I'm in need of my third set in 400,000 miles. I've used OE lines as it usually coincides with me needing to pull the Radiator & CAC to clean the cooling stack along with a drive belt, Idlers & Tensioner.
I have seen quite a few issues with aftermarket solutions, The "Adapt-A-Piece" kits uses compression fittings that WILL eventually leak because the OE lines are a pretty soft aluminum.....Instead of the brass ferrule getting a good bite like it would on a steel line, It just crushes the aluminum line.
Using a full hydraulic line kit requires you to remove the fittings at the radiator tank & replace them with AN/JIC fittings. Removing the fittings (Which you remove one at a time!) runs a high risk of coolant leakage after the install. This is most likely from over-torquing the fitting.
*I've also seen that folks will crack the tank while torquing the line to the fittings.
*You have to route them just so.....Chaffing is a big problem in the field with these kits.
***DO NOT assume a kit made for a Duramax truck will fit a L18 truck!!!!
"IF" I was going to use hydraulic patch lines......I would weld aluminum #10 -AN fittings to my lines after cutting the crimps off, Then have some hoses made at a local shop, I would just be cautious of the aluminum on steel connection by using anti-seize on the threads & not over-torquing them!
Just a note.....DO NOT think you can clamp new hoses on......They WILL blow off! Allison 1000's make A LOT of converter discharge/cooler pressure!!!
My opinion is to just use new OE lines & be done with it for 100,000 to 150,000 miles, The good news is.....This is a much easier job on a gas rig!
