Why the GM 4L80 is a Tough Fit for the Discovery
How spatial limitations make the GM 4L80 transmission harder to use in a LS Disco Swap
We recently acquired a partially completed Discovery 2 LS swap. The person that we purchased it from did not use our swap products, but did a good job. The unfinished swap used the GM 4L80 transmission. Part of the reason I thought this would be good to acquire was to see how the 4L80 worked with the Disco transfer case and frame. Before I saw this, I had some ideas about how some work was going to be needed to compensate for the extra length of the 4L80 plus the length of the adapter to fit the 4L80 to the LT230.
Let me just say this first — the 4L80 is BIG. The adapter is long enough to just allow the front driveshaft to fit. Furthermore, even with that long adapter, I still do not see how a double cardan driveshaft is supposed fit here. It’s very tight. Maybe with some shaving on the transmission pan.
Second, the transmission / transfer case mounts need to move back to compensate for the extra length. Round figures, the setup seems to be about 6 inches longer than our setup with the ZF 4HP24. The engine can’t move forward all of that difference. The transfer case can’t move back all that distance either: the parking brake drum will hit the floor of the body. While the floor of the body could be fixed relatively easily with a hammer, I think the best solution is probably to move the engine forward 2 inches and the mount setup back 4 inches.
That extra two inches in the front costs you a bit though. I really like that with our ZF 4HP setup we can retain the use of the factory clutch fan, avoiding the need for electric fans. That can’t work here though – the clutch fan will hit the radiator for sure. We will be needing an electric fan setup. The accessory drive is going to be a tight fit 2 inches forward. I think there will be some issues with hood clearance, but we will see.
Then there is the shifter and gear switch. Without the 4HP24 XYZ switch, you lose gear indication on the dash and everything that can go along with it — like neutral safety control, reverse lights, etc. We can get around that with our new electronics fortunately though. Another box to wire in…
Now there are some times when you may want to use the 4L80 — but those times are limited. I would suggest that the factory ZF transmission is fine for 95% of Discovery owners. The largest reason that I can think of using the 4L80 is if you wanted to make a large amount of power — like 450+ hp – and want to have basically the most rugged transmission setup possible. In that case, you probably also are going to be upgrading the axles / diffs (to deal with that big increase in power) and its probably no big deal to break out the welder and move the transfer case mounts around, because you are going to be doing extensive modifications. That level of build, with that amount of modifications, is really not what most people want out of a Discovery LS build and is certainly not what most people can do in a home garage or what most shops are capable of pulling off (short of custom 4wd shops). 4L80s are also becoming kind of expensive – a good used one is hard to find for less than $1,000.
Therefore, for a grand majority of Disco drivers, the most straightforward and best LS swap that will meet all of their needs is our swap kit utilizing the 4HP22/24 transmission. The 4L80 just doesn’t make a lot of sense unless it is for a very specific purpose, and even then — its a lot, lot, lot more work. The install time I would guess to be double or more than the install time of our 4HP24-based kit. That being said, I look forward to working on this truck and seeing what we can do with the 4L80.