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Discussion Starter · #1 · (Edited)
On a 2001 330ci, with the differential out and the subframe installed but not torqued, I want to torque the inner pivot bolts (15 and 8 below) on the rear upper and lower control arms, given this easy access. However, I understand these should be torqued in the loaded position. The problem is the car is on jackstands with the entire rear end removed, including the trailing arms (overall project: replaced lower control arms with adjustable ones; replaced all 13 rear bushings; replaced driveaxle/differential seals and diff cover gasket; repairing inner driveaxle bellows; replaced flex disc/giubo, trans rubber mounts, driveshaft center mount; etc.).

My question: Is there any handy way to estimate where the loaded position would be for these control arms? In other words, can you torque these bolts ***8220;under load***8221; but with the car on jackstands? I'm sure it would be easier to estimate/eyeball by installing the trailing arms, attaching the control arms, and jacking it up to what looks like a loaded position, but if I can torque these bolts now with all this access I***8217;d like to do so.

Thanks in advance for any advice.
 

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2004 325i automagic
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When I replaced all the rear suspension mounts/bushings, I don't recall having to worry about 'preloading' the inner control arm bolts. They will pivot in any case. I think you want to fully torque the subframe first then bolting in the control arms, then install the rear differential, but that's from memory and I don't have access to my notes right now.

I do remember the rear diff bolts have specific alignment sequence to assure it's lined up properly with the driveline.

Look up the procedure on www.newtis.info. Enter last 7 digits of vin#, then search for rear subframe removal/install procedure.

Edit: To answer your question, pretty sure you have to torque the inner control arm bolts with the diff removed. The only preload you need to worry about is the trailing arm bushing bracket, on the front part of the trailing arm that bolts to the side of the underbody.
 

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Discussion Starter · #3 ·
Thanks very much for your feedback, and especially for the introduction to the goldmine that is www.newtis.info. I found some helpful hints about ride height there and although it does seem the control arm angle is irrelevant to the torquing of those pivot bolts, I think I'll try to eyeball them nonetheless based on these measurements. That is, if I can decipher some of the turns of phrase, like, measuring from the "bottom middle of rim flange" (bottom middle?).

As for the diff getting in the way, yes, that's what I'm trying to avoid, though I have seen statements that it just needs to be moved a bit to get it out of the way. I just want to get these tight before I even put the diff back in.

Re. the trailing arm reinstall at the front bushing and bracket, I marked up all the pieces pretty good and am following Mango's lead as closely as I can, so hopefully it will all line up.

Thanks again for the tips, and www.newtis.info!
 

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Discussion Starter · #4 ·
As I tighten the inner pivot bolts it becomes clear that the position of the control arms does matter. They do not pivot freely when tightened so those inner rubber bushings will wear improperly if the arm is not in "normal position" under load. I'm going to spend more time trying to estimate that preload position based on newtis.info measurements for ride height.
 

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A case of how people go "Thanks! I'll do that!" to the very first reply they get.

That reply is false. On any car: Kia, Ford, Hyundai, Ferrari, you DO have to worry about the inner control arm bolts being torqued at a static "at rest" position. That's suspension 101.

Put the car up on ramps, wheels on, resting naturally, then torque them down. If you want to eye ball them and do them with the wheels off and suspension loaded (like with a jack or something) you can do that too, but it won't be as accurate.

you'll tear the bushings right off, or wear them a lot faster, if you torque the bolt while drooped. They are not spherical balljoints.
 

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Discussion Starter · #6 ·
Thanks for weighing in on this. Yes, tightening these quickly confirms the inner rubber bushings get locked in place and thus the importance of torquing the bolts with the arms in normal load position.

Question: If I reinstall everything (again, only the subframe and control arms are in place now) so that I can actually lower the wheels onto ramps so the car is "resting naturally," would I be able to reach that top inner bolt with a torque wrench? Or would I have to re-loosen and move the diff back out of the way again? If I'm only torquing that bolt and not removing it, can the diff stay in place? Is so, I would do it that way.

Thanks again for all the feedback.
 

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If what you are asking is can you leave the bolt loose and final torque it on the ground, yes you can. That's how you're supposed to do it. I don't know if you can fit a torque wrench in there though. honestly i wouldn't worry if all you can do is tighten by feel. it's a small bushing. doesn't take that much torque to where you can'd to it by hand. I'd get a feel for the torque by using a wrench and try to mimic that by hand
 

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Discussion Starter · #8 ·
That's exactly what I'm going to do. Thanks for the sanity. I get a little carried away with torque values. Which I know you're not discouraging, but I need to let my hands go, as Teddy Atlas would say, and get this thing buttoned back up. Thanks again.
 

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Yep. The only part of a car that's super critical for a torque wrench is the head bolts, really. Maaaaybe wheel bearings. But with enough practice, (like if you're a pro) you probably start to get a feel for how tight a bearing should be.

Everything else it's just more or less of a guide. i'm sure ou know this.

Don't get me wrong I use a tq wrench where possible but sometimes it's just unnecessary or not practical/possible to use a torque wrench. You can easily tighten suspension stuff by feel. What is that arm bolt? maybe 45-60 lbs? (it's been forever and i forgot) that shouldn't be that hard. get a wrench on the end of your wrench if you need a bit of leverage. just needs enough to lock the bushing in place. maybe put blue loctite if you want.
 

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This is awesome, Precisely the issue I'm facing. Torqued the upper inners and then stared at them for about 17 hours with something nagging at me about how they were way too bouncy and reboundy when I moved them up and down. But I had the same fear: I could never get a torque wrench in there once down and put together. Knowing we can use common sense for tightening is great.
 

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When I replaced all the rear suspension mounts/bushings, I don't recall having to worry about 'preloading' the inner control arm bolts. They will pivot in any case. I think you want to fully torque the subframe first then bolting in the control arms, then install the rear differential, but that's from memory and I don't have access to my notes right now.

I do remember the rear diff bolts have specific alignment sequence to assure it's lined up properly with the driveline.

Look up the procedure on www.newtis.info. Enter last 7 digits of vin#, then search for rear subframe removal/install procedure.

Edit: To answer your question, pretty sure you have to torque the inner control arm bolts with the diff removed. The only preload you need to worry about is the trailing arm bushing bracket, on the front part of the trailing arm that bolts to the side of the underbody.
Well, shit! That site got nuked. I'm right at that point where all this matters. Subframe back in, RTABs in place in pocket, upper and lower arms in and attached to the subframe but not to trailing arm yet. Diff still out. I didn't know there was a special alignment procedure for putting it back in.
 

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As a generality we almost always place the car onto the alignment rack, roll it forward and back a little (lets the suspension return to normal height) and then tighten all of the up/down suspension pivot bolts.

Cognizant that 99 out of 100 do not have a rack...
 

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One could also:......

Measure the center of any/each wheel position when the car is on a level surface. After repairs, jack that corner (under the respective arm) until the above measurement is achieved. Tighten the pivot bolts.

Move onto the next corner.
 

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Mango was right about the suspension bushings. Rubber suspension bushings need to have the proper preload, or they will be unhappy. As mentioned above, that means doing the final torque with the suspension at normal ride height.

That said, most non-rubber bushings (polyurethane, UHMW, Delrin, etc) don't need preload. Those bushings are usually designed to rotate instead of deflecting. Just FYI.
 

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Mango was right about the suspension bushings. Rubber suspension bushings need to have the proper preload, or they will be unhappy. As mentioned above, that means doing the final torque with the suspension at normal ride height.

That said, most non-rubber bushings (polyurethane, UHMW, Delrin, etc) don't need preload. Those bushings are usually designed to rotate instead of deflecting. Just FYI.
This.

Someone said above that the bushings would pivot regardless and that's incorrect. If not tightened in the correct position rubber bushings will tear themselves apart as they're being required to flex well outside of their designed range of motion.
 

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Drive the rear wheels up on blocks or something and crawl under there with a wrench to get them at ride height. Don't worry about a torque wrench.
 

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^^^
That.

The inner uppers should be the only ones that you can't get a torque wrench on easily IIRC.
with the diff back in, correct?
 
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with the diff back in, correct?
I haven't yet dropped my subframe, but I have done all the suspension bushings back there. Yeah, there's no way to have the car on ramps with suspension loaded with the subframe out, but you probably could put it in without the diff installed, torque the suspension bolts, then drop it back out to install the diff. I don't know if that buys you anything though.
Like I said, it's really only the upper inners that you can't get at with a torque wrench with the diff in place.
 

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with the diff back in, correct?
Yes, with the diff back in you can't reach the inner uppers with anything except a wrench, although an extra long wrench would likely get you to the correct torque.

Like VpointVick mentioned, a work around might be leaving the diff out, lowering onto ground and rolling car back and forth a little to settle the bushings (mindful of suspended axle shafts). Then lift car onto Rhino Ramps so you could get underneath to torque things correctly, before installing the diff and following the correct driveline torqueing sequence.
 
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