The center bearing moves about 1/4" vertically if I push it by hand. (The two ends seems solid.)

Is this amount of give clearly bad?

 

There is no movement spec in the center support bearing inspection procedure. That amount of movement you have seems excessive. You might have to get a new center support bearing and compare it with your existing one.


From '98 FSM

 

The only spec for the prop\driveshaft is runout (0.08''), and link angles which have an enormous 30 degree tolerance range.

Everything else is "to the judgement of the tech who visually inspects it".

 

How the carrier bearing moves.

 

SO I dropped the two bolts holding the center carrier bearing, and examined how freely it turns. It turns nice and smooth. But I'm not sure how much the rubber support is meant to 'give' vertically. It seems pretty flexible, like it moves more than 1/4" to 1/2" when I give it a shove.

At the rear, the rubber connector does have small visible cracks. The rear of the shaft definitely has more runout than the front.

What would your recommendation be? A complete new aftermarket shaft is around $500.

 

AFAIK, the driveshaft itself should be fine unless it's been hit, impacted or otherwise damaged. They aren't really a wear item. The wear items are the flex discs and the bearing. How were you able to determine the runout with it still attached to the car?

The standard playbook is to remove the driveshaft, replace the center bearing and the two flex couplings at either end. The parts should be about $280 from Amayama. I'm not sure if the bearing comes with that rubber surround, which yes should be there to support the driveshaft and act as an insulator. IF you're gonna pull the driveshaft, may as well replace the bearing.

For the record, I'm not sure if this will address your vibration concerns. I'm also not an expert on this w\ driveshafts and such. What else have you replaced on the suspension\driveshaft of the car? But I am curious, if you do go ahead with this, what the results would be.

 

For the runout I just held a thin screwdriver so it's side is pushing on the shaft, and seeing how much the handle moved - around 3mm at the rear and maybe 1mm at the middle of the front section. By geometry divide that but about 3. Up by the transmission it was basically zero. In other words, much more runout in the rear. I had it in drive and spinning the wheels up on the lift.

To remove the whole shaft, it looks like I do NOT need to remove the exhaust. Can anyone confirm whether this is the case or not?

 

The movement of your center support bearing is normal, it is designed that way. The proper way to measure runout is with a dial indicator and spinning the shaft by hand in neutral. With your screwdriver test the rear suspension was unloaded and fully extended so the difference in “runout” of the two shafts you measured is most likely normal. Did someone sit in the car while it was running on the lift to confirm the vibration is still there?

I have been chasing a vibration in my LS for years and put in three different driveshafts only to find out it’s not the driveshaft. It has been confirmed the vibration is coming from the torque converter. Not a cheap fix. Vibrations can be very difficult to diagnose.

Yes you can remove the shaft without removing the exhaust but it’s a bit more complicated and not recommended. Mark everything before removing the shaft if you insist on removing it. You must rule out the engine mounts as well, if they haven’t been replaced by now then do that before messing with the driveshaft.

 

Ok thank you for the info. I just replaced the front right control arm, as it knocked on bumps. Suspension seems good now on bumps, but not like new. I replaced the rear engine mount (back of the transmission that is) last summer. Checked it just now and it looks good, all bolts tight, mount looks good. I'm debating whether to just get a whole Dorman drive shaft and replace it, and then (if it is fixed) rebuilding my existing one for when the new one fails, as they do.

The magnitude of the vibration is very big. (I had a center carrier unbolt itself on a car in Costa Rica a couple of years ago and it was literally like whacking a sledge hammer under the car. The LS is not that bad, maybe more like just a small nail hammer. )

Is there anything else that can bang that much. It is speed dependent, does not go away when in neutral. When I pull over for a minute and drive of again, it can clear up for a while.

 

The fact that the vibration can go away is weird and doesn’t typically point to a driveshaft related issue. The driveshaft spins at the same exact speed no matter what the engine is doing. The faster the car goes, the faster the driveshaft spins. If it was driveshaft related it would happen at the same speed no matter what and always be replicable.

 

Rev the engine in park. Go to 3000rpm. Do you feel it then?

 

When it's happening and if I shift into neutral or way up into high revs 3rd, there's no change at all.

 

So it's something rotational then. Wheel balance, axles, driveshaft, differential, who knows.

My ride quality was significantly improved when I rebushed all of my suspension. It's not perfect or where I want it, but it's better, especially at high speed.

But I don't know how to compare what I had vs. what you have. I wrote a lot about it here

https://www.clublexus.com/forums/ls-...-solve-it.html

and BROADLY speaking it's solved. The suspension still feels really stiff and over-sprung at low speed. But the car rolls a lot smoother now, especially at speed. Or maybe my expectations have changed. I don't know.

 

UPDATE:
The knocking is pronounced and matches the wheel rotation speed, at least when it's moving just a few mph. I jacked up the rear onto stands, and tested if there's any play in the wheels. There is, mostly in the 12 - 6 o'clock direction, a little in the 3-9. Top of the wheel moves 1/8". Everything seems tight underneath except for the bushing shown here, which is shot - I can see and hear it hitting inside if I put a bar on one of the wheel nuts and lift it up and down with some unfortunate part of my body.

The rotor is also superficially marked at intervals, and this brake show strong premature wear (4mm remaining compared to 8-9 on the other side). That's probably from the vibrations.

Could anyone let me know - is this an easy fix? And could this be the ultimate source of the


problem?

 

It’s highly possible.
Start with the suspension before messing with the driveline!