Quick update: I spoke with my mechanic again. He still believes the front control arm bushings and rear trailing beam bushings are likely contributing to the instability and wandering.

The problem now is parts availability. Honda apparently only sells some of the rear components as complete assemblies, which makes the OEM option extremely expensive. He has been trying to find quality replacement bushings, but finding rear trailing beam bushings for a 2011 Fit in Canada has been more difficult than expected.

If he can't find an exact replacement, he is considering measuring the original bushings and matching them to another available bushing. He says he has done that successfully in the past, but I admit I'm a bit hesitant about going that route.

At this point I'm trying to decide whether it's worth replacing all four bushings, only the front ones, or continuing to investigate other possibilities such as steering or ball joint issues.

Has anyone here actually replaced the rear trailing beam bushings on a GE Fit and, if so, what parts did you use?

Thanks again for all the help.

 

I saw that - they only sell the whole rear beam with the bushings in it. They did something similarly dumb with '90s era Civics, but eventually caved and made them available. The trick was, they weren't listed on the regular Honda parts diagrams. You had to find the part number in a relevant service advisory. Aftermarket companies later started selling them too.

 

I'm seeing lots of ebay and amazon listings showing Honda-like labels (with "Honda" conspicuously missing) and bushings listed as fitting GE and GK fits, as well as HR-Vs, and GE-era Civics and Insights. Searching for their part numbers (ex. 42100-SMG-E05 or 42100-TM0-T12) on a Honda parts site comes back with nothing, though that may be a regional thing (E and T in the last 3 of the part numbers - North America is A, or a number for no region). The dodgiest part of those listings: the bushing shell is plastic? Looks like nylon to me - it should be steel.
I see some "NISTO" brand bushings that look like they have steel shells, but they're more than twice the price of the plastic bushings (~$50 vs $120 for a pair). There's a few brands of urethane bushings, but they have a floating center bar which can cause problems in some applications, and usually needs regular lubricating or they get noisy. Looks like the relatively-well-known brand Hardrace sells replacement bushings (using harder rubber) at a wallet-scorching $305. Given those options, I think I would go with the Nisto bushings.

edit: Here's a supposedly Canadian company selling urethane bushings with fixed centers: Siberian Bushing.

... And there's always bushing-in-a-tube.