vu ute knocking when coasting @ 60kph

[twowheeldan]

hi guys, had my diff cones replaced today cause they were chattering, but now driving home there is a knocking noise when backing off around 60kph. braking can make it come on more consistantly can't yet isolate where its coming from but i think its in the rear somewhere. its a consistant knock pattern that decreases as the speed decreases? but as soon as you get on the gas at all it goes away??

any ideas guys??

cheers daniel

[Sabby]

have you got a modified exhaust?
if you have an aftermarket one it could be the tailshaft hitting the exhaust pipe near the diff end. coz it would be bigger than stock one.

ive got the exact problem, but i have it in all gears but when i stop accelerating, it goes away. its nothng bad, but gives me the shits all the time.

orrrrr it might be something more than this.

[graham7773]

If the knocking was not there before the work was done, I would take it back to the people who did the work.

[304runner]

Id say its your pinion. Its moving in and out as you apply/remove tourque

[twowheeldan]

took it back to the diff guys and they said nothing they did/touched would be making that noise...... i smell bullshit but anyway.

only does it between 60-80 kph. It doesn't give any vibes through the car or steering wheel, doesn't seem to be affected by braking but is somewhat dependant on speed ie the rythm of the knocking decreases as the speed decreases. it doesn't doi it everytime you got over 60 but often enough to worry and shit me.

checked for loose wheel and exhaust (stock "sabby") hitting anywhere. whats the best way to tell if a wheel bearing is shagged?? or if the pinion is cactus?? (though i would have thought the diff shop would have mentioned it.....

cheers daniel

[304runner]

Yeah the best way to check is to jack up the rear and lay under the car while twisting the tail shaft back and forth (or turning a rear wheel). If its the pinion, the tailshaft will rotate slightly before the wheels start to spin.. But as I was reading your last post I was also thinking it may be a wheel bearing....

[madcapmagician]

hmmmm... I had the EXACT same issue with my VXII berlina. I mean, IDENTICAL. Off the gas, coasting, 60 KMh clunking coming from the diff. It has done this since the car was under warranty and holden replaced my diff no less than 3 times to try and fix this with no success. I put up with it for ages and ages and now the car has 180K on it. I just did the shocks and springs on all four corners and bushes etc and lo and behold the noise got worse. Like, 200% worse. All I can think is that the changed driveshaft geometry has influenced it. So, being fortunate to work for a car dealership (not holden BTW) I put my car on the hoist and started looking at things. I grabbed the right hand drive shaft and pulled firmly outwards and the drive shaft pulled out of the side of the diff! The retaining clip was still attached in its groove but had never expanded out to hold the shaft in so for about 8 years it has been floating. I got a new clip from holden and a replacement diff out of a VY commo from the wreckers that felt ok, put the VY diff in and problem is gone. I now have another noise that sounds kind of like a scraping, whispery noise that can be heard under power up to about 70 km/h but no knocking. I'm suspecting front pinion bearing might be the culprit. Next project is to pull my old diff apart and see if I can figure out what's going on. Can't say if the loose drive shaft actually caused the knocking, in fact I doubt it would. While my old diff was still installed with the tail shaft dropped out I turned the pinion and the diff made a cack noise like it has stuffed bearings inside so its still anyone's guess what the knock is but I hope to be able to figure it out one of these days.