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1

Engine + Driveline / M42 Vibrating

« on: February 25, 2012, 09:46:56 AM »

Motor (and trans) mounts? . . . looked OK . . . but we'll check for a 'cracked tab'

Drive shaft? . . . my M3's had a drive shaft service, as I recall --- the whole thing came out, got re-built/re-balanced. I asked about this --- 'looked fine' --- but I'll follow-up.

Wheel bearings/dragging brakes-bad caliper/tweaked half-shaft-bad diff? At one point, we had the car up on the lift, all put together, engine running . . . Mechanic put his hand up against the bell housing . . . could feel the engine shaking, like crazy --- even at idle/low power. Thought it might be the clutch had lost a chunk, was causing it. But the clutch looked fine.

Understand, this motor rarely sees the other side of 4k --- there's just no power up there. I bought the thing as a 'hooptie' --- not a racer, but I take good care of her --- she's spotless, garaged, serviced, etc. Always start off slow, warm 'er up, then hum along. Even at 200k, only uses a qt of Redline 20/50 every 3k mi. (I expect to put a million miles on 'er!)

So all of this trouble feels a bit odd.

Monday, I want to start from the top --- visual checks, etc. Then? Fuel/spark/ignition --- basics. Then? Compression/leak-down. Then? Guibo/harmonic balancer/dual-mass flywheel/obstructed exhaust?/??? --- we'll pull the effing motor, if we have to.

Mechanic is flummoxed, now --- and fired-up. (Big Racer, so he's not about to let my little sh!t-box antique get the best of him!) I'll let everyone know how things turn out.

R

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Engine + Driveline / M42 Vibrating

« on: February 24, 2012, 02:28:48 PM »

First post.

I own a ’91 318iS.

Love the car. Bought it for fun and fuel economy. Only had it 6 years or so --- but I’ve already put almost 170k miles (200k total) on her. Rims, suspension, brakes, driver’s seat . . . all up-graded. No wrecks, mostly original paint, regular service, never been apart.

A few weeks back, getting off the freeway, coming down from ~70 MPH, I noticed a shake. Light, almost like a tingle, high-frequency, but felt not so much heard --- kinda like driving on a grooved road surface. Went away as I stopped, but came back again at city-traffic speeds. Got so intense that at one point, all the junk in the door pouches was buzzing from it.

Next morning, I started the car, half expecting it to've cleared up --- no. And then, driving on the freeway? . . . . whole car groaned/vibrated/moo’d. It was awful.

And scary.

I’ve been driving e30s for almost 20 years, owned 5 --- all 4-cylinders . . . either M42s or S14s . . . never felt or heard of anything like this.

Took it to the Mechanic, explained the issue, they drove it, experienced the issue. Pulled the trans --- found a damaged pilot bearing. Swapped out the original open 4.10 diff, put in a used 3.91 LSD. Looked at drive shaft, half-shafts, CSB . . . nothing amiss.

Got the car back, but . . .  not fixed. Buzzes so bad at 3k/5th on the freeway, car feels like a gigantic electric razor. Un-effing-believable.

Never the smoothest car, always been a bit 'buzzy' . . . but nothing like this. Apart from some odd buzzes over the years --- gave no warning.  (And I did have the car smog-tested just before.)

The only recent issues have been the hydraulic tensioner (replaced ~1k mi, ago) and some racket from the exhaust --- light rattle at start-up . . . cat + silencer are original.

Any suggestions, insights, conspiracy theories to share? Car's a Keeper, always cherished, so . . . .

RVK