I just want to check that a few assumptions are correct. I have the front portion of the driveshaft off from behind the articulated washer at the transmission to just beyond the U joint and intermediate bearing. I will remove the intermediate bearing and the clamping ring. I assume this is the only portion of the driveshaft needed to shorten it 3.75" and to balance it. They don't need the entire driveshaft back to the rear end to balance do they? Also is there a recommended place(front, middle, or rear) where to cut, shorten, and reweld the driveshaft? Thanks. Jeff
shortening of driveshaft for 5 speed
- Thread starter Jeff
- Start date
decoupe
(deceased)
Jeff:
On both of the driveshafts I have had shortened - they asked for both pieces and the adjustment was done at the tranny flange. Change the centre hanger bearing when this is being done.
Doug
On both of the driveshafts I have had shortened - they asked for both pieces and the adjustment was done at the tranny flange. Change the centre hanger bearing when this is being done.
Doug
Jeff
I concur with Doug. They will need both pieces of the drive shaft. While they might only alter the front piece, I beleive the 2 are needed together for balancing..
That is how they did mine when I upgraded.
Gary
I concur with Doug. They will need both pieces of the drive shaft. While they might only alter the front piece, I beleive the 2 are needed together for balancing..
That is how they did mine when I upgraded.
Gary
steve in reno
Well-Known Member
I agree with others. They need both front and back.
Most driveline places will cut and balance and install a new center bearing.
I had mine done last year.
$150 with new bearing, cut and balanced.
steve
Most driveline places will cut and balance and install a new center bearing.
I had mine done last year.
$150 with new bearing, cut and balanced.
steve
Honolulu
Well-Known Member
soooo...
why can't/doesn't the shop balance each shaft segment separately? If done, they should balance when together.... right?
why can't/doesn't the shop balance each shaft segment separately? If done, they should balance when together.... right?
x_atlas0
Well-Known Member
Re: soooo...
Sometimes you get higher order harmonics that don't affect the shorter segments but will have an impact on the whole. It is the same reason that engines are balanced as a complete bottom end, rather than just a crank.
Honolulu said:
Sometimes you get higher order harmonics that don't affect the shorter segments but will have an impact on the whole. It is the same reason that engines are balanced as a complete bottom end, rather than just a crank.
cpeavey
Well-Known Member
It's generally a package deal - rebuild the U-joints, shorten and re-balance (and repaint for good measure), and includes a new center support bearing. So don't buy a separate support bearing.
I ran into trouble earlier this year with a vendor who apparently was measurement-challenged, and I had to send mine back to shorten it another inch! I recommend that you measure the length of the front half from flange to U-joint centerline for reference. (This dimension can be found in the specifications section in the relevant chapter of the blue books.) Then you can check the length when you get it back, before you try to reinstall it, to confirm that it is actually about 3.75 inches shorter.
Charlie
I ran into trouble earlier this year with a vendor who apparently was measurement-challenged, and I had to send mine back to shorten it another inch! I recommend that you measure the length of the front half from flange to U-joint centerline for reference. (This dimension can be found in the specifications section in the relevant chapter of the blue books.) Then you can check the length when you get it back, before you try to reinstall it, to confirm that it is actually about 3.75 inches shorter.
Charlie
blumax
(deceased)
driveshaft balancing
Also--you may want to consider
while going through the modification of shortening and re-balance for your 5 speed installation--recommend that your u-joints be inspected and if dry replaced--at 35 years the BMW sealed "permantently lubricated" u-joints are often completely dried out and offer much greater resistance to spinning--as a result can become a source of drive shaft vibration and the need for removal again if renewal is not done when out.
My philosophy of maintenance has always been to "get it right the first time" and go on to the next issue--perhaps this has been an underlying reason I've never been stranded by any system failure in over 500,000 miles of driving my own E-9's--and still counting.
Also--you may want to consider
while going through the modification of shortening and re-balance for your 5 speed installation--recommend that your u-joints be inspected and if dry replaced--at 35 years the BMW sealed "permantently lubricated" u-joints are often completely dried out and offer much greater resistance to spinning--as a result can become a source of drive shaft vibration and the need for removal again if renewal is not done when out.
My philosophy of maintenance has always been to "get it right the first time" and go on to the next issue--perhaps this has been an underlying reason I've never been stranded by any system failure in over 500,000 miles of driving my own E-9's--and still counting.