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E36 M3 (1992-1999) {Euro - S50 B32 321hp @ 7400 rpm} {U.S. - S52 B32 240 hp @ 6000 rpm}
Total Produced: 71,212 - Years Produced: 1992 to 1999


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Old Mon, Mar-20-2017, 12:26:59 AM   #1
tripitz
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Default Cracked Rear Shock Tower

After having my RTAB pocket and subframe reinforcements welded in, I realized that my right rear shock tower is cracking.

It looks like I have two options... weld in the AKG "repair plate" or replace the entire shock tower. Is the AKG repair sufficient? The cracking is actually very minor right now as the broader area is still undamaged and the holes for the shock mounts still have some integrity. Can I get away with the AKG plate or do I really need to do the full job?

http://imgur.com/a/LrQyo

Last edited by tripitz; Mon, Mar-20-2017 at 12:55:34 AM.
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Old Mon, Mar-20-2017, 12:32:02 AM   #2
westopher
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Default Re: Cracked Rear Shock Tower

How bad is it? Pics will go a long way.
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Old Mon, Mar-20-2017, 12:47:00 AM   #3
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Default Re: Cracked Rear Shock Tower

Link to top and bottom... can see hairline cracks from top and also from bottom. Bigger cracks near the mounting hole.

http://imgur.com/a/LrQyo
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Old Mon, Mar-20-2017, 12:49:14 AM   #4
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Default Re: Cracked Rear Shock Tower

+1 Pics would help. If it really is minor, the plates are likely fine.

Are you on stock, or aftermarket suspension?

Don't forget, the towers don't hold up the weight of the car, so there isn't a huge amount of force on them. They usually fail due to worn mounts, or from blown shocks that let the suspension bottom out and allow big blows to the towers under shock compression. I'd definitely replace the mounts. If the shocks are questionable, it's time for new shocks as well.
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Old Mon, Mar-20-2017, 12:55:16 AM   #5
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Default Re: Cracked Rear Shock Tower

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Originally Posted by fiveightandten View Post
+1 Pics would help. If it really is minor, the plates are likely fine.

Are you on stock, or aftermarket suspension?

Don't forget, the towers don't hold up the weight of the car, so there isn't a huge amount of force on them. They usually fail due to worn mounts, or from blown shocks that let the suspension bottom out and allow big blows to the towers under shock compression. I'd definitely replace the mounts. If the shocks are questionable, it's time for new shocks as well.
This is for a track car build. Going to be running MCS with rogue shock mounts. Not running coilovers in the rear so spring rate won't matter. It's definitely an issue; I'm not sure if I can get away with just welding in the AKG plates or if I have to plan on a full repair.

Pics are linked above.
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Old Mon, Mar-20-2017, 01:09:55 AM   #6
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Default Re: Cracked Rear Shock Tower

I would just weld the plates in for now but I would run a bead along the cracks first and grind smooth. You'll definitely be able to salvage that without replacing the tower
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Old Mon, Mar-20-2017, 01:44:11 AM   #7
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Default Re: Cracked Rear Shock Tower

Agreed. Fill any cracked areas, grind it down, and weld the plates in. That will be fine. Look at it this way, a new tower would have a lot more welding involved than filling the damage you have, and the metal isn't separated and deformed. Right now, everything is lined up as it was from the factory and the damage is very minimal.
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Old Mon, Mar-20-2017, 02:27:33 AM   #8
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Default Re: Cracked Rear Shock Tower

This may seem like a silly question... how do you grind that area? Since most of the damage is from the bottom, it is going to be crazy hard to get to. Do I need one of those long angle grinders and go with something like rolocs to grind it? If so, it may be cheaper for me to replace the shock tower.
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Old Mon, Mar-20-2017, 10:45:42 AM   #9
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Default Re: Cracked Rear Shock Tower

Pull the shock out and use an angle grinder without a shield. For a little more reach in that area from underneath try using a wire wheel.
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Old Mon, Mar-20-2017, 12:12:29 PM   #10
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Default Re: Cracked Rear Shock Tower

Quote:
Originally Posted by tripitz View Post
This may seem like a silly question... how do you grind that area? Since most of the damage is from the bottom, it is going to be crazy hard to get to. Do I need one of those long angle grinders and go with something like rolocs to grind it? If so, it may be cheaper for me to replace the shock tower.
it will absolutely not be cheaper to replace the shock tower. Also if you replace the tower you risk it not being aligned correctly and ruining the car forever. As said get in there with a angle grinder of dremel with a cutoff wheel. If you weld from the top it will be a lot easier to get to
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Discussing Cracked Rear Shock Tower in the E36 M3 (1992-1999) Forum - {Euro - S50 B32 321hp @ 7400 rpm} {U.S. - S52 B32 240 hp @ 6000 rpm}
Total Produced: 71,212 - Years Produced: 1992 to 1999 at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)