M Coupe Differental Mount/Trunk floor Tubular Steel Reinforcemt

[Delaware30]

Inspired by Vorshlag's work, I decided to take on my buddy's Supercharged Estroil M Coupe's trunk floor/diff mount. He was starting to tear the floor out, and with 400whp it wouldnt have been long before destruction.

Here is one of the spot weld tears


Floor cut out...



Plates welded to frame


Template for 3"x3" tubing made



Beam cut to shape and fitted


Beam and capping plates welded in


Subframe and diff test fitted and mounts fabricated





everything painted with POR15 and Sealed with WURTH undercoat



Only took about 2.5 days of work, and my Mcoupe will be going under the knife next week!!!

[jajou318]

Haha, I was looking at the pictures first and I said to myself hey that looks exactly like the work that was done on mine. Looks good man!

[Delaware30]

Haha, I was looking at the pictures first and I said to myself hey that looks exactly like the work that was done on mine. Looks good man!

Yup! Your car was the inspiration. Its done the right way in my opinion.

Thanks for the compliment. Ill post pictures of my car when I do it next week.

[Itsablurr]

Looks great! Exactly how I did mine. I took a bit longer though.... probably about 6-8 weekends what with all the anal trimming and grinding and aligning to get it all perfectly square, aligned, and zero gaps. Impressed at how quickly you turned your project around. Looks great! Did you consider putting a strip of angle stock along the main cross brace to lap weld the trunk floor to at all?

[traumawolf1]

Very nice job....that 3x3 tubing looks bulletproof.

[FinnNiks]

Very nice, very solid solution.

[Delaware30]

Looks great! Exactly how I did mine. I took a bit longer though.... probably about 6-8 weekends what with all the anal trimming and grinding and aligning to get it all perfectly square, aligned, and zero gaps. Impressed at how quickly you turned your project around. Looks great! Did you consider putting a strip of angle stock along the main cross brace to lap weld the trunk floor to at all?

I just welded the floor directly to the cross beam in several areas since the gap was very small. Wurth seam sealer was used to make everything watertight and look good. The angle stock is a really good idea, and I may do that on my car this week.

[Z3MRacer]

I like this repair! There's a certain simplicity about it.

[Mr Bingley]

Looks solid, but I have to ask--if you are going to go to this much effort, why not install the RF kit, I mean it's a known solution--tried and true, and, except for the dual ears, it's basically invisible?

[FinnNiks]

Just curious, did the rear carpet fit afterwards?

[rsalicrup]

Hello, I'm considering buying a M Coupe but of course one of the items that has my biggest concern is the diff mount issue. It isn't a show stopper, just would like to know what I'm getting into. I don't track my cars even though I am gaining interest on it but more like once in a while thing. I do like to go on spirited drives in the mountains though. With that being said, do I need to go to this extremes to prevent a failure and what would be the cost for it to do it? Thanks

[Flak]

Hello, I'm considering buying a M Coupe but of course one of the items that has my biggest concern is the diff mount issue. It isn't a show stopper, just would like to know what I'm getting into. I don't track my cars even though I am gaining interest on it but more like once in a while thing. I do like to go on spirited drives in the mountains though. With that being said, do I need to go to this extremes to prevent a failure and what would be the cost for it to do it? Thanks

It depends on if there is already trunk floor damage on the car you're looking at and how extensive it is. If there is none, running polyurethane subframe bushings is good insurance. I discovered 1 popped spotweld on mine. Not long after I installed poly bushings and have had no popped welds since then.

If the damage is worse, say multiple popped welds, your chances are much higher since the the extra load on the fewer good welds. It'll be a snowball effect essentially. At that point, the RF kit or some other form of trunkfloor/dual ear diff mount is recommended.

[rsalicrup]

I'm basing my purchase on mostly on this. Looking for one without damage of course. Now I also see some with single ear and others with dual ear mount. From my understanding, the dual ear mount isn't original? It is a E36 M3 cover, right? Sorry for all the question I just want to make sure I understand this because as soon as I purchase one, I want to do something to prevent it. Where can I source a RF kit?

[BMWBergy]

Where can I source a RF kit?

Why, from Randy Forbes, of course! Randy can also tell you who in (or near) your area has experience performing the repair. Since you're in El Centro, I'm assuming the best bet will be somewhere in San Diego, unless there's experience in Yuma...

[jajou318]

You might be able to find a coupe with the subframe fix already.

And Delaware if you need any measurements my car is apart (6speed time) Dont think that you will since that first one looks like it came out quite nicely

[Flak]

I'm basing my purchase on mostly on this. Looking for one without damage of course. Now I also see some with single ear and others with dual ear mount. From my understanding, the dual ear mount isn't original? It is a E36 M3 cover, right? Sorry for all the question I just want to make sure I understand this because as soon as I purchase one, I want to do something to prevent it. Where can I source a RF kit?

Any e36 dual ear cover will work. Though I believe you need to source a new reluctor wheel (speed sensor) if you're putting an e36 cover on an M diff. I'm told that if you have a non-M diff, the e36 cover will work fine with the stock reluctor wheel.