10 speed in our 4th gen’s
Joined: Nov 2001
Posts: 34,602
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From: Schiller Park, ILL Member: #317
Oh, I agree. It sucked. I just didn't know any better at the time. I hope other people will read this and avoid the same mistake(s) I made. If I could do it over again, I would just get headers and a 3k stall for the 4L60. I would have left everything else stock. It wouldn't be fast, but it would be fun. It would have saved me lots of $$$ too.
I have spent way too much $$$$ on this car. The 6L80 sure is fun though. I wish the 6L80 was an option when I did the 4L80 swap. I probably wouldn't have done the heads/cam. I just heard way too many stories of the 4L60 coming apart to leave it in there. I wanted to make the car more reliable, so I got the 4L80. I didn't know it was gonna make the car slower. oh well. lesson learned.
When I say slow off the line, I mean 2008-ish Mustangs got 1-2 car lengths on me before I ran them down. I usually caught up to them around the 1/8 mile, and won by 1-2 car lengths. My best 60' was a 1.9 sec. That was with amazing DA, 40 degree air temps, and really good track prep. My typical 60' with the 4L80 was about 2.2 sec. I haven't had the car on the track since the 6L80 swap, but I can tell it is much quicker. It only drops about 1k rpms or less between shifts. The 4L80 dropped way more than that.
I have spent way too much $$$$ on this car. The 6L80 sure is fun though. I wish the 6L80 was an option when I did the 4L80 swap. I probably wouldn't have done the heads/cam. I just heard way too many stories of the 4L60 coming apart to leave it in there. I wanted to make the car more reliable, so I got the 4L80. I didn't know it was gonna make the car slower. oh well. lesson learned.
When I say slow off the line, I mean 2008-ish Mustangs got 1-2 car lengths on me before I ran them down. I usually caught up to them around the 1/8 mile, and won by 1-2 car lengths. My best 60' was a 1.9 sec. That was with amazing DA, 40 degree air temps, and really good track prep. My typical 60' with the 4L80 was about 2.2 sec. I haven't had the car on the track since the 6L80 swap, but I can tell it is much quicker. It only drops about 1k rpms or less between shifts. The 4L80 dropped way more than that.
I can't imagine how a stock ~2008 4.6L Mustang would be able to put 1-2 car lengths on even a completely stock LS1 4th gen at any point in the 1/4 mile, much less launch, unless you just totally blew the tires away off the line. Even with the extra weight and softer 1st gear of the 4L80E, launch should have been better with that converter. I wonder if the converter was somehow defective or the wrong stator was used for the requested stall speed?
12 Second Club
Joined: Dec 2017
Posts: 1,022
Likes: 215
From: San Antonio
There's no way I would put a bigger gear in the rear end with the 4L80. I try to keep my highway rpms close to 2000 or less. 2600 rpms on the highway is absolutely unacceptable. With the 6L80, I'm close to 1700 rpms at 70 mph, and I get off the line much quicker. The 6L80 gives me the best of everything I want.
I don't know why I got blown away so bad with the 4L80. I think my car is just slower than most. It took every mod I have done just to run mid-12s in the 1/4 mile. Before the heads/cam, it was a consistent 13 second car in the 1/4 mile (with 4L80). That's when I was thinking about adding a Pro-Charger, but never got around to it.
I don't know why I got blown away so bad with the 4L80. I think my car is just slower than most. It took every mod I have done just to run mid-12s in the 1/4 mile. Before the heads/cam, it was a consistent 13 second car in the 1/4 mile (with 4L80). That's when I was thinking about adding a Pro-Charger, but never got around to it.
There's no way I would put a bigger gear in the rear end with the 4L80. I try to keep my highway rpms close to 2000 or less. 2600 rpms on the highway is absolutely unacceptable. With the 6L80, I'm close to 1700 rpms at 70 mph, and I get off the line much quicker. The 6L80 gives me the best of everything I want.
I don't know why I got blown away so bad with the 4L80. I think my car is just slower than most. It took every mod I have done just to run mid-12s in the 1/4 mile. Before the heads/cam, it was a consistent 13 second car in the 1/4 mile (with 4L80). That's when I was thinking about adding a Pro-Charger, but never got around to it.
I don't know why I got blown away so bad with the 4L80. I think my car is just slower than most. It took every mod I have done just to run mid-12s in the 1/4 mile. Before the heads/cam, it was a consistent 13 second car in the 1/4 mile (with 4L80). That's when I was thinking about adding a Pro-Charger, but never got around to it.
Joined: Nov 2001
Posts: 34,602
Likes: 2,502
From: Schiller Park, ILL Member: #317
I guess it might bother me if I was building a daily long distance commuter and looking for every ounce of MPG - but for a toy?...no worries. 
Glad the 6L80E is working well for your application.
12 Second Club
Joined: Dec 2017
Posts: 1,022
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From: San Antonio
I basically built it to be a daily driver that can be drag raced as well. I don't drive it to work everyday, but when I do, it is about 26 miles one way. About 23 miles of that is highway, so yeah, the rpms are kinda important. I don't want my engine screaming down the highway that far. I like driving my car. It's not a garage queen. I also don't want to choose between a drag car and a street car. The 6L80 allows me to have both with one car. It has the better gearing to get off the line, and for cruising down the highway long distances. We used to only have the option between good off the line and weak (4L60), or slow off the line but strong (4L80). The 6L80 gives you the best of both. You don't have to decide between a drag car and a street car anymore. You can have both with one of these newer transmissions.
Joined: Nov 2001
Posts: 34,602
Likes: 2,502
From: Schiller Park, ILL Member: #317
4L80E + 3.73s = ~2600rpm cruising at 70mph with a 25.66" tire. That is in NO way a drag car to me, perfectly fine for the street. Back in the old days, factory BBC cars came with ~26" tires, 3.31 gears and a TH400 with no OD and no lock up. They all turned ~3,000rpm at 70mph right off the showroom floor, and engine lubricants of the day were inferior to what we have now. Nobody considered that to be drag car territory (if you wanted to drag race, you ordered the car with 4.10/4.11 or numerically higher).
I don't feel confident that a 6L80 is proven to be a "better" (i.e. more durable) unit than a 4L80E, so in my eyes there is still a trade off and I would always pick the 4L80 for a street car when the 4L60 isn't enough.
With that said, if you are in fact building a commuter and worried about MPG then yes, I do understand your goal and it's great that the 6L80 gives you everything you want.
I don't feel confident that a 6L80 is proven to be a "better" (i.e. more durable) unit than a 4L80E, so in my eyes there is still a trade off and I would always pick the 4L80 for a street car when the 4L60 isn't enough.
With that said, if you are in fact building a commuter and worried about MPG then yes, I do understand your goal and it's great that the 6L80 gives you everything you want.