confab

For the sake of tunability (Something the 85 lacks) and what I believe will be a significant improvement in drivability, I considered EFI Connection's 24XX LS PCM upgrade a while back.

Now I see they have a 58XX system. It is here:

I nixed the idea because I really didn't want to go to all the trouble and hack the wiring up. But, I now have a 6L90 laying in the floor of the shop here. It is pretty impressive and would make a great upgrade.

The Transmission is rather large and I would have to test fit it, because if it won't go under the floorboard I'm not hacking the car up with a saw to make it fit.. But if it does:

1) There is no reason I am aware of that a person with the LS IV conversion couldn't steal harness and all and include the 6L90 in the swap, is there? I'm not sure about spedo output, (Ideas are very welcome!) but I have been told the 85 PCM can be piggybacked to run the dash and the rest of the car, while the LS PCM just runs the engine and trans. Is this correct?

2) I understand these are very tunable PCM's. Are they tunable enough to suppress the like, ten zillion error codes I will get when I first key it on?

3) Think it'll go under the floor?

4) What do you use to tune these PCM's with?

5) What is with the 1X and 4X cam signal stuff? Which one would you want for a mod like this?

6) Is this swap a mistake to even consider for reasons I have not yet considered?

I am new to all of this tuning stuff, and welcome any input whatsoever. Good, bad or otherwise.

If I don't do this, then I guess I'll buy a Moates kit and work with the 85 PCM I have. But the idea of a 6speed and the wonderful LS controls is SO APPEALING. I have the LS III in my truck and it just idles and runs so perfectly, I'm just in love with it.. But if it's going to get too terribly complicated, or if it takes floorpan mods, I'll just scotch the whole idea.

Thoughts please?

badboyrides71

please post your results,i also want to put the 6l90e ls3 into an 92 vette so i will be watching.

badboyrides71

please post your results,i also want to put the 6l90e ls3 into an 92 vette so i will be watching.

bjankuski

Please read the answers above.

JoBy

As long as the transmission can fit the tunnel the major fabrication work would be to solve the C-beam issue as it is needed both for the transmission and the rear end.

confab

Good post. Thanks!

As far as the size goes, I'm not sure? It looks fatter.. But I don't have an 80 on the floor to compare right now.

I'll get some pics tomorrow.

Appreciate you help!

confab

Not even worried about it.

Something like this:

https://www.corvetteforum.com/forums...post1590484632

Or this:

https://www.corvetteforum.com/forums...post1574358771

Would work fine, I think.

I'm mainly worried about the control side. If I start this, that's where I'll have spent a lot of money and end up screwed if something doesn't work together.

This is a fairly expensive proposition. Probably a couple - three thousand bucks by the time I rebuild the unit on the floor, buy the 58XX kit, buy a shifter, source a PCM and a custom driveshaft, and connectors and whatever little stuff it will inevitably take. I'm terrified of committing to it, getting in the middle and getting stuck.

confab

Some comparison pics here, if anyone is interested. 6L8/90 VS TH400.

http://www.pirate4x4.com/forum/gener...l#post14386493

I really think this could be an excellent C4 upgrade.

DVNCI

I'm 99% sure the 58X requires electronic throttle controls, i.e. drive by wire.

I didn't want to do that, so I went with 24X.

SpedRacr93

I'm 100% sure it does.

Also with the 58X, you'll have to run the updated knock sensors which may prove difficult unless you can get a custom bolt for the standard thread.

The system will not come with tuning software, that will be up to you.

58X will leave you learning how to play with Virtual VE tables.

Honestly... I doubt that the 6L90 is going to fit without modification, but won't know till you try.

confab

Sadly, from what I am reading, this appears to be impossible with the Gen1 SB and TPI.

confab

Anyone familiar with this?

https://www.powertraincontrolsolutio...on_Controller/

SpedRacr93

That's not true. It's possible with the right parts; however it's not cheap and it's not simple. The EFI Connection 58X conversion will do it, and the GM TCM is compatible with the E38 PCM, so you can control the 6L90 with the GM computer.

If you've never tuned an engine though, I wouldn't advise it. Making the PCM control a SB is a lot different than the LS.

I have a 24X system and putting it together was the easy part; tuning it has been the real challenge; but my cam is not helping that.

383tpimachine

24x here. worked great but had limitations. Just swapped to a ms3pro using the same sensors and coils.

58x will not be a huge difference over the 24x.

6L90e will not fit from what I recall.

confab

You mean physically, or the controls? Because the controls are the problem I keep running into.

The GenIV PCM will run a 6L90 just fine. But it won't do anything else well.

I'm reading posts from blogs, thirdgen, LSTech and the like. But if they're right, some of the sensors are digital instead of analog. No provision for an IAC. ALL Gen IV are drive by wire, and no way to back away from that. Just a host of issues, none of which is insurmountable, but are a giant PITA when taken together.

The real problem is me. Everyone else wants to swap the LS engine as a package, and that is doable. I really don't. It's never going to be a race car. It is never going to be the fastest thing on the road. I grew up with the G1 SB and I like it. It's a nostalga thing the performance guys wouldn't understand, I just really like the 6L90 and modern controls.. and I hoped they would be easier to utilize than they apparently are.

It really isn't looking good, but I'll call Speartec and PCS next week and talk to them about it and see what they have to say. I know the standalone controller option scares me a little because if it's not right it will burn transmissions on the street, even if it works just fine for jaunts down the track. (Which seems counter intuitive, but that's how they work. You can do things with line pressure and engagement that work well for 1/4 mile, that would destroy a transmission in a daily driver.) If it is not comprehensive enough street performance will be subpar, and I don't want that either.

383tpimachine

physically without cutting the tunnel. To fat to far back. I had to mod the tunnel to fit a t56 and the 6l90 is bigger.

As for controlling it, that would take a badass tuner, electric pedal assembly (which will suck to install), and then there is tb issues.
One solution is to run a edlebrock intake and use a LS dbw throttle body.

yedister

Just saw this thread, I am also thinking about this addition in 2 years after kid has finished college. Check out this site,
http://tbmsport.com/projectnextnongm.html
It might say Non SBC but your concerned with fitting it in the tunnel

http://tbmsport.com/6l8090econversionfaqs.html

TBMSport

A member brought this thread to my attention and as I've already walked down this path from a R&D technical perspective, I figured it would be helpful to the OP and others to save you a lot of money, time and effort of what is and isn't possible, based on the OP's project parameters.

First, the 6L80, let alone 6L90, will not fit in a C4 (or any similar generation) vehicle without modding the floor pan or MAJOR front end work to reset the engine height and angle. There just isn't enough room to accommodate the nearly horizontal and tall upper surface of the transmission. The pictures are slightly misleading because what you don't readily notice is that the top of the 6L80 transmission case is high and effectively at the top of the torque converter, where as the TH400/4L80/4L70 case top is lower and behind torque converter. Plus notice how the 6L80/90 transmission bellhousing face/case and driveline are at 90 degree angle. The old 4 speed's case and driveline are not, which is why the 4 speeds attach to the engines at angle. And even if you did modify the floor pan, what of the center console and seat frame attachment points? Plus, there is the overall point of diminishing return on your investment?


See attached photos.




6L80 Transmission Side Profile



TH400 (4L80) Transmission Side Profile




C4 Corvette FloorPan.




But no worries. We're bringing our 'minimally invasive' retrofitting engineering capabilities to address this problem. A more compact 6 speed automatic transmission will be released at SEMA 2017 with our standalone controller. So you can use it with ANY Chevy engine (BBC, LSX, SBC Gen I) with ANY management system (from stock TPI/LTI, PCM's, carb-some mods necessary to 58x).

TBMSport

A member brought this thread to my attention and as I've already walked down this path from a R&D technical perspective, I figured it would be helpful to the OP and others to save you a lot of money, time and effort of what is and isn't possible, based on the OP's project parameters.

First, the 6L80, let alone 6L90 will not fit in a C4 (or any similar generation) vehicle without modding the floor pan or MAJOR front end work to reset the engine height and angle. There just isn't enough room to accommodate the nearly horizontal and tall upper surface of the transmission. Also note that the casual eye won't notice that the top of the 6 speeds is near the top of the torque converter diameter and the top of the 4 speeds is behind and closer to the middle of the torque converter. That is a good inch or so of centerline difference before even addressing the angle towards the back. Next, the 4 speed case (when attached to the engine) is a sideways V shape "<", while the 6 speed is more like like a rectangle "=". That present clearance issues top (trans tunnel) and bottom (ground clearance and exhaust). Lastly, overall girth. The 6 speeds are just overall fatter from front to back than the 4 speeds. Think pinky finger compared to thumb. And even if you did modify the floor pan, what of the center console and seat frame attachment points? It becomes a project with a rapidly approaching point of diminishing return.


See attached photos.



6L80 Transmission Side Profile



TH400 (4L80) Transmission Side Profile




TBM 1994 C4 Vette former R&D vehicle



C4 Corvette FloorPan.





Front to back girth difference. 4L70-6L80-6L90






Because the 6 speed auto's have lower/deeper AND longer transmission cases, there will be little, if any, room for large exhaust systems to fit in/through existing floor pan space.


But no worries. I've been retrofitting 6 speed autos since 2010,so we're bringing our 'minimally invasive' engineering approach to allow retrofitting by working on a more compact 6 speed automatic, with a standalone controller, for release at SEMA 2017. So you can use it with ANY Chevy engine (BBC, LSX, SBC Gen I) with ANY management system (from stock TPI/LTI PCM's, carb-some mods necessary to 58x).

confab

Thanks for that.. I own a transmission shop, so I'm a bit of a transmission "fetishist" I guess you could say.


Not sure if I'm done with this or not. I keep looking at it. For a thousand bucks there's a retrofit controller I'm told will work. If you want GM, it's 58X, drive by wire only.

Other priorities right now, but I'm not going to be able to let this go without test fitting it at least once to see how bad it is.

I will say that I'm not sure ground clearance is a major issue. When viewed relative to the flexplate location, It looks fine. But, a test fit would tell just how much floorpan, exhaust, etc, work would be required.

I thank everyone for their input. It's been very educational.