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Old 09-02-2019, 08:02 PM
brc5 brc5 is offline
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Don't buy cheap thrust arms for your E70 - graphic images

Just finished a hellish ordeal to replace the thrust arms on my e70.

I did read some threads where people optimistically said 'a few hours to replace both'.

I've done the job before (twice) on E39s so I figure what the hey and got stuck in.

Right hand side : got the star nut off OK. All the DIYs and videos I saw said no need for ball joint separators or pickle forks. Just a gentle tap on the thrust arm and it will pop right out!

NO. Not at all.

First I tapped on the thread. That soon turned into a mushroom. So I got a punch and wailed on the punch with my mini sledge. That drove the punch well into the end of the ball joint thread. On close inspection I realized that the press-fit ball joint adapter was actually starting to push upwards out of the steering knuckle. That ball joint was not letting go.

I gave up and ordered a ball joint separator from Amazon and waited for it to arrive (next day delivery on everything now, it seems). Oh-ho-ho that didn't fit, the design of the ball joint was too wide for the fork in the ball joint. So I had to modify it with a file until it fit comfortably around the ball joint. I tightened and tightened and finally POP. Thankfully the pop re-seated the press fit ball joint receiver back into the knuckle - it had risen up about 5 mm proud.

That covers about 4 hours of work with various thumping, banging, punching, straining and cursing, and riding to the FLAPS to get bits and pieces.

Onto the left hand side. Better prepared this time, going to use the ball joint press right away. Just spin the star nut off. OH @#$(@&**%$ the nut is just spinning on the thread. It didn't take any torque at all to turn, so it's been loose for a while.

On close inspection the outer part of the nut that bites the thread has completely broken off and disappeared. Part of the thread from the ball joint is sticking out like a piece of broken wire.

Ordered a new dremel (clone) from Amazon plus a set of dremel (genuine) cutting discs. Next day delivery again. Straight into cutting, and I have to cut more than 50% of the nut off in chunks to get it off. I broke too many of the cutting discs so in the end I got the chisel out and smashed the rest of it off in frustration.

Carnage. Hard to see with the remaining shrapnel, but the removed nut was much smaller than the one from the other side (intact). The disc is the washer that attaches to the nut but turns independently.

So then straight on with the ball joint remove. Crank, and crank, and crank, and crank. Holy crap the thing is bending backwards. I try a tap on the arm and the steering knuckle to see if it will help - the ball joint remove flies off like it was shot like a cannon and embeds in the side of a cardboard box (the amazon one the dremel came in). I look at what happened and the soft end of the ball joint thread has rounded off like a half mushroom and let the ball joint remover free. I get the dremel out again and chop a 5 mm slice off the ball joint thread to get it square again. Spraying penetration oil on the joint and lube on the threads, I crank it down again. It gets to within 10mm of the end of the thread for the remover. Then the rod for the hinge in the ball joint remove shears the end off right where the little ball bearing is. Crap - I didn't have it pushed through far enough. Luckily if I push it right through, there is enough to hinge off. I crank it down again. No budging, so I leave it over night. Which doesn't work - i was hoping to see a popped ball join sitting on the garage floor.

With the nut gone, you can actually see the stripped threads. I didn't do that, apart from just turning the nut with the right size socket.

Next day with a fresh head and determination I take it off and inspect everything. I decide that the other one came off with a combination of bashing with the punch and clamp. So I spend 10 minutes bashing with the punch in the end of the ball joint thread. The press-fit receiver starts to lift out like the other side did. Stopping that, I try the pickle fork. But it cant' go far because of the design of the steering knuckle which doesn't allow you to go past the joint. So I get the dremel out and chop the end of the pickle fork off, leaving it blunt but allowing it to go further. I wail on that for a bit but realise the soft crap fork is just digging into the side of the ball joint ridge and not actually lifting anything.

So then I remove the sway bar end link for more clearance and bash the ball joint remover on, file the end of the threaded rod on the ball joint for a bit more purchase and crank, and crank, and crank, and crank on the end ball joint remover. Finally when I think I can crank it no more, a humble little 'pop' and the whole thing falls off.

My diagnosis is this - someone replaced these arms before (what do they last, 20k?). The LHS had a proper sized star nut, but the RHS had one half the size, which had broken off. I have never seen thread shear off and never seen ball joints get stuck like that. I think the problem was soft metal that formed down into the taper, or maybe it was just over-torqued to begin with.

Crap (black) and Lemforder (silver). Did BMW ever make black suspension arms? I've only ever seen silver.

On inspecting the old thrust arms, they are heavier and just lower quality all round. Did the cheapness of the part cause the thread to strip and cause the removal being so difficult? I don't know for sure but I wouldn't save 50 bucks with a part like this. Meyle and Lemforder aren't that expensive to get, so spend the slight extra.

Limiters limiting the fun

Last edited by brc5; 09-02-2019 at 08:04 PM.
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