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E36 /7 Z3 (1996-2002)
E36/7 Z3 roadster and coupe talk with our gurus here.

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  #1  
Old 04-16-2013, 02:38 PM
diva_3181377 diva_3181377 is offline
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Differential moving up and down at the bushing area !!!

I replaced the differential mount and bolt (OEM) to fix the clunk sound but it didn't fix it. Upon checking, it happens

1) When moving from D-N-R or R-N-D, i can reproduce the sound with the rites on ramp.
2) When coasting to stop, at the end the transmission engages and makes sound
3) No sound in accelerate or braking.

Also found that the rear of the differential where the bushing is, is moving up and down (with new bushing, bolt and nut). The clunk sound is clearly coming from the differential area (on ramp i confirmed it), and looks like the differential when moving up and down is making the sound, (hitting some where on the way).

The differential bolts (4) are loose? Or the mount is bad? I put the new new bushing exactly like the old one. Is the differential allowed to move up and down on D-N-R and R-N-D?

Thanks in Advance..

Last edited by diva_3181377; 04-17-2013 at 01:06 PM. Reason: blot to bolt :)
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  #2  
Old 04-16-2013, 03:20 PM
gmushial gmushial is offline
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Since you have an E30 tail Z3 - have you checked the spot welds that hold the box element the diff bushing hangs from? The easiest place to check the welds is in the floor of the trunk: there are two rows that run from side to side (just forward of the battery box). End up with more than a couple broken and you'll hear the box element slapping away. You can also have the hangers which the diff bushing is bolted to, come free from that box element - you might check that.

How many miles on the Z? Have you replaced the subframe bushing? They can be another source of noise.

The other, since you mention deceleration vs acceleration - have you check for slop in the driveline? There are two u-joints in the drive shaft that tend to need replacing at around 100k miles; likewise there are four cv joints on the half-shafts (one at each end of each half-shaft) - they can go away, inducing slop, which you'll hear as the driveline loads and unloads.

good luck - greg
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Old 04-16-2013, 04:29 PM
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vintage42 vintage42 is offline
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Quote:
Originally Posted by diva_3181377 View Post
I replaced the differential mount and blot (OEM) to fix the clunk sound but it didn't fix it...
What do you mean by "blot"? And where is this "bushing area" in your title? Your gears show you have an automatic, but you don't give us the year, miles and engine. All these factors are important in diagnosing your problem.

Edit: I understand you heard a clunk when shifting from Drive to Reverse, and have replaced a bushing, perhaps the one on the differential mount? And you have put the rear of the car on ramps so you can watch the differential. And you have had someone shift the automatic transmission through Drive and Reverse, and you have then seen and heard the differential move and make a clunk sound?

Last edited by vintage42; 04-16-2013 at 04:36 PM.
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Old 04-16-2013, 06:11 PM
Bob2.8 Bob2.8 is offline
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blot = bolt?
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  #5  
Old 04-16-2013, 08:05 PM
Blacklane Blacklane is offline
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There are 4 bolts in the top of the diff that attach it to the subframe. They do sometimes back out if not torqued to the specified 100 ft lbs. There is no way to get a torque wrench in there anyway, so just give it all you've got.
The differential mount bolt itself gets torqued to 75 ft lbs, but you have to do it with weight on the wheels to align it properly. I set my car on a stack of 2x8 wood blocks to do that.
If the entire subframe is moving with the differential, your problem is Rear Subframe Bushings.

Last edited by Blacklane; 04-17-2013 at 09:46 AM.
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Old 04-16-2013, 08:54 PM
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Randy Forbes Randy Forbes is offline
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Any chance that the rear crossmember looks like this one?



If the differential, bush and bolt, are all moving up and down, then what they're attached to isn't attached very well to the bodyshell...
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  #7  
Old 04-17-2013, 07:33 AM
diva_3181377 diva_3181377 is offline
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Sorry..Car is 2000 Z3 2.3 Auto with 117K on it

The differential bushing on the ear is replaced along with bolt and nut with OEM part. Also the rear shocks and mounts + hardware is new.

gmushial - The box where the bolt connects on the bushing looks solid.Subframe bushing, RTAB, never changed. Have no driving issues like wandering. Need to check that. The drive line is also original. Need to check that. Also no tear in the trunk.

vintage42 - Yes the one on the differential mount. I replaced that bushing and yes some one moved through Drive and Reverse and saw the differential move up and down (not in front, but on back where the bushing is) and making the sound. I am trying to capture a video of this thing.

Blacklane - No the subramr does not move. Except the differential, nothing else moves (the cv shaft tries to move a little, but with the brake on, it wont). Checked the CV, no radial play, but it have horizontal play. Can it cause this? Heard this is normal?

Randy Forbe- It looks solid. No welding issues there.Only the differential moves up and down. Everything else stays solid.

I am trying to capture some photos and video. Will update soon.
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Old 04-17-2013, 09:01 AM
gmushial gmushial is offline
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Quote:
Originally Posted by diva_3181377 View Post
Sorry..Car is 2000 Z3 2.3 Auto with 117K on it

The differential bushing on the ear is replaced along with bolt and nut with OEM part. Also the rear shocks and mounts + hardware is new.

gmushial - The box where the bolt connects on the bushing looks solid.Subframe bushing, RTAB, never changed. Have no driving issues like wandering. Need to check that. The drive line is also original. Need to check that. Also no tear in the trunk.

vintage42 - Yes the one on the differential mount. I replaced that bushing and yes some one moved through Drive and Reverse and saw the differential move up and down (not in front, but on back where the bushing is) and making the sound. I am trying to capture a video of this thing.

Blacklane - No the subramr does not move. Except the differential, nothing else moves (the cv shaft tries to move a little, but with the brake on, it wont). Checked the CV, no radial play, but it have horizontal play. Can it cause this? Heard this is normal?

Randy Forbe- It looks solid. No welding issues there.Only the differential moves up and down. Everything else stays solid.

I am trying to capture some photos and video. Will update soon.
Then: if the box channel is solid against the trunk floor and isn't moving, then the "only" thing it can be is as suggested above: the four bolts which tie the diff to the subframe "must" have come loose... two of them are easy to get to, the other two are a PITA. The assumption is that all have come lose (how or why???)... but try tightening the two that are easy to get to and see if that doesn't improve things a bit. If so, then fight to get to the upper ones. The other place you might look is the subframe bushings: with the car on stands (but make sure up have backups under there also, given what you're going to do), put a jack under each end of the subframe (one at a time), with a 2x4 or 2x6 to distribute the load, and gently jack it upward and see how much give there is. There should only be a mm or two. The OEM bushing have two legs which tie the inner part to the outer part - if they have broken then you can get subframe flop which might be what you're seeing. (Clearly, also check that the nuts at the bottom of the bushings are tight - 100ftlb-ish; likewise the two allen head bolts the hold the retaining piece at the bottom of each bushing are tight - you may need to clean the crud out of the allen holes, and make sure you get the bit well seated in the holes so that you don't strip them out, causing more problems than solving.) But in doing this (jacking) be very careful, in that the car will be initially resting on the stands, and when you jack the subframe, you potentially will be upsetting the configuration. If you have them, instead of stands, use something more substantial, and something that's not inclined to fall over - personally I use log rounds some 20" in diam, ie, they're good for 40ish tons apiece and there is no way they're going anywhere. Be careful and good luck.

Last edited by gmushial; 04-17-2013 at 09:04 AM.
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  #9  
Old 04-17-2013, 09:46 AM
diva_3181377 diva_3181377 is offline
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gmushial..Thanks..I will try that and update.

Forgot to add this. When moving from R-N-D and D-N-R, it will try to rotate the drive shaft (CV). With the brake is ON, it can rotate and i can see that the Inner part close to the differential is moving, but at the wheel is not moving. Can this cause the differential to move up and down? The differential moves maximum in the void gaps inside the bush and stops there. Seems not moving the bracket.

Last edited by diva_3181377; 04-17-2013 at 02:59 PM. Reason: More information
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  #10  
Old 04-18-2013, 03:54 AM
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vintage42 vintage42 is offline
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Quote:
Originally Posted by diva_3181377 View Post
... When moving from R-N-D and D-N-R, it will try to rotate the drive shaft (CV). With the brake is ON, it can rotate and i can see that the Inner part close to the differential is moving, but at the wheel is not moving. Can this cause the differential to move up and down? The differential moves maximum in the void gaps inside the bush and stops there. Seems not moving the bracket.
So the brake is holding the drive shaft from rotating, while you can see the inner side of the CV joint try to rotate. I don't know how much play is normal in the joint. Does the play in the CV joint make any of the clunking that you hear?

You said you just replaced the differential mount bushing with an OEM rubber one. The movement inside the voids of the soft bushing under torque is probably normal.

Did you already tighten all the bolts between the top of the differential housing and the rear axle carrier (aka subframe) as suggested here?
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Old 04-18-2013, 07:39 AM
diva_3181377 diva_3181377 is offline
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vintage42 - The sound, can't pin point if it is coming from differential or the inner CV Joint. It is definitely in that area. Tried to rate it by hand, but too tight. With both wheels up on air, tried to rotate left and right. No clank in the CV joint, but a faint one in the central part under the heat shield. Must be the place where the Central shaft bearing is. But the clank sound i am hearing is definitely not from that area.

Oh ok..So the movement vertically in the voids is normal. Good to know. I was thinking something wrong there. I followed the TIS and the original bushing on installing it.

Checked the front bolts and looks tight. Need to check the top one's. Seems not easy. Wonder what is the proper procedure on doing that.
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  #12  
Old 04-18-2013, 07:46 AM
Blacklane Blacklane is offline
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The top differential bolts are pretty easy to torque to spec once you remove the entire subframe/differential/trailing arms/hub assembly, but I don't think you want to do that. I would just use the biggest breaker bar you have and give it all you've got.
But if they aren't visibly loose, that's not your problem.
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Old 04-18-2013, 03:46 PM
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What exactly is the symptom you're feeling? I've got a feeling it's the way the rear of the car squats down when you shift from Park to Reverse or D. My car has done it since I bought it with 63xxx miles on it. Just replaced the shocks and struts and it seems to do it a lot less.
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Old 04-19-2013, 08:15 AM
diva_3181377 diva_3181377 is offline
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Yes it does that. I can see the rear of the car going up and down when R-N-D or D-N-R. All 4 shocks/structs are new and also the RSM. Checked them last time and all of them are in good shape. Also no sound when driving over bumps or anything like that. It seems happening when getting torqued like coasting to stop or D-N-R / R-N-D. Because we sit almost on top of the differential, it is easy to hear it.

Planning to check the bolts this week end with my friend's help who is more mechanically inclined than me. Searched the internet. Seems this sound is a common problem

Please see this..
http://forums.bimmerforums.com/forum...-and-clunks-WT

It says "here is a bushing on the front of the rear end just like the one on the arm. Give it a check and see if its worn down or gone like mine was. ". Is this the RTAB or Subframe bushing that he is talking about?

Last edited by diva_3181377; 04-19-2013 at 09:29 AM.
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Old 04-19-2013, 11:13 AM
gmushial gmushial is offline
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Quote:
Originally Posted by diva_3181377 View Post
Yes it does that. I can see the rear of the car going up and down when R-N-D or D-N-R. All 4 shocks/structs are new and also the RSM. Checked them last time and all of them are in good shape. Also no sound when driving over bumps or anything like that. It seems happening when getting torqued like coasting to stop or D-N-R / R-N-D. Because we sit almost on top of the differential, it is easy to hear it.

Planning to check the bolts this week end with my friend's help who is more mechanically inclined than me. Searched the internet. Seems this sound is a common problem

Please see this..
http://forums.bimmerforums.com/forum...-and-clunks-WT

It says "here is a bushing on the front of the rear end just like the one on the arm. Give it a check and see if its worn down or gone like mine was. ". Is this the RTAB or Subframe bushing that he is talking about?
A badly written posting (the one you quote, not yours)... there are basically seven bushings which affect the rear suspension (ignoring the RSMs): there are the two large subframe bushings on either end of the subframe, which are used to connect the subframe to the body; and the trailing arm bushings: two per trailing arm, at the pivot points of the trailing arms where they attach to the subframe. I'm hard pressed to think of any geometry where the TABs will be causing your diff to be moving up and down; but the RSFBs could clearly be doing such (beyond possibly the four diff mounting bolts).
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Old 04-19-2013, 06:15 PM
diva_3181377 diva_3181377 is offline
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http://www.realoem.com/bmw/showparts...98&hg=33&fg=30

Here item 3 is the RSFBs i need to check for? Will they cause noise when going over the bumps? If this is, i can check this area when we do the D-N-R and R-N-D test.
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Old 04-19-2013, 08:06 PM
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Just another aside, if you're talking about the squatting when moving the automatic shifter into D-N-R that is normal for Z3 models with automatic transmission. I have yet to see one that doesn't do it.
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Old 04-19-2013, 08:28 PM
diva_3181377 diva_3181377 is offline
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Will it make sound (when squatting) ? All my friend's who have BMW, is 3 series. None have Z3. So no way to compare..
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Old 04-19-2013, 08:38 PM
gmushial gmushial is offline
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Quote:
Originally Posted by diva_3181377 View Post
http://www.realoem.com/bmw/showparts...98&hg=33&fg=30

Here item 3 is the RSFBs i need to check for? Will they cause noise when going over the bumps? If this is, i can check this area when we do the D-N-R and R-N-D test.
Yes, #3 is the RSFB - there is one on each side. You might be able to see something with the D N R test... but I would suggest the jack as described above: where the suspension is unloaded fully, and by jacking it, will become fully loaded - if the bushing is good, there should be a mm or two at most movement. If the bushing is bad you'll see more... and if that is the case, with the suspension loaded, eg, with the wheels on ramps, if you remove the two #5's and then #4 in the image (only one side at a time), you'll be able to look at the lower end of the bushing, and just might find the legs which connect the inner core to the outer ring cracked - if that's the case, then time to replace.

W/re the squatting on accel - that's nominally a case of worn out shocks [something I came to appreciate when I replace my toast Boge's with some fresh KYBs... and the squatting was reduced by 99%] The RTAB will have little to do with such. Generally with shot RTABs you'll find the alignment is all over the place and the tire wear is likewise. You can test the RTABS by simply putting a very large screwdriver btwn the subframe and the holders for the bushings, and try to pry them about. If they're gone, you'll be able to move the trailing arms a bit; if they're ok you're move inclined to dent the subframe (don't do).

But, bottom line: test the RSFBs first (this is assuming you're already checked the diff mounting bolts and found them tight)... and if you don't find the problem there, then look elsewhere.

... hopefully this will be the weekend you get some help in looking... suspect the cause will be found in a few minutes. The very best of luck to you - greg

Last edited by gmushial; 04-19-2013 at 08:46 PM.
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Old 04-21-2013, 08:07 PM
diva_3181377 diva_3181377 is offline
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Checked and confirmed with my friend.
1) 4 differential bolts are really tight. No way to turn them by hand.
2) Next tried subframe bushing. it is not moving at all.
3) Checked the welding part again. All in real good shape.

Then during our R-N-D and D-N-R testing, we found that the clunk is generated by a sudden power transfer from differential to the cv shafts. As soon as i put it in R from N, Propeller shaft turns immediately up to the differential end and it takes a sudden jerk before the power gets transmitted to the cv shafts (confirms up to this point all is good). Also found that D-N and N-D is lot quieter than R-N and N-R. N-R is really noisy. If i hold the drive shafts (CV) while doing this, i can feel the sudden jerk really good in my hand.

So this all points to either bad differential or bad cv shafts. I cant turn the half shaft by hand and my friend says that the right side have move clunk/jerk than left side. All the CV boot looks fine and i cant rotate either one by hand.

Finally narrowed it down to differential or CV shaft. Planning to change only right side CV shaft and see if it comes back. Any way the differential can generate a play inside? Also why N-R is lot noisier than N-D? So far no clue. Also the differential have the infamous "whine". Not real bad, but at low speed, it is noticeable.
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Old 04-21-2013, 08:45 PM
gmushial gmushial is offline
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Yes, a differential can become loose inside, but that's generally further down the road than 117k miles. ... unless it's been allowed to run dry. Have you checked the oil level in it? On a level surface, if you remove the fill plug - the upper one, the oil level should be right at the lower edge of the fill hole. ... but beyond that I'm a bit confused: this started as "Differential moving up and down at bushing area"... and now we're talking about a clunk. ?? Is this possibly a case where a clunk was interpreted as a diff moving up and down?

W/re CV and/or half shaft vs diff as source of looseness - that's not too hard to determine... With the trans in P and one wheel off the ground slightly - if one rocks the tire back and forth (rotationally), while first holding the center part of the halfshaft, and then the flange at the diff, one should be able to feel any slop, where the tire is moved, but the halfshaft or flange doesn't. First one can do such one one side; then the other. If one still hasn't found the slop, then put both wheels on ramps (so one can get under the car), block the front wheels super well, set the parking brake, and put the trans in N. One can then either by hand, or with a 16mm wrench on the input flange nuts, rotate the input to the diff. Since the outputs are locked (the wheels can't move), any slop you feel, will be inside the diff. A Torsen diff will have a little slop, given that the carrier has four torque sensing gears - but the slop should be just perceivable, no more. If there is more then that, then you have a loose diff. What to do about it? One can replace it with a junkyard one - which may have as much slop, or less; or, one can ignore it until the whining becomes more than one cares to put up with. The diff is a std E30 differential, so there are lots to be had in the junkyards - though you may have to swap covers and speed sensors.

My impression is that you're learning more about your Z than you ever expected to - hopefully it hasn't been time badly spent. Best of luck - greg

ps. by using the wheel to rotate the half-shafts, you will be able to get enough leverage to feel something, if there is something to feel - have to agree though, almost impossible to impart enough force via the flanges by hand to detect any motion.

Last edited by gmushial; 04-21-2013 at 08:48 PM.
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  #22  
Old 04-22-2013, 09:37 AM
diva_3181377 diva_3181377 is offline
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Yes..actually when i bought the car, did all the fluid changes almost immediately and when i did the bushing change, changed again. It was clean. No metallic particles. Dont know if it is good or bad, but the internal mechanism look kind of black color and when i wipe them, it became steel color as normal.

The rear of the differential moves up and down during the testing and it looks normal to the mechanism. It actually moves in the voids in the OEM bushing. Looks like designed like that. The bolt does not move at all. Sorry for the confusion. Also about the rear end moves up and down, since the shocks are news, checked big spring. Don't exactly know how to check them, but seems it lost its tension or moving smoothly.

Yes..thats true Greg. I am learning a lot than i expected. It is my third car, so i can play with it

I will check the CV and differential. The differential seems like somebody worked on it before. It have number '4' written on bottom of it (with a metal blade or some thing). Kind of like an inventory number. Also my friend says that it is coming from (clunk) right side for sure. So will try that side first.

Thanks a lot Greg. I will update you.

Also found this..http://forums.bimmerforums.com/forum...ferential-play

Last edited by diva_3181377; 04-22-2013 at 10:00 AM.
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  #23  
Old 04-26-2013, 09:04 AM
diva_3181377 diva_3181377 is offline
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Tried it by my self (CV check). Not so good test (laying down on floor and holding the cv with one hand rotate tire by other hand), but seems there is slight play in the outer section of the CV. But no torn boot or grease outside. Right side seems to have slightly more. Finally found something.
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Old 05-01-2013, 08:33 AM
gmushial gmushial is offline
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Been on the road for the last several days... but wondering, and when I got home last night had a chance to measure... the diff bushing needs to be installed with a specific orientation, and if it's not, then one might see the up/down motion that you've been describing. The center part of the bushing - the aluminum piece in the center through which the mounting bolt passes - is not circular, but an elongated circle - I measure .490 x .640" and where the thru bolt is .475", ie, in the correct orientation, with the wider direction of that mounting being horizontal, then there is only .015" of slop btwn the thru bolt and the aluminum piece, ie, not much room for the diff to move (up and down); but if the bushing was 90 deg out, then there would be significant room to move within the slot of the bushing, and I suspect given what the diff weighs and the momentum it would have when it hit the end of the slot, would be able to compress the rubber of the mounting, and have even more movement... just wondering if the bushing is with the correct orientation: slot horizontal, and above center?

W/re learning more than you were planning on: you couldn't have picked a better car to do such with/on - of all the cars I've owned/worked on over the years, the Z is by far the most rational and mechanic friendly for such, to do such on/with - not the malicious nature I've encountered with a lot of Japanese iron (Acura was the worst: huge number of special tools required, and many unreachable places); or just badly designed like too much American iron. ... although I'd rather being driving the Z, I don't fear having to work on it when necessary - have come to understand that "surgery" will be rational, with plenty of access room, and with the minimum of special tools (only special tool needed so far, and which I built, was the waterpump pulley holding tool).

And finally: w/re your discovery - there really should be no perceivable slop in the CVs... yes one can drive them that way for quite a while, but eventually they will beat themselves to death, and then one will have to replace them. If at this point you have "some" play, I'd continue to drive it, and keep an eye open for that degrading, but at the same time, keep an eye open for new replacement half-shafts (a reasonable price for), and likewise the tool (buy, rent or make) to pull the replacement half-shafts back through the rear wheel bearings [sometimes one get's lucky and by wire brushing out the old splines and cleaning the new ones, one can get them to hand slide into place; but all too often they need to be "pulled" through, which is where the tool come into play]... from [I]The Art of War "Security is knowing where the exits are, before one needs them," ie, if one knows they're going to eventually have to replace the half-shafts, but if one has a pair of good priced ones sitting in the garage waiting, and likewise the pulling tool... then it's just another job and not a terribly difficult one at that; conversely if one has to buy them at the last moment and doesn't have the tool and needs it... a whole let less than pretty picture comes to mind... and a bad one at that.

good learning - greg
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  #25  
Old 05-01-2013, 09:09 AM
diva_3181377 diva_3181377 is offline
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Location: Dallas
 
Join Date: Apr 2013
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Mein Auto: 2000 Z3 2.5L Auto
Thanks Greg. That is what i am planning. Keep it driving till it is really bad. Once find out what is wrong and it is not crucial, then it is a peace of mind. CV, from my experience, if it not leaking (boots looks ok) it is safe to drive for a while.

Yes i double checked the orientation with the TIS and also with the existing bushing before removal. The bolt does not move at all in vertical direction because the hole is like rectangle to the horizontal direction. But in vertical, there is void's in the OEM bushing. Horizontally, there is nothing. It only moves in that voids (the rubber part in the bushing moves) and it looks like designed for that to absorb the shock. Please see http://www.ecstuning.com/ES56689/. The second image shows it clearly. There is gap on top and bottom part and center part is the one which moves and the maximum it can move is not much.

I also have a VW, on which i started working first (as usual, ripping off by the dealerships). The funny thing is that, it's CV boot is torn now (grease all over). This is the third time i am going to replace it(~25 K is the average life - not lowered..bone stock). Very common problem with VW/Audi. Compared to that BMW does a really good job. Also have a Honda, which is still ok. So far didn't had to touch the mechanical. I always thought Acura which is Honda it self is easy to fix. Good to know that it is not that easy. Since the Z is the third car, i am not hurrying..
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