Drive train vibration

[5KWattson]

its been awhile now since i swapped the M50 in my car, everything is good except i get a small vibration at lower RPM's in each gear. im using the gatrag 260 with stock drive shafts and a 4:10 lsd...i checked the vibration dampener it was a rotted POS so i chucked it calmed down the vibration some but not all the way. Any one got an idea?

[herlsy]

Center support bearing, driveshaft not straight, driveshaft not balanced, bolts to flex disc and diff tightened.

Thats pretty much all i'd check.

[5KWattson]

all checked out fine...kinda the only thing i am concerned of is the drive shaft not being straight when i did the M50 i made solid motor mounts, but i didnt have a e28 mount laying around for proper height so i guessed. it worked does not hit the oil pan nor too high but the motor/trans angle may be slightly F*ed off, anyone know the angle it should sit?

[herlsy]

Seems like a common issue for the motor to twist slightly to the passenger side, causing the transmission to be slightly to the right. Take a look at your trans mounts and see if they look like they have any uneven pressure.

What trans are you using?

[5KWattson]

my apologies i meant to mention this too im using solid trans mounts as well as motor mounts, i racked it like 6 times tryin to find out what was wrong but with out a angle gauge i cant tell if its off or not eye balled looks fine but you know how that goes

[surebimmer]

I would say with solid motor mounts that a small vibration would be normal operation.

[5KWattson]

its not that i cant distingush a difference in vibrations, its @ low RPM's in every gear than it goes away above 2500-3000rpm's

[Wh33lhop]

Wait, you've got solid metal mounts and you're wondering why your car is vibrating?

Edit: I assume you mean more of a low-frequency oscillation ("vum-vum-vum") than a vibration. Does it do it in neutral? I recently shimmed the motor mounts without shimming the trans mounts (not even sure how you'd do that, seeing as the trans mount studs are so short) and I think I'm getting what I think is a little guibo shimmy around 2k in second and sometimes third. Interestingly, it goes away at higher RPMs and is not present in 4th or 5th.

[5KWattson]

it does not vibrate in neutral...it is present in all gears...untill are 2.5-3k

[Wh33lhop]

Describe the vibration. If it's at the same RPM in each gear it's probably not the driveshaft/guibo. Hell I'm not convinced my vibration is the guibo because it's only present at about 2-3k.

[bloodshot-e30]

check a loose bolt in the guibo that was my problem at low R's and when slowing down

[z31maniac]

It's the fact you are using SOLID trans mounts.

They transmit a TON of NVH into the cabin. You'll have to deal with it or change them out.

[bloodshot-e30]

^^ or this lol i forgot about ur solid mounts

[z31maniac]

^That's going on the assumption that everything else is good like he says.

But seriously solid trans mounts are not ideal for a street car, I'd never do that again.

[5KWattson]

Forgot to post up what the prob was and my correction. So when I was doing the swap my friend thought we were going to pull the trans out(which we didn't, but while I was prep'n the motor to go in, he loosened the guibo, so 3 of the 6 bolts were loose causing the vibration, it was NOT from solid mounts...I do know the difference between harmonics and a violent vibration. Tightened up the bolts and was good to go. Solved this along time ago just went to the back of my mind