14 bolt clunks on throttle release

[vkh]

So my dad and I swapped my gear ratio a couple weeks ago from 3.73 to 3.21 in my 14 bolt ff. Changed out the bearings and installed the new ring and pinion, did the break in procedure then I had about a 200 mile drive back to college. I didn't notice anything on the freeway, but I was driving it quite gently. Now that I've done some in town driving I've noticed a mild clunk whenever I release the throttle. I haven't heard it under any other scenario, just letting off the gas. I feel fairly confident in the pinion preload and backlash. I'm wondering if maybe we didn't get quite enough preload on the carrier bearings so under load my backlash is changing with a load. It had a good contact pattern in the gear paint and we had .005 in. backlash. I haven't crawled under to check u-joints but the felt solid when we did the diff so I'm doubting it's them. Also we replaced motor mounts and trans mount with poly mounts less than 4000 miles ago. Any suggestions what could be causing my clunk? I feel fairly certain it's the diff but I'm more than open to it being caused by something else. Worth noting this was my dad and I's first diff, we followed this guide very closely http://www.pirate4x4.com/tech/billavista/PR-ARB/articles/14b_Gear_Setup/.

Next weekend I'll be driving back home, we were gonna change the fluid anyway so we'll have it opened up to check. Thanks all.

 

[Rusty Nail]

I vote u joint!

 

[vkh]

Well I put the parking brake on, threw it in neutral and crawled under. My u joints are fine, no slop in them. I have about 10-20 degrees of movement in the pinion, was kinda hard to judge how much travel there was so I may be a bit off.