Help needed to diagnose something on a classic.
 

Right had an eventful trip to Castle Combe today, and nearly didn't make it.

I'll say what happened and then you can see what I'm trying to determine, as I just want to narrow it down so I can spend less time faffing around with me on my back.

Basically did 50+ miles and not an issue, then Newport M4 Tunnels, decided by a look to a mate in a Pulsar lets hear the noise :D.

BUT changed down doing 60ish (matching a tanker truck), and intended to overtake the tanker. But on doing so there was a VERY heavy and repetitive clunk/knock, so firstly I stamped on the clutch, and held the revs at 1500-2k, and noise stayed the same getting slower and quieter as the MPH dropped.
Revved the engine, not a change. By this time I had slowed to about 45-50mph ish. And the noise was a LOT quieter but still noticeable, and felt like it was coming from the rear, in particular the rear passenger side.

SO next I put it in 5th and checked gears, and all seemed well and pulled, no crunches nothing. So slowly increased speed to 60, slight feel of a knock and slightly hear it, 65 noisier and don`t have to listen for the noise, 70 really bad now and making the back end feel as if the rear passenger wheel was about to shear off. My mate who I'd rang via my hands free kit, confirmed that there was no outward sign of anything. All wheel tracking true, no wobbles, nothing visibly hanging off, or different to normal. And wasn't feeling like she was losing power, dragging to one side, or anything untoward, other than the rumble/knock/vibration.

So slowed down to 60 and pootled there.

When I got there a quick inspection determined nothing, other than a pin hole leak in my Forge Ally expansion tank :( (which lost me a LOT Of water).

Now on the way home I was contemplating all things ending up on an RAC lorry, but nothing. Not a single issue :wonder: :wonder: Being 100%, I was aware of something but I'm not confident it wasn't my imagination, but sat at between 50, and 80 (ish), it was a LOT different, but there wasn't any hard acceleration like earlier.



Right, my first reaction is the Prop UJ Do-nut. After that I'm at a slight loss, as it didn't feel driveshaft related, deffo wasn't box or engine demise. Just that the only thing I know that would cause such a heavy thud and decreasing in frequency as speeds decrease would be the propshaft do-nut.


Anyone had similar and know, or has any inkling???

Anyone??

By the way you describe it it definitely sounds prop/rear diff/ driveshaft related. The fact you said it seemed to be the rear passenger side makes me thing possibly your C.V. joint on that side is on the way out?

Only reason i didn't think cv, was on previous cars they have a distinct noise. But this seemed a LOT heavier noise. But deffo worth a look.

Checked the rear wheel bearings?

Nope, but will be checking everything once I can get her on a ramp.
May end up renewing or replacing a lot, but meh gotta be done, may even treat her to some of those new CDF Racing roll bars.