Please Help: Rear Subframe cracked?

panoptio · 06-23-2007, 10:35 PM

I want to buy this 87 325is. And from what the seller told me is that the rear subframe is cracked? I have no idea what this means. He said some round piece that connects the driveshaft to the body? Is this fixable and is it really expensive. Thanks

FuryriderX · 06-23-2007, 11:10 PM

maybe the center bearing on the driveshaft? i dont know how difficult this is....pretty sure its fixable though, depending on what and where its cracked.

Axxe · 06-24-2007, 05:15 AM

Subframes on e30's don't crack. This is no E36

.

It's probably driveline related, CSB, flex disc, etc.

static · 06-24-2007, 02:37 PM

Quote:

Originally Posted by Axxe

Subframes on e30's don't crack. This is no E36

.

It's probably driveline related, CSB, flex disc, etc.

subframes on e36s don't crack either. The mounts where sheetmetal meets the subframe is what tears away if no reinforcement plates are installed.

**NickP** · 06-24-2007, 04:52 PM

He may have meant that the rear subframe bushings are cracked.

BmW1819 · 06-24-2007, 10:11 PM

yea it's prob the cross memeber mounts

take to shop that no bmw's before you get ripped

oldskool3 · 06-25-2007, 11:55 PM

A center support bearing for the driveshaft is ~$40 and a flex disk is ~$90 (at least in Ottawa) plus install. If you aren't sure what he is talking about take it to a mechanic. But if either of those things are really bad the car will shake badly while driving.

panoptio · 06-26-2007, 10:58 AM

This is the best pic so far. What do you guys think. The red line is where an attempt to weld is

oldskool3 · 06-26-2007, 11:20 AM

Looks like the rear subframe. Can't believe it cracked in two places. Depending on how cheap the car is you could pick it up and swap for another used subframe but its a pretty big job. Call around to bmw specific places like bimmersport and get an estimate for the work. Im sure you could find a used subframe on here for cheap.

panoptio · 06-26-2007, 12:15 PM

I called around one guy told me 2500$ i was like WTF thats insane. Thats more than the car is worth

oldskool3 · 06-26-2007, 01:06 PM

how much does the guy want for the car? I live in Ottawa so I don't really know any shops in the GTA but everyone says that bimmersports is awesome in mississauga. Give him a call and see what he quotes you. He seems to be pretty farily priced from what ive heard. The shop number is 905-670-9200 plus he's a member and sponsor of maXbimmer

Vincas · 06-26-2007, 07:05 PM

I had the same problem on my 85 325e, I bought the car with it... The rear subframe rusted out and broke on the drive side of the driveshaft tunnel. This cuased the entire rear suspention to sag and it looked like I had a masive amount of camber on the back wheels. I went to BMW and they said a new subframe was $1300, so I decided to install a temporary fix.

I installed a temporary fixed by buying a piece of 1/8 thick steel 1.5 inches in with by 4 feet long. I cut notches in it and welded the notches so that I could curve the piece of steel to the forward arc of the rear subframe. From there I installed it on the car by forcing the subframe back togther so that the crack was closed. Then I drilled holes in the frame and bar and installed it using 1/2 threaded rod and lock nuts. I drove the car like this for 8 months.

I found a rear subframe in very good condition at Cookstown Autowreckers, I pulled it out myself and paided $100 for it. Now the installation is quite a bit of work, it took my an entire week end to pull the old one out and install the replacement. This included installing new rear subframe bushing and trailing arm bushing.

I can go into extreme detail if you so wish as to how to go about doing all of it if you so wish.

Striker · 06-26-2007, 10:34 PM

I have snapped a half shaft into two with my 87 325is in 1998 and my sub frame stood up to the torture. Though they are light, they are a two piece component welded together.

The sub frame endure torsion (twisting) forces nothing compressive or tension so they should not fail by cracking.

What you might have seen is the seam where they two pieces of metal joins and the overlapping metal looks like a crack. I have attached a pic of my sub frame with drawings on it. Since it's difficult to tell from your pics what the crack looks like, indicate if it's a crack looking like 1 or 2 with reference to my pic.

Either way, thats a very easy fix welding two metal patches shaped closely to fit the profile of diff mounting area, you do not need another sub frame. If the welder is good he can mig weld it without using a patch once there is no rotting around the area.

Though mine looked fine, I sandblasted it, ran a 3/16" bead of welding all around the factory welding, primed and painted it.

Striker · 06-26-2007, 10:54 PM

Front subframes crack where the engine mounts sits. This is caused by torsion forces exerted buy the torque from the engine. If ever you have the engine out, you should reinforce that area.

I made two steel patches and welded them in as shown in the pic., holes have to be drilled for the engine mounts. This is a known weak point on the front sub frame.

static · 06-27-2007, 10:50 AM

Hey Raph, long time no post

hmm you brought up a very good point: once i was examining my motor mounts while having a bright light underneath the car. To my surprise, at one point i saw the light shining through a small slot (maybe 0.5mm to 1mm wide) in my front subframe. I asked Charlie whats up and he assured me that this is because of construction of it and they are all like that.
So you are saying that can be a crack? (it looked a bit too straight for being a crack, more like a split between the pieces of metal constituting the subframe)