Sorry that my advice will not be specific to the Dakota, but a month or so ago I did all three of my lines on my '02 GMC Sierra (it has an aux cooler mounted in front of the rad, hence, the 3rd line). The lines were not leaking (yet), but there was some severe corrosion going on. For two of the lines (the line out of the transmission & the line returning to the transmission) I wound up doing some surgery & then, after I had them the lines connected at both ends, I spliced in a very short section of 5/16 rubber transmission hose. I bought fuel injected fuel line clamps to secure my splices with, & I actually used 4 clamps per splice, so that each clamp had a back up clamp. I would also say that if your return line is leaking due to corrosion, you might as well change your pressure line at the same time.
I wish you well on that.
Something else I'll throw out there: I am assuming that your line on your '06 was leaking due to corrosion (a little while back I replaced my PS cooler & lines on my rust bucket due to leaking due to corrosion which is what got me looking at my transmission cooler lines). I have become a big believer in the Flex-Seal product, & after I got all my transmission cooler lines installed I painted them with a coat of Flex-Seal. I probably didn't need to go this far since the original lines lasted 19 years & I don't think that either I or the truck have 19 more years left in us, but, who knows.
Good advice. Lowering the front differential will be an adventure. It will probably not come down enough on the passenger side without removing the axle nut and give the axle some play. It is going to be a PIA. Splicing might be the way to go. I cut the old metal lines where it was leaking and snapped, have clamps and hose ready to go. Did you have to do anything to the metal ends before connecting them with the hose?
All I did was to take a file & clean the burrs off the outside & inside of the cooler lines after I cut them. Then I pushed the 5/16" rubber transmission hose up as far as I could get it to go on both ends of the splice (I was able to push the rubber line up several inches of the metal line) before I clamped it. I'd never used the EFI line clamps before, & one thing I did find out about them is to get them where I wanted them to be the first time, because they are kind of a prick to get loose once they are tightened down on the rubber line. I wasn't super crazy about the idea of putting splices in my transmission cooler lines, but in reality, the length of the hose splices was very minimal, & I tried to do a good job of making the spliced area as sanitary as possible.
Thank you for the helpful information. I was able to install new pre-bend lines without splicing them. For all those who need to install trans cooling lines for 2006 Dakota: Take photos of the line route. Remove crossmember below, 4 bolts. Remove bumper cover, remove bumper, remove radiator bottom plastic cover. Remove wheel and wheel liners. Remove and install the lines. It was a project but satisfying to get it done.
I'll bookmark this in case I ever have to do my Dakota, although I probably won't, as it's never seen salt & it oughta outlast me.
As far as my Sierra cooling lines, I was able to snake mine into position, but I was unable to get the terminating ends to line up perfectly close enough. Removing the right side cat would have gave me better access to get my hands up there to finagle things on the transmission, but my work ethic isn't as good as yours is. As I previously typed, I wasn't thrilled about cutting my brand new lines, but I did order the cheapest ones Rock was selling, they were branded "Sumsong" & I think they were about $11 each, so I figured what the hell, I can always buy another one if this doesn't work out like I want it to. After I completed my splices, I designed a shield that I installed over the spliced area, so I am thinking it will hold up & should withstand the test of time.