Just wanted to thank the folks in this excellent forum for the info required to fix the squeak from the drive belt. I had previously updated the tensioner so when the squeak appeared a few weeks ago I replaced the drive belt with an after market one. Lesson #1 learned here, don't buy after market belts buy the OEM Nissin one. Rib shape and spacing are markedly different.
The squeak quieted down with a new Nissan belt installed, but was still noticeable. Lesson #2 review TSB's on Nissanhelp to determine that squeak can also be caused by misalignment of oil puimp to crankshaft pulleys. The TSB says to put a flat edge across both pulleys to check for offset. Its a bit of an awkward spot to do this without pulling the fan so I just went ahead and completed the TSB on loosening and re-torquing the four bolts mounting the oil pump to the engine. The two bolts on the front are easy enough, but the two on the side are very difficult to get to. The TSB does not mention this but to even see those side bolts you need to remove a bracket, held on with one bolt, from the back of the oil pump to be able to move a large cable bundle held by the bracket out of the way. Then you can see the bolts but you can't reach the bottom one until you remove the heat shield over the exhaust manifold.
This is where things went sideways for me. I have removed a few heat shields in my past and its always the same problem, the heat cycling weakens the bolts holding the heat shield to the manifold while somewhat welding them to the manifold. The result for me was 2 out of 3 bolts broke off nice and flush with the manifold.
To make things worse there is just enough room to move the heat shield backward to get access to the bottom oil pump bolt but not enough to get the shield out completely so that I could attempt to remove the busted bolts. I didn't feel like taking the entire truck apart so I got out the JB Weld and used that and the busted off bolt heads to glue things back together.
(Just don't tell my wife, it's her truck, that I used the JB on her truck...please
The re-torquing was effective following the torque values and order set out in the TSB. The tension in the belt has definitely gone up and it must have fixed the alignment because I got a happy wife again.
No more squeak.