6L80/90
- Thread starter btfelker
- Start date
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goldpack
Full Access Member
- Joined
- Jul 8, 2025
- Posts
- 825
- Reaction score
- 1,465
- Location
- Adirondacks, NY
- First Name
- Donnie
- Truck Year
- 1986
- Truck Model
- GMC C2500 Camper Spec.
- Engine Size
- 350 with 350 3 speed
@NickTransmissions ?
any suggestions ?
(to me the last good thing is a 4L80....
vs. all the complaints about the 6 speeds that came after)
any suggestions ?
(to me the last good thing is a 4L80....
vs. all the complaints about the 6 speeds that came after)
NickTransmissions
Full Access Member
- Joined
- Aug 3, 2023
- Posts
- 663
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- 1,336
- Location
- Las Vegas
- First Name
- Nick
- Truck Year
- 1987
- Truck Model
- R10
- Engine Size
- 350
The 6L80 is roughly the same length as a 4L80E and the 6L90 is about 4-6 inches longer. You can use that information to determine what you need to do with the x member and drive shaft(s).
You will obviously need a means to control the transmission - the main options are a complete powertrain swap with the factory wiring harness and ECM or an aftermarket controller with the matching harness.
You will have to investigate (or others can respond) to what may be needed to mate the 6L80/90 to a Gen 1 small block or big block if you’re not planning on doing an LS/Gen3 or 4 engine swap.
Lastly, the transmission will have to be built based on what you plan to do with the truck, engine power, etc.
You’ll need to share that info if you want any guidance beyond the highest of high level…
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