vikinginz28

My restoration project of a wrecked 91 Z28 Convertible has been "moth balled" for 3 years but now finally moving forward. I have had to outsource the actual engine/transmission swap to a local shop that has done LS swaps in the past into various GM models. The shop called today telling me the trans will not fit without major modification to the tunnel and that I would be better off getting hold of an 4L60e instead from an 98-02 F-body. When I got the Engine/trans from a wrecked G8 GT with less than 10K on the odometer 2 years ago I didn't realize this would cause a problem.
Before I go looking for 4L60e transmission, has anyone heard about a successful swap of an 6L80e into a third gen? I believe Speartech Inc. in Indiana has done something similar with an LS9 but I don't know what transmission they used (Will call them on Monday) Anyway, thought someone may have attempted this already and would share their experience. I was hoping to keep the interior stock (4th gen) and therefore prefer not to make too many modifications to the tunnel and center console.

Thanks

abray1

I looked into a 6l90e swap and went to Street and Performance in Mena Arkansas and looked at them. The trans is huge and you will not like what they have to do to the car to make it fit. I decided on a 4l80e which is super strong and will fit without any cutting. The crossmember will have to be made and will sit back around 9 inches or more and is computer controlled but your LS computer should control it. I haven't installed mine yet but I have it and have compared it to a 700 and looked at other members cars who have installed one. They are bigger and heavier but if you want an overdrive automatic with ba!!$ then it is the one. They will handle around 1000 HP. The 91-96 are the first type and the 97 and newer are the second type. Don't really know the difference but when ordering parts they always ask if it is a 96 or older.

kestell123

I am just finishing a 6l80 swap into a 1991 camaro.The car is running and in for a dyno tune right now. I did need to raise the tunnel 1.5 inches .I cut the same amount out of the side of the console and used a standard size radio inplace of the stock double din unit. It looks very good! I used an LC9 5.3 from a 2011 silverado with an LS2 intake and a 6l80 from a 2011 camaro. I used Spohn engine mounts with 4th gen isolators. For the trans. I used a Spohn cross member and tourqe arm for a t56. With the 2011 camaro trans mount I needed a 1.25 inch spacer to raise the back of the trans.When I cut the tunnel I all the console mounting points on the peice I cut out . I cut just in front of the floor brace to leave that intact. The front cut was just behind the dash so there would be no welding right under the dash. I spaced up the console part 1.5 inches and I then cut slots in the bellhousing area and bent that up to meet the spaced up console area. I then Had I local fabricator fill in the gaps.

Atilla the Fun

Have you looked into TCI's 6X? It's based on the 4L80E, they just give it a much-needed low-ratio gear set, then calibrate a control module to offer OD on 1st and 2nd as well as 3rd. This offers paddle-shifting possibilities very easily, albeit at extra cost. Taking full advantage of a 6Lx0E in a work truck is a much different proposal than trying to do so in a 3500# car that'll never tow anything. I'd do a 4L65E or if I could find one, a 4L70E, and call it good. I've driven a 6L90E-equipped 6.0L pickup, the extra gears are no help when not hauling anything.

jmd

iTrader: (4)

Look at all the old men who insist on using the old style bellhousings with adapter plates to put a T56 into old pony and muscle cars. They hack the floor with no regard. I'd say a 6L80-E would inspire me to do the same.

kestell123

Having done this swap into a third gen and although mine is still not running perfectly I can tell you the extra gears DO make a differance. This is very doable I did most of the swap in my small two car shop with basic tools and a modest budget. The interior look stock , including the stock shifter. I do plan on adding paddle shifters in the next year but for now it works fine with the stock shifter. I can't wait to get it back from the dyno and do a road trip to see what the DOD can do for MPG. Power tour next year should tell the tale!

Atilla the Fun

I know what I'm talking about, I've driven a 2010 camaro SS automatic. It's not worth it. For cruise MPG, all we're interested in is the final ratio. The 6L80E is 0.667:1, not far from the 4L60E's 0.696:1. The goal here isn't the lowest possible cruise RPM. If it was, then the 6L80E's too-deep 4.0272727:1 first would work well with the requisite 2.41:1 or 2.56:1 axle ratio. when GM tested a DOD, non-VVT LS2 in an '05 'vette with T56, MPG climbed to 35 MPG. Fine. But forget trying to have both the ultra-low cruise RPM and the effectively-4-cylinders both at the same time. That won't fly.

Atilla the Fun

Look at the math: LS1 will do 31 MPG hwy geared for 1450 RPM at 65 MPH. That's running on all 8. No DOD. Our cars use tires in the 25.7" range, such as 245/50R16, 275/40R17, 315/35R17. With a healthy V8 in the 346-383 cube range, ideal combined first gear with an automatic is in the range of 10:1-11:1. closer to 10 for a 383 or a 6.2, closer to 11:1 for the 346. Divide that by the 6L80E's 4.03:1 first, that calls for an axle ratio in the 2.48:1-2.73:1 range. 2.733:1 axle and 0.667:1 OD gives a cruise RPM of 1550 at 65. Not enough for a 3.1L 4-cylinder. More than necessary for an LS1 running on all 8. To get enough cruise RPM for a 3.1L 4-cylinder, you need more axle ratio, rendering first gear useless with the 4.03:1. Also, just because you figure out how to spike 35 MPG running from Denver to KC doesn't mean that you can use that same gear trying the opposite. You'll be running in 5th, NOT getting 30 MPG, let alone 35. Real-world MPG is best when you don't have to downshift for every little breeze or overpass.

jmd

iTrader: (4)

Right, so let's look at it another way.
Basic drag car, ideal ratios in a LOT of cases are the TH350 or TH400.
The 700/4L60-E are too wide to be ideal, but work with an EFI engine that's very tractable on shifts and doesn't temporarily falter like a carb does.

Closer ratios in gear shifts are needed but that requires more gears.

If a given powertrain is overgeared with that first gear in some conditions, tune it out except in high TPS value situations. Or use 2nd for starts in low-traction scenarios.

The 6L80 isn't too much; we just need to re-think what rear axle ratio is ideal. Having lower driveline rpm is helpful to high speed vehicle use, so the super tall OD ratios are a double edged sword. The .67 is a pretty nice one IMO.

And I think we can agree that real world mpg is best in a 4 cylinder Malibu with 6 speedo auto that shifts to keep the engine in its powerband vs. an 8 cylinder 2002 F-body that pulls uphill without downshifting. Yes, apples and oranges, but we're just not going to rest on the laurels of ratios chosen in 1980. We're going to move onwards and upwards with 6 (and more) speedo autos.

kestell123

I don't see the the down side to DOD.The car goes from 4 cyl mode to 8 and back nearly seamlessly It requires no input from the driver.In a full size truck it will have trouble staying in 4cyl mode but in a lighter car like a third gen with less frontal area you would be surprised how well can pull that way. The exaust on my car is fairly loud and I have to admit I don't like the sound of the car in 4cyl mode but otherwise it is all gravy!

Lsfreak427

Hello sir, I am doing a 6L90 from a 11 CTS-V and would seriously love to lean on some of your experience. I can give you any details you may need. I will anticipate your reply

427seven

If you have to pay them to do it, you're gonna PAY. If you can do it yourself, you will find that it's not as bad. On the other hand, a turbo 400 with a GVO will fit with only a crossmember change and you may need to adjust your exhaust system.... Cheaper too, at least as strong and you don't have to f or k around with a computer.

kestell123

PM sent

kestell123

Did you decide to go LS or gen 1