BMW E21: 1-Piece Drive Shaft
Posted by benc1399@reddit | projectcar | View on Reddit | 22 comments
Hi everyone, I am having a hell of a time fighting a driveline vibration starting around 61mph and getting worse as speed increases.
My setup:
Chassis: BMW e21
Drivetrain: M20B27 with Getrag 260, both from an e30
Driveshaft: Custom 1-piece from local driveshaft shop
Diff: Stock e21, raised 3/8” off the subframe for u-joint clearance
Misc: KPower Adapter between Getrag 260 and driveshaft. Confirmed concentric by machinist
Work done so far:
1) Driveshaft confirmed balanced and straight by builder
2) Adapter “guibo” confirmed concentric by machinist
3) Confirmed transmission output and diff angles are within 0.1°
4) Engine mounts, trans mounts, subframe mounts, ALL suspension bushings are new OEM.
Does anyone have any ideas for fixes or solutions?
Minuuven@reddit
Why not put it on jack stands and check that way
benc1399@reddit (OP)
I have been.
It’s on 4 stands with the rear wheels off spinning up to freeway speeds. Visually, there is no indication of anything wrong. Everything spins dead straight. It’s hard to isolate since the diff is hard mounted to the subframe.
rudbri93@reddit
Sure you didnt chuck a wheel weight?
benc1399@reddit (OP)
100%.
Vibration frequency is much too high to be a wheel.
rudbri93@reddit
How are the cv joints in your axles? Sloppy or tight?
benc1399@reddit (OP)
They’re tight, but I’m at the point where I might remove them and spin up the driveshaft just to eliminate the possibility
Minuuven@reddit
Stupid question but have you tried tightening the u joint bolts again? My brother in law lost 3 bolts in the rear luckily he was in the garage when the shaft dropped
benc1399@reddit (OP)
Man that’s lucky. But yes they are all torqued and double checked.
pistonsoffury@reddit
Maybe take the driveshaft to a different shop and get a 2nd opinion.
540cry@reddit
Ill bet $5 it's your driveshaft but I can't prove it
Far-Plastic-4171@reddit
Get a Go Pro or similiar and mount underneath and record and see where it is coming from.
TealPotato@reddit
Possibly dumb idea:
Rent a U haul car dolly, pull the drive shaft and see if it still shakes when towed with just the rear wheels rolling.
Idk if there is a safe way to also tow it on the dolly with the rear wheels on the dolly and the front wheels rolling?
This might help narrow down if it is the front or the rear or driveline related.
I don't know if there's a way to rent whatever is needed for an RV to flat tow a car and instead use a pickup or something to tow the car with the driveshaft pulled and see if it vibrates then?
benc1399@reddit (OP)
I appreciate the idea, but I am 100% certain the issue is between the transmission and the didf
Raider5151@reddit
Where do you feel the vibration?
Steering wheel? Wheel out of balance, bad tire, flat spotted tire, rack and pinion or pitman arm issue
Shifter knob? Transmission input shaft bearing, u joint seizing or improperly installed, clutch/flywheel issue
Brake pedal? Warped rotor
benc1399@reddit (OP)
I feel it in my ass, the whole interior resonates.
Absolutely not an out of balance wheel, the vibration frequency is much too high.
Raider5151@reddit
Does it do it in neutral while coasting? Does it do it when reving the engine while sitting still?
benc1399@reddit (OP)
Yes, in any gear including neutral. It is vehicle speed-dependent, no relation to engine RPM.
Raider5151@reddit
So if I was you and I had access to a 2 post lift or 4 jack stands I would get the car off the ground and run it through the gears until the vibration presented itself and have a buddy help me try to pin point it.
This is dangerous and I'm not a very smart man.
benc1399@reddit (OP)
Honestly not a bad idea.
I’ve climbed under there with the car idling in gear, I’ll have to find some brave/stupid to do it with the drivetrain spinning at freeway speeds lol
IBIKEONSIDEWALKS@reddit
Shifter shook in e36 till new shifter+bushings. Hope it helps
Driveline vibes are satan, could be a bunch of stuff, bad tires, bent rims, bad bushings from front to rear, have fun!
benc1399@reddit (OP)
I am on the struggle bus for sure. All shifted-related wear items are brand new.
IBIKEONSIDEWALKS@reddit
Damn well i don't want to send you in the wrong direction. Shifter bushing was my issue aside bent rims (17in low pro tire)
Hopefully it's something simple, good luck! Keep us posted on the fix or just fuckin send it