shardul

iTrader: (1)

lol never though of that.

if you look at the unibody behind the wheel housing liner it will be clean free from road grime. So if the cut area is masked off some more I think you will fine.

GregMB

Just fill those spaces with spray foam after the repair is completed!!!! J/K.


On a serious note: are the bolts in this DIY a larger diameter than stock, or are they identical to the originals (except for the higher bolt grade and PSI rating?)

Just curious if you needed to open up the through-hole at all to get the new bolts in place.....

Even with a set of aftermarket toe links installed, and multiple alignments I still have a slight rear end "wiggle" under hard acceleration. It's unstable enough that it makes me nervous about doing full throttle 1st and 2nd gear pulls. I don't have the "body thump" symptoms of a broken subframe bolt, but maybe there is still something wrong???


-G

2000UZJ

Yes. It's called 550+ TQ through two back tires. The tires slipping and the open diff shifting power back and forth causes a little wiggle in the rear. The bolts are longer and stronger than the OEM bolts. They sandwich the subframe to the body via large washers instead of the subframe bolted to the captive nut which pulls through the body. For you guys up north, I would treat the underside with POR15 for a little extra protection.

Better yet, your car is about to snap in half. Better send it to me for evaluation .

SICAMG

We Lovvvvve salt here in New England. They spread it around like candy and now even spray it down on the ground to boot .Heading up to Boston soon for a vist. Where abouts are you located, I am in Ct

JoeJErnst

The bolts I used are the same diameter as stock, but they have a different thread pitch and they are about 30mm longer.

If your bolts are not yet damaged, then I suspect your "wiggle" is caused by the sloppy stock rubber bushings and/or the rear tires aren't aligned properly. That's where the rigid toe-link kit would help.

GregMB

Actually, I already have a Quaife LSD installed. The wiggle isn't coming from an open diff....


Do you think the stock rubber subframe bushings are worth replacing at the same time....are they a "consumable" on these cars like door handles and rear tires? . I've got a set of rigid rear toe links (MB Arts) and have had the alignment done about 5 times in the last two years to address this "wiggle"... That's why I am starting to suspect that my issue is elsewhere (like a broken or loose subframe bolt or bad bushing)


-G

55fanatic

Just outside of Boston. I'm in Metro west about 20min outside of Boston

55fanatic

could the wiggle come from airmatic? I mean everyone who makes the switch talks about how much more planted the car feels with coils

2000UZJ

Like I said, send your car to me . One day I'll do the Quaife LSD. Did it make a big difference?

GregMB

With the LSD and the aftermarket toe-links the car really wants the plant the rear hard and launch..... The problem is that it's also doing that "wiggle" at the same time and it makes it hard to stay in the throttle with confidence. Things happen quickly, and a small wiggle could end up being large tail wags that end up being a spin into oncoming traffic.

Really want to get this figured out. Are you guys with 500+RWHP able to just mash the throttle from a dig and go straight (albeit with some tire spin) or are you holding on for dear life making small steering corrections to keep the car pointing straight ahead? There's no point adding my larger crank pulley (and another 70HP) to the car if I'm already too nervous about the wiggles to go WOT....


-G

StarvingArtist

There is a lot of flex in the rear suspension under load. Even with links your wheels could toe out and cause this. Factory specs are drastically toed in and will scuff your tires in 10,000 miles or less. Try toeing them in just a little bit more than they are now.

SICAMG

Just did my bolt replacement. $11.45 for the four bolts and nuts with washers. Took about 2 hours stopping a couple times, welding up the holes and shes good to go with never another worry. Just one more thing to never worry about. Good stuff thanks to the guys on this site!!!

1911jon

Ok...so mine broke today....

How bad is the repair now?

JoeJErnst

I can't tell from your picture if the mount broke or just the bolt. If it's just the bolt, extract the piece that is still stuck in the frame and put in a new one. If the mounting boss ripped off the body you'll need to do the through-bolt method of repair. See my original post in this thread.

1911jon

Ok, thanks for the quick response. Either one seems relatively straight-forward. I am just glad to hear it isn't as catastrophic as it sounds and looks, haha.

1911jon

Turns out the mount broke.

What's the best way to compress the bags?

Will it work to just jack it up by the diff with the wood block and the key turned on, and it will deflate them slowly to where they need to be?

JoeJErnst

The best way is to use STAR to deflate them. If that's not an option you could get a 10mm line wrench and slowly crack open one of the lines at the Y fitting mounted on the rear subframe.

StarvingArtist

That didn't work for me. I didn't have star when I put the k-mac in, and I fought the bags the whole time. There is some kind of valve in each bag that doesn't let the air back out.

JoeJErnst

Now that I think about it, you're absolutely right. When I installed my coilovers I emptied all of the bags using STAR, then I disconnected the Y-fitting at the rear but the rear bags were still putting pressure on the lower control arms. When I disconnected the big hoses at the top of the bags the air all came out then.

I bet there's a way to apply some voltage across the right two terminals in the bag's electrical connector to make it release the air. I have no idea what the voltage would be, or which terminals though.

I guess OP could remove the big hoses from the top of the bags.

1911jon

What's Standard Procedure for the repair on the body/chassis?

BoostedAero

No standard, read the entire thread, lots of intel on how past repairs have been accomplished.

In short, 2 plates of steel are used (above and below) to sandwich the frame and and longer bolts to hold the subframe onto the chassis

/-\ Nut (wheel well area on top
---------- steel plate
^
======= frame
^
---------- steel plate
^
=-=-=-= Subframe
\-/ Bolt (Bottom under carriage side)


*lil more accurate ASCII lovin'*

JoeJErnst

+1 for the awesome ASCII schematic!!

BoostedAero

Thanks for the awesome write-up... I am going to knock this out on my car and my dads designo. Seems like some solid insurance for sure!

E55amg0220

So the links dont seem to be wking anymore to get the proper bolt nut an washer .... whats the proper size an is ARP needed or what grade. Id rather be proactive rather than let a problem arise an then take care of it. An is only the rear sub bolt needing done or is there more than 2? Thanks great write up an good mod especially when i drive extremely aggressively

JoeJErnst

Well, it looks like Marafast was the only company making the bolts in the Class 12.9, and they seem to have gone out of business. The only ones I can find on Google now are Class 10.9, which is the same as the stock bolts. It's still worth doing the modification because the increased tensile strength of the Class 12.9 bolts was only half of the benefit. Using the washer and nut on the top, creating a sandwich, will still prevent the mounting boss from being ripped off your car.

So what you need are two bolts that are M12-1.75 x 110 mm Class 10.9, plus two nuts and washers to go with them. The washers are M12X35 DIN6340 (5mm thick hardened steel).

You only need to replace the rear two bolts of the subframe. They are the only two of the four that are under tension during hard acceleration (because they are behind the axle).

Notes:

1. Make sure you get class 10.9 or better (not 8.8)
2. The threads on the factory bolts are M12-1.25 (fine) but you will drill them out with a 13mm (or 1/2") drill bit, so you can use M12-1.75 (coarse) threads on your new nuts and bolts.
3. I used a 2" hole saw to drill the access port, but you can use something smaller, as long as the 35mm washer will fit through the hole and you can get a wrench on the nut.