Half shaft broken!

[pnosker]

Just cause I couldn't figure out the most appropriate place for this, if you're going to push 200+ hp, make sure you have different half shaft retainer bolts. Mine shredded up today and left me stranded. Luckily, I have BMW CCA Premier roadside assistance and they towed me for free. Now I have to find some strong bolts!

[cooljess76]

Was it just the bolts that secure it to the differential output flange or did the CV joint get damaged? If you're running a medium case diff, you should run e30 halfshafts since the 318ti halfshafts are a bit too long and cause excessive strain on the CV joints, bolts and flanges. Of course this requires ABS equipped e30 halfshafts which will also require shimming the ABS sensors. Make sure you torque the bolts to 100Nm(74 ft-lb) if you're using M10 bolts, 64Nm(47 ft-lb) if you're using M8 bolts. And be sure to use blue loctite.

[xxxJohnBoyxxx]

Pat are you still running the stock clutch? If so be ready to replace that with an upgraded one. I burned up a new stock clutch in one month with my stock motor, broke the driveshaft universals (rear), shreaded the Guibo, broke the transmission crossmember. It was eating parts until I did a full swap to a 328i driveline w/3.23lsd

[pnosker]

I'm running an m5 clutch with a 11.5# fw and a 2.93 med case LSD. I have a new guibo ready to go in though. I guess I'll eventually go e30 axles when I get some money...

[marko]

**** man, sorry to hear!

guess I should look into it soon...

[pnosker]

Turns out that the half shaft is ok. The bolts cracked though due to stress. Don't put back bolts you already used a few times. Each torque cycle damages the crystal structure of the steel. Get new bolts every time. That's a good lesson to learn from this. The grease plate needed to be hammered back into the right shape, and repacked with grease, but otherwise, not too bad. The only bad part is the labor + out of commission for a few days issue. Also, some reason my driver's rear wheel is stuck. Thinking it might be a locked caliper or a piece of rubber might be lodged in the brake hose. I will thoroughly check it out when I get the car back and some free time. Also, the CF hoods can't be picked up this week since they're being held by customs. Should be out next week.

[cooljess76]

Turns out that the half shaft is ok. The bolts cracked though due to stress. Don't put back bolts you already used a few times. Each torque cycle damages the crystal structure of the steel. Get new bolts every time. That's a good lesson to learn from this. The grease plate needed to be hammered back into the right shape, and repacked with grease, but otherwise, not too bad. The only bad part is the labor + out of commission for a few days issue. Also, some reason my driver's rear wheel is stuck. Thinking it might be a locked caliper or a piece of rubber might be lodged in the brake hose. I will thoroughly check it out when I get the car back and some free time. Also, the CF hoods can't be picked up this week since they're being held by customs. Should be out next week.Patrick, make sure none of the hard brake lines were smashed when the halfshaft broke loose. It could have spun around and smacked something. Also, I don't think the bolts snapping can be attributed strictly because of their age. When you use a medium case diff and 318ti halfshafts, you literally have to force the halfshafts onto the differential output flanges because they're too long. When I installed my e30 shafts, they slid onto the flanges easily with maybe 1/8"-1/4" to spare. Think of it this way, with all of that stress on the flimsy 318ti halfshafts, everytime you go over a bump or the suspension fully extends, it's stopped by the CV joint because it no longer has the range of movement to pivot. The medium case diff is wider, therefore you need shorter shafts. E30 shafts are not only shorter, they're also significantly beefier. I rebuilt my e30 shafts with new cv boots, dust covers, clamps, snap rings, flange bolts and grease. The 4 boot kits came out to about 100 bucks on pelicanparts. When you do get e30 halfshafts, make sure they're off of a 6cyl and have ABS tone rings as some of the older ones didn't come with ABS. IIRC, Tony broke a Ti halfshaft to. Not sure exactly what broke on his, but it's definitely not a good idea to run ti shafts on medium case diffs.

[Isis07]

Hey Pat,

I'm debating cannibalizing my e30 for the engine... if I do, you're welcome to my half shafts if you're interested?

[pnosker]

I know I should use E30 shafts. Wayne, when/if you tear it down I'd love to buy them. I'm assuming it has ABS? In any case, my mechanic said it's a common problem with diff-half shaft bolts. Since this is my 4th differential, and I had to use heat to loosen them last time, the many-time stressing of the bolts led to the failure. I'm sure the extra stress of size wasn't helpful, but neither was the 270 hp. Eventually I'll swap to e30 shafts because it's the right way to do it.

[Isis07]

It does have abs and it was a 325is.. I guess with the engine swap it's still a 325is for that matter. Someone is looking at purchasing the car this weekend but if they aren't interested I'll tear her down within a few weeks.

[cooljess76]

I know I should use E30 shafts. Wayne, when/if you tear it down I'd love to buy them. I'm assuming it has ABS? In any case, my mechanic said it's a common problem with diff-half shaft bolts. Since this is my 4th differential, and I had to use heat to loosen them last time, the many-time stressing of the bolts led to the failure. I'm sure the extra stress of size wasn't helpful, but neither was the 270 hp. Eventually I'll swap to e30 shafts because it's the right way to do it.

Yeah, that'll do it for sure, lol. I didn't realize you've been through so many diffs and that you had to torch them hahaha. I'm sure you already have new bolts ordered, but if not, I have my old ones that you're more than welcome to. They've only been torqued once and you can have them for the low cost of free:tongue:

[pnosker]

Thanks Jess... I already ordered a set of new bolts for both sides. They're going to be liquid nitrogen tempered too so I never have this problem ;)

And yes, Stock 3.45 diff, 3.45 LSD (now Waynes-- how is that working out for you wayne?), 2.93 LSD, and 3.23 LSD. All in all, the 2.93 is the best I think since it gives me a really high top speed (and thus better fuel economy ~15%) and I still have plenty of torque... just ask Marko.

[Isis07]

I don't know how I ever drove my ti with an open diff for as long as I did... It's awesome!

I was contemplating taking the e30's rear setup but I'm pretty sure the lsd needs to be rebuilt and I don't plan on modding the m50 for a while so I'm sure the stock ti everything else will be okay.

[pnosker]

Plus, I ran that diff with 203 hp and it was clean as a whistle when I took it off. I think that will be set even with a 6 cyl if you eventually swap.

[tiFreak]

you don't necessarily need new bolts after every time you torque them, but definitely after putting the torches to them, I always replace bolts that have been heated at work, just cheap insurance against having a really pissed off customer ;)

[small_m]

I have a small case e30 lsd diff. Never had a problem with my bolts! I do know that my outer cv's are toasted right now! I am running 245 rear tires and can light them up in 2nd. I am always waiting for something to break!