Any blown up 6L80E/90E's yet?
06-14-2008, 11:38 PM
#81
This transmission could not have existed without the level of TCM control available from the fast processors we have now. Because they only overrun in first gear the TCM programming needs a lot of attention to make upshifts and downshift happen when they should. Having put a few thousand miles on one myself I can say that this setup is sensitive to rapidly changing throttle position. If, for exmaple, you mash the throttle to get a downshift of a few gears and then lift right away, the feel you get is a lunge forward. Without an electric throttle body the affect would be felt much more. That's something for anyone looking toward swapping in this trans in the future needs to keep in mind. With a stock 6.2L and 4L90-E combination there are still certain conditions that produce some sloppy or jolting shifts. I don't think it will be impossible to adapt one for performance use but I know for sure the programming is going to need a lot of fine attention.
Fuel economy was always a major consideration in the design, to my knowledge. A lot of the parasitic losses in automatics come from un-engaged clutch pack dragging. Overrun packs on one-way mechanical clutches contribute a lot to that in a normal auto. The "clutch-to-clutch" system in the 6L80/90-E eliminates a lot of the energy lost to that friction.
From a performance perspective, a lot of guys feel like these have the potential to be the next swap of choice for high powered vehicles. On the basis of specs alone it looks pretty good. They have a very wide ratio range and a high torque rating. The 6L's are rated for higher RPM too. There's more to it that this and I'm not as optimistic. The low ratios still feel far apart, like the 1-2 shift in a 4L60-E. I also don't think they have as much potential for power-handling overall as the proven 4L80-E does. The torque rating of an automatic is misunderstood, in my opinion. The factory torque rating is based on how much input torque the clutches can overcome during a shift while doing it so smoothly you cannot even feel it. Smooth shifts under power more friction heat. The rating alone has less to do with the hard parts and everything to do with clutch capacity. The 6L80/90-E gets 6 gear ratios out of 3 planetary gear sets. That means there are shared clutch packs. There are certain shifts in the 6L that are dual-event, a disengage taking place at the same moment another pack is engaging. (Exactly like the 2-3 shift in a 4L60-E and why that shift is always so sloppy) The 4L80-E has 3 planetaries too but only 4 speeds. No clutch packs do double-duty for any pair of shifts in the 4L80-E like they would if it had more speeds. All of the drums and planet carriers in a 4L80-E are steel. I have not been inside of a 6L80/90-E but have every reason to think that GM used aluminum in favor of steel for every component they could get away with, not just for cost but weight too. This is why I'm saying the quoted torque capacity can be misleading. Looking solely at GM torque numbers the 4L70-E and 4L80-E should be very close, but we know from experience the internal parts have completely different capacities. I think some of the same difference may exist between the 4L80-E and 6L80 or 90-E. 4L80-E's are based on the TH400 that was designed in the early 1960's. Back then less consideration had to be given to the cost of raw materials and weight, and that minimized the penalty of "over-building" something because it didn't hurt the bottom line. It worked pretty damn good for almost 30 years until the Hydramatic division weakened it by adding overdrive with a undersized roller clutch to it. (That was fixed in 2001 with upgraded design.)
The 6L80/90-E was designed from the ground up all-new. In an era where pinching every tenth of a penny and shedding every tenth of a gram possible increases the products ability to compete and make profit, I just can't see how there could be very much "safety margin" engineered into "overbuilding" these trannies. I think we'll find they will handle just about exactly what they've been designed to do and not much more. Time will tell...
That's my opinion.
Fuel economy was always a major consideration in the design, to my knowledge. A lot of the parasitic losses in automatics come from un-engaged clutch pack dragging. Overrun packs on one-way mechanical clutches contribute a lot to that in a normal auto. The "clutch-to-clutch" system in the 6L80/90-E eliminates a lot of the energy lost to that friction.
From a performance perspective, a lot of guys feel like these have the potential to be the next swap of choice for high powered vehicles. On the basis of specs alone it looks pretty good. They have a very wide ratio range and a high torque rating. The 6L's are rated for higher RPM too. There's more to it that this and I'm not as optimistic. The low ratios still feel far apart, like the 1-2 shift in a 4L60-E. I also don't think they have as much potential for power-handling overall as the proven 4L80-E does. The torque rating of an automatic is misunderstood, in my opinion. The factory torque rating is based on how much input torque the clutches can overcome during a shift while doing it so smoothly you cannot even feel it. Smooth shifts under power more friction heat. The rating alone has less to do with the hard parts and everything to do with clutch capacity. The 6L80/90-E gets 6 gear ratios out of 3 planetary gear sets. That means there are shared clutch packs. There are certain shifts in the 6L that are dual-event, a disengage taking place at the same moment another pack is engaging. (Exactly like the 2-3 shift in a 4L60-E and why that shift is always so sloppy) The 4L80-E has 3 planetaries too but only 4 speeds. No clutch packs do double-duty for any pair of shifts in the 4L80-E like they would if it had more speeds. All of the drums and planet carriers in a 4L80-E are steel. I have not been inside of a 6L80/90-E but have every reason to think that GM used aluminum in favor of steel for every component they could get away with, not just for cost but weight too. This is why I'm saying the quoted torque capacity can be misleading. Looking solely at GM torque numbers the 4L70-E and 4L80-E should be very close, but we know from experience the internal parts have completely different capacities. I think some of the same difference may exist between the 4L80-E and 6L80 or 90-E. 4L80-E's are based on the TH400 that was designed in the early 1960's. Back then less consideration had to be given to the cost of raw materials and weight, and that minimized the penalty of "over-building" something because it didn't hurt the bottom line. It worked pretty damn good for almost 30 years until the Hydramatic division weakened it by adding overdrive with a undersized roller clutch to it. (That was fixed in 2001 with upgraded design.)
The 6L80/90-E was designed from the ground up all-new. In an era where pinching every tenth of a penny and shedding every tenth of a gram possible increases the products ability to compete and make profit, I just can't see how there could be very much "safety margin" engineered into "overbuilding" these trannies. I think we'll find they will handle just about exactly what they've been designed to do and not much more. Time will tell...
That's my opinion.
Last edited by James B.; 06-14-2008 at 11:51 PM.
06-16-2008, 03:15 PM
#83
Adkoonerstrator
Thread Starter
iTrader: (4)
Join Date: Nov 2001
Location: Deep in the seedy underworld of Koonerville
Posts: 21,436
Likes: 0
Received 3 Likes
on
2 Posts
Thanks James, it will be interesting to see the guts once people start tearing into these things. I hope they can at least hold up to a radix. 
10-02-2008, 04:08 PM
#87
Adkoonerstrator
Thread Starter
iTrader: (4)
Join Date: Nov 2001
Location: Deep in the seedy underworld of Koonerville
Posts: 21,436
Likes: 0
Received 3 Likes
on
2 Posts
So far it's holding up to 600+hp and 6100lbs pretty well. Still shifts nicely. 
Anyone have any horror stories yet?
Vince - Any looks inside one of these suckers yet?
Anyone have any horror stories yet?
Vince - Any looks inside one of these suckers yet?
10-04-2008, 07:19 AM
#88
13 Second Truck Club
Join Date: Apr 2006
Location: Cajun Country...Lafayette, LA
Posts: 698
Likes: 0
Received 0 Likes
on
0 Posts
10-04-2008, 10:35 PM
#89
Adkoonerstrator
Thread Starter
iTrader: (4)
Join Date: Nov 2001
Location: Deep in the seedy underworld of Koonerville
Posts: 21,436
Likes: 0
Received 3 Likes
on
2 Posts
Yep, 6L90E. I am not sure exactly but, probably a few thousand miles with the blower. The transmission is still internally stock. I did raise the shift pressures a tad, lower shift times a tad, and raise shift rpms a tad.
It gets at least a few WOT blast every week day.
It gets at least a few WOT blast every week day.
