My 2000 ZR2's reverse seems different these last couple days. The engine seems to have to work harder than usual to back up. I don't hear anything out of the ordinary (clicking etc) other than higher rpms. Almost like it's in 4 wheel drive or the brakes are being applied. Moving forward seems to be normal. Should mention I used 4x4 on a pretty rough and muddy road recently. Any ideas?
New: After driving it a bit and trying reverse a few times, when I put it in reverse I can hear a clang as the gear sets (sounds like a bell). And it sets more forcibly than usual, giving the truck a good jerk in the process.

 

Well that was easy. Turns out there was so much dried mud packed on top of skid plate it was affecting something (linkage maybe?). Anyway, mud is out, reverse is normal again. Thought I'd leave this up for anyone who might run into something similar with their ZR2. Whew..