LT1-DAN

I wanted to know if the '05 c6 4speed 4l65-E trans is better/worst in terms of durability/reliability compared to a '06 6-speed auto trans.? What one will hold the power of a h/c swap better? Can both of them be beefed up??

ChocoTaco369

The A6 6L80E is leaps and bounds better than an A4 4L60E/4L65E. They're not even close. The 4L60E/4L65E is a medium-duty transmission put in heavy duty situations thanks to torque management. The 6L80E is an actual heavy duty transmission. Everything about the design is better. Everything about the internals is stronger. The 6L80E can hold some 150hp/150tq more stock than a 4L60E/4L65E can. Best of all, they're roughly the same size and the same weight thanks to the sophisticated design and electronics of the 6L80E. I'm not sure about parasitic loss, but given the size and weight, it seems like it's a rather efficient trans, at least compared to the TH400/4L80E, but correct me if I'm wrong.

Of course, problem is, there is virtually no aftermarket for a 6L80E yet. I don't think people know what its true power handling capability is yet. They're still too new and people don't know how to build them yet. It takes years before that kind of knowledge is known.

LT1-DAN

Thanks, Do you know if the A6 can be beefed up? So it would be better to hold out for a 06+ versus a 05 A4? I am just worried about the whole paddle shifting deal becoming a real problematic/expensive problem down the road since the A6 is pretty new and not really proven longterm yet.

poorhousenext

Take a look in Hybrid fourm if you want to know a little more about size difference...LOL Below link has best info on the 6L80 I've found.

https://ls1tech.com/forums/conversions-swaps/898899-6l80-6l90-into-68-camaro-does-go.html

Total overall length and rear Trans mount bolt locations are about the same for both trans, but after that, they are not even close...LOL

I have projects in work using both trannys and 4L60/5 fits with no tunnel modifcation, while the 6L80 required modifing tunnel to get it to fit.

Bottom line, the 6L80 is not a drop in fit for most cars like the 4L60/5 is.

Does this look like a 4L60/5 and it are about the same size..



With a 4L60/5 I can run 3.0" exhaust through the crossmember...LOL



Like I said, overall length and mount bolt hole location.

ChocoTaco369

I said they were about the same size, not exactly the same size. The 6L80E is much more compact than a 4L80E considering what's in it. It has 2 more gears, is rated at a higher hp/tq and manages to be smaller and lighter. That's impressive IMO.

poorhousenext

It does have 2 more gears and I guess you could call it compact, but the 6L80 may not be as strong as the 4L80. For that, you might want to consider the 6L90 as a better match up.

Even a 4L80 transmission fits with only problem being exhaust not fitting through the Vette’s stock trans crossmember openings locations.

While the 6L80/90 presents that same problem, it also requires major tunnel modifications to get it to fit. Same goes there for most older cars, so calling the 6L80/90 compact compared to 4L60/5 or 4L80, is like calling my 5 ft 1 in 170 lb wife compact when comparing her to Jessica Alba IMHO.

Sure they are the same height and their butts are the same distance from the floor, but,,,, when you take even a not so close glance at them you can see my wife’s girth is going to make for a lot tighter fit when you try to get her to fit in size 2 jeans that Jessica can slip right into….LOL

It may be that I should have chosen the 6L90 over the 6L80 with LS7 engine. The only thing that may help with the 6L80 handling the LS7 HP & TQ potential is my GVW will be around 2700-2900 lbs.

4L60/65
Weight 163 – 195 lbs application specific,
Max engine Power 360 bhp,
Max Gearbox TQ 610 lbs-ft,
Max validated Gross Vehicle weight 7400 lbs (application and axle ratio dependent).

4L80
Weight 254 lbs,
Max engine Power: Not listed. See engine application range gas and diesel,
Max engine Torque 440 lbs-ft,
Max Gearbox TQ 885 lbs-ft,
Max validated Gross Vehicle weight up to 18,000 lbs (application and axle ratio dependent).

6L80
Weight 207 - 229 lbs,
Max engine Power 449 bhp,
Max engine Torque 439 lbs-ft,
Max Gearbox TQ 664 lbs-ft,
Max Gross Vehicle weight Target, GVW: 8600 lbs, GCVW 14,000 lbs.

6L90
Weight 240 lbs estimated,
Max engine Power 452 bhp (Truck) & 555 bhp (Passenger car),
Max engine Torque 520 lbs-ft (Truck) & 550 lbs-ft (Passenger car).
Max Gearbox TQ 885 lbs-ft,
Max validated Gross Vehicle weight Target, GVW: 15,000 lbs, GCVW 21,000 lbs.

ChocoTaco369

The 6L80E is rated higher than the 4L80E in stock form. The 4L80E just has a reputation for being strong because it's been out forever and there are tons of aftermarket parts out there and they're easy to build since they're so old and simplistic.

Wait for the 6L80E to be 20 years old. You may see that behind 1200 hp race cars as the choice overdrive transmission. In stock form, according to GM, the 6L80E is stronger.

I don't trust that number for the 6L90E, BTW. Why? Because it is rated at 452bhp on that info you gave, but it's going behind the new 550bhp supercharged CTS-V. The 6L90E is going to get a 100,000 mile warranty behind a SUPERCHARGED 550bhp heavy luxury car, and we all should know that FI is tough on internals parts because the power comes on more suddenly and smacks them around harder. That's 98bhp more than your info shows, so I don't trust your info.


Engine
Type: 6.2L supercharged V-8 (LSA)
Bore & stroke (in): 4.06 x 3.62
Block material: cast aluminum
Cylinder head material: cast aluminum
Valvetrain: overhead valve, 2 valves per cylinder
Supercharger: Gen. 6 R19 with single brick intercooler; 1.9L displacement w/4-lobe rotor design
Compression ratio: 9.0:1
Horsepower (hp @ rpm): 550 @ 6200 (est)
Torque (lb-ft @ rpm): 550 @ 6200 (est)
Additional features: pan-mounted oil cooler; cast pistons; high-flow cylinder heads; block-mounted piston squirters; steel crankshaft w/ 8-bolt flange; close-mounted converters; acoustic engine cover; E67 engine controller
Transmissions
Type: Tremec TR6060 six-speed manual; fully synchronized with two overdrive gears
Gear ratios (:1)
First: 2.66
Second: 1.78
Third: 1.30
Fourth: 1.00
Fifth: 0.80 (Overdriven)
Sixth: 0.63 (Overdriven)
Reverse: 2.90
Final Drive Ratio: 3.73
Type Optional Hydra-Matic 6L90 six-speed electronically controlled automatic overdrive with torque converter clutch
Gear ratios (:1)
First: 4.02
Second: 2.36
Third: 1.53
Fourth: 1.15
Fifth: 0.85 (Overdriven)
Sixth: 0.67 (Overdriven)
Reverse: 3.06
Final Drive Ratio: 3.23

http://www.cadillac.com/09ctsv/html/specs.jsp

poorhousenext

Taco,

The info on all the transmissions is from GM's Powertrain website and easily verified. As for trusting my info, since I typed it in Vs copy and paste, I could have made a mistake in my typing.

Now what I believe is the problem is not my info or typing....LOL

I think you might want to go back and read my info on all the transmissions again, but this time when you get to the 6L90 read the HP ratings twice and then maybe, just maybe we will be on the same page on the 6L90 and you want be so hard on this old man...LOL

Then if you read the next to last line of the 4L80 info and the next to last line of the 6L90 info and compare them to the next to last line of the 6L80 info, maybe just maybe you'll understand why it's my belief the 6L90 is the transmission that matches and maybe, just maybe beats the 4L80 in stock power handling strenght and why I think my choice of the 6L80 behind a LS7 is risky with maybe, just maybe the only thing that will allow me to get away with it is my car's 2700-2900 lbs weight and fact that the 3.07 rear end will help out with that load as C6/A6 at 3100 lbs uses a 2.56 or 2.76 ratio rear end with 6L80, but then again they use and engine that is rated 69-75 HP less so it's a real coin flip on if it will IMHO.