The diff on the old girl is starting to get a bit whiney so gonna change the oil on her!

Looking for some advice as to what oil/additives to put in the LSD and how muhc is needed? :helpsmilie:

 

Cheers, Mark.

http://www.300zx.co.uk/cgi-bin/manual.cgi?list=ma&dir=&config=&refresh=&slide=10&cycle=off&scale=0&design=default&total=33

 

Online manual states 1.5 litre for non europe, and 2.1 for europe

http://www.300zx.co.uk/cgi-bin/manual.cgi?list=ma&dir=&config=&refresh=&slide=10&cycle=off&scale=0&design=default&total=33

 

Online manual states 1.5 litre for non europe, and 2.1 for europe

 

Thanks dude I wasn't sure as the online guide for changing diff oil states this -

 

6) Refill the diff with your favourite brand of oil- API GL 5 specification, viscosity SAE 80W-90. The turbo diff will take 3.1 liters (5 7/8 imp pts), and the non turbo 2.8 liters (4 7/8 imp pts). [Andy: my '93 TT takes 1.8 litres. I'd suggest checking your own service manual for the year, model and possibly country the car is manufactured for.]

Just a word of warning, most of the time if you can hear a whine coming from the diff, it's on it's way out, changing the oil MIGHT extend the life, or in some cases shorten it. The new diff oil will give it more pressure and make the LSD able to perform better, this of course is the desired result from changing diff oil, but not if the diff itself is already weakened.

 

Keep an eye/ear on it for a while and see if the whining goes away/comes back/gets worse etc.

My diff went very wrong and had to be replaced it was the loudest thing ever and sounded like a tractor!

 

oh ye it took me like 12 hours to swap it over aswell!

I was told when I bought it that it was an aftermarket diff but I've no idea how to check this as there's no receipt for it. I just took it for granted that he was talking sh** and it was a standard diff lol

 

This may sound strange but when I come off the clutch in neutral the revs die down a tiny bit with the drag from the diff :/ Maybe a sign of it going down the tubes? Or in fact its a different diff!

Just a word of warning, most of the time if you can hear a whine coming from the diff, it's on it's way out, changing the oil MIGHT extend the life, or in some cases shorten it. The new diff oil will give it more pressure and make the LSD able to perform better, this of course is the desired result from changing diff oil, but not if the diff itself is already weakened.

 

Keep an eye/ear on it for a while and see if the whining goes away/comes back/gets worse etc.

 

The stock z32 diff is a sealed unit viscous type. Changing the diff oil has no effect on the unit whatsoever.

Could be either or really. If it's an aftermarket diff, as in off the shelf but not standard, it'll have a marking somewhere, stick your head underneath and have a look, by have a look, I mean REALLY look, because I never realised I had a Veilside exhaust on my GTR until I broke the car because it was only when I took the exhaust OFF the car and could see the upper side of the back box that we saw the Veilside plate!

 

If it's been played around with by someone (i.e. re-conditioned, turned IN TO a Slip Diff from a Non-Slip-Diff etc) then it probably won't have a mark on it, but the diff casing should be a bit rotten, where as the seal between the two parts of the diff casing will be newish.

 

If there is drag from the diff, it most likely means it's paggered, sorry, although some race diffs do cause drag when they are not on load.

I have a good spare TT diff if you need it......

Does the Zed have a LSD as standard? I'll need to get a look under it and see if there is any signs of it being different.

Thanks for the advice guys and zed-racer i may need to take that off your hands if it comes to it mate lol.

Does the Zed have a LSD as standard? I'll need to get a look under it and see if there is any signs of it being different.

Thanks for the advice guys and zed-racer i may need to take that off your hands if it comes to it mate lol.

 

Yep LSD as standard.

I'll try and get a video from in the car tommorrow to let you hear then noise from it and my (still undecided) straight cut box. I love the noises the gearbox etc. make up until the diff started to make a bit of a whine other day there :/

The stock z32 diff is a sealed unit viscous type. Changing the diff oil has no effect on the unit whatsoever.

 

Changing diff oil always makes a difference, oil only lasts so long, sealed or not, the diff oil will not last an eternity and it still has numerous properties other than lubrication.

Changing diff oil always makes a difference, oil only lasts so long, sealed or not, the diff oil will not last an eternity and it still has numerous properties other than lubrication.

 

the LSD unit is sealed for life. changing the oil in the diff casing doesnt affect the LSD operation.

I've never seen a "sealed for life" diff before, I'll have to go check mine out. Unless you're saying the diff is in a separate casing, inside the standard diff casing, which is completely sealed? Which would negate the point completely of having oil in the outer diff casing at all, because it would simply be a dust cover?

 

I changed the oil in my GTR's sealed LSDs twice in the time I owned it, and can swear that it made a huge difference the first time, the second was simply for good measure, the same reason I always do two oil changes within a few weeks of each other and two gearbox oil changes within a few weeks etc, to completely flush the bad oil and residue build up of metal shards etc from the device. I'll have to research what you're referring to.

I've never seen a "sealed for life" diff before, I'll have to go check mine out. Unless you're saying the diff is in a separate casing, inside the standard diff casing, which is completely sealed? Which would negate the point completely of having oil in the outer diff casing at all, because it would simply be a dust cover?

 

I changed the oil in my GTR's sealed LSDs twice in the time I owned it, and can swear that it made a huge difference the first time, the second was simply for good measure, the same reason I always do two oil changes within a few weeks of each other and two gearbox oil changes within a few weeks etc, to completely flush the bad oil and residue build up of metal shards etc from the device. I'll have to research what you're referring to.

Its not the diff thats sealed its the LSD unit is that sealed. It sits inside the crown wheel. The oil in the casing is to lubricarte the crownwheel and pinion as they turn and the output shaft bearings.

Dont confuse a viscous LSD with a plate type LSD which is exposed inside the crown wheel cage. Ie a salisbury type unit. The popular one from Japan is the Kaz unit. These require special diff oil

Just ordered 2 litres of oil from Opie, can I just fill it till its overflowing like the gearbox or does it have to be specific amounts i.e. 1.5 Litres I think as mines is a 1990 Jap Imp!

Just ordered 2 litres of oil from Opie, can I just fill it till its overflowing like the gearbox or does it have to be specific amounts i.e. 1.5 Litres I think as mines is a 1990 Jap Imp!

Pretty simple really.

open bottom plug to drain. replace plug. open top plug to fill. Fill gradually till it Just trickles out. replace plug.

The fun bit is getting the plugs loose if nobody has ever been there before.:sad:

Ah right, I do get what you're talking about then. Although I understand what you're saying about changing the oil won't affect the operation of the diff, it will, just not in the absolute sense of the word as it would if the entire diff were exposed inside the casing.

 

Changing the oil in the outer casing does have an affect on the diff itself, because as the oil in the outer casing loses viscosity and wears out, it also loses weight, which directly affects the sealed unit inside. You can run differently weighted diff oils with them, in order to change the reaction and operation of the sealed unit, many people change the diff oil in the outer casing on a track day for example.

 

That being said, I'll refer to my original comment even more so, which is that once the diff has started to whine, it's unlikely to be repairable by changing the oil, it will simply go one way or the other, increasing the weight of the diff oil (By changing it to newer oil in the outer casing) will have a direct affect on the diff, that may be to release tension on it, or increase, either way, there is no way to really tell without changing it, the existing diff oil may have been changed recently, in which case, changing it will have NO affect at all, where as if it hasn't been changed for a while, it could be well worn and lost weight and viscosity. I would certainly have a replacement diff available to buy/fit shortly after changing the oil.

 

Unfortunately as Slick Pete has said, the actual diff itself is sealed, thus the other part of my original comment, that there would be a marking on the outer casing to signify it was an after market diff, is no longer valid. I was not aware until now that the diff on the 300 was viscous and a sealed unit. If it has been replaced for an after market one, then it most likely will not be marked on the outer casing at all, as they would have simply disassembled the outer casing, fitted the new diff, then re-assembled the outer casing and filled it with oil.

 

Either way, I wish you luck with it. I've had a diff blow up on me before, and it happened while going round a roundabout, not fun!

Pretty simple really.

open bottom plug to drain. replace plug. open top plug to fill. Fill gradually till it Just trickles out. replace plug.

The fun bit is getting the plugs loose if nobody has ever been there before.:sad:

 

Cheers dude I'll probably have no skin left on my knuckles by the weekend lol

Pretty simple really.

open bottom plug to drain. replace plug. open top plug to fill. Fill gradually till it Just trickles out. replace plug.

The fun bit is getting the plugs loose if nobody has ever been there before.:sad:

 

I'll second that, I had to use a torque wrench on one car just to get the drain and fill plugs out!

Cheers dude I'll probably have no skin left on my knuckles by the weekend lol

 

You may well need a 24" extension bar. Im not kidding. Steel plug into ally housing= bimetallic corrosion. spraying them with penetrating oil etc wont help as its wound in about 10mm of thread..

I'll second that, I had to use a torque wrench on one car just to get the drain and fill plugs out!

thats not going to do yer torque wrench a lot of good:scared:

Pretty simple really.

open bottom plug to drain. replace plug. open top plug to fill. Fill gradually till it Just trickles out. replace plug.

The fun bit is getting the plugs loose if nobody has ever been there before.:sad:

 

So on that note, attempt to remove the top filler plug 1st, because if for some reason you can't and you've already drained the diff.....:sweatdrop:

So on that note, attempt to remove the top filler plug 1st, because if for some reason you can't and you've already drained the diff.....:sweatdrop:

 

Did you find that out the hard way then???:innocent:

Or are you just a methodical clear thinking mechanic:biggrin:

Make sure you open the filler plug first!!

 

Pretty simple really.

open bottom plug to drain. replace plug. open top plug to fill. Fill gradually till it Just trickles out. replace plug.

The fun bit is getting the plugs loose if nobody has ever been there before.:sad: