Noisy NV4500

[rgunlock]

I recently swapped an NV4500 into my '78 K15. This NV4500 came from a donor truck and I had it rebuilt (supposedly) by a drivetrain shop 6 years or so ago. It's been stored since then. I've had other issues with this shop, so I am not ready to vouch for the thoroughness of the job done.

I am getting two distinct noises when I go into 5th gear OD. First is a fairly loud high pitched whine/drone. This noise definitely does not exist in 1st-4th. It seems to fade the longer I'm driving in 5th, but doesn't stop and certainly comes back after downshifting and then back to 5th.

The other is a metallic rattling noise while in 5th. This noise might exist in the other gears but is not nearly as noticeable as it is in 5th.

I've tried to search for this topic without a whole lot of success. One thing that comes up is bad driveline angles. I can't swear that mine are ideal yet, but the noise only exists in 5th and doesn't appear to matter whether RPMs are high or low while in that gear. The rattling noise doesn't seem to be affected by putting pressure on the shifter in any direction.

Granted, I've got gaping holes in my transmission hump that i haven't patched yet, and I was driving without carpet or boots to block the noise. I suspect the noises won't bother me too much once I've finished the flooring. The reason I'm posting this is to get you guys opinion on whether this sounds like anything I should be concerned about. Other than the noises the NV4500 seems to be performing just fine so far.