AlabamaGuy

iTrader: (5)

Like I said in the other thread...

There isn't a 6 speed trans with a higher power rating. It'd be a lot of work for a transmission that'd just blow out quicker than the stock one...

Besides, traction would be even more of a joke with gears that steep/close...

StealthV8

iTrader: (1)

there is a guy in toronto that has taken a g6 gtp 6speed transmission, beefed them up to handle 1000hp, and swapd them into atleast one 04 GTP that i know of. I assume if that can be done, we can get it done too because we just have a hd version of the trans that was swapd out .. I think the going price was $5000 or more to do the swap.. I was going to do it but i quit my job so i needed my savings for abit

nmp0098

Other than the case (trans mounted starter) and the controller (seperate TCM instead of dual function PCM), we have the same transmission as the GTP (they both have the HD differential). The custom fabrication for the trans mounted starter that will push that cost over 5k. IMO, a 5/6 speed manual would be the hot swap.

GXP25

iTrader: (3)

I don't think you like to read.

Maybe you and I aren't clicking or reading the same set of information. Maybe you should take the time and read about Loyde and all the swaps he's done.

FastFieros of Dallas

If the guy is swapping the 6T75 into a Fiero and matting it to the L76 (6.0L V8 - 361HP/385TQ) and makes the claim of "a nice 6 speed transmission rated to 400HP stock in a high HP - high torque application," then I believe him.

People complain day and night about how we have no options as LS4 owners, yet nobody shows interest. Except for the few brave souls (williamGT and BuickRacer to name a few) that go that extra mile.

Even those Fiero guys go the extra mile. They use our engines and transmissions and work wonders with them. They don't sit around waiting for things to happen (the engine isn't even theirs!).

I currently have a total of seven (7) back and forth emails with Loyde about the issue (September 2009). He was close then and was in contact with GM's lead engineer on the 6T75 (ex-engineer lead on the 6L80/90).

I know one thing is for sure, if this transmission goes out and I have to eat the full cost (post 100k warranty), I would like to have the option of putting in something other than that blasted 4T65E-HD. Only to have it potentially die on me again.

You can find the 6T75 from around $600-$1000 easy. A "simple" conversion/install kit from whomever would be appreciated when the time comes.

All we need to do as a community is show interest. Shoot some emails. I believe that's how the headers started. I know I've already done my part.

And here is one naysayer's comment:
To which he replied:

GXP25

iTrader: (3)

And I'm sure the more people show interest, the lower the price may be.

I would lean more towards FastFieros due to this connection with the GM engineer.

JP_GXP

Trust me if I had the money I'd have a turbo 6-speed manual bored-over GXP running 10s. I can show interest all day long doesn't mean I can act on it.

GXP25

iTrader: (3)

Showing interest does not necessarily mean you plan on making a purchase any time soon. What it does, however, show is demand for a certain good or service to which a supplier might want to entertain.

A perfect example is the headers. Thanks to everyone who showed interest (whether they plan on purchasing them now or later), I now have the option to purchase headers when I feel that I'm ready (post warranty period). Had williamGT and BuickRacer not gone that extra mile, I'd probably be here with the rest of you envisioning a way for someone to fab up some headers.

Supply and demand.

GXP25

iTrader: (3)

And let's be realistic here. I don't think the LS4 can be bored over anymore than it really is to achieve any significant performance. I believe I read that there's a physical limitation.

nmp0098

Modern iron-sleeved aluminum blocks can't be over-bored much, but they can be re-sleeved for more displacement. We have the same bore centers and head bolt locations as the 6.2s. There is very little difference between the various gen IV castings. If you know what you are doing and have the tools, you could convert to LS7 heads and displacement.

There can be minor differences in the internals of transmissions from year to year and model to model, but there are definitely major differences in their calibrations. You can certainly run more power through a transmission than it is rated for without upgrading internals to handle the torque or recalibrating for the increased clutch energies during shifting, but you should not expect the same service life. It's like overloading a truck: you can do it, but you shouldn't be surprised if you break something if you hit a nasty pot hole.

I definitely agree that a 6 speed swap is possible and would be fun, but I don't have the slightest bit of buyers remorse with TEP built transmission either.

AlabamaGuy

iTrader: (5)

I would rather spend the 2k building my transmission to handle whatever I throw at it, than spend 5k+ plus parts to put a 6 speed in that will still break if it gets traction in a high horsepower LS4. We're traction limited at the moment anyway, close ratio, steep gears are not the answer. Money is best spent in other areas, imo.

GXP25

iTrader: (3)

Sounds like you have a chip on your shoulder WRT this transmission. Or is it your lack of TAPshift/a manual mode? 6T75: P, R, N, D, M, (DSC+/-) & L (MU/MD)

High horsepower LS4? LOL!

Regardless, everything I've found on this transmission seems to fit the bill. In fact it looks pretty damn good:

Don't like the tall first gear? Start in second.

Sources attached (you can also find them at GM).

JP_GXP

Sounds good, who wants to buy it and put it in my car? It's TapShift ready.

SigmaX6

ive owned my 07 gxp since new. Every summer I change the filter and tran fluid. its just over 99000 km now and off factory warrenty with a shift kit and tran cooler installed a week after i bought it. I change the tranny fluid and filter myself. Stealership tries to get 100+ of my dollars to do sumthing that takes half a hour. btw is the tranny pan seal reusable Ive never replaced it or thought to replace it lol

AlabamaGuy

iTrader: (5)

Starting in second defeats the point of even having a 6 speed lol.

JP_GXP

Back on the original topic, I tried to replicate the incident by running the hell out of my car. Got the trans temp up to 226* and... It shifted normally... So I'm leaning towards freaking occurrence.

And to the other subject, I guess if I ever get a job and get some money saved up I could guinea pig the 6T75.

GXP25

iTrader: (3)

Great info. Thanks!

That would just give us a 5 speed then. Still better than 4.

nmp0098

JP, one thing that will cause the trans to go to 3rd, TCC locked, is over-temperature like you were thinking... were you by any chance running around in TapShift mode when you had this issue? Or doing highway driving (4th gear) in TapShift? The TCC won't lock up in TapShift mode, and it is possible to overheat the trans without the TCC being locked. 3rd, locked TCC, gives the best cooling. One thing I did when I retuned my trans was lower the threshold to get into trans over-temp mode to better protect my trans from myself. Maybe your tuner did the same thing.

@ the side conversation - one thing that would make that steep 1st in the 6 speed really worthwhile is a really aggressive cam that kills the bottom end torque in these engines. By aggressive I mean something in the 235+ range.