Understandably, I get the stress. Having gone to multiple mechanics, if no one is giving you an answer, you can either keep going to other mechanics, sell it, or start digging into it.
Im of the view that when you get to that point its time to start diagnosing and going through a process of elimination.
Here's how I would be looking at it before loading the parts cannon or going to another mechanic
The issues are
20-60km, you get a clunking -
Id be thinking something mount/balance related
Are the wheels all balance?
Are all the wheels not buckled?
Is the tail shaft bearing stuffed?
Are the tail shaft couplings stuffed?
Are all the bolts in the drive line tightened?
Are the mounts (Trans mount, tail shaft bearing mount) tightened?
Diff mount bushings, are they buggered?
Gurgling sound
That to me flags something related to fluid, and gurgling means id be looking to the gearbox
Is something going on with the torque converter?
Is something going on with the fluid pump in the trans?
Are all the fluids at the correct level?
Unlikely, but worth checking the diff fluid too?
Clunking noise going to reverse
Right, something is likely loose
There is a Service Bulletin that describes this exact issue (seemingly)
I have attached the bulletin. Read it back to back, start considering it
In addition
There is movement in the diff, and you said you had it replaced.
Was it a brand new replacement?
If it was second hand, what was the condition?
Are the mounts stuffed?
Are the tail shaft couplings stuffed?
Could the drive axles themselves be stuffed?
If I disconnect the tailshaft, and rotate the wheels or rotate the diff back and forth, can I feel a clunk?
If I disconnect the tail shaft, and rotate the wheels or rotate the diff back and forth, does everything rotate smoothly?
If I put the gearbox into neutral and go underneath it, can I rotate the drive shaft by hand and does it feel smooth?
This is a long list, but it's going to give you some things to start considering and beginning your process of elimination. There is many more knowledgeable people on this forum who hopefully will add some things in too.
You've got a transmission, tail shaft, diff, and axles. Bearings and bushings mounting the various bits and bobs. Need to start at one end and work your way back.
An early investment in a 3 tonne Repco MechPro low profile jack and 4 axle stands has payed itself off many times over for me fixing and upgrading my car
There is a complete factory service manual on here. Search for it, download it and start reading. I have learnt so much from when I got my car to now just by literally sitting down and reading/studying that manual
Hopefully this gives you some pointers!
