diedroopy

I have a 1996 lexus ls400, when going from park into drive i heard a thump coming from the rear end. I got back there and i only saw the rear knuckle bushing looked bad. so i changed it and it was still making the clunk/thump, i really looked and i took a video and i see the rear end of the driveshaft where it’s connected to the differential move up and hit the top, is there any way i can get this to stop? along with this, when im braking and coming to a stop the car starts to vibrate and is followed by the clunk, what could be causing these issues? any suggestions or advice? has anyone dealt with something similar?

TominPT

I believe there are two flex discs in the drive shaft, one at the rear axle and another one at the forward end of the drive shaft. If you changed out the one at the rear axle check the forward one too, it may be toast and causing the movement you are noticing. Look for deep cracking/degradation and if present replace it. The vibration when braking could be caused by warped rear rotors.

400fanboy

I have the same "thump" going into drive from within the car. . It can't be the flex discs, their failure couldn't possibly cause this much driveshaft deflection right?

have no idea if it's normal or what the cause.

diedroopy

yes, i’ve changed the flex discs and still get the same amount of movement, there’s no way it can be those. I’ve been trying to figure it out for a while and i just can’t seem to find anything, i’m sure other people have dealt with something similar

bradland

Have you considered the transmission mount?

timmy0tool

iTrader: (7)

i second this! check the mount.

CLLEXUSS

Interesting problem. If its not the flex discs that rules that out. I'm looking at the first seconds at the start of the video, you can see the drive shaft flex disc rotate sort of harshly and then stop as it makes full contact. From what I can see as I play this in very slow motion settings the very first second of the video that's exactly where you can see it. So if we do a generic search of what a cause can be, things to look at could be Universal Joints, bad differential bushings, motor or transmission mounts, or possible worn bearings and springs. Probably the question is is it anything to do with the differential, or is it traced further up the drive train that is the root cause. I think when the search indicates "worn bearings and springs" they might be referring to the inner workings of the transmission. But understand I just performed a search of a generic cause of clunking when putting it into drive. In my mind I am ruling out the mounts but I am not sure. So if a determinization cannot be make with certainty, then process of elimination steps in at some point I would think. I don't know how else it could be solved without eliminating some of the common causes but like you say maybe someone else has had the same exact problem and will chime in.

400fanboy

My transmission & motor mounts were replaced about 5 years ago. I haven't investigated them again at all, but they don't present any of the normal symptoms.

I don't know about OP, but I suspect that would also be a similar story.

diedroopy

transmission mount was the first thing i changed in the car about 2 months ago, it definitely helped but after i changed it, it felt as if the strain of the movement was moved somewhere else in the rear

fondu

This is my guess. It's most likely torn completely causing up and down movement. 90-97 have this style differential with one mounting point.

If you check out from 10:47-10:59 in this video it shows what you could be experiencing.

diedroopy

looks exactly like the type of movement i’ve been having! gonna check this out when i get the chance, thanks for the advice