Rear whine sound - fixed!

[Tweaksta]

The whining sound from the back of the car (stock 2000 GT / 130,000km) was getting louder and louder so I had to take action as it was ruining my Foz experience.

Step #1 was to replace the diff oil. I used Castrol Synthetic. The old oil was 130,000km old and was very stinky and dark in colour, however there were very few metal filings on the magnetic drain plug.

Step #2 Replaced rear wheel bearings. This fixed the noise.

Step #3 While the workshop had the wheels off they found that the rear drivers side driveshaft had broken at the splines. Apparently I had no drive to one wheel. How this didn't blow my diff I do not know.

Step #4 The also said the rear brakes had 1000km left so I did them too.

TOTAL COST = $990.00 at Jax Artarmon.

Does anyone know more about the rear diff on a manual (50/50 torque split)? How could one drive shaft be loose giving me 3-wheel-drive without causing strain on the diff?

 

[Kevin]

Maybe you had just FWD and the rear open diff was directing its share of power to the "freewheeling" drive shaft.
Glad the noises have gone!

 

[Tweaksta]

That sounds highly possible. I wonder if fuel economy would've improved whilst it was FWD.

NEXT WORK TO BE DONE:
- Standard Height HD Springs x 4 (front & back).
- KYB Excel-G Struts x 4 (front & back).

Once all this is done, my 130,000km Foz should be like new again.

Has anyone installed Standard Height HD springs on the front? Many people just whack 'em on the back to help maintain levelness when towing and carrying loads but I want them all round. Will this affect braking performance?

 

[benwarn]

shouldnt u loose heaps of power if this is the case

 

[Kevin]

^ I was thinking that too but I'm not sure how the manual GT distributes its power other than a usual 50/50 split for a manual. Usually when the shaft can run free, be it broken or a wheel in the air, all power is directed to that corner (with an auto at least) but locked in 50/50 you may just get away with it.

 

[simxs]

Does anyone know more about the rear diff on a manual (50/50 torque split)? How could one drive shaft be loose giving me 3-wheel-drive without causing strain on the diff?

The centre viscous LSD is not designed to cope with this situation - ie driving the car completely by the front wheels on a constant basis. I'd have expected a lot of 'free-wheeling' of the busted driveshaft (especially on a torquey GT), noticable slip in the drivetrain and, eventually, a toasted centre viscous coupling. You may want to check that the centre viscous LSD is not seized. Do you get 'binding' when turning with the steering on full lock?

Hopefully they are mistaken and there was at least some drive still being transmitted by the broken shaft and no further damage has occurred.

Good to hear all seems to be well now anyway.

 

[Tweaksta]

I do get a lot of tyre squeal on roundabouts at very low speeds - like 15 km/h. Could this be binding?

Hopefully I just need an alignment and the workshop did that trick that all workshops do, and that is trick me into paying for something I didn't need, and there was nothing wrong with the driveshaft.

Somehow I believe the workshop though. It feels stable and sure footed again - especially on corners. It had been quite odd on corners before they did the work. I dunno. Weird.

 

[joel.dedman]

I do get a lot of tyre squeal on roundabouts at very low speeds - like 15 km/h..

Maybe check your tyre pressures. When my car used to squeal around roundabouts, I had 28psi in the tyres (went by placard) and the tyre shop said they were too low, and pumped them to 34 psi for on road, and the tyres haven't squealed since.

Regards,

Joel

 

[benwarn]

well now i think about i once left the circlip on the inner end of the shaft causing it to come out and lost drive to the front right wheel.

the car was reeaaaally slow, when i put my foot down it acted as if i had my clutch in most of the way.

 

[simxs]

well now i think about i once left the circlip on the inner end of the shaft causing it to come out and lost drive to the front right wheel.

the car was reeaaaally slow, when i put my foot down it acted as if i had my clutch in most of the way.

That is interesting and even worse than I thought things would be in that situation. Doesn't offer much hope for our centre VLSD being of much help in offroad conditions.

Tweaksta - I think either:
1. your driveshaft was fine, or at least was still sending drive to the wheel, even if there was some slack/backlash; or
2. your centre VLSD is seized so you effectively have a locked centre diff, which prevented the kind of slip Ben is talking about if in fact your driveshaft was totalled

To check number 2, drive slowly on full lock on gravel or some other loose surface and have someone watch to see if your inside rear wheel is spinning faster than it should.

 

[Tweaksta]

OK - will do.

I'm also thinking of taking it back to the Jax Quickfit that did the work and giving them the old "please explain" as it just doesn't make sense and I'm too curious about mechanicals to allow the wool to be pulled over my eyes...