What’s with all the control arm mount breaks?

[Runner-Wannabe]

I’m seeing a lot of broken control mount brackets out there. What’s the cause? Abuse? Poor design?

I’m a capable welder, is this a cut and dry repair or is there more to it?

I’m considering picking up a cheap 96 with a decent body. Looks heavily under oiled over the years. Not sure if frame has other issues...I will be looking closely.

Any other bad areas to check?

 

[phattyduck]

Rear lower link mounts, you mean? Its just rust. Not a design issue (assuming all the metal is there). They rust because that's where the salty water sits inside the frame...

-Charlie

 

[Jubsz]

There are seam welds where the rear trailing arm mounts connect to the box frame. I can't speak about the metallurgy as to why oxidation forms at the seam welds but it is clear that it does. Beyond that, the mount that usually breaks off is on the inside of the frame next to the exhaust. This part is relevant because the heat of the exhaust catalyzes the oxidation reaction that causes the rust. That side (passenger) tends to go much sooner than the other side for that reason.

This gen 4runner clearly had issues with frame rust, as with all Toyota trucks of the era. Again, I can't speak to the metallurgy or chemically why that happens. It is clear where it happens with these trucks becoming 20-25 years old. Mine didn't break off but I just had it welded up the Safe-T-Cap kit and POR-15'd all over. If you need to patch yours, google Safe-T-Cap for the kits that they make. you can buy pre-fabbed frame portions to purchase and weld in.

 

[Runner-Wannabe]

Thanks guys, they are definitely broken. Almost torn right off both sides. Right along the weld seam.

And correct, they are the link mounts.

So this is rust driven failure?

The underside has a heavy layer of cake everywhere. Like dirt stuck to underoiling

 

[brillo_76]

The upper control arms brackets snap off too. Mostly do to frame rot. What can contribute to.this is bad bushings. Mostly the the brackets are weak from the rot and just come loose or off . This is from my experience only though.



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[Runner-Wannabe]

Will definitely do a lot of poking around. If it looks rough everywhere I’ll take a pass or maybe grab it to part out. It’s had a ton of service done to it over the years so lots of good stuff and new parts in it

 

[19963.4lsr5]

I just repaired my drivers side with a Safety Cap sleeve.


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[phattyduck]

So this is rust driven failure?

The underside has a heavy layer of cake everywhere. Like dirt stuck to underoiling

Yes, rust. If the inside of the frame wasn't coated, they can still rust from the inside out even if the outside was well treated.

-Charlie