Differential Mount Cover Bushing

[zedonist]

Hi Deano, I agree the failures will have been through fatigue, but I don't think the OEM bushes would be contributor, I think they would have damped the effect. The quality of the welding is for me the biggest suspect, which allows for a bigger bending moment and hence over stress situation leading to the material failure, this would be exasperated by solid bushing.

 

[deano1712]

zedonist - if you 'think' the OEM bushes don't make the situation worse you should substantiate this. My previous post explained why soft bushes make loads higher. The OP asked if standard or hard bushes are better and to offer unsubstantiated opinion is not helping anyone. Debate is fine. I made a factually correct statement but you are effectively saying I am wrong.

 

[zedonist]

I don't have to substantiate it, BMW already have and chose to fit the bushes it did, I'm changing mine now and I am using OEM bushes. I agree when they wear or perish they will allow more movement, but it is my opinion that solid bushes will just transmit more forces through to the subframe, I am sure it's an easy calculation to do just using the shore hardness of the different types of bushes to get a comparison. But I don't see any reason to bother as OEM have lasted 16 years so far, and so has my boot floor. As I have said previously, people are confusing a quality issue into a design issue.

 

[t-tony]

It would seem to be common sense to assume that a solid rubber bush would transmit more stress and force than a non solid "void" type of bush. That was the reason Ford introduced "void" bushes in the rear axle mountings of their range of rear wheel drive cars over 40 years ago. I don't see what has changed to alter that outlook.

Tony.

 

[tartufo]

I picked up the Z3 M that I purchased from a private party on Tuesday, in Oregon. Prior to purchase I took it into a BMW facility for an inspection and rectification of any issues prior to the almost 10 hour drive I needed to take to get the vehicle home. This is a 2000 3.2L Z3 M with around 57,500 miles on it from a single owner, with the car having been well maintained. It probably did not hurt that the owner of the car was a female who was in her mid-40s at the time of purchase . . . . probably indicating that the car was not likely to have been abused.

At the dealership I inspected the rear frame from both the trunk side and the underside, with the technician who knew exactly what I was looking for. What he said to me was that this sort of thing is very rare in Z3s, however he had seen a number of them with e46 models. He also said that in his experience it comes from people who track or otherwise abuse their cars, with repeated jackrabbit starts, for example.

Various bushings were replaced on the car at the dealer 10 to 15,000 miles ago (need to review the voluminous records supplied with the car).

 

[zedonist]

The way I look at it, people mainly only talk about problems on a forum, so when a handful of members get the issue, it must be a global epidemic (ties in with how governments work). Truth is it is not many vehicles out of the many sold. You Also have to consider it was a new car down a brand new car line, processes will not have been as optimised as for example the 3 series line in Germany, next you have to consider that welding is also considered to be a special process, in that you never really know what you get at the end of the process, however if applied consistently the outcome can be controlled. Unfortunately the plant had its quality issues which resulted in the failures we see today, but it is not a design issue that's for certain.

I'm glad you've got a nice example and you enjoy every minute of it.

 

[t-tony]

You took the words out of my mouth there Rich.

Tony.