert long screwdriver. Being in the front you have good visibility on it. iv. Gently push on the connector from the TOP and pull the leads. Remove wires from 4 pin connector and replace with new wires in the following order (with respect to below diagram of pin numbering):
- pin 1 to GCU FREQ_in3 (B3)
- pin 2 to GCU s_GND (L2)
- pin 3 to GCU AN_in9 (E1) IMPORTANT: Add 2k2 pull-up to +5v_out (M1)
- pin 4 not used.
It’s possible to connect this sensor without removing it’s connector but it requires to label wires connected to original main connector (MC) prior to cutting them. To do so label wires going to original MC pins 4, 5, 6. OEM MC pin 4 is sensor’s pin3 (AN_in9), OEM MC pin 5 is sensor’s pin2 (s_GND) and OEM MC pin 6 is sensor’s pin 1 (FREQ_in3).
3. To remove control unit unscrew all the bolts shown in the picture below (11 positions).After removing unit it is strongly recommended to degrease whole assembly to improve ease of modification and keep your workplace clean. Universal degreaser works just fine as well as brake cleaner or so.
4. Remove plastic covers from solenoid connectors by gently levering.
5. Unscrew T10 TORX bolts holding aluminum cover of electronic control unit. Carefully remove rubber seal to avoid damaging it at further modifications.
Pay attention to pad nomenclature and numbering order, since correct wire routing is mandatory for transmission to function with standalone HTG Gearbox Control Unit.
6. Stock controller is connected to pads around it with thin aluminum wire. Remove all of them with tweezers. While removing pay attention to hold them as close to soldering pads as possible so minimal length of them remains (preferably none).
7. Clean solder pads MECHANICALLY. Degreaser / nitro / acetone does not remove gel cover. Easiest way is to remove it with tweezers and ear cleaning sticks.Connectors A and B require additional cleaning with Dremel type tool with abrasive disc to remove coating preventing soldering.
8. Measure length of connecting signal (0.2mm2 or 24AWG) wires that are needed to be done. Wires shouldn’t be too short to avoid connection failure in future. Apply tin to tips of wires before soldering on to pads.
Make sure there is no short to thin trace between pads C2 and C3.
9. Perform soldering listed below:
| E1 | A2 |
| E2 | B2 |
| E3 | C2 |
| E4 | C3 |
| E5 | C4 |
| E6 | C6 |
| E7 | C8 |
| E8 | keep unconnected |
| E9 | C10 |
| E10 | C11 |
| E11 | C12 |
| E12 merge with E13 | D2, D3, D6, D7, F2, F3, F6, F7, F10, F11 |
| E14 | C5, B1, A1 |
| E15 | C13, C9, C7, B3, A3 |
10. After soldering ensure there are no short circuits between pads. Apply silicone seal on solder pads, and on wires to prevent them from moving around and avoid connection failure.
11. Reinstall rubber seal before mounting the cover back.
12. Tin all soldering pads on solenoid connectors. Each connector has signal and VCC wire. It is recommended to wire all of them in the same way, for example pad 1 signal and pad 2 VCC (+12v on ignition).
13. Measure wires to be long enough to allow easy connection outside of transmission. Label signal wires from 1 to 10. It is crucial to label them reliably to minimize risk of incorrect wiring. Each solenoid has to be connected to corresponding output of HTG GCU unit. For ease of wiring solenoid consecutive numbers match consecutive output numbers.
Photograph shows which pad has to be soldered to PWR_out wire. Remaining pads are joined together with VOLTAGE supply – Results from point 9l
14. Connect solenoids with the GCU Skip to the end to see HTG GCU pinout diagram
| Solenoid | GCU pin | Solenoid soldering pad |
|---|---|---|
| Solenoid 1 | GCU PWR_out1 (H1) | S1-A |
| Solenoid 2 | GCU PWR_out2 (H2) | S2-B |
| Solenoid 3 | GCU PWR_out3 (H3) | S3-A |
| Solenoid 4 | GCU PWR_out4 (H4) | S4-B |
| Solenoid 5 | GCU PWR_out5 (J1) | S5-A |
| Solenoid 6 | GCU PWR_out6 (J2) | S6-B |
| Solenoid 7 | GCU PWR_out7 (J3) | S7-A |
| Solenoid 8 | GCU PWR_out8 (J4) | S8-B |
| Solenoid 9 | GCU PWR_out9 (K1) | S9-A |
| Solenoid 10 | GCU PWR_out10 (K2) | S10-B |
15. Either apply tin to wire tips of main mechatronic connector (MC), and prepare set of wires to solder to them in a way that total length would match length of solenoid wires, or make new wires using GS7 Main Connector terminals. Those terminals are available for purchase from HTG. 20-18 AWG wires are used for terminals MC 1 – 12 while 15-13 AWG for MC 14-16. Terminal numbers are described on the connector itself. See diagram below for confirmation.
16.
| MC | GCU connection | comments |
|---|---|---|
| MC 1 | GCU AN_in1 (C1) | |
| MC 2 | GCU AN_in2 (C2) | |
| MC 3 | GCU AN_in3 (C3) | |
| MC 4 | GCU AN_in4 (C4) | |
| MC 5 | GCU FREQ_in1 (A3) | |
| MC 6 | GCU AN_in5 (D1) | Add 4k7 pull-up to +5v_out (M1) |
| MC 7 | GCU FREQ_in2 (A4) | |
| MC 8 | GCU AN_in6 (D2) | Add 4k7 pull-up to +5v_out (M1) |
| MC 9 | can be removed | |
| MC 10 | GCU AN_in7 (D3) | |
| MC 11 | GCU AN_in8 (D4) | |
| MC 12 | ||
| MC 13 | GCU_+5v_out (M1) | |
| MC 14 | joined with GCU_+12V_main (M3, M4) | fuse (15a) +12v supply |
| MC 15 | GCU_sGND (L2) | |
| MC 16 | joined with GCU_+12V_main (M3, M4) | fuse (15 a) +12v supply |
It is STRONGLY RECOMMENDED to separate loom of valves from sensor loom, so noisy wires are not braided with noise vulnerable sensor signals.
It is also recommended to put all wires in heat shrink sleeves inside transmission case to maximize protection
Round connector will only be used as a passage through transmission case – please drill a hole in it and lead all the wires through it and seal it with silicone packing afterwards (f.eg.Victor Reinz Reinzosil).
HTG GCU requires main (MAIN RELAY’ed) battery +12v applied to +12_main (M3, M4), as well as ignition +12v signal applied to +12_IGN (L1).
Even though HTG GCU has internal protection it is advised to secure IGN signal with 5Afuse to prevent failure of the device.
Ground connections GND (L3 and L4) should be made on engine or chassis, as long as chassis ground point is confirmed to be efficient.
+12v_out (M2) can be used as supply for shifter, paddles or other low power auxiliaries that needs voltage feed.
For proper functionality HTG GCU needs to be fed with ECU signals. Those signals are usedto configure and map transmission operation.
To communicate with ECU AN_out1-4 (A1, A2, B1, B2) can be used and CAN_1 and CAN_2
This guide is just INFORMATIONAL one. It shows quite easy and safe method of wiring GS7d36sg transmission to work with HTG GCU, but it can be also done with different method as long as connections remain unchanged between point and GCU.
