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4th gen LS1 to LS2 questions

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Old Feb 18, 2025 | 07:26 PM
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Default 4th gen LS1 to LS2 questions

Hello, I'm in Sydney, Australia and I have a 98 Formula. It's the stock Ls1 with the 4 speed auto.
I'd like to know if anyone has swapped out, not just the LS1 for LS2, but the engine and auto? Here in Australia, there are still quite a few LS2 Holdens with the 6 speed auto. I'd be keen to know how much work is involved in getting the LS2 and 6 speed auto into my car?

It's either that, or I consider a rebuild on my LS1 and swap it to a manual, but this might be a bit of a PITA, considering the steering has been converted to right hand drive (I've got the horrible hump in front of the right hand seat, to accommodate the cat)

Any details, links, hints, tips, thoughts are welcomed. .. .
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Old Feb 19, 2025 | 09:26 AM
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On the engine side, your LS1 has a 24x reluctor and likely uses the unique '98 PCM. Early LS2 are also 24x and would be trivial to swap in, needing only a tune change for the engine size difference, possible injector size difference and a harness extension for the front mounted cam sensor. The knock sensors also are different; not sure if the '98 PCM supports side mounted LS2 knock sensors, but I simply ignored them.
The 6 speed auto is a bit more complicated as it has its own controller built in and expects to talk to a more modern ECU (over CAN bus I think). Several aftermarket 6L80E controllers are available which only need basic sensor values from an existing setup.
The "Automatic Transmission" section of this forum had many older threads on how to swap to a 6L80E on LS1 powered cars. Do an Advanced search and limit the search to that forum section.
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Old Feb 19, 2025 | 01:47 PM
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Originally Posted by mrvedit
On the engine side, your LS1 has a 24x reluctor and likely uses the unique '98 PCM. Early LS2 are also 24x and would be trivial to swap in, needing only a tune change for the engine size difference, possible injector size difference and a harness extension for the front mounted cam sensor. The knock sensors also are different; not sure if the '98 PCM supports side mounted LS2 knock sensors, but I simply ignored them.
The 6 speed auto is a bit more complicated as it has its own controller built in and expects to talk to a more modern ECU (over CAN bus I think). Several aftermarket 6L80E controllers are available which only need basic sensor values from an existing setup.
The "Automatic Transmission" section of this forum had many older threads on how to swap to a 6L80E on LS1 powered cars. Do an Advanced search and limit the search to that forum section.
I was actually thinking of swapping the whole kit and kaboodle... I figured it might be less of a hassle adapting things...?
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Old Feb 19, 2025 | 07:56 PM
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From what I know of these cars over the years, this is do-able.

If you pull a complete LS2 & 6L80E setup from a Holden you'll need to get the Engine, Transmission, PCM, TCM, Gas Pedal, and TAC Module.

The 1998 Car is fine, you'll have to install the electronic Pedal, obviously the Engine & Transmission, then install the newer PCM, TCM somewhere, and the TAC somewhere also. Then you have to wire it all together correctly. TCM with the PCM communicate on the CAN-BUS wires.

Installing all the extra stuff requires more 12v fused power sources, the Factory Fbody Fuse Box will run the PCM so it's a matter of adding a couple inline fuses for the TAC Module & TCM. Pedal in the car you might be able to tap into a circuit in the interior.

The Gauges would work as long as you use the 1998 ECT and Oil Presure Sensors, ECT will work with the Gen IV PCM as long as Pins A & B are wired to it, Pin C goes to the Gauges. Oil Pressure Sensor becomes the obstacle at this point with the Gen IV PCM because it's a little different than that 1998 one. Gen IV stuff the Oil Pressure Sensor is a serial data signal to the Gauges if I remember right. That and it needs oil pressure signal from that Sensor to even run, it had something in the PCM to where it won't throttle up if there is no oil pressure. 1998 it was purely Analog to the Gauges and grounded through that circuit. 1998 was the oddball here, that Gauge Cluster won't use anything but 1998 Sensors.
Speedo and Tach would work as long as those signals from the PCM were wired to the Gauges, Fuel Gauge is from the PCM and can be calibrated actually. Voltmeter is wired from the Alternator, that would be fine.

So it all can be done, just a matter of it showing oil pressure correctly on the Gauge Cluster.

Swapping to a 99-02 Cluster might work if the Serial Data outputs from the Gen IV PCM will communicate with it, but I don't think they do.
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Old Feb 19, 2025 | 07:56 PM
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Originally Posted by Peter Windle
I was actually thinking of swapping the whole kit and kaboodle... I figured it might be less of a hassle adapting things...?
By that you mean also the ECU, electronic pedal and all? That would simplify many things.
Others will have to chime in about how difficult it is to connect the existing gauges to the new ECU and harness. It might then be easier to go with aftermarket gauges, Speedometer, Tachometer and such.
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Old Feb 19, 2025 | 08:01 PM
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Originally Posted by the_merv
From what I know of these cars over the years, this is do-able.

If you pull a complete LS2 & 6L80E setup from a Holden you'll need to get the Engine, Transmission, PCM, TCM, Gas Pedal, and TAC Module.

The 1998 Car is fine, you'll have to install the electronic Pedal, obviously the Engine & Transmission, then install the newer PCM, TCM somewhere, and the TAC somewhere also. Then you have to wire it all together correctly. TCM with the PCM communicate on the CAN-BUS wires.

Installing all the extra stuff requires more 12v fused power sources, the Factory Fbody Fuse Box will run the PCM so it's a matter of adding a couple inline fuses for the TAC Module & TCM. Pedal in the car you might be able to tap into a circuit in the interior.

The Gauges would work as long as you use the 1998 ECT and Oil Presure Sensors, ECT will work with the Gen IV PCM as long as Pins A & B are wired to it, Pin C goes to the Gauges. Oil Pressure Sensor becomes the obstacle at this point with the Gen IV PCM because it's a little different than that 1998 one. Gen IV stuff the Oil Pressure Sensor is a serial data signal to the Gauges if I remember right. That and it needs oil pressure signal from that Sensor to even run, it had something in the PCM to where it won't throttle up if there is no oil pressure. 1998 it was purely Analog to the Gauges and grounded through that circuit. 1998 was the oddball here, that Gauge Cluster won't use anything but 1998 Sensors.
Speedo and Tach would work as long as those signals from the PCM were wired to the Gauges, Fuel Gauge is from the PCM and can be calibrated actually. Voltmeter is wired from the Alternator, that would be fine.

So it all can be done, just a matter of it showing oil pressure correctly on the Gauge Cluster.

Swapping to a 99-02 Cluster might work if the Serial Data outputs from the Gen IV PCM will communicate with it, but I don't think they do.
>>>> Would you happen to know if there are any major size differences/issues with the 6 speed auto going in??? PS: I'm trying to find the thread about the auto, not found it yet...
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Old Feb 19, 2025 | 08:05 PM
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Oh it's definitely bigger, it'll be tight. Never done one in a 4th Gen Fbody but the tunnel helps they came with a T56 from the factory.
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Old Feb 19, 2025 | 08:10 PM
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IIRC it only takes a few swings with a "bashometer" to make it fit. Trans mount likely moves back, but easy to drill new holes in the frame rails for that. And a shorter driveshaft.
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Old Feb 19, 2025 | 08:14 PM
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Originally Posted by mrvedit
IIRC it only takes a few swings with a "bashometer" to make it fit. Trans mount likely moves back, but easy to drill new holes in the frame rails for that. And a shorter driveshaft.
You haven't been under a 4th Gen Fbody, there's no Frame Rail.

Transmission Mount bolts to four threaded holes in the middle of the Body. This is something that will have to be fabricated and the Torque Arm situation addressed as well.
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Old Feb 20, 2025 | 01:56 PM
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Originally Posted by the_merv
You haven't been under a 4th Gen Fbody, there's no Frame Rail.

Transmission Mount bolts to four threaded holes in the middle of the Body. This is something that will have to be fabricated and the Torque Arm situation addressed as well.
Sorry yes, I was thinking Gen 1 and 2. Helping someone with a Gen 1 LS swap now.
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Old Feb 21, 2025 | 06:30 PM
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Why not use a Holley Terminator system instead of replacing the entire harness with a LS2 harness?

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Old Feb 22, 2025 | 03:00 AM
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Pedal in the car you might be able to tap into a circuit in the interior.
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