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6 speed automatic

27K views 79 replies 13 participants last post by  55ChevDelray 
#1 ·
Anyone put the new 6L90 6 speed automatic transmission into a tri-five?:)
 
#4 ·
I been thinking about it in my 56 project. The limiting factor is the motor has to be a Gen IV and have the 58x crank trigger or modify Gen III and use a E38 PCM and 58x trigger. They have a TCM that contorls it but you need the PCM to talk to it. There are no aftermarket controls for them yet.

Physically it should fit but you might have to mod the trans tunnel alittle be cause its bigger around then the 700r/4l60. But weigh about the same as the 4l80.

With the nice first gear 4:1 and double overdrives. 3.55 rear gears would be as deep as you would want!



 
#7 ·
I was originally going to go with the 502 ramjet and 4L80e. But now have decided to go with the LS376/480 and the 6L90E. :) We'll see how much the tunnel needs to be opened. Should be a good combo. I have 3:07 rear gears which should be good with the 4:02? first gear.

Which pan is that that is on the 6L90E? I understand there are at least two different ones.
 
#8 ·
The one I installed on the 54 was behind a LS engine. I had to locate and fabricate the engine mounts and trans crossmember. The transmission is quite a bit larger than the 700R4 so the choice was either move it up into the floor tunnel or let it hang low and reduce the ground clearance of a lowered car. My choice was to mount it into the tunnel. The tunnel was widened and raised in order to get the trans to fit. The trans I used, came from a new pick-up.
 
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#13 · (Edited)
You proably already know this, but I didn't, TCI has an ad for a 6 speed automatic in the May 09 Car Craft. Low gear is only a 2.97 and OD is .75. It doesn't look as large as the factory 6 spd and it is rated to 850HP. Check their web site www.tciauto.com, they have the package priced at $6064.35 with paddle shifters, transmission control unit, cooler, and harness. Very interesting:)

Chuck
Its a 4l80 that they turned into a 6 speed. That's not really worth it for those gears ratios. The 700r is better than that.
TCI 6sp 2.97, 2.31, 1.57, 1.18, 1.00, 0.75


But for $6k dang!:eek: The 6l80/90 new are around $2k. And figure another $1k for any special shifter, mounts, etc...

6L80E Stock:
Maximum engine torque: 439 lb-ft
Maximum gearbox torque: 664 lb-ft
6L90E
Max Eng Tq = 531 ft lbs,
Max Eng Pwr = 452 hp,
Max Gearbox Tq = 885 ft lbs

The 6L80-E is a clutch-to-clutch transmission. That means that the gear it's in, no matter what, will feel like engine braking if you lift the throttle quickly because there are no freewheeling mechanisms. Despite having 2 more gears, the 6L80-E is more mechanically simple than the 4L80-E.
If you have ever driven a 5 or 6 speed Allison 1000 you know how shifty those are under certain driving conditions. The Allison is clutch-to-clutch also. The 6L80-E takes some getting used to just as the Allison does.
 
#17 ·
Nothing at this point. Still doin research. :bebored: I'm thinking that the new Cadillac CTS-V is my best option. At some point I'm going to see if I can get a hold of a schematic for it. I'm a long ways off from being able to drive the car anyway; although I'm starting to put the chassis back together. I'll be buying my fuel tank soon. I'll be posting some new pictures soon showing my chassis at it's current stage. Started bolting the suspension back on after painting the frame.

As a last resort John Spear's harness will work, but he wants $1600.:hmmmm2: It's just a matter of time and someone will offer a cheaper solution to get this retrofit option to work. There certainly is a LOT of interest in getting the 6L90 into older cars. If I'm not able to get it to work by the time I'm ready to transfer the body over to my new chassis, I'll look into a 4A to put behind it temporarily.
 
#28 ·
:( Unfortunately, no progress. Haven't been working on that lately or much of anything else. Weather is starting to warm up, so I can get back into the garage. I have a fall back to purchase a harness from a vendor. Chevrolet (GMPP) says they are working on a retrofit harness to work with the LS motors. Right now the motor and tranny are just sitting in the frame.

I'm hoping that I can get to the electronics portion after i get my exhaust/fuel/brake systems done. The list seems to be getting longer instead of shorter. :ashamed0005:

I'll definitely post something when I make some progress there. Thanks for asking!
 
#29 ·
I would like to see it setting in the frame rails? Any pictures.


Are you wating on GM harness.

Did you check Speartech or even Mast Motorsports Mast has there own ECM as well.

Most harness will be over $1000.

I am really wanting to do a 6l80 in mine, heck everything! :D
 
#31 ·
I would like to see it setting in the frame rails? Any pictures.


Are you wating on GM harness.
Sort of. It'll be a while before I'm ready to start it, so that gives GMPP more time, so I'll hold off on buying Speartech's harness. If GMPP comes out with theirs, I'll buy it; if not, I'll have to give John at Speartech a call. Only thing is I've already spent money on the E67 ECU, and the harness for the LS376.

Did you check Speartech or even Mast Motorsports Mast has there own ECM as well. Yeah, and John wants $1500.

Most harness will be over $1000.

I am really wanting to do a 6l80 in mine, heck everything! :D
 
#30 · (Edited)





Fits nicely between the rails. Pan does not hang below K-member. Headers are above the bottom edge of the frame rail. Nice clearance with the rack and steering link.

Not sure yet about clearance on the floor pan. I suspect I'll need to do some cuttin'.
 
#34 ·
Haven't made any progress lately. I did not get the trans wiring harness with the trans. Probably have to purchase or make the harness.

I'll certainly have to modify the tunnel. I have plenty of ground clearnance with the stock pan that came with the trans. Everything is above the bottom of the frame.
 
#40 ·
I just bought a L92 and 6L80E for my 56. What headers are you using? I plan on pulling the frame and doing the initial install very similar to yours - just with te stock frame at this time. Any inputs on this that you learned from your setup?

Thanks.

Alan
 
#41 ·
Hey Alan, Thanks for your interest. I'm in New Zealand so we drive on the ohter side of the road, but my car is from US. So I'm converting usings rivers Rack & Pinion steering to RHD. I'm thinking Hydraboost brake booster so that will help with clearance. I've got a mast motorsports harness and ecm cause it can talk to the transmission, and got my gauges from Livorsi casue they plug straight in. My body is getting walnut blasted at the moment. Not too much panel to do, but I have a new floor and will have to alter the transmission tunnel to fit the shorter fatter box. StreetRodGarage are building my chassis and so I may look at them fitting the headers as they are cheaper to buy there so I will probably get them to fot the whole exhaust since it goes through the chassis anyway. I have mini tubs and will go with 20+18's. The gearbox is programmed with 20's cause its easier to do that with it our of the car.
Please keep me posted on how you are going. I expect my body to be going back on the chassis and firing it up around June 2011.
 
#43 ·
Yeah mate - I want to use it as a daily driver. I've asked around a number of blokes who just use theirs as a sunday driver and it seems they don't daily it - cause they don't stop, turn or go close enough to a modern car to make them want to. I'm not in the position where I can afford $ or garage space to have two cars, so I need a daily driver. So that is why I have gone with modern suspension, brakes, efi engine etc.... to make sure it drives well. Each to their own I guess. Apart from bigger wheels though the rest of it will look stock. So RHD is part of that. Like going in and out of a parking buliding and trying to get ya ticket, parking, passing etc.... all a lot easier with RHD as you'd appreciate coming from the Tron. And I guess these have to be one of the easier cars to convert and starting from the ground up on a rebuild - it seems like a good idea. Of course you're welcome to have a gander in March. My chassis is just started and takes 3 months, then xmas etc... plus extras and shipping - I don't expect to see that before May 11 so I'll just be doing body stuff and might not be that exciting by March but thats cool. I've got most of the body parts but haven't done anything about seats or carpets etc... yet. Also I have to work out and get electric windows and door locks and switches. I like the stock look. So a bit more stuff to get but coin is tight at the moment so will wait to get those next year. I'm having a lot of fun though and now the sun is out I can get my bike out too. Cheers
 
#50 ·
Well, here it is! A 6L90 behind an LS3. I was hoping I wouldn't have to cut so much of the tunnel, but I guess considering how big it is, it's expected. I really hated to have to cut such a nice floor. Got a bit apprehensive about making the cut, but once started, away I went. But for everyone who was wondering how it fits... here's a pic. Will need to nudge the firewall a bit near the passenger side rear coil. I tried to keep my exhaust as close as possible to the rear batwing, but looks like I'll need to make a small cut & patch in the trunk to give adequate clearance for the 3" exhaust.
 
#51 ·
#54 ·
#56 ·
6l90 working well?

Could you please give us an update on how this engine/trans combo is working! I'm just getting ready to pull the trigger on a LY6 with a 6l90, spoke with many people about tuning the transmission and i get good and bad comments. Any info would be much appreciated! Thank you
 
#57 ·
The bad about tuning the trans itself is the tuner has to have the TCM itself or be with the car to tune it. Which the TCM is inside behind the pan of the trans so its a pain to get to, then you have to ship it to the tuner.

If you do get the 6l90 make sure to get the slip yoke for it as well as the 90 is a unique spline count.
 
#58 ·
Could you comment on the driveability with this trans. How does the trans shift up and down through the gears, is it set up with tap shift etc. What rear gear ratio are you using, to much or not enough gear with that 4.02 1st gear in the trans. Any comments would be appreciated, just want to know (i my mind) that this is the way to go. I was ready to buy a magnum T56 really for the double overdrive, but with a bad knee i'm not sure how long i can comfortably shift that T56. How does the trans perform ie. wide open throttle etc. Who did the tuning for this trans? Was it ultimately worth the mods etc to run this trans? Thanks again!
 
#64 ·
The way it is now, it shifts like the truck it came out of. I'm going to tune it to shift at a higher rpm and to get the converter to lock up sooner. I like it. I have 3;07 and will be changing to 3:45 rear gears.. The trans has engine braking which is kind of neat. At WOT, it'll spin the the tires in first, Shifts and then spins through 2nd gear, shifts and then into 3rd, catches traction and then shifts back into 2nd. Some tuning of the shift rpms will help with this....but it is a VERY strong transmission. I have not had any trouble with normal driving with this transmission.
 
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