R200 Diff Noise.

[MaximG]

Hi Everyone,

I have just spent the last few months doing a strip down a rebuild of the rear suspension and drive train on my 240. Part of the rebuild process started last year when I acquired a 3.9 R200 diff to up rate the original. This is possible where I maid a mistake because apart from replacing the Oil seals changing the back plate and painting it black that’s about all I did to it.

Upon getting the car back on the road I now have an excessive amount of Diff wine confirmed by a good mate of mine after taking him out for a spin.

It sounds like it has no Oil in it but I can confirm that it has. The Diff casing is getting very hot to the point where if you put your hand on it you can only hold it there for a couple of seconds. Now the temperature issue might be normal, I haven’t put my hand on many diffs after a run if you no what I mean.

Does it sound terminal and maybe I should not use the car until the diff is looked at. If this is the cast can someone recommend somewhere is the Herts, Beds, Bucks, area where I might be able to get he diff rebuilt.

I would have a go myself but I would like to drive the car this year rather that next.

Any help greatly appreciated.

Mike

 

[Rob Gaskin]

IMHO a whining diff is not terminal, my old 180 made a terrible noise for a couple of years! The temperature may be normal as you say.

Did it spin freely when out of the car?

I would say a rebuild would cost more than sourcing another proven S/H unit but a 3.9 is more difficult to find than a 3.7. I'd get a second opinion from a local club member.

In the mean-time if I manage to get out in my car today I'll see what the temp is like.

Rob

 

[Ian Foxley]

Hi, i'm an automotive driveline NVH engineer although I don't profess to be an expert.

The heat sounds normal to me, have you made sure that the propshaft is lined up correctly to the position you dismantled it, the prop could be out of balance causing misalignment of the hypoid gears.

The gears / bearings could be damaged, is the oil clean? it might be worth putting a magnet in the oil filler hole to get an idea of the quality of the internals.

Also as mentioned before do the shafts rotate freely by hand?

Are all the bolts tightened, is there any play in the propshaft / diff, this could promote missalignment of the gears ?

A lot of old cars have whining diffs so it may just be something you have to put up with, it's been so long since I ran my 260 I can't remember if the diff whined. By fitting a non standard diff you will have changed the resonances in the transfer path of the system, and it may be something you have to live with. As long as there is no damage to the gears / bearings you'll probably be ok in terms of life of the diff.

Is the noise definatly the diff?, whines in all gears, the noise is road speed dependant.

I'll have a chat at work and see if there is anything else obvious to check.

 

[Zed2k]

I too have the same problem I updated my 240 with a R200 after blowing my R180 on a trackday, and it is supposed to be a very low mileage one I thought the rear wheel bearings were going so changed them but, the noise was still there.
So it looks like my diff is a little noisey too but deosn't seem to cause any problems. at the moment fingers crossed.
I would also like to know somewhere good to have it overhauled in the future as it would be good to have a noise free rear end ( if you know what I mean)!!!!
Nick..

 

[Ian Foxley]

Hi again,

I may be going too deep into this, but by putting a higher rated differential into your car, the hypoid gear teeth will be thicker and stockier, therefore deflecting less under load and transmitting more of the vibration from the tooth mesh to the bearings (less deflection of the teeth to damp out energy). More energy will be put through the transfer path of the vehicle, causing more energy to be transformed into whine noise. It is an inherant risk you take when uprating your diff. If there is nothing wrong with the diff, it shouldn't harm and you will have to live with the noise unless you go through a full development exercise, or are lucky in changing the natural frequencies of the transfer path / propshaft.

I don't know how many pinion teeth are on either diff, but if you have gone to a pinion with more teeth, if there are natural frequencies in the driveline / vehicle you have just brought them down in the speed range of the vehicle, and so the noise will be more apparant as it isn't masked by engine/exhaust noise.

I suggest checking the state of your diff, if there is nothing wrong with it then you've just been unlucky with the system. Rear wheel drive vehicles can be difficult to design / develop for no whine and by changing the system you may have made it noisy.

I will shut up now as this is not usefull info to you, and i'm probably sounding like a prat!

Ian

 

[MaximG]

General reply to all.

Oil is fresh new clean Castrol 80w/90 gear oil. As far as i am aware the R180 I took out was also 3.9 ratio so the R200 for all intence and perpose is a direct replacement just stronger.

The noise is excessive as confirmed by a friend who has a 260. He had the same missgivings about level of noise untill I drove him round the block.

As for the prop shaft it is an all bolted type only found on early models. As it had nothing to do with the Diff untill I married it up there were no marks to line up.

The shafts rotated freeley by hand before instalation.

Back to the floor,

Mike

Thanks to all for replying so far.

 

[Ian Foxley]

HI,

It could still be the propshaft, does "all bolted" mean that it doesn't come in two parts connected by a spline? It should do to allow for travel in the suspension. You could try pulling the two halves apart (disengaging the spline teeth), and rotating one end around and engaging again, you can try a few angles and see if the noise is sensitive to position, as the propshaft will have been balanced for one position.

Also is the prop you are using the correct one for the diff? If not the balance specs on it may not be tight enough for the diff, so you could be misaligning the gears through propshaft being out of balance. The only way I can suggest testing this is to take the one you are using along with the correct one for the diff to a prop manufacturer and get them to test the balance on both, you can then get them to adjust the balance apropriatly. This is not guaranteed to be a fix, as gear whine is a bit of a mine field. The work would probably cost around £100.

The only way your going to know it is / isn't the diff is by taking it apart and looking at the gears / bearings.

Ian

 

[Nigel Brook]

You guys are getting a bit deep with this one. If there is excessive whine then there is something wrong with the diff. My guess is worn bearings causing "tilt" on the crownwheel. Very basically there is a design contact measurement between the crownwheel and pinion. This is controlled by the depth the pinion goes into the diff casing and the lateral position of the crownwheel. The correct positions give you the design gear "backlash". I personally wouldn't use the car until youv'e had it checked although the damage may have already been done.

 

[Black Bug]

It's an interesting point raised by Ian with regard to thicker teeth causing more energy (resulting in noise) being passed to the chassis. The current crop of short nose R200s use different CW/P rations to achieve similar ratios to the old long nose diffs:

Long nose:
3.7:1 = 37:10
3.9:1 = 39:10

Short nose:
3.69:1 = 48:13
3.92:1 = 47:12

Somewhere along the way the diff designers must have decided that more teeth = good otherwise what would be the point in having to redesign the crown & pinions to achieve nearly identical ratios?


Regarding the diff heat, I guess they must get hot as there are various finned rear covers to help disipate the heat. Also external coolers are used regularly, more so with LSD diffs that generate more heat by their action, but there's no reason not to consider cooling an open diff.

Cheers,
Rob

 

[MaximG]

Ok so I might have some idea why the Diff is noisy. I think it might have something to do with me taking the front input flange off to change the oil seal.

When looking at the Nissan Workshop manual it talks about putting a prelode of between 120-140 ft-lb (or something like that). Now is this to take up gradual ware in the Diff. I ask this because when I removed the nut it came undone quite easy, certainly not to 120ft-lb plus. Now when I put it back on I plumed for a mid point in that torque range which might have pulled the pinion out of line? It also stiffend the diff up a degree or two.

Does this sound like I may have caused the problem? And possibly undoing the nut slightly might rectify things?

Mike

 

[Ian Foxley]

Hi,

Sorry if i've been a prat and gone a bit theoretical.

If you diff is excessiveley noisy, it is probably the thing at fault, if the preload has been lost then I'd suggest you take the diff apart to find out what's wrong.


Regarding long nose / short nose. They have probably changed the ratios to move the resonances around in the speed range of the vehicle, normally you try and reduce teeth numbers to move the noise up in speed range so that it's masked by the engine revs. There must be a reason for them increasing the teeth numbers, the tooth mesh combinations may have coincided with ones in the transmission / engine?. In order to reduce the stiffness of the gears they would normally reduce their pressure angle.

Sorry I can't be of more help to your whine issue,

Ian

 

[Nigel Brook]

Ok so I might have some idea why the Diff is noisy. I think it might have something to do with me taking the front input flange off to change the oil seal.

When looking at the Nissan Workshop manual it talks about putting a prelode of between 120-140 ft-lb (or something like that). Now is this to take up gradual ware in the Diff. I ask this because when I removed the nut it came undone quite easy, certainly not to 120ft-lb plus. Now when I put it back on I plumed for a mid point in that torque range which might have pulled the pinion out of line? It also stiffend the diff up a degree or two.

Does this sound like I may have caused the problem? And possibly undoing the nut slightly might rectify things?

Mike

Firstly, don't slacken the nut, you need to be tightening it.
As I said before one of the critical settings of the diff is the depth of the pinion in the casing giving the required amount of gear backlash [ free movement ]. It sounds like your pinion is too deep into mesh with the crownwheel. Thats why your diff stiffened up. Also the pinion nut may not have seemed very tight when you took it off because there is a spacer on the pinion shaft which crushes slightly on original installation with a 120/140 torque. Tighten your pinion nut up to 120lbsft and you might have got away with it. Check to see if youv'e got backlash by tweeking the pinion left and right. If not, take the torque up another 5lbs or so until you have.
Best I can offer without actually being there.

 

[Ian Foxley]

Hi,

I have just discussed your problem with my manager and a group of technicians at work (Automotive rear diff manufacturer).

If the diff has a collapsable spacer on the pinion shaft, the reason why your nut being loose is that it was originally torqued up to 120 / 140 ftlbs to collapse the spacer and bed the bearings in, and that has now happened. This is the correct setting for the nut and what it should be torqued back to. By increasing the torque to 120 /140 ft lbs you have increased the bearing preloads massively, you are going to cut their lives down extensively, it may cause some of the whine you are hearing, but I doubt all of it as you have chadged the NVH characteristics of the vehicle / driveline system by changing the diff.

You have two options:

1) Undo to pinion nut and try and torque it back to just slightly over what it was when you took it off. You could ask some one with a working diff to take it out of their car and see how much torque on the pinion it takes to rotate the crownwheel around freely, you then torque your pinion nut up to get the same movement.

2) Replace the bearings and collapsable spacer and then torque it up to 120 / 140 ftlbs as design spec. You may as well look at the gears at the same time.

Ian

 

[Nigel Brook]

Can we establish what the nut was torqued up to? I took it as being too little rather than too much.

 

[Ian Foxley]

I agree Nigel,

This is getting a bit confusing now.

Just to add more confusion: One other thing to find out is if, when the pinion nut was taken off initially was there any pinion end float? indicating something is up with the gears and the crownwheel forcing the pinion out of mesh. I agree totally with what your saying about the backlash of the gears.

Ian

 

[MaximG]

Well I must admit things are rather confusing but I thing im getting the general gist of what’s being suggested.

Nigel, When you refer to a crushable washer is this between the pinion nut and drive flange? Because I think you will find if that is where you are referring to then the R200 does not have one.

Ian, as far as I can remember there was no perceptible end float on the Drive pinion. We do seem to concur with the theory as far the torque settings go though.



Many thanks for everyone’s input so far it is much appreciated.



Mike

 

[Nigel Brook]

Nigel, When you refer to a crushable washer is this between the pinion nut and drive flange? Because I think you will find if that is where you are referring to then the R200 does not have one.


Crushable spacer, not washer, and the R200 does have one. Can you run through what you have done from the beginning.

 

[MaximG]

Nigel it’s pretty much summed up in my first post. No more no less.

Please understand that although I am no expert I do have a farley good working knowledge of thing's mechanical. I can also read a sectional diagram provided by Nissan and it shows quite plainly no spacer between Pinion Nut and Pinion drive flange. I would also add that there was no spacer there when I took the drive flange off. The only spacer and shims that I can find reference to are inside the diff so I would not have touched them.

But any way if im wrong I apologise but I can only go on what I have seen.

Mike.

 

[Ian Foxley]

HI Mike,

If we're still talking on the same lines, I would say you have damaged the bearings by torqueing the pinion tail nut up too high. If your getting as much noise as you say you need to replace the bearings and the collapsable spacer (if there is one?). I wouldn't like to recommend driving the car until you've replaced the bearings. If you're going to get the diff referbed or replace it you may as well take the cover plate off and inspect the bearings & gears.

Sorry to be the bearer of bad news & good luck with getting the Z back on the road,

Ian

 

[MaximG]

I will take on board what you have said Ian. As the car only went for an MOT and new exhaust I will cross my finges that mabey not alot of damage has been done. (If any, well i can all ways live in hope. )

I think I will slacken the pinion nut to a reduced torque and see what happens. Then make a decision as to getting the diff rebuilt.

Thanks to you and Nigel for your valued input.

I will try to and put an update post on my findings in the future.

Thanks,

Mike