Light Sqeak from Drivetrain under Decelleration

Hey Guys and Gals
2004 Jimny 16v

Got a problem on my Jimny which is baffling me...

So if I am driving along under acceleration or any throttle applied it sounds perfectly fine, however if I go from say 3rd down to 2nd and let it roll along under engine braking it gives off this light squeaking sound from around 2500rpm down to 1200rpm (it sounds almost like a slightly damp fanbelt but its 100% not) it also shuts up as soon as you depress the clutch. Also should I note it doesn't do it at all speed.

So I have had it up on the axle stands and tried to diagnose it, also greased the prop whilst it was up, you would think its the clutch release bearing ect because of the nature of it shutting up as soon as you depress the clutch but it sounds very much from the rear of the Jeep!

I have looked and felt for play in everything and still no luck, also sprayed all flanges ect just to see if I could pinpoint it.

it doesn't affect drivability but its starting to annoy me.

my culprits are:
Possible U/J worn?
Diff Bearing starting to go?
Gearbox?

Has anyone encountered something similar? if so what is it likely to be?

Thought I would ask first before replacing a long line of drivetrain parts, thanks
Matty

I'd start by looking at the engine.
Under deceleration there is a high level of vacuum in the inlet manifold, check for disconnected/broken pipes such as the servo pipe, the feed to the vacuum hubs, and the evaporation cannister purge system.

Sounds can travel, I changed the rear wheel bearings and the diff on mine to try to cure a rumble that was definitely from the back axle, and eventually found that it was a front wheelbearing when the brakes developed massive freeplay.