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Old 01-03-2011, 12:42 AM   #1 (permalink)
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Default How to Replace a Rear Lower Control Arm Bushing

Just finished installing a set of MS6 struts/shocks and springs on all four corners, and everything went relatively smooth until I got to the rear drivers side. When trying to remove the spring, I found that the 15mm bolt had SEIZED to the metal sleeve inside the lower control arm bushing, so I was unable to remove the bolt and drop the control arm/spring cup. Since I started on this project on New Year's Day and had to get my DD back on the road by Monday, ordering a new control arm wasn't an option. Necessity is the mother of invention, right?

I searched but couldn't find anything to help, discovered that they don't make a bushing kit for this (which sucks!), so I decided to make this thread so that fellow 6 owners can have some guidance. . . I did all the hard work for you. MS6 will be slightly different, as their rear control arm is shaped differently (measure the hole in the control arm), but the process is the same.

**********************************************
What you will need (for each replacement bushing):

1 x Duralast FB781 (control arm bushing). I searched 3 parts stores, box by box with my set of calipers and found a reasonable replacement at AutoZone, with some slight modification necessary. Cost = $8.99

1 x Grade 8 (150,000# tensile strength) SAE Hex Cap Bolt, 7/16 - 14 x 3 1/2 (Hillman part number 880203). Cost = $1.39

1 x pack of Grade 8 Hex Nuts, 7/16 - 14 (Hillman part number 880271). Pack of 3 cost $1.04. You may also decide to purchase a locknut (same thing with a nylon insert, but I opted to use Blue Loctite instead).

1 x pack of Grade 8 Flat Washers, 1/2 - 13 (Hillman part number 880258). Pack of 3 cost $1.04

1 x can of Rustoleum black semi gloss

***If you don't think that Grade 8 (SAE - 150,000# tensile strength and zinc coated) is strong enough, then go to Jiffy Fasteners or Fastenal and get something stronger. . .this is completely up to you. It was a Sunday, so I didn't have that option. If I see anything that convinces me that the Grade 8 hardware isn't strong enough, I will update this thread immediately.

***If your bushing is shot BUT you can remove the 15mm bolt, then all you need to do is buy the new bushing, reshape it, and then reinstall.

**********************************************
Tools needed (other than usual):

Various sized pry bars

Bench vice

Safety glasses/gloves (safety first!)

Big hammer (hand sledge)

Drill w/a 1/8" bit (slightly larger is ok)

Dremel with a cone shaped bit that you can use on metal

Vice Grips

Angle grinder

Bench grinder - I don't have a bench grinder, so I attach my angle grinder to my bench vise to make a make-shift bench grinder. You will need this when modifying the new bushing to fit.

Large C Clamp

**********************************************

Step 1 - Remove the old bolt and welded nut. First you will need to use your angle grinder and cut the head off of the 15mm bolt. Once you have cut it down flush to the trailing arm assembly (which surrounds the control arm and bushing), use your Dremel and grind the bolt out as best you can (without destroying the hole in the trailing arm). Do the same to the welded nut on the other side.


This is the bolt/bushing in question, although the picture above is from a Speed6.

Step 2 - Once you have the bolt trimmed down and recessed slightly, do whatever you can to get the control arm free from the trailing arm. This took my brother in-law quite some time. . .very frustrating, but stay with it. We had to give up late last night due to fatigue and cold (garage floor), but I got it out the this morning after 30 minutes.

THIS IS THE HARDEST PART OF THE JOB!

You will probably have to bend the trailing arm in order to get the control arm to drop, but you can hammer it back into form when you reinstall the new bushing. Try your best not to tear the steel on the trailing arm when you pry on it; bend the trailing arm sides outward enough so that the bolt can drop out of the hole.

Step 3 - Remove the old bushing. I used a my C clamp and a 17mm socket to press the old bushing out of the control arm. Put the socket over the remaining part of the exposed bolt, and put the other side of the clamp against the control arm:



It will help if you drill around the perimeter of the bushing with a drill bit (1/8) and spray some lubricant in. Force the bushing out with the C clamp press, and I ended up twisting it the rest of the way out with the Vice Grips. The bushing will look like crap.

Alternately, you can use a torch and melt the bushing out, but be advised that graphite impregnated rubber is toxic when you burn it. . .

Step 4 - Modify the new bushing to fit. The diameter of the rear lower control arm bushing hole is approximately 35.42 mm, or 1.394 inches, and the length needs to be approximately 2.00 inches. The FB781 bushing is slightly larger in diameter and length, so you will need to modify both. Go over to your bench vice and lock the bushing into place. Grind the FB781 on both sides so that you have the desired length:



In the above picture, I had used the grinder on the right side only. Try to keep both sides as even as possible because the bushing is tapered on both ends, which is how the OEM bushing is designed.

When you finish, it should look something like this:



Now, mount your grinder to your vice (or use a bench grinder is you have one), and slowly grind the diameter down as evenly as you can. It helps if you roll the bushing upward between your fingers as you grind on it so that you don't cause flat spots on the bushing. It doesn't have to be perfect, but you want to decrease the diameter of the bushing to approximately 35.1 mm. Slightly larger will be harder to install, less than may have some play in the bushing when installed. Make fine adjustments as needed. Finished product:



Step 5 - Install the new bushing. Your C Clamp and the socket will come in handy again, and you might find some Vaseline or axle grease may help you get the new bushing into place:



Step 6 - Reconnect the rear lower control arm and the trailing arm. Use your new hardware, with the washers on the outside. My trailing arm was abused quite a bit, so I opted to use 2 washers on the rear side of the hole (bolt head) and one on the nut side. Use some blue Loctite on the nut, or a lock nut if preferred. Torque the bolt/nut to 32-39 lb/ft. I didn't take a picture of the final assembly because I was so happy to be finished.

Use a big hammer to reform the trailing arm back into shape. . .forgot to write down this measurement, but you can get it from the other side of the car.

Hit everything (other than the bolt threads) with the black paint, especially anything that the angle grinder might have touched when you were grinding the old nut/bolt off.

Step 7 - Test drive. After a day or two double check the torque on the bolt/nut.

There you have it!
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Old 01-05-2011, 02:55 PM   #2 (permalink)
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Just wanted to comment that the replacement bushing is working great, and no issues with hardware either. Ran my 6 through one of my favorite twisty back roads that I shred in my Z, and the 6 did great.
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Old 02-13-2011, 02:03 PM   #3 (permalink)
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Just wanted to post an update after driving on the new bushing for over a month. No problems at all, and after tire removal and inspection of the replacement bushing everything looks tip top.

Curious if an admin would make this a sticky, as it is a very feasible and cost effective option for the rear control arm bushing versus the complete replacement of the rear control arm.
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Old 04-20-2011, 06:25 PM   #4 (permalink)
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Great write up! I will have to do the same thing soon.
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Old 05-01-2011, 11:48 AM   #5 (permalink)
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A bump of sorts I guess. . .the pictures were missing for some reason, so I copied/pasted the code back in.

An update also - It is May 1st and everything is still working/no issues at all.
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Old 05-07-2011, 09:22 PM   #6 (permalink)
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Got mine frozen in the bushing hole too, driver side. The impact wrench can loose the bolt by 3-4 turns, even with a ratchet by hand I can move it. Then the bushing sit on the bolt head side and pull back any shot of impact wrench like hammering on a spring. If I force it with a long force bar, the bushing entirely turn into the lower arm and because the bolt can't escape from the hole, it split the lower arm fold. I'm wondering why the bolt is free in the bushing for 2-3mm and then stick in it.

Nice write up! :-)
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Old 05-11-2011, 03:51 PM   #7 (permalink)
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BTW, a new lower arm is around 75$ at the dealer. So if you are not stuck on a Sunday night and you can wait 2-3 days for the part, you better order a complete arm than building a new bushing. I'll get mine tomorrow.
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