If that guy can sell his parts for what he's getting for them, then GV is making a killing on their stuff.
All the drawbacks that the GV/Laycock unit has I made my decision a long time ago to use the mostly trouble free 4L80E. They both need electronic controllers to be used automatically. Everyone always says they want the GV unit because the 4L80E needs an electronic control module, so does the GV unit. I also don't have to change fluid in my 4L80E every 5,000 miles. The deep finned pan the guy is selling is because heat is a definite factor in the GV/Laycock unit.
If you run it with a manual switch and forget to turn it off when you come to a stop, or put it in reverse, it's going to smoke the clutch immediately. The GV unit connected to a T400 also is larger overall than a 4L80E.
The 4L80E is proven since 1991 in GM HD truck applications and uses about 75% T400 guts, It can take as much abuse as any T400 can and has a built in OD. The 4L80E can also use the aftermarket TCM to make adjustments to the shift points and hydraulic pressures on the fly. You can't do that with any GV/T400 unit.
I'm not trying to change anyone's mind, but I did a lot of research on auxiliary OD units compared to a 4L80E and the 4L80E is the winner in my book, hands down. Plus I own a 1993 K3500 dually with a TD 6.5 and know how tough these transmissions are. 248,000 miles on it and it will pull/haul anything I ask it to. I use it regularly to haul a 35' Holiday Rambler fifth wheel camper.
