GTOFAN91

Hey guys! I have been playing around different builds and picked one.

A simple head,cam, FAST on a 100-150 shot. Rear is 3:91, and my 04 currently still has the M12 6 speed.

Questions are as follows.

1. Can I re-use my cross member? I read you can but IDK

2. I just figured my BCM/ECU and key FOB nightmare, and was wondering if i have to re-program anything going from a stick to a fully manual valvebody automatic? I think a clutch pressure safety switch is what I heard floating around would need to be sorted...some say just tuck the clutch pedal under the carpet compressed again IDK if it works im down for some easy rigginz

3. Which trans TH400 is obviously beefier but will I need more.

Thanks guys

GTOFAN91

noone?

dw456post

You can use the stock crossmember and add a plate on the back side to extend the mounting holes for the 400. Or, You can buy a storebought crossmember from Hutter. That is what I did. It comes with a trans mount.
I did a 4L80 in a 2005 so it is a bit different from the 2004 swap. I still have my clutch pedal and have not moved it yet---LAZY---. I removed the clutch master from the firewall. When somebody sits in my car, they look at the pedal and then the stock auto shifter a couple of times. WTF is this?
A couple of guys on LS1 GTO have done the 400 swap, so check on there. ToroToro has an 05 with a 400 and he may be able to help you. His is manual shift also. (Dennis Kirkland). I think your swap is pretty easy since it is fmvb. You will need a driveshaft, LS style converter, oil cooler and lines, shifter. A built (Level 2 or 3) 400 can take all you will be able to throw at it with your setup.
Let me know if I can help.

GTOFAN91

Excellent thank you, i was just wondering about the tune mostly, and if the car will have any whacky stuff going on after the swap. I would hate to have to get my car tuned 2-3 times it gets expensive. I suppose you wouldn't know much about the tune? also do you have to push your clutch pedal in to start the car?

dw456post

No wacky stuff. The trans swap will not affect the engine tune unless you have a lightweight flywheel now, and that's just some idle tuning (torque). With HP Tuners, You will need to go into the trans section and change the trans to auto and also change the new gear ratios in the chart along with the trans pulses to 40 so your speedo will be correct. The change to auto should take the clutch switch out of the loop so you don't have depress it to start. You will however need a neutral safety switch in your shifter. Have fun.
I hope this is going to be a weekend driver. The 400 has no overdrive.

402GOAT

iTrader: (2)

If you're going from a manual car to a mvb th400, the computer stuff is pretty simple. It's the auto car to th400 that's a little trickier but still doable.

RacerBill

iTrader: (20)

Great advice here. Going from a manual to a non-E controlled setup is cake. On the electrical side, basically just swap over the PNP signal/switch (previous clutch pedal switch), cruise control cancel (other previous clutch switch; also tied to brake signal, which is already in place), reverse light signal (comes from passenger side of trans), and VSS (comes from tail shaft of trans). I think that is about it.

I went from a manual to a 4L80E, but I chose to let the computer control the shifts instead of a FMVB type "controller". I have 99% of the bugs worked out, but I still have a few little items I am in the process of addressing (been at this last 1% for over a year now).