XC V70 2000 AWD Disable Relay/Fuse

Hi,
Been having issues with the Viscous Coupler and driveline noises (been replaced) and now have a thump thump noise coming from the rear right. Have had this car for 3 years and have replaced loads of parts including having the Auto Transmission done at $3000. So its getting expensive but we still love the car and it ticks alot of boxes for us.
I understand that you can remove the Prop Shaft to run it as front wheel drive. But I also read somewhere that you can just remove the AWD fuse? But I cant find the fuse (or is it a relay??) anywhere. Its not labeled in the rear boot fuse compartment. Can anyone guide me to the right one? I even went to the extent of removing each fuse to see if that does the trick....but no. So is it the larger relay ones I am meant to be looking at?

Here in New Zealand, since the car is registered as a AWD, we cannot remove the prop-shaft permanently so thinking to just pop the fuse out.

Any wisdom would be great!
Thanks

Quote:

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Originally Posted by Rudd

thump thump noise coming from the rear right.

I understand that you can remove the Prop Shaft to run it as front wheel drive.

But I also read somewhere that you can just remove the AWD fuse?

here in New Zealand, since the car is registered as a AWD, we cannot remove the prop-shaft permanently

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"Thump thump" from RR is not really an AWD problem noise, but

Yes you can remove the driveshaft and the angle gear if needed and the car will drive normally

"AWD fuse" - there is nothing electrical with the AWD system, it's purely a mechanical system, consisting of the angle gear, driveshaft, viscous coupler, rear diff, axles. The ABS/Traction control (if equipped) is electronic but usually does not make noises, just the control units go bad.

Will NZ actually look to make sure there is still a driveshaft in place?

So if disable the traction control would that stop the rear prop/diff/coupler engaging? And then become only FWD?

I understand that its all mechanical underneath. But from what I gather the rear only engages in this car when it is at low speeds/turning sharply/needing more power for hills/reversing etc ie: when it thinks it is in a 4WD environment

We couldnt find a new coupler and got a second hand one and thats making a whining noise aswell. So we have 2 issues with the slight thunk thunk. Could be a wheel bearing at a guess. Just wanted to see if I can disable the rear from moving without taking out the prop shaft to start troubleshooting the problem/s.

In NZ to have a safety cert, they look everywhere including under the car. So cant take the prop out permanently.

Quote:

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Originally Posted by Rudd

So if disable the traction control would that stop the rear prop/diff/coupler engaging?

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No, the angle gear, driveshaft, coupler, rear diff and axles spin all the time (the car is moving), when the front tires spin faster than the rears the viscous coupler slips less (the fluid heats up and becomes thicker) and transfers more power to the rear wheels.

The electronic traction control system built into the abs system (if equipped) may try to brake an individual wheel if it is spinning faster than it should be and/or reduce throttle opening (on a 99 or 2000) to help regain traction.

The later AWD cars (2003+) use an electronic clutch (and failure prone expensive parts) instead of a viscous coupler. Everthing spins all the time with that system also, but you can stop the rear wheels with the fronts spinning on a lift, you can't with the viscous coupler system.

Thank you so much for your detailed reply. Have gotten more help and answers on this forum than any mechanic. All makes sense now you have explained it.

You're probably reading about newer Volvos.
As stated previously, the AWD system in a P80
AWD is ENTIRELY mechanical. No electrics at all.

The VC is what engages the rear diff with stacked
plates ( like a clutch) rotating in a viscous fluid. As
long as the input and output shafts of the VC match
RPM, they don't engage. If there's a difference, the
fluid causes he plates to engage.

The short story? Nope - There's nothing you can do
except remove the DS if you wish to disable the AWD.

FWIW, the P80 was originally designed as a FWD,
the AWD was added as a later feature. Maybe the
powers that be will give you a pass based on that?

Best of Luck!