noise/vibration on overrun

[sirrom]

My car has this noise/vibration when you lift off the pedal, but no noise/vibration when under load driving. Its like a rattling noise.
Could it be in the drive shaft?
Does the front yoke of drive shaft wear where it slides into rear of gearbox - could it be this?

Its not exhaust pipes etc

Any ideas

[bmcecosse]

Could be the prop shaft - or the axle loose in it's mounts. Engine mounts ok?

[sirrom]

Thanks for that Roy. Will check these out as soon as I can

[hanvyj]

It may just be the frequency of the vibrations coming from the engine. I get loads more rattles when the engine is idling - the resonance frequency of the kind of things that make noise tend to be in the low range of the engine.

Like on the bus when the windows start rattling at certain accelerations - the engine hit the natural frequency of the windows.

[kennatt]

check the bushes in the engine steady bar

[sirrom]

Roy the rubber bushes look OK but just a matter of interest how tight should the bar be adjusted

[MarkyB]

It should be neutral, neither pulling or pushing the engine.
If the rubbers are crushed by the washers there wont be much give left in them.

[bmcecosse]

As above -it's just a steady bar - so the bushes should just be lightly 'nipped'.

[MarkyB]

Also have a look at where the back axle mounts onto the springs, there is a rust trap there and if the axle isn't properly located it can rock under deceleration.

[sirrom]

I suspect it is the engine steadier. The bracket that is fitted onto the headstud is facing downwards not upwards and only has two rubbers instead of 4. The 2 are on the inside and none on the outside. Have ordered 4 new rubbers so see how that goes after fitting them.

[bmcecosse]

Meantime - take it off and see if the vibration disappears. Early models didn't have one anyway.......

[sirrom]

Took it off when I got home from work today and took it for a short run around the block and it certainly wasnt as harsh as it was. Looked like the rubbers that were there were the tie rod bushes.
Will refit when the new rubber bushes turn up.
Roy thanks for that

[sirrom]

Took car out for longer run only to find I still had the problem. Ended up replacing the 2 gearbox and 2 engine mounts. Seem to have improved overrun vibration. Think it was rear mounts. But now have another vibration when starting off I get loud rattle vibration on right hand sidein engine compartment, sounds like its just on engine side of firewall. Also if car is idling and you have hand on right hand and give a bleep on the throttle you can feel it even on the guard. Engine mounts are tight, get rattle vibration whether engine steadier fitted or not.

Anybody got any ideas

[MarkyB]

That sounds like pinking, try retarding the timing a bit.

[sirrom]

Its not pinking but more of a metalic vibration rattle. Its only starting off but once driving it seems to go but comes back when the revs get a bit low for whatever gear you are in. If you chnage down and go on the throttle its the momentarily and then gone

[Neil MG]

Is the exhaust touching the body?

[sirrom]

May have solved my problem. Found that the wadding between the rear bonnet cross brace (under bonnet) was missing. Have put something there and driven around block and certainly sounded better but will drive it to work tomorrow and see how it goes over a longer distance. Will post something tomorrow night if problem really resolved.