Would using hex bolts to replace these allen bolts work?

[xcastaway]

I'm replacing my differential clutches on the Touring, and should have ordered replacements for the allen screws that were practically welded in there. I would have, if I could have found a part number for them. It took everything my HF impact driver had, with me bearing down as hard as I could to try to keep from tearing the heads up in the process to get any of them out. I had to let it hammer away for several seconds before any of them came loose, and the last one, after nearly a minute of pounding on it stripped out totally. I finally had to chisel it counterclockwise long enough to finally break it loose.
The rest are distorted and I wouldn't use them again anyway.

I got a ride to Ace Hdwe this morning, and the closest thing they have in allen screws are 5mm too long, and, looking at it after getting home, I don't think there is 5mm of extra depth for them to fit into. And, from my experience with the local dealership, they probably don't have them and wouldn't try to look them up without a part number anyway.

Ace did have hex bolts the correct grade, pitch and length. Checking with the knowledgeable folks here to see if they might work instead of the allen screws that came out of it, or, alternatively, if somebody can come up with a part number for the correct bits so I can hold the dealer's parts guy's hand for him long enough to see if they have them. The offending items are number 4 in the diagram.



Thanks!

[demetk]

I've done it on an m30 clutch with some Loctite. Can't you use lock washers on the allen bolts?

[xcastaway]

I borrowed a car and tried Home Depot and Lowes before heading off to the dealership. The parts guy was actually helpful and looked the part up. It has been superseded several times and now comes as a hex bolt. A
$5.21 hex bolt. They of course didn't stock them, and the part number he gave me for it is for the same 25mm length as the higher quality Allen bolts than came out I got from Ace for .69. I swear it looks like they are going to bottom out before getting tight, but I may be wrong. I should probably have tried them before giving up on them. I was having a hard time getting in the mood to wrench today anyway. It didn't used to hurt so bad afterwards!

I still need to pull it all back apart to satisfy that nagging uncertainty that I got two of those little washers in the proper order. I found a DIY for my task last night that explained things better than the vids on You Tube had, and I have to be sure I didn't mess it up now, while it's easy to straighten out. I hate building in things that will bug the heck out of me in the future. I have to know for sure.

If they do hit bottom during assembly, a flat or lock washer could do it if it doesn't bottom out right after the 20 mm the original bolts fit into. And I could always go pick up the hex bolts of the right length, since I did get that question answered. So dilemma solved, and one way or the other it will be back together manana.

For anyone doing a similar repair on their diff, this one gives the best explanation of how all those little shims are supposed to go in as any I have found. It's for an E30, but it's the same 188mm diff as 525's use, give or take the odd bit.

http://buildraceparty.com/diy-tech-h...-differential/

[ross1]

Are you talking about the axle/halfshaft bolts?
These deserve some cleaning of the "socket", hammering the bit in fully(a bit of valve grinding paste gives the tool some additional bite) and penetrating oil before attempting removal, at least in the rusty part of the world where I live.
I have a big jar of those bolts from many parts cars. Send me a PM if you'd like some of them.

[xcastaway]

Nope, but thanks. It's the number 4 bolt in the diagram above that I'm after, and one way or the other I have that figured out. The axle shaft bolts I had read could be stripped out easily before the first time I messed with them. That led me to treat them carefully, because they looked like they would be a royal pain to have to figure out how to get out if you were to tear out the allen socket. It's served me well, since they've been apart a few times. I do have a problem getting them torqued, though. My HF allen socket snaps in half about 5 ft-lbs or so from spec. I tested that a couple of times, and settled on around 5 pounds shy, well into cringe territory, just before I think it's going to snap. Again.

[circuit.heart]

Hex bolt heads, at least for my car, would bite into the rubber axle boot and sooner or later tear it.

You can definitely replace with E-torx, it'll help make removal easier in the future.

[xcastaway]

Oh, boy, what a clusterbleep this has turned out to be! I had been planning on doing this repair in April, once it warmed up and was dry. But I found out two weeks ago that I get to have a pretty awful surgery again the beginning of March, and there is no telling how long it will take to recover enough to do any wrenching. So I decided to do what should be a relatively easy 2 day repair as soon as I had a decent weather report, as I'm out in the elements wrenching. The weather guessers got it wrong, anyway, and the second day it rained most of. Cold and wet is not conducive to pleasant wrenching.

I have a road trip planned for April/May, searching for somewhere tolerable and still semi affordable to live in Southern Oregon. I, after an embarrassingly long time, finally figured out that the slipping in the rear I feel under acceleration in the lower gears had to be due to the clutches in the LSD being toast. As it has been getting a lot worse of late, and I wanted to make it home from said road trip, I've planned to fix it before heading out. Surgery accelerated my plans by a couple of months.

Everything went great until those allen bolts proved impossible to remove without resorting to an impact gun. The ring gear carrier assembly is really awkward to handle, and would be tough to put into a vise without damaging something, and I don't have a vise. I tried hard not to damage the bolts, which I could not find replacements for without the part number I still don't have. I've found several dozen charts like in the first post, but not one key anywhere to give me a part number for those pesky #4 bolts. I still have to find torque settings for these and for the side and rear covers, Bentley should have the last two..

The BMW parts guy almost certainly was looking at the wrong part when he gave me that number. 25mm would put the bolt well into the ring gear, and the 20mm bolts I have bottom out well shy of where it needs to go. It would take quite a stack of washers to make up the difference, which I would not be comfortable doing. The ring gear spins pretty quickly, and it would no longer be balanced properly. Since he was looking at the wrong part, I can't count on his info regarding using hex heads instead, either.

I've been to all of the local Hardware stores trying to find something suitable to replace them with,and I've spent hours on the interwebs using every search criteria I could think of to find them. The offending bolts are m8 1.0 x16mm shcs. Not one available anywhere locally, nor anything that might work, but I finally found some online last night, and thought I'd post a link for anyone in the future who is contemplating a similar repair. You will need these, guaranteed, so have them before starting the project! Since I didn't, I get to be a very displeased pedestrian until at least the middle of next week.

https://streetdrivenindustries.com/c...erential-parts

My kingdom, such as it is, for $11.99 worth of bolts!

PS. I did have all the washers in the right order, but one of the little conical washers was going in the wrong direction, which I would not have realized had I not found the earlier link I posted. It pays to check your work!

[ross1]

FYI
I gather this is an internal part of the diff. (I see no diagram posted) and as such was very likely installed with thread locking compound, the reason for your struggle.
I'd confirm that and be sure to use the proper juice when re-assembling.
When removing fasteners that have "LocTite" or similar heat is your friend. The glue gives up at high temps.
Good luck under the knife.

[xcastaway]

Thanks, ross1. Yep, there is no doubt they used some sort of loctite to weld those suckers in there. I'll be using blue loctite to stick it back together. when I get that option. I do appreciate the heat tip, I hadn't come across any bolts before that couldn't be defeated by enough brute force until these things came to haunt me, so I didn't even think of using my heat gun on them.

Thanks also for explaining the confusion as to which bolts I am messing with, since I can see the diagram just fine here. I'll try again to get it to post. Somebody let me know if it didn't post again, please. If not, it is copied from the first link I put in up above.



This is gonna be the 3rd surgery in 11 months, and I'll take any luck I can get. Thanks.

[moroza]

In places with adequate clearance, anything other than hex bolts is just dumb. I routinely replace Torx, E-Torx, and Allens in places where they don't belong. I'ven't worked on a 188mm diff carrier, but going by photos, there is more than enough room.

Bolts can be trimmed. Balance can be (in theory) preserved by using the same washers everywhere, though in practice it doesn't always work that way. Parkrose Hardware probably has what you need, otherwise try McMaster, Grainger (one or both of these have a warehouse in Portland), MSC Direct, Fastenal, Belmetric, Bolt Depot, and many more.

EDIT: ok, now that I see the spec M8x1.0x16, that is a semi-exotic one. McMaster does have them, part 91180A527, class 8.8.

One of several BMW part numbers, apparently the last supercession, is 33147740005.

Hope your surgery goes smoothly!

[xcastaway]

Thanks, Geva. It sure gets easy to find them when you either know what to call them or have a part number. I did check online at several of those places, since getting to them is currently a problem. The car I had been borrowing went to Springfield for the weekend. I've not had luck shortening bolts when I didn't have a tap and die set to clean up the threads afterwards. I don't want to bugger the threads on the ring carrier up. I'm going to get the dremel out and modify one of the bolts that came out of it to use for chasing the remaining loctite out of the threads, since the 20mm bolts should not be bottomed out yet.

I have to admit I haven't figured out the different bolt grades as well as needed for this situation. The ones they shipped me this morning I believe are grade 12.9, I wasn't positive that grade 8.8 would be adequate. Lack of knowledge on my part. In looking at the carrier more closely, the SHCS head covers the spot they bolt through perfectly, so hex bolts or shoulder bolts would hang over a good bit. I should have been able to answer my own original question without posting about it, by looking at it more carefully. Hex would be iffy in this instance.

My concern with stacking washers, at least two, and possibly three on each was that it would shift the ring carrier balance a bit to the drivers side, in ways it wasn't designed for. The going around part could be balanced equally and still place an extra bit of load to the drivers side bearing and the ring gear. I'm willing, given that I have little choice, to wait the extra several days and have peace of mind. Even if it did work perfectly with the washers, it would bug the heck out of me knowing something as critical as this wasn't exactly how it is supposed to be.

Thank you much for that part number, it would have made finding some quickly much easier, and I wouldn't feel caged for as long. I do hate being stranded. But gonna suck it up, and do some cleanup and painting and end up with a nicer looking, totally hidden from view, diff in the end.

Thanks for the last part as well. The recovery is the part that gets you with this surgery.