I have someone who is willing and interested in an LS4 for his kit car, hopefully we can justify and fit in the budget a testing of the 6T75 with it.

 

Get with TrueBlueGTO as I'm sure he'll be able to accommodate you.

I just hope you're close to New Jersey.

 

I for one am still interested in this, but am looking at the 6T70. Isn't the 6T75 a little bit bigger than the 70 for a W-body???

I would be up for this, but i would need the new trans first, the spacer plate and the starter bracket first wouldn't I??? Would love to get and have something better than the 4T65E in our cars, and hope to avoid having to go the TEP Stage 2 route for what i want to do with mine...

 

This mod is still plenty doable the best thing is I think the 6t75 is a standard bellhousing pattern which means any LS motor could make its way in a Wbody we all know the 6xx series will work in a Wbody since the 12+ impalas came with them from the factory.

 

I cant even imagine how an ls4 would do with a 6 speed. I would die to get one swapped into my gxp! Im sure she would roast the tires even easier than it does already Especially with shorter gears. Maybe the 3.69s or 3.73s.

 

I think the programming is the final hurdle to making this swap work, and for the reasons you mention above.

 

Well the good thing is we already have T42 Trans controllers which also control the 6t75 so some minor wiring and software change and it should work

 

So there's a certain model 6t70/5 i would need for use in my Impala? And is the T42 controller the same in mine, or is mine in my '07 a different model/number???

Trying to weigh my options, and see which I'd be better off with - a built TEP trans for the 300 whp project i am looking at doing, or trying my luck with the 6T70/5...

 

This would be really cool if we could ever get it working.
The gains in acceleration and mileage on the highway would be pretty good for a project like this.

I have an Allure (Lacrosse) Super now and I know a new transmission is in my future no matter what; it would be worth paying for a more modern 6-speed over a re-built 4 in my mind..

 

Thats what I was thinking. The acceleration with shorter gearing would make our cars rockets. A 6 speed with some 373s would be awesome and way more enjoyable to drive

 

I'd run drag radials for summer tires

 

Thats always an option! I just wish it was a manual 6 speed instead of an auto

 

No, the new six speeds have the T43 which is located inside of the transaxle.

Programming for this has already been taken care of and this transaxle can handle an LS2 without issue.

 

So there shouldn't be any issues with this swap?

 

Sorry to be a nag, but if there are no programming issues or power handling issues does anyone have any details or links to where we could get what we need?

If there are truly no programming issues all you'd need are mounts, programming, possibly custom axles, and a plate to adapt to the ls4 pattern and house a starter?

Thanks,

Mike

 

Seems the real barrier is the width - there is very little room left in the LS4 W body engine bay, so adding 2.5" for the trans plus an adapter plate would mean sectioning frame rails and/or strut towers.

Would be cool though..

 

Here is where a guy working for PCS (Powertrain Contol Systems) did a LS2/6T75 swap in the back of a fiero... He uses a PCS controller for the transmission, not the stock GM ECM.

http://www.fiero.nl/forum/Forum3/HTML/000136.html

Also, the LS4 bolts directly to the 6T75 w/o needing any adapter plate.

Even if you go the same route, the LS4 ecm calibrations are auto only, which means they have to keep their TCM's (or you can try setting the Manual Transmission flag in the calibration and see what it does). This means the P/N start interlock is within the TCM and it communicated that signal to the ECM via the high speed GM LAN wires. Also, the VSS is wired directly to the TCM and it sends the vehicle speed info to the ECM over the GM LAN wires as well. The guy running the 6T75 with the LS2 is using a factory Manual transmission calibration for the LS2 engine, so he can wire the P/N and VSS directly to the ECM

If the Manual transmission flag allows a P/N and VSS signal to be wired direct to the ECM, then that would greatly simplify things. But unfortunately, no one has confirmed what happens with you set this flag on an LS4 calibration (E40 or E67).

If you have to turn off the DTC for the 4T65e-hd, then you will need to find someone with TunerCat as HP Tuners does not have access to most of the Transmission DTCs in the LS4 calibrations.

So I would say it is premature to state that the wiring/programing issues have been figured out for the LS4/6T75 swap.

For my 6 speed manual transmission LS4 swap (also in a Fiero), I kept the TCM and did some hard wiring and resistor work to get as many of the signals as possible to be within the expected range. I still had 2 DTC from the missing transmission, so I had them turned off by a guy with TunerCat.

 

Thanks for the link!
Read through the whole thing and it looks like doing this swap first would be a long-drawn out process that may not necessarily be successful.

First gear also looks bad enough on a Fiero, can't imagine how it would be in a FWD where the weight squats to the rear pretty good!

If someone had this done/documented I'd be much more willing.

Here's hoping that this does indeed happen one day (hopefully before my 4T45E blows).

 

Fiero how was it possible a ls2 and ls4 both bolt up to the same 6t75.

 

Adapter plate on the LS2 to convert from the RWD SBC pattern to the GM Metric pattern: