Pulsing Vibration

[drmike]

Hi Everyone,
New to this forum/BMW so after browsing a lot here and also some other bmw forums I come to you with my problem in my otherwise solid 88 325 ix.

I have a pulsing vibration at 50mph+ worst around 70 and then 80+

So far I have ruled out wheels and tires by trying a complete different set i borrowed. I am quite confident it's driveline anyways, but figured it wouldn't hurt to try. Additionally I have replaced the guibo and rear driveshaft with a reman one, which resulted in no change. Additionally the wheel bearings all feel perfect, and the front drive shaft although the splines have some wear it is not stripped.

With that said, I put it up on the lift at the shop I work at and had someone inside run it right up to 90 mph where the vibration was really noticable. It felt like the front diff was vibrating quite a bit, and once we shut it back down I could feel what I considered to be excessive play in the drivers axel at the output of the diff. (the play was perpendicular to rotation, aka up and down, not really in/out) The passenger side had no play at all. Anyone experienced this? I am considering dropping the front diff and examining the bearings (although I have never had it apart so I'm not sure how it's built in there, any drawings anywhere?)

So, anyone have any thoughts, my other thought was it would be nice to just drop the front shaft and drive axels and drive it around to see if the vibration, but i suspect the front axels are part of the front wheel hub assembly and can't be removed without making the car immobile.

So thats my story, any thoughts?

TL/DR pulsing vibration, not rear drive-shaft, guibo or wheels, maybe front diff?

[z122643]

Do you feel the vibration in the steering wheel? or in your seat?

[nando]

you can't drive without the front CV shafts installed, you'll destroy the front bearings.

it could be a bearing in the front diff. the best option there would be to replace it with another diff - just make sure the ratio matches.

also check all the flex couplings (there are 3 on a manual). how are the CV boots?

[drmike]

Vibration is mostly in the seat/floor. You can feel it in the floor more at certain RPMs. The steering-wheel doesn't have much vibration in it.

I have inspected (visually) all the flex joints, replaced the one for the rear driveshaft, the others appear to be in okay condition. Maybe some slight dry rot but not anything bad enough to cause the vibration I'm experiencing (i don't think)

Any reason in particular you suggest swapping the diff instead of just replacing the bearings/seals? I'm plenty capable of replacing all the bearings and have the tools on hand, is it a total PITA or something? I guess for the sake of saving time it would be more efficient but unless you know of a diff near Boston of my ratio I could probably have the job done before I found a diff.

How do I find my diff ratio?

[nando]

because it's not really worth it. ix front diffs aren't that expensive, and replacing a bearing on a front diff isn't going to be cheap, and you have to goof around with spacers to get the ring/pinion to mate together properly after replacing something like that. check ebay, there's ix stuff there all the time, or there's always an ix being parted on the forums.

there should be a tag, it will either be a 3.91 (manual) or 4.10 (auto), but don't go by your trans because they could have been swapped.

of course, if you can do it cheap/easily, by all means go ahead. that's assuming the diff is the problem to begin with, of course.

[drmike]

I'll check out ebay and all the forums for a used one and see what I can find. I suppose buying another diff is not all that bad an idea, worst case scenario it doesn't fix anything and I re-sell it or keep it as a spare...

Anyone have a breakout diagram of the front diff? I've looked a bit but can't find a good one. Alldata one sucks and doesn't look like the bentley manual covers the front diff...

[nando]

the best one is going to be in the ETK. try www.realoem.com

[audiquattrot]

My car has been out of commission b/c of a crazy vibration coming from underneath the floor board. The culprit is #19 in the diagram. Completely shredded. Started as a slight vibration on occasion, to a full blown hitting against the canal of my floors.

[nando]

you mean #18?

that won't cause vibrations. If that is bad, something else destroyed it, likely the rear flex coupling or rear driveshaft U-Joints

[audiquattrot]

you mean #18?

that won't cause vibrations. If that is bad, something else destroyed it, likely the rear flex coupling or rear driveshaft U-Joints

yeah i mean #19. I'll send a pic when i take it out. Its just flopping around.

[drmike]

Huh, I've checked that bit out on mine and it appears to be in okay condition. What was your vibration like? Mine is very very consistent. It happens all the time at the same speeds. The vibration itself is pretty high speed feeling. I'm still leaning towards the diff in the front for now. Going to drop the bottom cover on it and see if I can tell where the play is.

[drmike]

So Just an update, after swapping out the front diff the vibration is still there and unchanged. While I was down there I replaced 2 torn CV boots, a ball joint and inspected everything else and it all seems to be in order so I think I can eliminate the front end being the cause of the problem. At this point I am considering just driving it as is until something breaks or I come across a second hand Tcase or something I can swap out.

Anyone want to buy a perfectly good 3.91 front diff?...

[audiquattrot]

Huh, I've checked that bit out on mine and it appears to be in okay condition. What was your vibration like? Mine is very very consistent. It happens all the time at the same speeds. The vibration itself is pretty high speed feeling. I'm still leaning towards the diff in the front for now. Going to drop the bottom cover on it and see if I can tell where the play is.

yeah mine was very inconsistent. #18 in the picture has a metal backing plate, that twisted, and ripped the rubber off it, and the rubber in turn shredded the bolts holding the guibo in place.

I think i've felt the vibration you're talking about in a couple iX's i've test drove in the past (including my old iX). I never got around to looking into it in my last iX, but in my case it felt like a driveshaft issue since i felt it directly beneath my seat/floor.

Have you checked the splines of the shafts?

[nando]

how rusty is your car? one thing I can think of is the slip yoke has been pulled out of the rear driveshaft, and put together wrong. there should be a marking on both peices to align it correctly. might be worth looking into, that will cause a pretty awful/consistent vibration.

bad splines will cause a "nuts & bolts in a blender" sound, not a vibration.

[drmike]

Rear driveshaft has been replaced with a reman one. The splines on the new one were never separated when it was installed and the guibo was also replaced. The front drive shaft splines showed wear but not bad (in comparison to some of the pictures I've seen on here) and I don't think that is the cause anyways, there is no play in the splines that you can feel and like you said the symptoms it would create are not the ones I'm experiencing.

I think it's reasonable to rule out the transmission as I feel absolutely no vibration in the shifter. I know it's connected through some linkage but you would think some of the vibration would transfer...

At this point I'm probably just going to start driving it until it gets worse or something breaks that I can at least pinpoint. I've put too many hours and dollars into trying to find the vibration. I'll just stick to driving at 65mph where it's not bad.