Jump to content
SAU Community

Recommended Posts

Ive had a noise from the rear of the car which has been there for a couple of years, but most recently has become loud enough to be a concern.

Its hard to describe it exactly, it is loudest at around 90km/hr , its pulsing low dull roar sound, im wondering wether its a wheel bearing, cheap crap tyres or a diff thats going, ive jacked the car up and the back wheels are solid.

one point relevent or not, whilst hard acceleration in second i get massive wheel spin which sometimes starts to grip and shake the driveline, and also last time at drags it started gripping during the burnout too,

so question is ... what does a dying diff sound like? how can i distinquish the problem without wasting money...

Link to comment
https://www.sau.com.au/forums/topic/418598-noise-from-the-rear/
Share on other sites

Dying duffs are more whiney droaney than dull roar. Wheel bearings can roar. Your car is old enough that they could be dead. They are quite good at being stuffed in Skylines without letting on too much.

If you have an original viscous diff with the listed mods above, I'm not at all surprised that you get wheelsping and variable performance from your diff. The VLSD is poor enough with standard power let alone with a lot more. You will benefit from a decent mech diff for drags anyway, so start looking even if the rest of your existing diff is fine.

You should look into new diff mounts and subframe mounts (new Whiteline poly or harder ruber Nismo stuff for street comfort, solid mounts for stiffest location but with poor road noise isolation).

Dying duffs are more whiney droaney than dull roar. Wheel bearings can roar. Your car is old enough that they could be dead. They are quite good at being stuffed in Skylines without letting on too much.

If you have an original viscous diff with the listed mods above, I'm not at all surprised that you get wheelsping and variable performance from your diff. The VLSD is poor enough with standard power let alone with a lot more. You will benefit from a decent mech diff for drags anyway, so start looking even if the rest of your existing diff is fine.

You should look into new diff mounts and subframe mounts (new Whiteline poly or harder ruber Nismo stuff for street comfort, solid mounts for stiffest location but with poor road noise isolation).

Hoping its the wheel bearings, guess they should be replaced anyway, likely to be the originals..

I will look into the diff mounts and subframe mounts cause there is some movements happening at very low speed on a rough bumpy drive way..

So thinking bout diffs, id be after an improvement without any driveability issues like locking up wheels when doing a turn or harsh/rough with street driving, so whilst i will do some research , whats your opinion on a suitable diff ?

lastly, would i benefit from a slight step up in the diff ratio to make my gears a touch longer, eg couple hundred rpms and what ratio would that be?

  • 2 weeks later...

It will be a wheel bearing that noise, they give a similar noise to 4wd tyres, I have a rear wheel bearing noise in my car but won't do anything unless it sounds terrible. It has a roll over noise usually. Jack you car up, drive it to te problem speed and put a stethoscope on the hubs and that will tell you. Btw keep your head low while checking lol

A 1-way mech diff from Nismo, Cusco etc would be the best way. Will give you more positive drive at the drags and on the street without causing clunks and extra understeer etc etc.

I was under the impression you could only get 1.5 or 2's from Nismo?

It will be a wheel bearing that noise, they give a similar noise to 4wd tyres, I have a rear wheel bearing noise in my car but won't do anything unless it sounds terrible. It has a roll over noise usually. Jack you car up, drive it to te problem speed and put a stethoscope on the hubs and that will tell you. Btw keep your head low while checking lol

yeah im not sure, ive jacked the wheels up and theres zero movement, i guess they could be dry or worn still, the tyres i used to have on the front ( some hero crap) got so noisey i had to replace them, so the back ones are same hero crap tyres so im thinking its an even bet between tyres and bearings, the noise is pretty much always there but loudest on the freeway.

I was under the impression you could only get 1.5 or 2's from Nismo?

My Nismo was 2 way when i got it but i got it adjusted to 1.5 way, the housings on the Nismo and Cusco (I assume selected models) can be rotated to change the ramps etc.....

The noise you describe mark is kind of what i had when i put the solid locking rings in the rear, it went away when i changed my diff so i can only assume one of the axle bearings in the diff were shot?

As for the shudder on launch that sounds like axle tramp? Mine went away when i did the locking rings etc (mostly anyway)

i have heard tyres that are not even chunky (normal sports tyres) be noisy like a bearing but it seems rare, you could have a noisy bearing for the next 100000km and it wont fail, and as you go faster it will emit a louder noise, special if its a lubrication issue as it gets hot. you wont get play unless the bearing is on its way out, but wear and tear and they get noisy. if it was a soild rear axel its hard to check for play due long solid axel hanging off the end, lucky its not a dirty old holden :)

if its one bearing and not both try cornering hard left or right. If it is the cause, lifting the weight off the worn side will alleviate the noise. I currently have a worn bearing and this is how i was able to determine which side and that it was not a diff noise.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Get an inspection camera up there. 
    • Yeah, but look at the margin in viscosity between the 40 and the 60 at 125°C. It is not very large. It is the difference between 7 and 11 cP. Compare that to the viscosity at only 90°C. The viscosity axis is logarithmic. The numbers at 90 are ~15 and ~35. That is about half for the 40 wt oil and <half for the 60. You give up viscosity EXPONENTIALLY as temperature rises. Literally. That is why I declare thicker oil to be a bandaid, and a brittle one at that. Keep the oil temperature under about 110°C and you should be better off.   Having said all of that, which remains true as a general principle, if you have indeed lost enough oil from the sump that the pump was seeing slightly aerated oil, then all bets are off. That would of course cause oil pressure to collapse. And 35 psi is a collapse given what you were doing to the engine. Especially if the oil was that hot and viscosity had also collapsed. And I would put money on rod or main bearings being the source of the any noise that registered as knock. Hydraulic lifters should be able to cope with the hotter oil and lower pressure enough to prvent too much high frequency noise, although I am willing to admit it could be the source.
    • Thanks for the reply mate. Well I really hope its a hose then not engine out job
    • But.... the reason I want to run a 60 weight is so at 125C it has the same viscosity as a 40 weight at 100C. That's the whole reason. If the viscosity changes that much to drop oil pressure from 73psi to 36psi then that's another reason I should be running an oil that mimics the 40 weight at 100C. I have datalogs from the dyno with the oil pressure hitting 73psi at full throttle/high RPM. At the dyno the oil temp was around 100-105C. The pump has a 70psi internal relief spring. It will never go/can't go above 70psi. The GM recommendation of 6psi per 1000rpm is well under that... The oil sensor for logging in LS's is at the valley plate at the back of  the block/rear of where the heads are near the firewall. It's also where the knock sensors are which are notable for 'false knock'. I'm hoping I just didn't have enough oil up top causing some chatter instead of rods being sad (big hopium/copium I know) LS's definitely heat up the oil more than RB's do, the stock vettes for example will hit 300F(150C) in a lap or two and happily track for years and years. This is the same oil cooler that I had when I was in RB land, being the Setrab 25 row oil cooler HEL thing. I did think about putting a fan in there to pull air out more, though I don't know if that will actually help in huge load situations with lots of speed. I think when I had the auto cooler. The leak is where the block runs to the oil cooler lines, the OEM/Dash oil pressure sender is connected at that junction and is what broke. I'm actually quite curious to see how much oil in total capacity is actually left in the engine. As it currently stands I'm waiting on that bush to adapt the sender to it. The sump is still full (?) of oil and the lines and accusump have been drained, but the filter and block are off. I suspect there's maybe less than 1/2 the total capacity there should be in there. I have noticed in the past that topping up oil has improved oil pressure, as reported by the dash sensor. This is all extremely sketchy hence wanting to get it sorted out lol.
×
×
  • Create New...