I have an M52 swap and part of that is a Torsen diff.
I was braking from 60mph to 30mph to go through a town and as I got to 40/50mph, there was a sudden whoosh/whine noise which went from non-existent to very loud in a second or two, followed by loud grinding/shuddering coming from the rear and the wheels locked up, although I don't think both locked up completely. Just enough that I was fighting to keep control of the rear end as I came to a stop.
The car will drive very slowly under its own power but it has some resistance from the rear (can't tel if from both wheels or just one) and grinds/shudders as it does so. Pushing it with the engine off and in neutral is hard work and it grinds/shudders then too, so I don't think it's engine or gearbox related.
Through a process of elimination it sounds like a diff issue to me, although Torsens are meant to be reliable and very unlikely to break that suddenly without any warning. But what else could it be? Suspension looks okay. Wheel bearing? Brake issue? Propshaft?
Diff failure?
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Interesting. A chap on Facebook suggested the brake shoes had come adrift.
Gotta say, I hadn't thought it would be brakes at first but I'm really hoping it is. That sounds a lot easier and cheaper to sort than a diff!
Also, one side looks to be sitting lower than the other. I don't know if it's because of the hill I'm parked on, but could that be another symptom of brake shoe failure? I'm only thinking because I know when you jack a car up and let it back down, it doesn't settle back down properly until you undo the handbrake. Could it be pulling one side down or something?
Thanks for the help!
Gotta say, I hadn't thought it would be brakes at first but I'm really hoping it is. That sounds a lot easier and cheaper to sort than a diff!
Also, one side looks to be sitting lower than the other. I don't know if it's because of the hill I'm parked on, but could that be another symptom of brake shoe failure? I'm only thinking because I know when you jack a car up and let it back down, it doesn't settle back down properly until you undo the handbrake. Could it be pulling one side down or something?
Thanks for the help!
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Brianmoooore
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If it's brake related, a lot of heat will be produced when you drive the car. Drive a short way without using the brakes, then feel the rear hubs.
Okay, I got to the car today and did some testing. Here are my results. Sorry for the long post, I want to include as much detail as possible so you guys don't waste your time answering the wrong thing because I've failed to disclose something.
I took the rear left drum brake off (with difficulty, mind) and it seemed okay. The shoes were pretty tightly pressed against the drum so it was a fight getting it off, but when I did I noticed the pin which goes through the retaining spring for the left shoe had been ripped through the plate at the end of the spring, so the shoe was kinda bending out a bit. I thought this may have been the issue but I think I probably did this myself whilst getting the drum off. I managed to delicately hook the pin and spring back together and reassembled the brake, but the car felt exactly the same so I don't think it's an issue here.
I was going to do the same with the other brake but the hex screw was rounded and I didn't have the tools to get it off at the side of the road, so I instead jacked up both rear wheels and spun one of them.
I spun the left wheel forwards and it was quite easy for the most part, but about 1/4 of the turn was very stiff. When spinning this wheel, the other one spun the other direction, as is the case with Torsens.
My thinking at this point was that due to the inconsistent stiffness in the rotation, it wasn't a brake issue as that would more likely be consistently stiff as something was pressing against somewhere it shouldn't. It seemed more likely that some teeth in a gear (perhaps the big ring gear) were broken and every time the mating gear passed over them (the pinion gear perhaps), it was stiff.
Having said that, I've now done some more research on Torsens and watched some videos and discovered that with both wheels in the air, turning one will not operate the ring gear at all. The movement to the opposite wheel happens exclusively through the inner gears. Video here:
However, driving in a straight line as I was when the car failed, I believe the movement would have been with the ring gear and therefore all the inner gears would have been locked together and essentially not moving at all - also seen in that video.
A further thought - I didn't specifically check but I'm pretty sure the stiffness in the wheel rotation happened at the same point each time. If it's the diff which is broken, I don't believe this would make sense as the gears in the diff don't rotate 1:1 with the wheel do they? One rotation of the wheel doesn't equal one rotation of the differential gears. So if it were differential teeth which were broken, the stiffness in the wheel rotation would happen at different points each time. Does that make sense? I could be wrong.
When I get the car home I'll jack up both rear wheels and engage first gear on tickover. I believe that will rotate the differential without rotating the wheels as with a Torsen, if either wheel is off the ground you don't get any power. Thus the differential will be rotating around the driveshafts, which will be stationary. If I still get the grinding, I know it's the diff. If I don't, I know it's the brakes.
Thoughts?
I took the rear left drum brake off (with difficulty, mind) and it seemed okay. The shoes were pretty tightly pressed against the drum so it was a fight getting it off, but when I did I noticed the pin which goes through the retaining spring for the left shoe had been ripped through the plate at the end of the spring, so the shoe was kinda bending out a bit. I thought this may have been the issue but I think I probably did this myself whilst getting the drum off. I managed to delicately hook the pin and spring back together and reassembled the brake, but the car felt exactly the same so I don't think it's an issue here.
I was going to do the same with the other brake but the hex screw was rounded and I didn't have the tools to get it off at the side of the road, so I instead jacked up both rear wheels and spun one of them.
I spun the left wheel forwards and it was quite easy for the most part, but about 1/4 of the turn was very stiff. When spinning this wheel, the other one spun the other direction, as is the case with Torsens.
My thinking at this point was that due to the inconsistent stiffness in the rotation, it wasn't a brake issue as that would more likely be consistently stiff as something was pressing against somewhere it shouldn't. It seemed more likely that some teeth in a gear (perhaps the big ring gear) were broken and every time the mating gear passed over them (the pinion gear perhaps), it was stiff.
Having said that, I've now done some more research on Torsens and watched some videos and discovered that with both wheels in the air, turning one will not operate the ring gear at all. The movement to the opposite wheel happens exclusively through the inner gears. Video here:
However, driving in a straight line as I was when the car failed, I believe the movement would have been with the ring gear and therefore all the inner gears would have been locked together and essentially not moving at all - also seen in that video.
A further thought - I didn't specifically check but I'm pretty sure the stiffness in the wheel rotation happened at the same point each time. If it's the diff which is broken, I don't believe this would make sense as the gears in the diff don't rotate 1:1 with the wheel do they? One rotation of the wheel doesn't equal one rotation of the differential gears. So if it were differential teeth which were broken, the stiffness in the wheel rotation would happen at different points each time. Does that make sense? I could be wrong.
When I get the car home I'll jack up both rear wheels and engage first gear on tickover. I believe that will rotate the differential without rotating the wheels as with a Torsen, if either wheel is off the ground you don't get any power. Thus the differential will be rotating around the driveshafts, which will be stationary. If I still get the grinding, I know it's the diff. If I don't, I know it's the brakes.
Thoughts?
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DanThe
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You need to take both drums off and inspect before jumping to conclusions, also don't tighten the drum retaining screw as it pulls the drum off centre.
I would remove both drums before doing any tests on the diff
I would remove both drums before doing any tests on the diff
Okay, thanks for the advice.
As far as quick/easy tests go - I may as well remove the fill plug and see if I can see anything weird in there and if there are any/many metal filings on the plug.
The main thing though, I'll lift both wheels off the ground, remove both drums and spin one wheel as before. If I haven't already seen anything weird in the drum I'm yet to remove, that should let me narrow down whether it's diff or brakes for sure. If it still grinds with both drums removed - it's the diff for sure.
Plan sorted. Now to get the bloody thing home and that rounded retaining screw out!
As far as quick/easy tests go - I may as well remove the fill plug and see if I can see anything weird in there and if there are any/many metal filings on the plug.
The main thing though, I'll lift both wheels off the ground, remove both drums and spin one wheel as before. If I haven't already seen anything weird in the drum I'm yet to remove, that should let me narrow down whether it's diff or brakes for sure. If it still grinds with both drums removed - it's the diff for sure.
Plan sorted. Now to get the bloody thing home and that rounded retaining screw out!
Opened the diff up and seems fine visually.
I stuck a spanner on a propshaft nut and tried to use the leverage to spin the propshaft but it won't spin in either direction. Car is in neutral of course. I can spin the driveshafts easily but that just spins up the helical gears inside the Torsen - spinning the propshaft will spin the pinion gear and ring gear and leave the helical gears inside locked.
What further testing can I do to narrow this down?
EDIT: Chap over at MX5Nuts said the following:
I stuck a spanner on a propshaft nut and tried to use the leverage to spin the propshaft but it won't spin in either direction. Car is in neutral of course. I can spin the driveshafts easily but that just spins up the helical gears inside the Torsen - spinning the propshaft will spin the pinion gear and ring gear and leave the helical gears inside locked.
What further testing can I do to narrow this down?
EDIT: Chap over at MX5Nuts said the following:
What are our thoughts on that?I would take a good look at the center bearing of the prop shaft. Had it been a diff failure at 50 mph you would expect it to be in 1000 pieces. If you undo the two center bearing mounting bolts on the prop you will be able to drop it a bit and see if it's spins freely on the prop and doesn't have loads of slop.
Okay so I've visually inspected the prop and it seems fine: http://i.imgur.com/d8dMLMs.jpg
I was about to undo the 4 nuts that hold the prop to the drive flange on the diff but realised I couldn't get to the top one because I couldn't spin the propshaft around to reveal it. However, it suddenly decided to start spinning with relative ease. Relative ease being - I'm a skinny 23 year old who struggles to lift the weight of his own arms and I was able to rotate it by putting a regular sized spanner on the nuts and using that leverage to spin it. Because I could do this, I was able to inspect the full crown/pinion gears as opposed to just the side that was facing the rear, and it looked fine all the way around. I continued spinning it using this method for a reasonable amount of time - probably about one full turn of the wheels and it seemed to be the same amount of effort required throughout.
I'm tempted now to just put the diff back together with some oil and try running it with the engine. I'm really bored of clambering about underneath the bloody thing on a cold wet driveway. If it still makes horrible noises I'll get another diff.
I was about to undo the 4 nuts that hold the prop to the drive flange on the diff but realised I couldn't get to the top one because I couldn't spin the propshaft around to reveal it. However, it suddenly decided to start spinning with relative ease. Relative ease being - I'm a skinny 23 year old who struggles to lift the weight of his own arms and I was able to rotate it by putting a regular sized spanner on the nuts and using that leverage to spin it. Because I could do this, I was able to inspect the full crown/pinion gears as opposed to just the side that was facing the rear, and it looked fine all the way around. I continued spinning it using this method for a reasonable amount of time - probably about one full turn of the wheels and it seemed to be the same amount of effort required throughout.
I'm tempted now to just put the diff back together with some oil and try running it with the engine. I'm really bored of clambering about underneath the bloody thing on a cold wet driveway. If it still makes horrible noises I'll get another diff.
Sure it's not a CV joint rather than the diff? If the diff made the sort of noise you describe, the damage would likely be pretty clear. What did the oil look like when it came out? Any metal?
If you remove the diff completely and get it on a bench (or disconnect prop and driveshafts) you can turn it by hand and feel for any stiffness or grinding throughout the range of movement.
If you remove the diff completely and get it on a bench (or disconnect prop and driveshafts) you can turn it by hand and feel for any stiffness or grinding throughout the range of movement.
I'm pretty sure it's not a CV joint. I don't know how I would check, but the driveshafts look fine and I can spin them both very easily.
I didn't get the oil out in one go so it's hard to tell. It seemed to begin dripping out from the moment this happened and I didn't get the back plate off for a few days so most of it had dripped out by then. I'm sure it wasn't dripping before else I'd have noticed. From what did come out when I removed the back plate though - no obvious signs of metal. Maybe a few tiny grains of grit or something but nothing more than I'd expect from the inside of a massive heap of oil metal. It ain't gonna be surgically clean in there after all.
As I said, it does spin but I have no idea how stiff it's meant to be so I don't know if it's spinning normally or if it's too stiff. Bare in mind the back plate is still off and the diff is pretty dry now so it's not gonna be the smoothest of mechanisms.
I didn't get the oil out in one go so it's hard to tell. It seemed to begin dripping out from the moment this happened and I didn't get the back plate off for a few days so most of it had dripped out by then. I'm sure it wasn't dripping before else I'd have noticed. From what did come out when I removed the back plate though - no obvious signs of metal. Maybe a few tiny grains of grit or something but nothing more than I'd expect from the inside of a massive heap of oil metal. It ain't gonna be surgically clean in there after all.
As I said, it does spin but I have no idea how stiff it's meant to be so I don't know if it's spinning normally or if it's too stiff. Bare in mind the back plate is still off and the diff is pretty dry now so it's not gonna be the smoothest of mechanisms.
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Brianmoooore
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You've kept this little nugget of information to yourself! Pretty much confirms the diff. is at fault.ACJJ619 wrote: It seemed to begin dripping out from the moment this happened and I didn't get the back plate off for a few days so most of it had dripped out by then.
Where was the oil escaping from?
Well it was dripping slowly out of the bottom where the back plate meets the main case. I don't know how any kind of failure could have created a leak like that so I was sort of assuming it may have been leaking all along and I just didn't notice but I'm SURE I would have noticed. How would a diff failure create a leak like that?!
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Brianmoooore
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The way a diff. failure would have created an oil leak is by cracking the casing, or a bearing failure allowing oil past an oil seal. Oil doesn't really drip from a diff., even if it's assembled without a gasket.ACJJ619 wrote:Well it was dripping slowly out of the bottom where the back plate meets the main case. I don't know how any kind of failure could have created a leak like that so I was sort of assuming it may have been leaking all along and I just didn't notice but I'm SURE I would have noticed. How would a diff failure create a leak like that?!
There's not a great deal of oil in a diff. in the first place, so if it's leaking as fast as that, it's going to go 'bang' anyway.
The oil was leaking from the bottom literally at the join. It was as if the bottom bolts weren't on tight enough or something. It wasn't an unusual place to leak from. It's kinda like what you'd expect if you used an old shitty gasket and the back plate didn't meet up with the case correctly.
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gareth
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The number 1 cause of sudden diff failure is a lack of oil. If it was leaking, you've probably run the pinion bearing dry and that's now pretty angry and molten.My next step would be to scoop the oil from the bottom of the casing on a cleanish rag and check for metal debris to confirm this.
It'll be fixable for less than the cost of a replacement though
It'll be fixable for less than the cost of a replacement though
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gareth
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They saw you coming....! PM me if you want a sensible quote 
You'll feel the bearing - rough as hell and notchy. And also probably metal debris around the oil somewhere.
You'll feel the bearing - rough as hell and notchy. And also probably metal debris around the oil somewhere.
Sole founder of Fe2O3-12V it's a lifestyle
LSD rebuilding / modification services provided, PM for details
LSD rebuilding / modification services provided, PM for details