300tdi weird transmission noise while coasting.

Hi all, went off roading on Sunday with a cracked propshaft coupler ( doughnut) but had a new genuine replacement in boot So just went for it. The doughnut held up remarkably well so I thought as I returned to tarmac. But vibration at first getting rid of excess mud from places. Then loud thunk from what I can only assume was the remainder of doughnut letting go. Anyway havin replacement several of these over the years I reluctantly nursed it on as light was dying but vibes got too much so pulled in to services and took rear prop off and put in diff lock and drove the rest of the way in front wheel drive. Once confident there was no funny noises I drove the 30+ motorway miles at 70 back home.

Replaced the doughnut with the new one. Now getting vibes at 70mph but more importantly when I dip clutch coasting in traffic or coming up to light. I get a strange back lash noise and shudder through the disco, which seems to be worse. It is fine taking up drive with no noise or clunk and pulls very well, slight wine at speed.

Any ideas, Have a rear trailing arm Bush to replace which is gubbed but wouldn't of thought and it would give this shudder and noise on coasting through the transmission.

Oh and this.noise seemed worse without the prop on I just thought it was maybe the handbrake drum loose. could this be the transfer gear?

check front diff oil and flange if it was worse running on front axle

Cheers James I'll hopefully check that tonight. Inhopenits not the front diff gunned as hoping to sell it soon. So don't want to fork out too much on it.( more than I do now anyway �&#56835

Never got a chance to check oil in diffs which I think will need changed anyway ( any recommendations for dif oil/fluid) . What I did find was the bolt was loose on the axle end of the trailing arm . I had play in n/s swivel, and track rod was loose at the adjuster rod. So tightened everything up and seems really solid.

Weirdly, when I rotate a wheel ( other three on ground) it has a bind almost every rotation of the propshaft. It feels like the brake pads binding, although it is not. Not long replaced the rear pads and discs though so wonder if ice set the bearing a bit too tight as its not that noticeable on the front two wheels, mainly the back two. Hmmmm. Wouldn't have thought it was cause the rattling and surging while coasting though.

Discophil34 said:

Never got a chance to check oil in diffs which I think will need changed anyway ( any recommendations for dif oil/fluid) . What I did find was the bolt was loose on the axle end of the trailing arm . I had play in n/s swivel, and track rod was loose at the adjuster rod. So tightened everything up and seems really solid.

Weirdly, when I rotate a wheel ( other three on ground) it has a bind almost every rotation of the propshaft. It feels like the brake pads binding, although it is not. Not long replaced the rear pads and discs though so wonder if ice set the bearing a bit too tight as its not that noticeable on the front two wheels, mainly the back two. Hmmmm. Wouldn't have thought it was cause the rattling and surging while coasting though.

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ep 90 or ep80w/90 or 75w/90 whatever is stocked locally
check ujs you need to remove one end of prop to see if either uj is tight in one direction as well as for play in joint
it could also be failing diff, try turning wheel again when props disconnected it will isolate it to front axle or not, same at rear, if wheel rotate fine whilst props disconnected from that axle you need to look at t/box

Good point James cheers