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6L90 or 4L80 for Cruiser C10?

 
Old 04-14-2019, 03:54 AM
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Default 6L90 or 4L80 for Cruiser C10?

Trying to decide which trans to run. Either a low mile 6L90 + LSA stall or rebuilt 4L80 + 300mm Circle D 2400rpm stall. These would be behind a 4000lb 2wd C10 with a 416 n/a LS3. The truck will always be a cruiser. It might see the dragstrip once, and when I get tired of the n/a power it could possibly get a Magnuson at low boost. Truck has a built 10-bolt with 3.42 gears and 28" 275/60/15 Mickey radial.

I definitely want to hook on the street and I'm wondering if the 6L90 first gear might be a bit much with the 3.42s. I'm also worried I won't ever get the 6L90 to shift as crisp/confident as the 4L80. I do know the 6L90 would be the better freeway trans, and some say they're fun for the street because they downshift to the right gear since there are more of them.

Any feedback guys? I know 99% of people will say 4L80 but I'm not building a drag truck, I'm building a cruiser to go wot on the street.
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Old 04-14-2019, 06:02 AM
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Originally Posted by lxcoupe View Post
Trying to decide which trans to run. Either a low mile 6L90 + LSA stall or rebuilt 4L80 + 300mm Circle D 2400rpm stall. These would be behind a 4000lb 2wd C10 with a 416 n/a LS3. The truck will always be a cruiser. It might see the dragstrip once, and when I get tired of the n/a power it could possibly get a Magnuson at low boost. Truck has a built 10-bolt with 3.42 gears and 28" 275/60/15 Mickey radial.

I definitely want to hook on the street and I'm wondering if the 6L90 first gear might be a bit much with the 3.42s. I'm also worried I won't ever get the 6L90 to shift as crisp/confident as the 4L80. I do know the 6L90 would be the better freeway trans, and some say they're fun for the street because they downshift to the right gear since there are more of them.

Any feedback guys? I know 99% of people will say 4L80 but I'm not building a drag truck, I'm building a cruiser to go wot on the street.
What are the plans for engine and transmission control?

Andrew
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Old 04-14-2019, 04:11 PM
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Originally Posted by Project GatTagO View Post
What are the plans for engine and transmission control?

Andrew
E38 PCM + aftermarket engine harness. Factory TCM inside the 6L90e or T42 TCM if 4L80e. Street tuned by nationally known local tuner.
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Old 04-14-2019, 04:19 PM
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Originally Posted by lxcoupe View Post
E38 PCM + aftermarket engine harness. Factory TCM inside the 6L90e or T42 TCM if 4L80e. Street tuned by nationally known local tuner.
I would probably do the 6 speed in a truck.

Andrew
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Old 04-14-2019, 04:20 PM
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Originally Posted by Project GatTagO View Post
I would probably do the 6 speed in a truck.

Andrew
Any specific reason?
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Old 04-14-2019, 04:22 PM
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Originally Posted by lxcoupe View Post
Any specific reason?
Better overall gearing for a heavy truck.

Andrew
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Old 04-14-2019, 04:24 PM
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Originally Posted by Project GatTagO View Post
Better overall gearing for a heavy truck.

Andrew
This truck might weigh 4000lbs...
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Old 04-14-2019, 04:44 PM
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Originally Posted by lxcoupe View Post
This truck might weigh 4000lbs...
I would consider that to be heavy. You asked for opinions, so I am offering mine. Do you have a preference?

Andrew
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Old 04-14-2019, 05:18 PM
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Originally Posted by Project GatTagO View Post
I would consider that to be heavy. You asked for opinions, so I am offering mine. Do you have a preference?

Andrew
I only have experience with the 4L80e in my old turbo Silverado RCSB 4WD. I bought it used off Craigslist, out of a 2500HD Suburban with 100k miles. I put a Transgo HD2 in it and a Circle D stall and drove it for years and ran 10s without issue (4WD launches). I really liked how firmly it shifted, never gave me a single problem, hiccup, noise, nothing. But I did think that I drilled the separator plate holes a bit too large when I did the shift kit. Even with the stall (which softens the shift kits), the 1-2 low speed shifts were real harsh. I know the 6L90e will probably shift smoother, and have more of a "pep" to it when it downshifts around town, and on the freeway. I don't plan to do anywhere near the amount of drag racing that I did with my turbo Silverado, which is why I'm considering doing the 6-speed on my n/a 77. Just something different ya know? You only live once lol. With the right engine mounts, the motor and trans can be positioned a hair lower than factory and the 6L80/90 will clear the transmission tunnel just fine on the 73-87 2WD trucks (low hump trans tunnel). The 4L80e is obviously easy to fit, no issues there at all. So to answer your question, I'm curious about the 6-speed autos and I'm inclined to do something different on every build I do. But one thing I don't like doing is doing things twice.
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Old 04-14-2019, 06:13 PM
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I think for what you want to do, and do something different, the 6 speed will be a good option. It should handle the power and be a lot of fun to drive.

Andrew
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