Dropping front crossmember, any guidance?

[jaredmac11]

I was reading through the Haynes manual. It seems like they recommend taking out the struts, keep the front end whole and going that route... but is it possible to just unbolt the wishbones, maybe move or remove the brake lines and drop the cross-member? The motor mounts are already removed.

I guess the thought is either I can defer rebuilding the front end and just remove the entire thing or remove the crossmember by itself and plan a front end rebuild.


I was hoping to get to the front end rebuilt down the road but I honestly havent even started to look at the what and how much to replace.

Anyone go through this recently and have any input?

[epmedia]

Depends on what you're trying to accomplish. When I replaced my bent front subframe, all I detached is the items that directly attach to the subframe, ie: rack, lower ca's and engine mounts.

[320iAman]

Front Axle Carrier which is bolted into Frame Carrier,, I'm not nit picking just using the vocabulary BMW Service Manual uses, The Blue Book. Robert read my mind,,that is exactly what I was thinking.

Randy

[jaredmac11]

The manual is just calling the cross-member the 'front axle support'. BMW/shop lingo aside, I think I got the gist.

I dont really want to put in money for a front end rebuild right now, focus is getting the engine in and running. Im afraid if I take on too much I'll get in over my head. I could easily throw $600 at that rebuild, another $500+ for the rear end, then $300 at the shifter, you get my drift. I sorta have to pick and choose.

Long story short, I was planning to follow your path, just wanted to check out my logic before I started turning bolts.

[epmedia]

Just a tid-bit: it's not uncommon for the front subframe bolts to come loose. It's highly recommended to use thread-lock on these bolts.

[wally509]

Another tid-bit: since you mentioned the Haynes Manual and front cross member bolts, be aware Haynes has a typo in the torque spec for those bolts. They show ~145 ft-lbs which is obscenely high. I don't know what the actual spec is off the top of my head but do a search here and find it before you strip/break the weld nuts in the frame rail.

[cgifool]

If you're just trying to rebuild the suspension, you don't need to remove the subframe at all. Just check that those bolts are tight as recommended earlier.

Remove the front wheels, unbolt the calipers and hang them up from the brake line bracket with a piece of coathanger (unless you're going to replace the rubber brake lines too, in which case just detach them and put a little rubber stopper over the metal line to keep it from dripping all over the place.) Remove the brake rotor too.

Use a come-along secured to the ends of the front sway bar to pull the ends in very slightly, and relieve the tension they put on the control arms before you try to remove them. You should be able to then detach the tie rods from the control arms, unbolt the control arm from the subframe, and finally remove the top strut-bearing nuts, and pull the whole control arm/strut assembly out as one unit.

Since the assembly is kind of heavy, I supported the whole thing with a floor jack under the control arm ball joint while I loosened the strut mount nuts, and then was able to lower it out of the car in a controlled fashion (same with reinstalling). Very hard to lift the things up with arms alone and hold them in place while you get the nuts started on top..

[jaredmac11]

The main goal is to drop the cross-member to send to the welder for modifications for the M42 swap. Right now, I have an M42 suspended over the crossmember but nothing is attached to the subframe from an engine perspective.

I am considering either dropping the whole front end, like you are stating (I think) or removing the crossmember and keep the front end mostly assembled.

To be honest, I've done neither so I dont know which would be best or easiest. I feel like it would be easiest to detach the steering rack and detach the control arms from the crossmember and that's it.
On the other hand, if I drop the entire front-end, I can get a better look at it all and convince myself to drop the $$$ to rebuild it.

[jaredmac11]

Not too much fuss on that one. It was pretty easy. Decided to just get the crossmember out and worry about the front end later. (it will need to be done, lots of old rubber) Since the engine is already out, I had easy access to the steering rack. From there it was just getting the control arms out from the crossmember.

I'll tell you what though, those bolts holding up the cross member to the frame carrier were loose. I read what you said and expected to not have to use the breaker bar, but they felt hand tight almost.

[epmedia]

Not too much fuss on that one. It was pretty easy. Decided to just get the crossmember out and worry about the front end later. (it will need to be done, lots of old rubber) Since the engine is already out, I had easy access to the steering rack. From there it was just getting the control arms out from the crossmember.

I'll tell you what though, those bolts holding up the cross member to the frame carrier were loose. I read what you said and expected to not have to use the breaker bar, but they felt hand tight almost.

I want to make sure that you do have some support under the car, because it can tip while the CAs are unbolted from the subframe...

Yea, those loose subframe bolts; both of my '78s had loose bolts too. I'm sure the common 'shimmy' had something to do with that on mine at some time.

[jaredmac11]

Yes car is still jacked up with a set of tires ready to catch. I don't mess with that much. I'm almost certain the shimmy is to blame for that.

[320iAman]

On that torque wally mentioned as ridiculous ,, these are M10 Bolts x 100 , x 28mm,, if 8.8 grade recommended torque is 55 ft lbs, 10.9 -75 ft lbs, 12.9- I'd quess around 90-95 ft lbs as M10 is 17 mm socket size. Grade of Bolts makes a huge difference in recommended torque. Dont settle for 8.8's 10.9's are much stronger and 12.9's stronger than 10.9's and harder to find.. I have 12.9's for the brake caiipers and had to order them from overseas.....

Randy

[epmedia]

On that torque wally mentioned as ridiculous ,, these are M10 Bolts x 100 , x 28mm,, if 8.8 grade recommended torque is 55 ft lbs, 10.9 -75 ft lbs, 12.9- I'd quess around 90-95 ft lbs as M10 is 17 mm socket size. Grade of Bolts makes a huge difference in recommended torque. Dont settle for 8.8's 10.9's are much stronger and 12.9's stronger than 10.9's and harder to find.. I have 12.9's for the brake caiipers and had to order them from overseas.....

Randy

I think those specs are closer for the 12mm thread size.

10mm should be closer to this:
(this is from a generic chart, this is *not exact for the subframe bolts)

10mm
grade: ft lbs
8.8: 33, 10.9: 47, 12.9: 57

[320iAman]

Your right Robert, Thanks- Its not ft lbs,, its Nm,, Class M10 Grade 8.8 55 Nm , Grade 10.9 75 Nm, Grade 12.9 ~ 90-95 Nm, which is 40.5 ft lbs,55 ft lbs 66-70 ft lbs , its in torque charts, I should have read that chart more carefully and not assume- ft lbs..

Randy