OK, that's sound advice. So you're suspicious after he made the low car, noisy car...thought it was weird, tbh. The bodywork guy has been saying the same: wondering if the mechanic has done something in the process of changing the driveshafts.
Wanted Potential Diff Needed
- Thread starter ktnez99
- Start date
If @Mnbrennan says the diff is not sounding good I’d have no reason to doubt it.
And only you know if the noise got worst after the driveshafts were done. But I think you’re saying it did.
So I would have my suspicions about how the work was carried out. Whether good quality parts were used, whether bearings should have been done at the same time. And whether the diff or anything else like bearings were damaged in the course of doing so.
Just standard questions to ask really, with slightly raised suspicions. Your mechanic might have done a first rate job, then the diff failed a few weeks later.
Seems a bit strange though doesn’t it? Unless the driveshafts killed the diff or vice versa. No idea if that’s possible btw. And he only did half the job.
And only you know if the noise got worst after the driveshafts were done. But I think you’re saying it did.
So I would have my suspicions about how the work was carried out. Whether good quality parts were used, whether bearings should have been done at the same time. And whether the diff or anything else like bearings were damaged in the course of doing so.
Just standard questions to ask really, with slightly raised suspicions. Your mechanic might have done a first rate job, then the diff failed a few weeks later.
Seems a bit strange though doesn’t it? Unless the driveshafts killed the diff or vice versa. No idea if that’s possible btw. And he only did half the job.
I know. You guys have been great and now I have to sort it out.
Where are you located? If you are concerned about the diff I would recommend pulling the rear cover and sending some pictures. You can feel damage to the carrier bearings easy enough. After this you can hold the crown wheel and feel the backlash in the pinion and see if there is any movement.
And for everyone else is there anyone who rebuilds diffs at a reasonable price? I have not looked into BMW ones as of yet but the years I have built a lot for off road. There are only a few styles for setting the bearing preload for the pinion and carrier. Nothing overly special if you have seen and done it before and have the measuring tools.
The diffs I build for off road got abused. Just sold this Jeep on and the front axle I built was cut down from a full sized pickup and had all aftermarket internals.
And for everyone else is there anyone who rebuilds diffs at a reasonable price? I have not looked into BMW ones as of yet but the years I have built a lot for off road. There are only a few styles for setting the bearing preload for the pinion and carrier. Nothing overly special if you have seen and done it before and have the measuring tools.
The diffs I build for off road got abused. Just sold this Jeep on and the front axle I built was cut down from a full sized pickup and had all aftermarket internals.
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I'm Birmingham based. Interesting idea.
- Joined
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- 231
- Model of Z
- Z3M Imola and Z4 (e89)
Is there a chance the wheel bearings have been seriously over tightened? They wouldn't last long and would get noisy.
More likely they've been under tightened.
Tony.
Tony.
Or the drive shaft has been hammered in
That was one of my thoughts. But the hammering would be done towards the wheel bearing side not the diff to put it back.
The only way the driveshaft could impact the diff is if it was hammered out from the hub while still attached to the diff the other end. But that makes no sense.
If the hub splines weren't cleaned properly there's a good chance that the shaft isn't fully "home" in the hub which will mean insufficient pressure on the two wheel bearings.
Tony.
Tony.
This is interesting. The mechanic changed only one driveshaft - said it only needed one. This pushed the one side of the rear up about 5 inches. I took it back as someone told me that both should have been changed to which the mechanic said he could do this - note: no wheel bearing was changed either side. The first driveshaft - aftermarket - was too long and had pushed the rear up. The second driveshaft was mine, reconditioned. I have the one he took off. He'd found what he called "pins" or "bolts" rattling around in, I think, the hub on each wheel; removed these. It still looks too high up at the rear to me. And, of course, is making this loud noise.
Thinking about it some more, this might also mean the driveshafts are exerting untoward pressure on the diff output flanges? Which might carry through into the diff?
If the shafts are to long they will not compress enough when the suspension goes up. Don't know if this is likely or not but if so it would be really bad.
- Joined
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- Points
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- Model of Z
- Z3M Imola and Z4 (e89)
Am I being totally stupid here, changing a driveshaft for the correct sized replacement should not affect suspension height in the slightest? Something very wrong here or am I missing something?
I can't see how it would push it up 5 inches. But if the driveshaft wasn't pushed in properly I think it could have the effect of making the trailing arm sit slightly higher.
But the bigger question is whether the right size driveshaft was used.
In either event, a mistake around the driveshaft selection or installation could be responsible for the noise, even in the diff by putting pressure on from outside perhaps.
- Joined
- Feb 18, 2016
- Points
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- Model of Z
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I agree
Juvvajuvva
Zorg Addict
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Hi,
5 inches is huge. Can I suggest you jack the back up or put it on a ramp and measure the drive shafts.
If they are the same length great. If the drive shafts are located in the diff correctly then great. I have a hunch that when the “mechanic” fitted the drive shaft he didn’t locate the CV joint and bearings correctly. This causes the joint lo lock out and not laterally flex inward and outward as the suspension rises and falls, hence your raised height!
This would also cause an awful grumbling noise.
Unbolt the 6 retaining Torx bolts from the diff end and try and pull it in and out and roll it around.If it is anything other than smooth he probably had the CV head fall off and didn’t put it back properly or just didn’t pack it with axle grease.
Just a thought.
Also if the driveshaft is a cheap Chinese replacement that is not correct for your car and is too long, the only way he could fit it would be when the car was off the ground with the trailing arm lowered. Then when you drop the car , that side would sit higher.
Basically when you fit the correct size shaft you push it into the wheel hub splines then raise the trailing arm so that the shaft meets the diff output flange. If it reaches when the trailing arm is right down low and it’s CV joints are compressed, then it’s too long and effectively in a Z shape.
The joints should be relatively centrally compressed when the drive shaft is level. This is because trailing arm suspension works in a radius arc. Joints compressed when the suspension is compressed and extended when the suspension is extended.
5 inches is huge. Can I suggest you jack the back up or put it on a ramp and measure the drive shafts.
If they are the same length great. If the drive shafts are located in the diff correctly then great. I have a hunch that when the “mechanic” fitted the drive shaft he didn’t locate the CV joint and bearings correctly. This causes the joint lo lock out and not laterally flex inward and outward as the suspension rises and falls, hence your raised height!
This would also cause an awful grumbling noise.
Unbolt the 6 retaining Torx bolts from the diff end and try and pull it in and out and roll it around.If it is anything other than smooth he probably had the CV head fall off and didn’t put it back properly or just didn’t pack it with axle grease.
Just a thought.
Also if the driveshaft is a cheap Chinese replacement that is not correct for your car and is too long, the only way he could fit it would be when the car was off the ground with the trailing arm lowered. Then when you drop the car , that side would sit higher.
Basically when you fit the correct size shaft you push it into the wheel hub splines then raise the trailing arm so that the shaft meets the diff output flange. If it reaches when the trailing arm is right down low and it’s CV joints are compressed, then it’s too long and effectively in a Z shape.
The joints should be relatively centrally compressed when the drive shaft is level. This is because trailing arm suspension works in a radius arc. Joints compressed when the suspension is compressed and extended when the suspension is extended.
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A driveshaft has to have a sliding coupling (the same as a front wheel drive propshaft does) to allow for the rise and fall in the rear axle (or in the case of the Z3 the rear suspension).
The driveshaft is at its shortest condition when it it parallel to the ground. As the suspension travels up or down the shaft has the lengthen which is made possible by the sliding part of the joint.
Tony.
The driveshaft is at its shortest condition when it it parallel to the ground. As the suspension travels up or down the shaft has the lengthen which is made possible by the sliding part of the joint.
Tony.
With the suspension set level with the shaft at its middle position you should be able to grip the shaft by hand and slide it in and out on the spline.
Tony.
Tony.
New joints are usually quite stiff and won't let you do this till they have done a few miles.
Tony.
Tony.