Re: THe NAC Lots-O-Stove thread
Mark - gimme a ring sometime. I can usually take calls at work unless I'm in a meeting. Hell, if you want, drop by the shop after work some night and I can give you a tour.
Got a new starter, drove it around and it didn't smoke or leak at all, went to crown and got a rear output seal for the trans and dropped the t case tonight. The seal still looks fine so I looked closer and turns out there's a hairline crack from the weep hole at the bottom up to the plug at the top wrapping around the right side of the output shaft and seal......too many clutch dumps I guess? :dunno:
except for the unbalanced driveshaft.
This is probably your issue. I found the tailhousing of the first AX15 from my MJ riddled with stress cracks when I pulled it. It may have caused my broken bellhousing on that one, too.
I've learned a lot about metallurgy in the last year working here. For instance:
- steel (and titanium) have a fatigue limit, below which amplitude you will never actually cause the part to fail.
- aluminum does not. Any level of stress or fatigue, repeated for enough cycles, will eventually cause a failure. It's just a matter of how many cycles it will take.
- cast aluminum alloys in the A300 family are fairly brittle compared to 6000 series.
We have to take this into account and compute expected stress cycles before a failure becomes even slightly probable, then spec in the POH (pilot's operating handbook) a maintenance/inspection/rebuild/replacement schedule for every significant drivetrain part that this kind of thing can occur on. Aluminum driveshaft yokes? A few billion stress cycles goes by a lot faster than you would expect.
All the cast aluminum parts (bellhousing, tailhousing, etc) are original factory parts that have been in vehicles for a decade or two now. Who knows how they've been treated, who knows how many cycles of stress they've already seen from unbalanced tires (one of mine was on the XJ that nuked two bellhousings...), bad driveshaft ujoints, etc.
Add that to my complete lack of mechanical sympathy (I did 103mph in that MJ with that transmission, with a completely unbalanced banana shaped rear driveshaft) and I wouldn't be at all surprised if the MJ's broken bellhousing was caused by that. The XJ I'm pretty sure was my fault too, most likely some issues on the back of the engine block I forgot about plus unbalanced tires shaking the crap out of it for 25k miles or so, but I won't know till I tear it apart and put a straightedge on the back of the block, it's still sitting in the corner of the yard as I've been busy as hell at work.
I still don't think it was motor mounts, but it was almost certainly something I did wrong.
So yeah, basically, fix your driveshaft balance/vibration issues or it'll probably bite you in the ass.
Who wouldn't want to miss a combined 89 horsepower dueling it out on the track?
I might have to show up for this in my new hot ride, I've got almost that many ponies all by myself.
