new diff but still slight knock

[kriminal]

Hey,
In nov i got a new diff with the harrop sports cover(went overseas) which stopped the knocking when turning and driving slow.
But there is still a slight knock when i release the clutch (in gear) and when i change gears. Ive gone back and got new drive shafts but the slight knock is still there and is annoying.
I have spent a fair but on it so not to keen on spending much more.

I was thinking of changing the diff oil to something like penrite 80w-140. I cant get mainlube this time as to much $$.

What are your thoughts or getting something else looked at or you think the diff oil change will help?

VY SS sedan manual 3.9 diff

Cheers

[Souljah]

Have you changed any of your suspension bushings to the aftermarket brands like Superpro or Nolathane? The harder bushes transfer noise a lot more than the factory rubbers do.
The noise your probably hearing on engaging gears is just driveline lash.

[SimonNQ]

Sounds more like backlash in the drive shaft to me? I have learnt to live with mine, but it is quite annoying!

[kriminal]

Yea I do have after market bushes etc.
It's pretty annoying ESP since I spent heaps fixing it.
Would the oil change even help?

Is there anyway to fix it? I prob won't since it will cost $$ but wondering

Cheers

[bush_basha]

Checked the rubber donuts that hold tailshaft to gearbox and diff? I also have a similar knock in my old car, used to get it with clutch in and selecting first and second repeatly. (bored at traffic lights and what not) as above I learnt to live with it.

[surfwagon]

I have the same knock as well and the noise did get worse when I fitted urethane rear cradle bushes.
Now seriously thinking about going back to new rubber bushes for the rear cradle.


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[dogsballs]

if my vz didn't have any knocks or noises it would surprise me.

[Mick1]

if my vz didn't have any knocks or noises it would surprise me.

If my car had some of your VZ's noises, I'd be stoked:yup:


My VX has the same backlash noise, also has urethane bushes!:banghead:

[VZ_V8]

I get the same noise in my VZ. Sounds like driveline lash. Happens going into gear, low speed gear changes etc. Gives me the shits but I cant find whats wrong. I have an eaton tru-track, 3.9 gears, harrop sports cover, the rubber donut on the tailshaft is fine and the CVs are fine.

[OPTIMUS]

is there a reason for no one making poly donuts? do they need a bit of play?

[WOKAZ]

I inherited a similar knock in vz after installing harrop true track and 4.11s Back to vcm to get stripped and tolerances all checked out ok. Still does it to this day, no worse but it's always there. Was a thread regarding this and apparently if the crush washer was not replaced it would cause a knock. Only reasoning with this I can come up with is when coasting the diff would drag and not unload fully so would be no backlash. You would still get it if role back slightly and feather clutch in out I suspect. Cam and sub have got rid of the knock noise now!

[dogsballs]

crush washer, ha! yes when they crush you'll get more play, but also more than likely chewed off gears. you have to build a diff with a bit of lash, cv's also have a fraction of lash as well. people these are commodores, not $100-200k mercs etc.

[jimco]

I inherited a similar knock in vz after installing harrop true track and 4.11s Back to vcm to get stripped and tolerances all checked out ok. Still does it to this day, no worse but it's always there. Was a thread regarding this and apparently if the crush washer was not replaced it would cause a knock. Only reasoning with this I can come up with is when coasting the diff would drag and not unload fully so would be no backlash. You would still get it if role back slightly and feather clutch in out I suspect. Cam and sub have got rid of the knock noise now!

Hi.
I had a similar problem after I had my Harrop Truetrac/Diff cover and 3.9's installed.Clunking when selecting 1st and general back lash noise.Dumped the run in oil after 1'000 klm's and replaced with Royal Purple 80w/140 and all went quiet and has never made a noise since.

Regards.

[surfwagon]

Mine is an auto and clunks each time it changes gears at low speeds, at moderate to fast acceleration the changes are smooth, so only clunks when moving slowly through the gears.
At first I was told by different people that it was because HSV set the changes in the auto above that of the normal power mode and made slow speed changes more abrupt but as time has gone on I have found that it affects both autos and manuals so has nothing to do with HSV settings etc.
My tansmission guy reckons the drive line clunk is normal and some are noisier than others and you do get the odd one rarely with absolutely no noise at all.

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[kriminal]

guess im living with it.. no cam n subs for me.. lol
i'll try the oil change and see if that help.. before my diff started to go it was perfect, no nise at all.

thanks guys, i'll let u know if the diff oil helps in a week or 2

[aratic]

Mine is an auto and clunks each time it changes gears at low speeds, at moderate to fast acceleration the changes are smooth, so only clunks when moving slowly through the gears.

Yip same here, had numerous people under the car to try and diagnose it but they couldnt find anything. Even replaced both rubber donuts. Have learned to live with it now.

Kriminal - what oils in it now?

[kriminal]

Kriminal - what oils in it now?

Not sure which oil, what ever marrano's used... i was going to put some penrite but then someone here mentioned royal purple, so i'll do some thread searching and see the prices and pick one.... no mainlube as to much $$ for a might work.

[JET-33]

i used to get the occassional knock in the m6 monaro and it was the CVs. they werent wrecked but there was some free play which caused the occassional knock when disengaging the clutch in 1st

[aratic]

Not sure which oil, what ever marrano's used... i was going to put some penrite but then someone here mentioned royal purple, so i'll do some thread searching and see the prices and pick one.... no mainlube as to much $$ for a might work.

I put Royal Purple 75W140 in mine at xmas, a guy on ebay sells it for $25/qt (2 needed). I decided on the 75W140 over the 80W140 as its a bit thicker at operating temp