Driveline Vibrations

i'd agree that driveshaft is a good place to start. could even be that one of the u-joints on the driveshaft just squeeked by quality control, but under load it's actually bunk.

no backup DS to test?

Are you running a solid diff mount as well??

Rear wheel bearings? We had a vibration/resonance starting at the top of third and would get worse as speed increased.

Sounds like driveshaft to me as well… that usually starts around 60mph and gets louder and heavier as speed increases.

Was the driveshaft made at a driveline shop? Did you notice any weights (usually look like washers) welded to the shaft? New yokes and u-joints?

Driveshaft was made at a driveline shop. It was balanced as there are weights, washer things welded to the shaft. Brand new yokes and u joints (replaceable).

Long story short I did not pick the shop, as it was outsourced from another. After getting the name and doing some quick google work; experience in "Monster Trucks, Race Cars, Antique Vehicles, School Buses, Tractor Trailers, and Tractors". Looks like they made there bread and butter in monster truck and mudbog racing. I contacted them about re balancing, but being out of state, and what seems long turn around not sure I want to deal with it. Plus they didnt exactly leave me feeling confident or positive talking on the phone (our products are perfect and never have troubles feeling). The company that outsourced did say they have had positive experience with them in the past with e30s and LS s-chassis conversions driveshafts.

There is just a lot of new new going on that while im confident its probably drive shaft related, it could be other items. I did not go through the junkyard diff and axles. Just changed the fluid and checked for play and everything seemed fine/normal. Looked at driveline angles and nothing unusual or noticeable with angles or misalignment from anything. Still on stock tranny mount, but I have poly bushing to replace it with, but the stock one seems really tight.

There is a company local, more of a machine shop that specializes in driveline components. More so for industrial world, but have engineers and make a lot of special application stuff. Seems a little more reputable and have some science to back products rather than just specialized experience. Going to drop it off their tomorrow and get it back the next day. I am keeping my fingers crossed that the previous company said "good enough" on the total run out and these guys can do better.

I had my custom drive shaft made at an industrial driveline shop for 200 bucks by some old fart and it came out wonderful. A second oppinon couldn't hurt. If they say it is good as well, I would start looking somewhere else.

I had an all-new driveline made at a local shop. Got bad vibes starting at 45mph. High frequency etc. Had him re-balance it twice. No change. I STILL knew it was the shaft. Ruled out all other components. Took it to a driveline specialty shop. They found .02" runout. Heat treated and dynamically balanced that sheezy and SHAZAM! Smooth as glass.

Solid mounts are much less forgiving to vibrations.

MORAL: Drive a BMW

Look whos fancy now, with your 740i pimp mobile. lol!

Adam, I still wouldn't rule out your cv axles amd those solid mounts make it known!

Adam,

If you don't find a local source you prefer, I recommend Powertrain Industries for an upgraded DS. I bought mine for ~$300 back in 2006 and its worked beautifully since. Its a much heavier duty unit with upgraded U Joints that are actually replaceable unlike the factory unit.

Dropped it off today. Still an uneasy feeling as I dont feel the guy was listening to a word I said. What would be a typical driveshaft RPM? Isnt 4th gear 1:1 so it would see the same as the crank shaft? I asked what they typically balanced too, and the guy said they do 80rpm but they can take it up to 3k rpm (top of the machines capabilities). Then told me my drive shaft would never see that high of rpms regardless. Im no expert at drivelines but im pretty sure thats incorrect.



I have a drive shaft, nice beefy with upgraded joints, new yokes ect… I just think it needs to be balanced to higher degree then typical cars with all the solid mounted suspension. Seems to be hard finding a source capable or getting someone to listen to the application.

You are correct, the drive shaft is 1:1 in 4th and over-driven in 5th, so it could potentially see over 7K rpm, if you are into that sort of speed…

But balance is balance, it doesn't need to be balanced at that kind of speed to be balanced. They don't spin your wheels at 1,000+ rpm to balance them.

^^Correct. If the place you took it too doesn't work out than there is also A-1 Driveshaft in Waukesha that has built a few for us in the past.

If this place doesnt work, I am going with Elkhorn Driveshaft. They dynamic balance with capabilities up to 12,000 rpm. Im done with the typical drive shaft places. Nothing against A-1, I just dont feel people listen when I am trying to explain. I am by no means an expert, but I am also capable of understanding. I dont need places to tell what "good enough". /end rant