lets talk driveshaft alignment

[gwb72tii]

there has been more than one post regarding how a driveshaft needs to be straight, there are tools fabricated/designed to determine how straight a driveshaft is aligned, etc.

question 1.

why? there is a u-joint in the center of the driveshaft that will make up for mis-alignment

question 2

there is no provision to align the center support bearing side to side or up (down with washers), and no provision to align the ass end of the tranny side to side.

and my problem, specifically, is the center support bearing in never too high, its always too low (especially with a 5spd conversion), where there is no fix possible.

[Guest Anonymous]

any 4x4 owner with a truck that has been lifted. The poorer the alignment of the shaft, the quicker the u-joint wears out.

Keeping the new mounts on the transmission tunnel at the same plane as the 4 speed mounts are, is the best strategy for having a shaft that is in alignment.

shermanmartinez@hotmail.com

[JohnC]

Keeping the new mounts on the transmission tunnel at the same plane as the 4 speed mounts are, is the best strategy for having a shaft that is in alignment.

Unfortunately, it's not always possible to have both a straight drive shaft and have the drive shaft perfectly perpendicular to the guibo. If you adjust the height of the transmission mount, you may stress the guibo.

At first, I focused on keeping the driveshaft straight. A couple of destroyed guibos later, I took the advice of a well-known supplier, and made sure that my guibo was perpendicular to the drive shaft. The two sections of the drive shaft are now not perfectly aligned. I've been running the guibo about a year and there are still no cracks. In other words, given the choice of an unaligned drive shaft and a guibo that is stressed, the unaligned drive shaft is the lesser of the two evils.

[TobyB]

universal joints aren't constant velocity, so the less they're displaced,

the less imbalance and stress there is on any drive system.

And as John says, there's guibo life to consider...

t

[PatAllen]

there has been more than one post regarding how a driveshaft needs to be straight, there are tools fabricated/designed to determine how straight a driveshaft is aligned, etc.

question 1.

why? there is a u-joint in the center of the driveshaft that will make up for mis-alignment

question 2

there is no provision to align the center support bearing side to side or up (down with washers), and no provision to align the ass end of the tranny side to side.

and my problem, specifically, is the center support bearing in never too high, its always too low (especially with a 5spd conversion), where there is no fix possible.

wrong...there is at least 3/8 inch of free play side to side on both trany and center mount, if you work them out.

The reason for this driveshaft to be aligned is its a 2 piece driveshaft with a center "soft" support. If it is not straight it will wobble "like a wet noodle" when torque is applied to it, as one already mentioned.

And the reason why it is a 2 piece type (instead of a straight pipe like an american muscle car of the same era) its because this type of DS eleminate the first natural vibration/harmonic.

IE less prone to vibration, when its all top shape of course

The u-joints on theses are there to compensate for SMALL miss alignments...nothing comparable to a jacked pick-up truck.

[c.d.iesel]

[gwb72tii]

there has been more than one post regarding how a driveshaft needs to be straight, there are tools fabricated/designed to determine how straight a driveshaft is aligned, etc.

question 1.

why? there is a u-joint in the center of the driveshaft that will make up for mis-alignment

question 2

there is no provision to align the center support bearing side to side or up (down with washers), and no provision to align the ass end of the tranny side to side.

and my problem, specifically, is the center support bearing in never too high, its always too low (especially with a 5spd conversion), where there is no fix possible.

wrong...there is at least 3/8 inch of free play side to side on both trany and center mount, if you work them out.

The reason for this driveshaft to be aligned is its a 2 piece driveshaft with a center "soft" support. If it is not straight it will wobble "like a wet noodle" when torque is applied to it, as one already mentioned.

And the reason why it is a 2 piece type (instead of a straight pipe like an american muscle car of the same era) its because this type of DS eleminate the first natural vibration/harmonic.

IE less prone to vibration, when its all top shape of course

The u-joints on theses are there to compensate for SMALL miss alignments...nothing comparable to a jacked pick-up truck.

my center support bearing (stock from blunt) has one slotted hole and one round hole - as in no side to side adjustment. do you manually slot the other hole? every center support bearing ive ever had comes with a round hole/slotted hole combo

[PatAllen]

there has been more than one post regarding how a driveshaft needs to be straight, there are tools fabricated/designed to determine how straight a driveshaft is aligned, etc.

question 1.

why? there is a u-joint in the center of the driveshaft that will make up for mis-alignment

question 2

there is no provision to align the center support bearing side to side or up (down with washers), and no provision to align the ass end of the tranny side to side.

and my problem, specifically, is the center support bearing in never too high, its always too low (especially with a 5spd conversion), where there is no fix possible.

wrong...there is at least 3/8 inch of free play side to side on both trany and center mount, if you work them out.

The reason for this driveshaft to be aligned is its a 2 piece driveshaft with a center "soft" support. If it is not straight it will wobble "like a wet noodle" when torque is applied to it, as one already mentioned.

And the reason why it is a 2 piece type (instead of a straight pipe like an american muscle car of the same era) its because this type of DS eleminate the first natural vibration/harmonic.

IE less prone to vibration, when its all top shape of course

The u-joints on theses are there to compensate for SMALL miss alignments...nothing comparable to a jacked pick-up truck.

my center support bearing (stock from blunt) has one slotted hole and one round hole - as in no side to side adjustment. do you manually slot the other hole? every center support bearing ive ever had comes with a round hole/slotted hole combo

true,not sloted and i didnt sloted it either, the fishbolt slides in a open slot and there is enough play in there to move the support by 3/8 on 4 cars i worked no recently.

My Automatic

a Tii

a 1600

and my turbo.

you may end up sloting them if necessary.

[rey949]

@Darien,

GREAT DIAGRAM. Great Post! Awesome information!

[gwb72tii]

wrong...there is at least 3/8 inch of free play side to side on both trany and center mount, if you work them out.

The reason for this driveshaft to be aligned is its a 2 piece driveshaft with a center "soft" support. If it is not straight it will wobble "like a wet noodle" when torque is applied to it, as one already mentioned.

And the reason why it is a 2 piece type (instead of a straight pipe like an american muscle car of the same era) its because this type of DS eleminate the first natural vibration/harmonic.

IE less prone to vibration, when its all top shape of course

The u-joints on theses are there to compensate for SMALL miss alignments...nothing comparable to a jacked pick-up truck.

the issue hasn't been side to side alignment, not withstanding your manipulation of the center support bearing, something bmw never intended in their original design.

yes, the rear of the tranny can be positioned from side to side (oem slotted holes), but that doesn't get you much with a fixed position center support bearing. it does allow for getting the output shaft parallel to the guibo.

and that hasn't been the problem on the last 7 tranny installs (4 and 5 spd) i've done in the last 3 months. its that its impossible to get the shaft straight and have the guibo alaign parallel to the output flange. the forward section of the drive shaft needs to be angled up slightly. the perfect solution would be for an center support bearing that allows for higher vertical positioning that, along with raising the rear end of the tranny, would position the guibo parallel.

[NullZwei]

I know exactly what you're talking about, I struggled with the same issue. About the only alternative I could see, although I didn't do it, was to relocate the center support bearing mounts higher in the tunnel. You could then shim as necessary to get the proper driveshaft alighment. As it stands without doing that, it's pretty much an either/or situatuion with having the driveshaft perfectly straight and a slight mis-alignment with the guibo or vice versa. I tried to do a compromise as much as possible with shimming the rear of the tranny but your very limited as to what you can do with that too. Anyway, so far, so good.