Tim.. about your hybrid 18/20 transfercase

The advantage of using a 20 housing vs a large hole 18 housing is the 20 housing is slightly beefier in the intermediate area and is MUCH more available for most people. If you have access to a large hole 18 housing than by all means use it. All the castings, meaning front and rear outputs, will interchange from one case to the other. One thing I should note here is you cannot make a centered output 20 out of a large hole 18 case as there is an extra relief and extension in the 20 for the longer shift rail in the 20 for the front output where the 18 uses a short one and does not need the relief. That's why the 20 has two relief caps in the back of the case that are pressed in and the 18 only has one that is cast as part of the case. One other thing that has been mentioned before, make sure if you use a 20 case you get one with the fill plug on the side, as some had the plug on the rear and can't access it with the 18 rear output housing in place. Or you can drill and tap the case on the side for the fill plug. Nickmil.

One other thing I should add here. The procedure for putting the 18 guts and outputs in a 20 case is EXACTLY the same as rebuilding a stock 18. There are NO mods required unless you need to drill and tap the housing for the clutch linkage pivot on the driver's side or you have a case with a rear fill plug and need to put it on the passenger side of the case. Nickmil