'08 Rav4: horrific "clunk' when backing up steep driveway

Our 2008 Rav4 (4 cylinder) has on more than one occasion come up with a loud clunking sound when backing up our steep (~ 20% grade) driveway. It feels like it has popped out of gear or even into a forward gear. The first time it happened (a couple of months ago) it was taken directly to the dealer who found nothing. It happened again today - on two attempts to back up the driveway. If the phenomenon correlates with anything, it’s higher air temperatures and after a longish (> 30 minute) drive. Any clues?

Sounds as if it may be drive shaft u-joints. Take it to an independent shop in the mechanic files at the top of the page.

I agree with knfenimore, but an inevitable question arises regarding “It feels like it has popped out of gear or even into a forward gear”:
When you were backing up, did the car stop moving at any point, and/or did it begin to move forward?

If the answer is “no” to either one or both of those questions, then I think it is obvious that the transmission did not pop out of gear or go into Drive, and that would help to point toward the u-joints on the driveshaft as the source of the problem.

Thanks for your replies.

Since the last time the “clunk” arrived the car continued in reverse, so it sounds like the transmission is no longer suspect. My wife (for whom this happened the first time, and who took the car to the dealer) finally revealed that the dealer said it was probably something with the brakes. So we’re back to square 0.

I was going to suggest the rear drums as well, the universals are also a likely culprit.
the dealer did not seem too helpful. since she took it there I would think that they should at least inspect it briefly

I agree. Our Rav4 made clunking sounds backing up and coming to a hault on occasion. Because I always owned rwd drive vehicles, many trucks, I never gave it a second thought. When it begins to vibrate or clunk more frequently during normal driving, consider having it repaired. Otherwise, turn up the radio…too bad they aren’t that good .