dobbo Posted 20June, 2018 Report Share Posted 20June, 2018 I have a 1980 928 millage unknown but showing 108000kms. I changed all the oils soon after buying it (diff oil 75w semi synthetic) and soon after noticed a whirrimg sound while driving at speed, the sound didn't change whether acc or decelerating. When I dropped the diff oil it seemed to have a molybond type additive so I changed the diff oil to 80/90w mineral oil with an additive as well but no change to the noise. Can someone recommend a solution to the noise and also what are the signs of worn torque tube bearings? The drive is smooth but just noisey over 60ks thanks Dobbo. Link to comment Share on other sites More sharing options...
tazzieman Posted 20June, 2018 Report Share Posted 20June, 2018 The guy who makes the armour plated TT bearings in the USA says "Noisy TT bearings usually growl at low speeds and change their pitch as the RPMs increase then get drowned out by other noises of the 928 under speed" What makes you think the diff oil had an additive? What happens to the sound when you shift into neutral on a downhill run? Link to comment Share on other sites More sharing options...
Buchanan Automotive Posted 20June, 2018 Report Share Posted 20June, 2018 Rear wheel bearings or just noisy rear tyres or both , TT bearings are noisy at idle ( in Park / neutral ) as as you rev the engine the TT bearings change noise( pitch ) with RPM , so in other words ( car stationary ) as you bring the revs up , so does the noise from the TT bearings , because the TT shaft is spinning with the engine at all times unless its a manual trans , with the clutch pedal depressed the T T shaft will slow down & stop , but with Auto Trans is is engaged all the time Had plenty of Porsche's over the decades with very noisy tyres when they are half worn or more ( there is one brand that real bad for that ) , you would swear blind it was wheel bearings Very easy to diagnose } A ) another set of wheels /tyres on the rear for a test drive , if noise goes away ( bingo )its shit tyres , if the noise still there then } B ) With the car on a hoist ,remove both rear drive shafts from the car Remove the rear brake pads Put the wheels back on With no back ground noise , spin one back wheel by hand and listen as its slowing , then do the same to the other side & listen With perfect rear wheel bearings you will hear NOTHING With worn rear wheel bearings you will hear a growl ( naturally the wheel being on not only helps to spin the hub stub axle in the bearing center but also give a little load to the old wheel bearing/s You will often find one side is a bit noisier than the other ( in old age ) If noisy , replace rear wheel bearings Note } if its a manual trans ( you do not mention it ) then there is a possibility that the diff pinion bearing/s are damaged , this only happens by neglect because when these old manual transmissions get oil leaks , they are very rarely fixed & they will keep leaking until they literally run out of oil & this badly damages the very large and very expensive pinion bearings & its COMPLETELY avoidable Neglect is a very human thing Link to comment Share on other sites More sharing options...
ANF Posted 20June, 2018 Report Share Posted 20June, 2018 +1 I was going to say tyres or wheel bearings but Bruce (or was it Sean?) beat me to it. Link to comment Share on other sites More sharing options...
dobbo Posted 21June, 2018 Author Report Share Posted 21June, 2018 Thanks for the replies. It is a 3 speed auto. tazzieman the diff oil was black but did not smell burnt so I thought it had a molybond additive. Sounds like TT bearings are ok. Will have to try freewheeling in N and check noise again. Tyres are new Bridgestone Potanzas. Will have to check wheel bearings when possible thanks all for your help Dobbo. Link to comment Share on other sites More sharing options...
dobbo Posted 22June, 2018 Author Report Share Posted 22June, 2018 Tried freewheeling in N no change to sound. Link to comment Share on other sites More sharing options...
Buchanan Automotive Posted 22June, 2018 Report Share Posted 22June, 2018 Check the wheel bearings as I described OR The Bridgestone tyres you have have a noise issue ( a bit unlikely ) but not impossible OR The diff ( center ) carrier bearings are shot ( very unusual on these Auto trans diffs ) but if it has been neglected ( low oil level & filthy oil for a long time ) then its possible Humans are fantastic at neglect Link to comment Share on other sites More sharing options...
dobbo Posted 23June, 2018 Author Report Share Posted 23June, 2018 Mulsanne Meister thanks for the reply will check wheel bearings first when time permits and go from there Dobbo. Link to comment Share on other sites More sharing options...
dobbo Posted 18July, 2018 Author Report Share Posted 18July, 2018 Mulsanne Meister you were spot on about the wheel bearings. Removed the RH one today rang local bearing supplier and he says no one local will have any he suggested HI-ROLL bearings in Melbourne. Number on side shield is 531492 any info on where to get two or cost involved would be appreciated. I'll search the internet tonight many thanks Dobbo. Link to comment Share on other sites More sharing options...
dobbo Posted 19July, 2018 Author Report Share Posted 19July, 2018 Bearings sourced from Simon from Autowerks $130 each. Also done a deal for a bit of bling carbon fibre shock tower brace as mine is dented and has a hole drilled in it. Link to comment Share on other sites More sharing options...
dobbo Posted 26July, 2018 Author Report Share Posted 26July, 2018 Finished fitting new bearings on Tuesday took it for a run today noise gone all good. Fitted cross brace this arvo looks good thanks again to the forum. Link to comment Share on other sites More sharing options...
ANF Posted 26July, 2018 Report Share Posted 26July, 2018 Good to hear dobbo Link to comment Share on other sites More sharing options...
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