I'm going through my um teenth transmission redo in my truck. I was given a trans and t-case (all I had to do was remove them. THAT was a PITA because of the donor vehicle.) I trust the 2 guys who gave the set up to me (they are like my brothers) it was rebuilt and ran fine 'til the motor went to shite. The donor vehicle was a 99 Jimmy (4.3) and mine is a 02 Silvy (5.3). Interestingly enough even though both RPO codes are IDENTICAL there are some differences. My t-case has 6 NUTS that go on studs the Jimmy has 5 BOLTS. Not a problem as I am keeping the set up paired. I know they used the t-case in all settings (as needed) so no need to split the 2 up and swap the tail shaft adapter. Near as I can tell all the plugs are the same (GOD KNOWS I'll know for a fact when I have the new ready to install.) Now the T-cases measure the same in length, the adapter from the Jimmy is a 1/2" shorter then mine the trans from the Jimmy measures 21 3/4" and the Silvy 22 1/4"-22 3/4" (hard to get a good measure) for a total of Jimmy: 45" and Silvy: 46"-46 1/2". One VERY important measurement I haven't done yet is bell housing to trans mount. I know the spline shaft (or slip yoke I think I've heard it referred to also ) has some play in how far it seats inside the t-case because you slip it in then pull back out to mount to the rear end. Also as you drive it slides in and out as the suspension flexes. Also with my truck being lifted it doesn't seat as far in as a factory one. My thoughts are an 1"-1 1/2" shorter on how far the shaft goes in (insert NSFW comment here____) shouldn't matter. Prior to removing the drive shaft, I plan on marking it then when re installing look at where the mark is. (in case I wasn't measuring right.) To an extent I will be fwonked if there is a problem as I am saving up on a shoestring budget and intend on having all parts and fluids in advance to avoid last minute parts runs. I do find it "funny" that all places I researched showed that the 4l60e all measure the same Any enlightenment or guidance would be GREATLY appreciated. Thanks in advance.