Pontiac G8 2008-2010 - TH400 Swap!

I undertook this swap due to limitations of the 6L80. The cost to rebuild the 6L80 with no guarantee was not inspiring, especially when I'm looking to push a good bit more power then I am now once I get the trans and fuel sorted out. I looked at 4L80's but didnt want to deal with electronics again interfering with my shifts.

My buddy Mike offered up his TH400 that last lived life in his 80's Suburban. I couldnt think of a good reason not to. I ordered an SFI flexplate, B&M shifter, and other small parts to make the swap complete.

We compared the lengths of the 6L80 and TH400 which were surprisingly close. Once the 6L80 was out of the way we mocked up the TH400. Lengths end to yoke were within a 1/4". I installed a Hughes Performance SFI Flexplate and converter spacer. Then bolted up the TH400, which all but three of the trans bolts went in. Obviously there is a slightly different bolt pattern between the trans, mainly the two oilpan bolts and the top center bolt the 6L80 uses. The existing crossmember that supports the 6L80 works for the TH400 without drilling any holes. I used an Energy Suspension TH400 mount which bolted right up to the cross-member.

I took off the 6L80 yoke adapter plate from my Driveshaft Shop driveshaft and removed the u-joint. I then installed a new 1350 u-joint to the driveshaft and a Hughes performance TH400 slip yoke to the u-joint. The driveshaft is the perfect length, carrier bearing is in the same spot. All is well there too.

Then installation of the B&M shifter. I used a piece of plate steel to block off the hole from the OEM shifter. I used existing bolt holes to secure the piece. Then bolted the shifter to the blockoff plate once I found a place that worked for my arm length. The only hole I had to drill was for the shift cable that went down to the trans. It's a 1" hole about 4" forward of the shifter. Ran the cable down to the B&M shift bracket and bolted it to the trans. Ran through the gears to make sure it was adjusted properly.

Removed the OEM trans cooler lines and installed a new trans cooler. Ran new 3/8" line from the cooler to the TH400 which worked great, took about 10 feet of line to run it cleanly.

I had to remove the TCM from the 6L80 and plug it in for the car to start. I ran the 6L80 trans harness up into the engine bay, put some heat resistant material on it where it came near the header. I notched the plastic area that holds the cabin air filter and ran the cable into this area. I connected the TCM and put it in this free space. really you cant even tell its not supposed to be there.

Car started up and runs fine, went and did some donuts for good measure to test it out. Really not a bad swap, surprised more people havent done it. Took about 7-8 hours of mechanical work taking our time, BS'ing, running to the store for stuff we forgot, looking outside at the snow, etc.. then about an hour of figuring out what the electrical system needed for the car to turn on, start, etc.

I adjusted my HPtuners tune and only have one code right now. That was only a quick look, I'm working on getting rid of the remaining code so I can be check engine light free with this swap.

Comparison pics... 6L80 and TH400
http://i51.photobucket.com/albums/f360/fhj178/e020877f.jpg

TH400 in the car:
http://i51.photobucket.com/albums/f360/fhj178/794ba885.jpg

Stock cross member works!
http://i51.photobucket.com/albums/f360/fhj178/69c4387d.jpg

Shifter removed:
http://i51.photobucket.com/albums/f360/fhj178/34d3efcd.jpg

Removed TCM:
http://i51.photobucket.com/albums/f360/fhj178/44913ee6.jpg

All the crap that comes out of the 6L80 that needs to be plugged in:
http://i51.photobucket.com/albums/f360/fhj178/7755d99b.jpg

Fitting B&M Shifter:
http://i51.photobucket.com/albums/f360/fhj178/ee5538e3.jpg

Shifter removed:
http://i51.photobucket.com/albums/f360/fhj178/b4641831.jpg

Driveshaft Shop 9"
http://i51.photobucket.com/albums/f360/fhj178/26dab2e4.jpg

Roll bar designed to allow rear seat use:

http://i51.photobucket.com/albums/f360/fhj178/5ff317fd.jpg
http://i51.photobucket.com/albums/f360/fhj178/b8461c56.jpg
http://i51.photobucket.com/albums/f360/fhj178/2dbb372a.jpg


Drivers Seat:

http://i51.photobucket.com/albums/f360/fhj178/0ba4cf87.jpg
And the engine bay!

http://i51.photobucket.com/albums/f360/fhj178/f238e224.jpg

Then a little test:
http://www.youtube.com/watch?v=GoBiYiK7DgQ&feature=player_embedded

I still have a few tweaks to make in HPtuners that I found. We are going to pull the trans back out to build it for some power, this was just a test to see that it would work and wouldnt have any gremlins holding us back.

Props on making this work.

Very nice! Hope better upgrades come for the a6. Seems like a step backwards :(

Props on making this work.

Thanks!

Very nice! Hope better upgrades come for the a6. Seems like a step backwards :(

Every other car I own is manual... I've hated the 6L80 since day one. Step forward for me! Next step would be a manual swap.

Have you ever broke the 6l80?

Have you ever broke the 6l80?

Thats the reason for the swap... my 6L80 was toast after two track days with the blower. It wouldnt hold any power on a sticky tire, just slipped. I looked at rebuilding the 6L80 but its fairly pricey with no guarantee that it will hold the power so I decided to go with a proven option. Plus the slow 3-4 shift of the 6L80 was really slowing me down at the track and I was sick of the electronic delays.

sounds like you needed more tuning work done to the trannys computer

sounds like you needed more tuning work done to the trannys computer

lol You cant tune out burnt clutches. My 6L80 lasted 62k miles and hundreds of quarter mile passes which is longer then some have lasted. My tuner did the best he could and I made improvements after logging many passes at the track. The trans held up ok for NA use and went 11.3 on motor, and 10's on spray so it was shifting fine and our tune was spot on. However with the added power/torque from the blower the trans just couldnt hold it. A 4k lb car with sticky tires and decent power is asking a lot from a stock trans.

Every single person I've seen with 550+whp, sticky tires, and repeated track use has had issues with the 6L80 holding, being consistent, etc.. Some decide to get Century to rebuild it, others do 4L80 swaps, etc.. but they have to do something.

Ahh ok. 550whp still aint to shabby for a factory unit though :nod: an upgrade over the 4l60e anyways

Nice work Sky. When did you get the blower?

Nice work Sky. When did you get the blower?

Thanks, decided to change things up end of last year.

Changed to a Holden sedan manual file and it works great without the TCM plugged in!

very interesting thread

I think this makes like 3 G8s running this trans now bring on 2012 lol

I think this makes like 3 G8s running this trans now bring on 2012 lol

Who are the three running it? I know gr8lover did a 4L80 swap to back up his big cube F1 setup and was working on getting the electronics working. One guy did a manual TR-6060 swap on his blower car. Another G8 owner purchased a TH400 but I dont think it ever made it in the car and is now for sale. Wreckwriter is planning to do the swap soon and currently acquiring parts. Other then that I dont know of anyone thats completed a trans swap on a G8.

I'm impressed that times got knocked down so much in 2011! I agree 2012 is gonna bring some fast times for sure, I know I'm not gonna stop making mine faster anytime soon.

Its just you and me Sky, unless there's someone out in the wild doing it. Yours is the only one running, for another month or so....

Who are the three running it? I know gr8lover did a 4L80 swap to back up his big cube F1 setup and was working on getting the electronics working. One guy did a manual TR-6060 swap on his blower car. Another G8 owner purchased a TH400 but I dont think it ever made it in the car and is now for sale. Wreckwriter is planning to do the swap soon and currently acquiring parts. Other then that I dont know of anyone thats completed a trans swap on a G8.

I'm impressed that times got knocked down so much in 2011! I agree 2012 is gonna bring some fast times for sure, I know I'm not gonna stop making mine faster anytime soon.

You and wreck and i thought someone else but i may have been mistakin i didn't mean as in they have had it just that they are commited and 2012 will be with this set up. This is gonna be a nice year for the G8s :) i wish someone would to a 1000+ rwhp blown set up :) and i really wish it was me lmao

I'm ready to see all these new set ups go down the 1320 including mine :)

Its just you and me Sky, unless there's someone out in the wild doing it. Yours is the only one running, for another month or so....

Yours should be fairly straight forward since most if not all of the details are figured out. The only gotcha I have left is getting the key to come out with the stock shifter unplugged. I know its only two wires I've just been focusing on other things, should be easy once I set aim on it. I took mine out for a maiden highway voyage this weekend to get the first 100 miles on her, so far so good.

Actually theres another gotcha now that I think about it... I havent wired up reverse lights yet. Not that you really need them.


You and wreck and i thought someone else but i may have been mistakin i didn't mean as in they have had it just that they are commited and 2012 will be with this set up. This is gonna be a nice year for the G8s :) i wish someone would to a 1000+ rwhp blown set up :) and i really wish it was me lmao

I'm ready to see all these new set ups go down the 1320 including mine :)

Yeah most people are still pushing the limits of the stock block, really only Dan has gone to a different block and pushed it. Some others have bigger cubes but arent pushing the limit, just street cars. I'm waiting it out until my block calls it quits... then it can get crazy, haha.

Hmmmm... Didn't know there was an issue getting the key out. As long as it turns off I guess I don't really care. I won't use or need reverse lights as my transbrake requires neutral and button push for reverse.

Same here on the block, run it til it shits the bed.

The key comes out if you leave the stock shifter assembly plugged in, unplug it and the key wont come out. Shouldnt be too hard once I look at the wiring, jump two wires and should be good.

Interesting.

Whats the final set-up going to look like in the console area?... Kind of the void with the new shifter or you have a finished plan in mind?

Very Good work guys

Whats the final set-up going to look like in the console area?... Kind of the void with the new shifter or you have a finished plan in mind?

Have no idea... its gotta go fast before I worry about prettying it up.


Very Good work guys

Thanks, I took it out today and ripped on it a bit. Then did a alignment on it. Gonna have to make some tweaks to give the 28" tires clearance. Good amount of traction though, I like them. Kinda big for the car but whatever.

Well that was my my trans, out of my truck. Turns out, my brother Mike Pressman went out drinking one night and wrecked his car. He came to his brothers house, "me", looking for another mode of transportation so he borrowed my Kymco scooter. A few days later he pulls up all bloodied because he low sided it and totaled it. No big deal right? He's my brother. So I give him my old suburban AKA the "white whale" as a last resort because he was out of options. Since this was a long term event and I trusted my brother (at the time) I gave him the truck under terms of returning it to me when he was done with because there was nothing wrong with it and had a good 400 trans engine parts etc.

Well one day the truck has an ignition problem he can't fix so he strips it and sends it to crazy rays for $300 and dupes me on any money and paying for my scooter too.

My brother and I haven't talked for 3 out the last 4 years over this and this stirs up some bad blood in the family, so I hope you enjoy my trans........

P.S. Don't let him fool you he is a worthless 31 year old golf cart mechanic that still lives at home with his mother so he can keep up with all the latest and greatest.

Feel fee to call me for questions and answers 240-832-4949

Slow Sedan, that is an awesome swap, and I hope, lol, that this should be enough for your car. Also the car looks sick and I enjoyed all the pics that you posted.

On another note, I find it tasteless and classless that someone would air their families dirty laundry on a public message board which is completely unrelated to what this forum is here for. The fact that it is being talked about here throws up a red flag to me. I would be very interested to here the brothers side of the story. If you want to find a forum to complain about with all your problems I am sure Oprah or Dr. Phil has a forum you tool.

Slow Sedan, that is an awesome swap, and I hope, lol, that this should be enough for your car. Also the car looks sick and I enjoyed all the pics that you posted.

On another note, I find it tasteless and classless that someone would air their families dirty laundry on a public message board which is completely unrelated to what this forum is here for. The fact that it is being talked about here throws up a red flag to me. I would be very interested to here the brothers side of the story. If you want to find a forum to complain about with all your problems I am sure Oprah or Dr. Phil has a forum you tool.


Thanks, yes so far the TH400 we rebuilt is holding well over 600hp through an unlocked converter.

Couple videos:

First start with new cam and pulleys:
http://www.youtube.com/watch?v=bRVWsfLQL-o&context=C43bb3dbADvjVQa1PpcFOfbIxfmFUlTN4LgJOUX4I_ rRQ8CO0DHsI=

Dyno run:
http://www.youtube.com/watch?v=hymKX0V6DQg&context=C4d32e2fADvjVQa1PpcFOfbIxfmFUlTKPthurYsLEr bDWNZvWQIRI=


Yeah what a great first post right! I've known Mike for years and is a good friend. The trans had been sitting in a shed for years, if he wanted it back so bad he could have got it well before I even thought about it. Deejay certainly left some details out of his little story...

Can't view the videos here but i will as soon as i get home glad its coming together.


And dude just made himself look bad so no worries. I can't wait to see how it fairs on the track :)