Under normal driving conditions, when would you start seeing wear in the bearings in the rear axle?

My truck has 90k miles on it, and I'm about to install a trac lok unit. If the bearings are going to be fine for another 90k miles I don't want to drop the extra $120 on a bearing set. I know it's always good to change bearing while you're already in something, but my labor is free and I'd rather defer the cost of it until later.

__________________
2001 4.7L A/T R/C Dakota, Patriot Blue.

I would think you would be fine as long as the bearings are in good shape now. My truck has 154000 miles now and still has the original bearings. If you can swing it the extra $120 sounds worth it to me just for the peace of mind.

__________________
98 Dakota Sport extended cab 4x4 5.2L/auto- green
150k+miles and counting...
Gibson cat back exhaust single in/dual out
aftermarket cold air intake w/heatshield
hitch
hinged soft tonneau
pioneer head unit
camo seat covers
Kenda 31x10.5x15

i agree if you got the funds do it

__________________
Blue 99 Dakota Sport 4x4 Ext.Cab
---------------------------------
318 engine
throttle body spacer (came with truck)
exhaust (came with truck)
31x10.50x 15 goodyear rt/s
Tonnoue cover