I just had new ring and pinion and Trak-loc LS diff. installed using a master install kit. When I picked up the truck the installer told me that there was gear whine but that this is normal and would decrease as the gears "wore in". Is the whine normal or is the installer blowing smoke?

 

What ratio?

 

It's an 8.8 in 3.55.

 

Sounds to me like they're set up tight.

The factory don't run them until they "wear in" and theirs don't whine.

 

3.55's shouldn't whine. 4.56's, now that may be a different story.

 

Will it cause any damage to run it this way?

 

It sure can. May already have done so.

If set too tight, they whine and run hot. How hot depends on speed and load and how tioght they are but it can turn them blue and essentially, burn them up.

If set too loose, they have excessive back lash and pressure is applied at the tips accelerating wear.

Eather way, running them set up wrong will permanently ruin them for quiet highway use though they might still work well enough in a "junkyard dog".