AHC Thumping noise when lowering

[818Toyotafan]

02 LX 470 - recently had all globes and bleeder valves replaced + flush and pressure adjustment done by a local respected Toyota/Landcruiser shop. Definitely an improvement in ride quality but when lowering from N to L the AHC seems to drop slower making a thumping noise and doesn't drop as smoothly compared to before the new valves.

Previously the front shocks were changed and new bushing installed before the globes.

 

[MongooseGA]

Is the thunk definitely from the AHC?

What kind of shape are your bushings in? What about your sway bar links?

It kind of makes sense that it would lower more slowly now- the system has adequate pressure/ power to actually support the weight while it comes down. Think difference between a weak arm holding up/ lowering a heavy weight vs a strong arm doing the same. The thunk, to me, is likely another component (not AHC) that you're hearing. Maybe it dropped fast enough previously that the thunk didn't have to happen or was quick enough it was indiscernible.

 

[2001LC]

Likely T-bar carrying to much weight, resulting on LOW front pressure. Check pressures!

 

[baltistyle]

Was the height properly adjusted? If it’s slamming into low, the travel range may be a bit low. I resolved this problem that occurred for me as well after replacing globes by making sure height was dead on, then making sure all driveshaft fitting were greased, and very last on my list was the front diff bushings. Whenever I have any driveline vibration, I first check the greasing of the driveshaft..

It could be any bushing that moves as the suspension moves, sorry I know that does not help. Fortunately these trucks are tall enough to lay under as someone cycles the positions.0