getrag rattle, how bad can it get??

[hot carl]

long time lurker, infrequent poster...

i'm getting a pretty bad vibration coming from the trans or front of driveshaft on my car. took the car out today and it sounds like it's going to munch itself. we did a little diagnosis, and it's only getting vibration when clutch is engaged, and it gets worse with engine speed.

i've had 'the rattle' for a while now, noise when idling in neutral, quiet when clutch pedal goes in, but it just got a lot worse.

i just did a major overhaul on my car, replacing all rear end bushings and installing DSSR type shift linkage. when the dssr was installed i went from the early style 'plate' shifter carrier to the later 'rod' type. i didn't know that when changing the mounting for the carrier i would need to plug the old bolt holes.... on my way back from the alignment shop i sprayed almost all of my trans fluid ( at least 1/2 qt royal purple 75-90) all over the underside of my car and hwy 280. so that's not good....

also, when the driveshaft was removed it was accidentally pulled apart. we lined the factory paint marks up and jammed it back in there. maybe we are off by a tooth?

we didn't really know the best practice for 'preloading' the CSB, pretty much just got everything in place, snugged up, made sure driveshaft rotated without binding or wanting to come to a rest at a certain angle, tightened everything up. we didn't know what the deal is with the big collar nut just behind the csb. does it need to be screwed all the way forwards or back? i'm pretty sure we tightened front and rear driveshaft halves to their respective ends and then tightened down csb bolts and put that collar all the way back. where should that collar be sitting?

all components look to be in good shape. i'm sure it was just us taking our best guess at reassembly and goofing something up. where shoud we look first for such bad vibrations? could it be 'the rattle'? the csb preload? the low fluid for 40-50 miles?

ps, the trans seeps from everywhere, so it will be getting pulled and replaced soon anyway. hopefully not too soon....

[hot carl]

update,
definitely a driveshaft issue. got under there and preloaded the csb as per bentley. tightened the collar down by hand as much as i could. took the car out for a drive and still had the vibration/thumping.
what i am worried about is the amount of play in the csb. the driveshaft can wiggle about 1/4" side to side or up and down. it doesn't look torn or blown out but that much play concerns me. i'm going to get the car back on jack stands, pull the heat shield, run the car and see how much play is in the shaft when in gear. maybe i'll be able to see where the vibration is coming from, either guibo or csb or what.
will take a second look at driveshaft alignment marks as well. try to determine if it is aligned correctly or not.

[86bmw325e]

Did you replace the CSB? Last time I had this issue it was due to the center support bearing and it wasn't torn or visibly damaged either


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[jlevie]

The thumping when driving sounds like binding u-joints in the drive shaft.

[hot carl]

got the driveshaft back out, the white dots for lining up the two halves looked a *tiny* bit off. i tried to reclock, but the splines are pretty wide, so it's either off one way or another.
the u-joints moved freely, no binding at all. i read somewhere last night that the u-joints should be aligned in line with each other? as well as the paint marks? it looks like one or the other on my driveshaft. they can't both be aligned at the same time. i took some pics, will try to upload soon.

also, before the driveshaft came out i had the car on stands and idled it in first gear to see if there was any play on anything down there. not the safest or smartest thing, i know. i didn't have an assistant, so i couldn't go through the gears or rev or anything. the only thing i noticed was the vibration damper (not the guibo, the bowl shaped piece that covers it) at the front looked a little askew. i may have tweaked it when prying the driveshaft off. i hope i didn't damage it because it mounts from *behind* the output flange.

at this point i'm leaning towards a new CSB. i don't like buying parts without being certain that they'll fix the problem, but i don't think i have many options. it does look a bit soft. maybe with the new bushings and everything being tighter it just gave the little push off the edge that finished it off.

i'm getting good at exhaust and driveshaft removal at least!

[hot carl]

some pics of driveshaft and alignment marks
sorry they're so massive, i'm new at this.

[hot carl]

ok, so i pulled driveshaft back out, again, and re-inspected the CSB and input bearing in the tip of the shaft (lolz) and they looked just as good as the new ones i ordered. since i didn't want to replace good parts, i separated the driveshaft, aligned the u-joints as best as i could, and stabbed it back in.
i took the car for a short drive and it doesn't sound like the driveshaft is going to punch it's way through the floor any more. hopefully it was just the shaft being mis-aligned.
still a lot of vibration and some noise, but i'm thinking that's down to the stiffer bushings that were just installed in the rear end.
i'll be taking it for longer and longer drives over the next week to see how it does.
fingers crossed!