I got DIFF WHINE :(

[Guest]

1999 Forseter s/tb type a. manual. 87,000kms. The diff had been serviced recently. Well looked after car.

Had a wee squirt in top gear in the foz this morning and my diff has developed a whine

Took it home and checked the fluid level - it was low but I got some oil on the tip of my little finger so not totally dry. So topped it up but the whine is there...and quite bad. It comes in around 2200rpm in top or 80km/h ish. and gets really bad by 2500rpm - 100km/h in top.

1/ is this even remotely common with these diffs?

2/ is there a particular part of this diff that may be at fault?

3/ fix or replace?

4/ fair price for used diff?

cheers

Andy

[driftrex]

how much oil did you need to add? and do you know what grade oil was used?

[Guest]

had to add approx 400ml. Dunno the exact properies of the oil that was in it but was definatly proper gear oil so unlkely to have caused the problem I would think.

[Guest]

You say the diff has been recently serviced !!

What did they / you do?

What oil went in?

and your 400ml top up is around a 1/3 of total capacity !!

Bet if you drain the oil out it will be metalic !

They cost a few $$ to rebuild so best go buy a second hand one and fill it with oil this time

[Guest boostcut]

they probably had the apprentice set the backlash, and heavy heel contact on crown and pinion.. it will be cood to see pics of it if you take it out.

[Guest]

Oh I've no doubt the oild was too low and will contain metal filings...that much is clear.

When I said serviced I just meant oil changed. No evidence of an actual 'service' with backlash adjustment etc.

I have the general gist of it. I'll get a used diff of similar age and pull this one down for inspection.

The diff was serviced prior to us buying it. I should take it up with the dealer so will phone them and propose a bargain..only had it 5 weeks. Bit of a hsame as the rest of the car is immaculate and well cared for.

I beter buy a haynes manual or smimilar to get this backlash setting correct! Any tips?

[Guest keltik]

If the backlash was never adjusted on the oil change then i Very much doubt it caused your issues.

Seems much more likely to me your problem is a gearbox whine. In my experience diffs seem to make a roaring noise then one day explode.

[Guest]

just fill the oil up after fitting. Dont touch the internals or settings they will be fine if they are not your replacement diff is roo ted

No way in hell would your backlash have been touched when they changed the oil !!

Double check tyre sizes (same brand / model /size etc, if not measure them for rolling circumference

Speaking of tyres are you sure it's not a tyre noise your hearing

MT max difference front to rear is 10mm

AT max difference front to rear is 18mm

[Guest boostcut]

a good indication as to wether its the diff or gearbox is drive in 1st 2nd 3rd then in 4th the noise will go away presuming the noise is on the gearbox layshaft bearings as fourth gear is straight thru the main shaft. or jack car up and get your mate to run thru the gears and hold your ear to a screwdriver handle with the tip on the diff housing and listen for the noise,

and setting backlash isnt a easy- at-home task. best to just wack a 2nd hand unit in there for the price of a rebuild as it can take anywhere from 3 hrs to 20 hours to rebuild a diff,

[Guest]

Boosty Boosty Boosty

Have you never hadd a Subi MT box apart ? None of the gears are straight thru drive !!!

Power flow is input shaft , mainshaft / layshaft (via gear selected), viscous coupling(or DCCD depending on model) then out to front pinion & tailshaft

[Guest boostcut]

no to be honest... but i have seen shit diagrams and my statement is pretty general and reading his previous statement he is rather certain its the diff...

[Guest]

 Ichi Ban said:

just fill the oil up after fitting. Dont touch the internals or settings they will be fine if they are not your replacement diff is roo ted

No way in hell would your backlash have been touched when they changed the oil !!

Double check tyre sizes (same brand / model /size etc, if not measure them for rolling circumference

Speaking of tyres are you sure it's not a tyre noise your hearing

MT max difference front to rear is 10mm

AT max difference front to rear is 18mm

Thanks mate. The tyres are all the same & as close to identical front/rear/left/right as ever likely to be. I'm well up with that requirement as GT-R's have the same requirement.

Now to discover final drive compatibility...I've located a non turbo diff...presumably still LSD but do the non yurbos all feature hi/lo and does that system use a different f/d? How do I tell f/d from marking on the diff?

[Guest]

Not many diffs are LSD, most are viscous coupling type

Not many N/A have hi/lo range system in the gearbox

[log1call]

Are you saying that it didn't have the whine before the mornings drive? You say you went for a drive and now it's noisy.

Diffs don't go bad that fast, not without warning!

Diff whine also tends to be spread right across the speed range, not just start at certain revs. If it is the crownwheel and pinion making the whine(which is what makes the whine), then it should be fairly throttle sensitive I would expect.

Not aimed at the original poster particularly but...

It is important to descibe noises very carefully too, a whine isn't the same as a hum isn't the same as a rumble isn't the same as a... you get the idea. Mechanics all talk the same language generally but if you are not a mechanic it is probably always a good idea to compare the noise to something... brake squeal, metal on metal, jet engine. Be creative, as long as it's a common noise we should guess what it is like.

[Guest]

Its a diff whine. The oils was low and there are filings inthe oil. Its throttle sensitive. Its load sensitive. There is always a point with all failures where one second there is no symtom then the next a sound or signal that something is at fault.

 Ichi Ban said:

Not many diffs are LSD, most are viscous coupling type

Not many N/A have hi/lo range system in the gearbox

I was of the understanding that Foresters had Viscous rear LSD diffs and that whilst the turbos dont have hi/lo gear boxes 100% of the non tubo ones I looked at did have hi/lo :\

[Guest]

viscous diff and LSD diff two different things

Just get a diff with the same ratio from similar MY (then the axles will fit)

There's another topic here, re diff ratios and easiest way to check if no sticker on diff

[Old Skool Subbie]

 Ichi Ban said:

viscous diff and LSD diff two different things

How so?

My svx is fitted with a viscous LSD diff.

as far as I know alot of the older subaru stuff has viscous LSDs.

Like RXIIs, SVX maybe even some brumbys? etc

[Guest]

Viscous is just that a viscous coupling almost identical to centre diff viscous coupling on non DCCD vehicles

It requires heat (from slippage ie wheel spin) to lock the diff

LSD is a load sensitive unit, the more torque applied the harder it locks

Viscous is a very basic LS unit

[Guest]

I would suggest that a more apt staememnt would be to say that a Viscous LSD and a Mechanical LSD are to different things. As to the task they perfom, whilst one is many times better, it is the same function. Only a worn Viscous LSD will fail to spin both wheels across an axle when total traction is lost.

[Guest]

Quick update: Finally got her onto a hoist and put a stethescope to the drivetrain and the diff is deffinatly at fault. Probably the bearing/s.

Have a replacement diff ready to fit thanks to LNEMUP

Will confirm the fault & post any pics relevant that show anything of interest.

Dunno weather to refurbish this diff and keep as a spare or fix & sell to recoup costs...guess I'll decide once the replacement is in and proves to be a keeper