Michigan pothole + alum SFB = torn subframe

[lowmile93]

Well... I learned that solid subframe bushings and potholes don't mix.. I actually tore one of the subframe corners (100% fracture) at the passenger rear mounting location. Anyone had this happen before? If so, any suggestions for repair? I don't plan to replace the entire subframe, but I just wondered if anyone has any experience/suggestions on this matter.

Thanks

 

[NotSoSlowSHO]

That has nothing to do with the bushings.

It has a whole lot to do with age and rust.

Curious though, did it have the recall performed?

 

[Cobraii976]

I live in michigan and have AlSFB's and I've hit a pretty nasty *** hole so far as to bend the inner tie rod, But I did not damage the subframe. I would be curious to know what bushings your using?

 

[lowmile93]

Many factors...

Well, to answer the questions, I did do the 'recall' fix for the front two mounts by replacing the nuts and bolts, but I could not bring myself to cut holes in my floorboards, so I did not replace the rear nuts before installing the aluminum SFB's. I am using a set of aluminum SFB's that I believe originated at ShoNut, but I got them second-hand on eBay.

I agree that the rust and age didn't help the situation, but replacing the stock rubber bushings with solid ones will undeniably increase the local loading on the subframe in the vertical, lateral, and fore/aft directions.. which aided in the quick demise of my subframe.. I plan to weld in some support straps next weekend and watch the road more closely from now-on...

 

[MI-SHOFEAR]

Im with dave here. I live near detroit and the potholes are the size of civics and I have never had a problem. I think a new subframe and holes in the floorboards are in order here.

JEff

 

[luigisho]

Cracked subframes are uncommon but not unheard of. Especially in *** hole and heavily salted states. I know Kirk had mentioned welding up more than 1 broken subframe. Maybe you can reach him or Chris (Mr. Anonymous) for more info.

 

[Racer X]

Im with dave here. I live near detroit and the potholes are the size of civics and I have never had a problem. I think a new subframe and holes in the floorboards are in order here.

JEff

Cosigned.

FWIW, I live in the NYC metro, and I have Aluminum SFB's, and I've hit potholes large enough to rip my balljoint almost out of the socket and wreck an inner tie rod end (I **** you not), and my subframe is aligned exactly where I had it when I replaced the transmission.

Remember, use a 3" hole saw to get in there.

 

[lowmile93]

I appreciate all the input from everyone. I plan to make weld / reinforcement repairs this weekend. I'll post afterward to say how everything turned out. I'm sure a little extra strategically-placed steel will solve the problem..
My SHO is my winter-only vehicle, so I'm not even considering replacing the subframe.. I'll just have to make some robust repairs.

Thanks again.

 

[NotSoSlowSHO]

Wait, the actual subframe tore?
I was under the impression that the subframe mounts pulled thru the unibody.

If the actual subframe tore, depending upon the extent of the damage, I would highly suggest finding a replacement instead of repairing your existing. In such a situation, welding isnt always the answer (unless it is shot-peened afterwards). The subframe is a very high-load item. I wouldnt chance it.

 

[lowmile93]

Wait, the actual subframe tore?
I was under the impression that the subframe mounts pulled thru the unibody.

If the actual subframe tore, depending upon the extent of the damage, I would highly suggest finding a replacement instead of repairing your existing. In such a situation, welding isnt always the answer (unless it is shot-peened afterwards). The subframe is a very high-load item. I wouldnt chance it.

Yeah, it was the actual subframe that tore; a vertical crack on the outboard side of the passenger-rear attachment (I'll post pictures later). I normally would go the safe route and start looking for a replacement subframe, but I have access to a hoist and I know a welding wizard who owes me a favor... He does racecar fabrication for a living, and does excellent work.

But just in case it doesn't work out, anyone know a source for a replacement subframe? Or possibly a cost guestimate?

 

[lowmile93]

Bushing diameter?

In preparation for the repairs I plan to make this weekend, I have to machine some reinforcement 'washers' to help restructure the fractured subframe. Does anyone know the inner diameter of the mounting holes in the subframe (or the outer diameter of a typical aluminum SFB)?

 

[TimboSHO]

My rusty car and ALSFBs hasn't had any trouble in the Michigan potholes yet. I can get you a measurement of the outer diameter of the ALSFB when i get home late tonight/early tomorrow.

 

[lowmile93]

My rusty car and ALSFBs hasn't had any trouble in the Michigan potholes yet. I can get you a measurement of the outer diameter of the ALSFB when i get home late tonight/early tomorrow.

Thanks for the response. I guess I'm one of the unlucky ones who hit a pothole 'just right'. I didn't mention previously that a chunk of concrete must have flung out of the pothole when I hit because my floorboard got dented and the fuel filter was punctured. And to add insult to injury, I was driving my truck after this happened and broke 3 of 5 wheel studs on one of my wheels while taking an exit ramp a little too fast (forgot I wasn't in the SHO..).

Just to clarify the diameter that I'm looking for, it's the smaller of the two outer diameters on the lower piece of a set of AlSFB's. In other words, it's the diameter that fits inside the surframe bore. Any help would be appreciated. If you can't get to it until tomorrow, then don't worry about it because I'll already be on my way to the welding shop with no internet access.

Thanks.

 

[Ace]

Cracked subframes are uncommon but not unheard of. Especially in *** hole and heavily salted states. I know Kirk had mentioned welding up more than 1 broken subframe. Maybe you can reach him or Chris (Mr. Anonymous) for more info.

my first 89 suffered its demise when my subframe broke while i was driving it....right on the passenger side front near the subframe mount...sent the motor right into the strut tower.....

 

[TimboSHO]

The diameter of the top part is 52mm. Just a little over 2". This should be the size of the hole in the subframe, as mine fit perfectly into mine. Hope you get this in time.

 

[lowmile93]

We completed the rapairs on the subframe this past weekend, with some help of a 220 MIG and some 1/8" cold-rolled steel. We had to cut off the entire mounting ear of the passenger side rear attachment point and build one from scratch, due to the extent of the damage. It is not the prettiest looking subframe any more, but it should be stronger than stock now.. I'd be glad to post before/after photos, but I am unsure how.. (please excuse me, as I am new to this forum)..

Thanks for all the input.

 

[TimboSHO]

I would love to see pictures! To post them on here, you have to have them hosted somewhere else (photobucket, cardomain, superford, msn, etc.), then you just hit the little 'insert image' icon and put the URL in there. I hope that's clear enough to understand.

 

[lowmile93]

Alright, with a little help from TimboSHO, here are some before and after photos. Like I said, it isn't the prettiest thing in the world, but certainly acceptable for a winter car.. Thanks again for all the input.


Torn POS
SFB Removed
Cut off tab
Repair 1
Repair 2
Repair and paint

 

[TimboSHO]

Wow, that looks really nice! Now you can list 'reibuilt subframe' as one of your mods

 

[NotSoSlowSHO]

holy smokes thats a lot of rust

Good to see you got it fixed. But I would still be worried about the connection beween the new portion and the existing subframe. If corrosion was that bad at the end, obviously enough to spell trouble, think about how rusty the INSIDE of the existing is.

My goodness Im glad I dont live there... the rust us scary.