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You will not believe or might believe what happened to my differential mount on my Roadster. IT HAS CRACKED!!! Last Saturday, October 20, 2001, after driving with my girlfriend Cindy on the Blue Ridge Parkway and having a picnic, we were driving home and I heard a noise when we were driving over small expansion joints in the road, she did not hear it. I was able to determine it came from the rear of the car.

I needed gas, so we pulled into a gas station to fill the tank. While my car was drinking, I started to look over the back end of the car to see if I could find anything loose. I did not immediately see anything (Note, it was already late at night and the sun had set), but still could hear a small noise when I hit the rear left tire. Looking around, I did not see any thing loose. Temporary satisfied that my car would not fall apart for the drive home. We left for home.

That Sunday, I put my car up and pulled the rear wheels off to see what I could see. Not finding anything, I pulled both rear brake caliper units off the wheel. I cleaned and reassembled them. I took a quick ride and still heard the sound, but not as loud. Good I thought. So I parked her. I wanted to mull around in my brain on what could be wrong.

Monday, I am at work and in the back of my mind, still thinking of what I could have missed. I decided to go home for lunch. So, during lunch, I go home. Put my car on stands and crawl under her to see what I could see. With my strong halogen work light in hand I saw it. A crack in the differential mount!

Starts from the right side to the left, approximately 3-inches long, it is located on the first bend from the rear cross member. I also reviewed the whole underside of the car and did not see any additional cracks. My mind raced as to determine what could of caused the crack, was it my racing, my use of a trailer, the hard driving at Deal's Gap or just poor design on BMW's part.   When I returned back to work. I remember seeing a post that mentioned cracks in the frame work. A quick scan through Robert's MZ3.net website, I found Dave Alsabery's posting. His MZ3's frame cracked at the cross member and at the differential mount. He was able to find a spare at a scrap yard and have a body shop do the reinforcement and repair. I have been in communication with him, to get his thoughts. I started communication with Dave Alsabery, because he has experienced this same issue. The only difference is that he hit something on the road to cause this crack. Since his repair, he has put on 18,000 miles, including autocrossing, with no new cracks.

Some Facts:
1.I did not hit anything on the road
2.I do have a Da 'Lan hidden trailer hitch
3.I do have a small trailer to pull my racing wheels, tires & equipment to Autocrossing events. Gross weight approximately 300#
4.I have aftermarket suspension system
5.I drive Deal's Gap more than most Z3'ers
6.My car is a 2000 model that I purchased in 1999.
7.My car has over 50,000 miles

What to do:
Since this might not be a warranty item, due to the things I have done to the car. I need to fix it my self, by either welding the crack, replacing the differential mount or make a mount that is stronger than stock. I plan to design and build a stronger than stock differential mount. I have a few drawings done on AutoCAD. I will keep everyone updated on this issue. Contact me if you have any questions.

UPDATE:
After talking with some friends, I dropped off my car at FLOW BMW in Winston-Salem.
After reviewing the car, Dan, who works at FLOW, said that the crack falls under the Body Warrenty, not the Drivetrain. I then remembered and informed him about my extended warrenty from Hendrik Motors. He said he would call them to see if they would repair the damage. That was Monday. Tuesday I was out of town on business. Wednesday, I called back to see if he had heard from Hendrick. Dan said that he called them and has not heard from them. He did place the order for the replacement parts. I did give him the authorization to order and fix it if Hendrick would not pay for the repair.

Then on Friday, I get a call from Dan, he told me that Hendrick would honor warrenty and repair the damage.   He also mentions that my car will go to their bodyshop to get the work done. The parts should arrive early next week and I should be able to pick up my car by Friday the latest. I would only need to pay the $100 deductible. Once the car arrives I will post new pictures. Stay tuned!
CONCLUSION - - sort of…
My car has returned to me - - happy days are here again - sort of....

Went to FLOW BMW to pick up my Z3. That was one of the good news. The car feels great, though I had to drive slowly through the rain. Today, the rain is to stop and the clouds to clear as the week continues. I viewed the repair, great job; they welded the original bracket, and then welded the new bracket over the old, thus doubling the bracket's thickness.

Note the pics are taken after I have washed my car.

Photo is taken from rear looking toward the repaired brace.

Photo of new brace, note the doubling of the metal.

Photo of close up of brace.

Here, you can see where they had to slice the outer bracket to make it align correctly to the bolt that holds the differential. It looks like the shop drilled out the locations of the spot welds and then did a regular weld to allow the outer brace to adhere to the inner brace.

Bad news:
I was informed by FLOW, that Hendrick would NOT pay for the whole repair job! Hendrick said that they would only pay for the original agreed upon quotation of $500. They would not pay for the additional $800. ARUGH!!!!
Hendrick sent an adjuster out last week to view the car and he said that because of the trailer hitch, it caused the Diff-Mount to fail. I told him the following: that I pull below the maximum pull weight, noted in the manual. I did not ask for a loaner car, for the 4 weeks that I had the car in the shop, plus, I have evidence of other cars that the Differential Mount broke with out any modifications.

It did not matter. Double ARUGH!!!!

I guess I should be thankful that they were willing to pay something and FLOW BMW did an excellent job on the repair.
TOTAL COST:
                      $500 from Hendricks
                  + $800 out my pocket
                      $1,300

I still plan to make my add-on brace to the differential mount.
(Update: I opted not to do a different modification)

If you have any questions, please contact me.

Summation:
FLOW 5 out of 5 stars on repair and service
HENDRICK 1 out of 5 stars on service