GT500 engine + DcT in a GT350 doable?

[T7TheLama]

Ok couple of updates. Drove the car for around 1000km so far so good)!
I'm currently in the process of making the oss sensor behave correctly for cruise control.

In the TCU software i can change a couple of settings. (VSS=OSS)
1) VSSPull Up 2.2k ohm (active)
2)VSS Sensitivity Voltage (currently 2.5V)
3)VSS Multiplier (currently 11.95)

VSS Multiplier is 60 tooth x ~12 = 720 pulses, so like oem

With that multiplier set the oss from the tcu and the pcm match and cruise control works again (for 20 minutes or so)

Issue is after sometimes 20 minutes or 1 or a hard pull i get a see manual error (DTC U0401)

After that i flashed the pcm with Hptuners to somewhat match the 8 gear ratio in a 6gear table.

Which seems to have done something but not with the error(( The active exhaust close works again but this time in 8 gear instead of 6/wish it didn't work haha. But i found out in Hp tuners you can now make the active exhaust behave like you want.

After playing a bit with forscan i looked at the signal from the oss sensor that the pcm receives (the green line)and it looks like the pcm misses a few pulses. So for now i try to lower the voltage sensitivity to get a better reading.

If that doesn't work, i'm kinda lost on the oss stuff

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[Rodpwnz]

I gotta glaze you here big dawg, your work is truly inspirational. I’ve dreamt of the possibilities had ford gone with the ZF8…

Cherry on top is that you’re on the up and up with Akiaura - I’ve been listening to deathwish on repeat since release last week.

 

[ZXMustang]

OSS=RPM divided by current gear ratio.

Example 5000rpm divided by the 10R80's first gear ratio of 4.69 would be 1,066 OSS. And it works in reverse. 1,066 x 4.69 = 5000rpm.

You need to know the 8 speed auto's gear ratio's for each gear. Then you can work out OSS per gear for what RPM scenario you are wanting - like part throttle shift or WOT shift points...

 

[ZXMustang]

From my Ford tuning trained AI.

Confirmed. The Turbo Lamik TCU for the ZF 8HP70 is widely used in standalone Ford applications (Mustang GT, GT350, etc.) and is known to interface via direct analog inputs (RPM, TPS, MAP) — not native CAN to the PCM. It broadcasts its own CAN stream, primarily for dash integration and logging, not for OEM-level ABS or PCM sync.

Here's what’s happening:

1. Cruise works at firstbecause VSS is being accepted by the GT350 PCM — likely from either:
   • ABS module (still active), or
   • the Lamik controller broadcasting a pseudo-VSS on the right frequency.
2. After a certain runtime or a heavy load event:
   • PCM performs a CAN message integrity check on 0x0A5, 0x0AA, or similar.
   • If the CRC, length, rate, or checksum fails — or if messages vanish (e.g., ZF TCU enters limp or resets) — DTC U0401 is triggered.
   • Cruise cancels, PCM exits decel fuel cut, torque arbitration errors cascade.

GT350 PCM Requirements Recap (for cruise to remain active):

Signal	Source Requirement	Method To Satisfy
VSS (0x0A5)	ABS-style CAN at ~10ms interval	Emulate using CAN bridge/gateway
Brake status	ABS module, 0x0AA	Emulate or keep ABS module present
Engine torque	PCM internal	Already present in GT350 ECU
No CAN error	No conflicting TCU messages	Filter or isolate Lamik TCU broadcasts

Recommended Fix Strategy (Specific to Turbo Lamik + GT350 PCM):
1. Retain ABS Module (even standalone)

• It’s the cleanest source of 0x0A5.
• GT350 cruise logic relies heavily on ABS-derived speed and brake status.
• Even if ABS is not controlling brakes, it can function as a VSS/CCM emulator.

2. Use CAN Bridge to Block or Filter TCU Conflicting Messages

• If the Turbo Lamik controller is broadcasting VSS or torque on conflicting IDs, PCM will reject them after ~20 minutes.
• Use a tool like:
  • CANBed Dual
  • SavvyCAN + GVRET
  • PiCAN2 + SocketCAN
• Filter out or rewrite the TCU’s VSS broadcast to prevent PCM arbitration failure.

3. Don’t Rely on Lamik’s VSS → PCM Behavior

• It was never designed to satisfy Bosch MEG17.8.8 cruise or torque arbitration.
• It works enough for the car to drive, but fails strict cruise/timer-based validation.

Actionable Options:

• You want cruise to stay active:Build a small CAN bridge to either:
  • Re-emit a valid 0x0A5 ABS message using ZF OSS data.
  • Block conflicting CAN IDs from Lamik TCU after initial boot.

I can supply exact Ford ABS 0x0A5 message structure and CAN bridge code if you tell me what hardware platform you're using (e.g., ESP32, Arduino CAN, PiCAN). Want to proceed with building the emulator?

 

[T7TheLama]

After wrist surgery, I’m back at it, still working on the frustrating VSS/OSS issue. At first, I tried using a Schmitt trigger to clean up the signal into a proper square wave, but I’m still getting the same random dropouts lasting about half a second. That makes me think it’s not a signal quality issue, but more likely the TCU introducing slight errors that are tolerable for the tachometer but not acceptable for the PCM i guess. So, I’ve decided to ditch the VSS output from the Turbolamik entirely and go with an external sensor instead.

For that, I needed a new output flange with an integrated tone ring. On the left is the old setup, on the right is the new single piece flange that also replaces the OEM output flange.

Red is the new OSS sensor just need to wire it in. Additionally I need something too divide the signal. I'm pretty sure the OEM teeth count is lower than I have.

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