rear knocking on VX II LS2

[Irish]

Hi. Have a VX II Calais Gen II with 75,000 ks. Always serviced, service booklet coupons completed etc. Notice rear knocking noises after motorway speeds. Symptons occur when sitting at lights after prolonged motorway use. Car seems to twitch/squirm softly from rear and with light foot on throttle as I creep forward, there is an intermittent knocking/thudding sound. Very distinct and feels like someone is kicking a rear wheel (usually RH). Symptons continue while car is moving/crawling again at low speeds but seems to go when car back up to 50kph+. No obvious tyre wear or alignment problems. Possibly axle twist or??. Did wonder if it might be rear brakes jamming/locking and then unlocking; brake pedal is heavy when stopping from speed although pads not worn. Any ideas out there. Car fine in other respects. Thanks.

[ACEMonkey]

Take the rear wheels off and have a look to see if theres anything loose. Else you'd have to take it to a mechanic and get them to drive the car the same way as you had described the problem.

Heavy brakes is an indication that your brake pump might be failing. Get that checked out and replaced.

[Ozzie]

i had the same problem with my old vn.

i told the mechanic bout it when it went for a roadworthy and asked them to fix it.... they couldnt find the knock and passed it

i dont think its a serious issue though if its concerning you you should get it looked at

[Irish]

Thanks for your advice folks. I also see related threads at the bottom of the page. One mentions a guy with a VT having a very similar problem and symptoms. His was an axle/diff issue solved with a new pinion seal and lube etc so maybe that's the answer for mine albeit at 75,000 ks I would like to think the car has 'low' K's and that you wouldn't reasonably expect any such faults! The same comment goes for having a faulty power pump! My wife's otherwise identical VX II Calais but with a V6 has never had faults so who knows.

[ACEMonkey]

There are many factors. How the car was driven, and also just luck of the draw.

[minux]

Easy fix, its the diff. You need to probably have it acid washed and then new fluid and additive. Common issue with the LSD's. You can try to simply do an oil and additive change, but the additive is quite dear to throw away if it doesn't fix. Once the new additive is in give it 50-100k's and the knock will be gone. Don't bother with pinion seal, just extra money.

For the record your engine is a Generation III LS1.

[Irish]

Thanks Minux, good advice. Will now go in for service with a reasonable expectation of what sort of answer I can expect to be thrown up by the experts to try and baffle/bull the punter. Yes I realised I had put it as LS2 rather than LS1 but had just posted it so couldn't be arsed to enter a new posting to change it. Would be very nice to have a LS2 though.

[lumina01]

very easy to do youself mate, and will also save yourself some cash.

[minux]

very easy to do youself mate, and will also save yourself some cash.

If it needs an acid wash like my VT did, best to pay someone for it

[lumina01]

yeh i'd pay for that to, i was talking about oil and additive