Rear End Clunking (under very specific circumstances)

[HashiriyaS14]

I searched around for this and I didn't find anything exactly like what I am experiencing, but I might've just misinterpreted.

Anyway, this is out of a 1993 Automatic 240SX Coupe (base), with 127k.

When I come to a stop, brakes depressed, I get no wierd sound, but the instant I let OFF the brakes, I get both the normal sound that goes along with that as well as a "clunk" from the rear of the car.

Now, it does NOT happen every time that I leave from a stop, but rather only when there's been a fair amount of braking involved just before. i.e. if I brake from 30mph, and my foot doesn't leave the brake, when I let up to go forward after stopping, I'll get this sound. If I then re-brake at like 2mph and then let up again.....no sound.

Also, if I brake *very* gradually (i.e. pulsing on and off the brakes) coming to a light, it won't make the noise when I let up.

It is worth mentioning that my left rear caliper has a dust boot that is wholly on its way out. Hopefully I am not hearing that piston sticking.

Anyway, I know I sound like I'm convinced its the brakes, but I guess it could also be a transmission thing....who knows.

Any advice would be greatly appreciated. Anyone ever had this happen?

[180fan]

A clunk from the back, have you checked out the center bearing for your driveshaft or the differential? Since it's an auto, it's probably coming from when the transmission catches and sends power to the back which would explain why you're not really hearing it when you're completely stopped but when you let off the pedal.

[HashiriyaS14]

A clunk from the back, have you checked out the center bearing for your driveshaft or the differential? Since it's an auto, it's probably coming from when the transmission catches and sends power to the back which would explain why you're not really hearing it when you're completely stopped but when you let off the pedal.

That's a good idea.

No, I have not checked (nor did I even think of) the center bearing. In fact, I probably couldn't even find it without my FSM (hey, I'm not a tech mod, lol).

I just searched and I couldn't find a whole helluva lot about the center bearing on 240's (more stuff on G50s). Is this something I could just look at and ascertain whether or not it's the problem? I mean, I can locate it with the FSM, but can I just eyeball it and know if it's gone bad or not?

And more importantly, if it is the problem, can it be unsafe to drive with the bearing like this, or is it just more of an annoyance?

[180fan]

The center bearing is at the center of the driveshaft. It's connected to a rubber surrounding thing and has a nother metal U shaped bracket that keeps it close to the chassis. It could be bouncing around when it picks up power. check the driveshaft for play at the usual u joints while you're down there cuz they could be doing it too. Otherwise if it aint in the driveshaft, might be having the problem i'm having with a worn down ring gear.

[Arrow]

As far as telling if the bearing is bad, you would have to check the play in it - that can be done by moving the driveshaft up and down at the center bearing - I am not sure the amount of play that is allowed. But if the rubber part of it is damaged (it surrounds the actual bearing and provides support and dampening) then it should be replaced for sure.

As for the safety of operating the car w/ the bearing bad IMO it would be just an annoyance - that is inless the rubber boot thing gets damaged too badly b/c then the driveshaft could really get kicking around in it's support

[HashiriyaS14]

Ok, so I'm pretty confident that this is what my problem is.

Does anyone know how involved the procedure of replacing this thing is?

Does the driveshaft, or worse yet, the engine/transmission need to be out of the car for me to access the thing? Is it a 1-man job? Think I'll need air tools?

[180fan]

The back end of the driveshaft needs to be out, otherwise I believe you can leave the front end in the transmission.

[HashiriyaS14]

So basically I just have to disconnect the axles and pull the differential off the car?

That doesn't sound like the end of the world. It'll give me a chance to inspect my axles, I do have a set of used spares.

[ricebike]

meh? u don't need to drop the diff or disconnect the driveaxles...

there's 4 bolts holding the back end of the propeller shaft to the diff... just put a match mark between them then unbolt...

drop and pull it from the transmission...

oops forgot about the 2 bolts on the center support bearing...

Quote »If you pull the driveshaft ( two 17mm bolts in the centerbearing housing and 4 12mm at the rearend)... Keep in mind you will lose most of the gear oil from the transmission when you pull the driveshaft...have something nearby to catch it. [/quote]

basically, pulling the driveshaft is a 1 man job. but u will need some special tools to replace that 1 bearing as per FSM

here's 2 threads i found via search, but can't find another where I replied to this similar topic a while ago...

zerothread?id=153592

zerothread?id=70259
Modified by ricebike at 2:16 PM 5/9/2006

[HashiriyaS14]

meh? u don't need to drop the diff or disconnect the driveaxles...

there's 4 bolts holding the back end of the propeller shaft to the diff... just put a match mark between them then unbolt...

drop and pull it from the transmission...

Cool, even better.

What's this "match mark" you speak of?

[ricebike]

HASH! u have the FSM!!!!! come on, man! LOL

matchmarks between the diff flange and the driveshaft so u can reinstall it the same way (to avoid unbalancing issues, is my guess)

reading more about carrier bearing: isn't search wonderful?

zerothread?id=36530

zerothread?id=5505

so after all that searching for you, it may not be the cause... but good to check anyways, along w/ your brakes/rear suspension subframe bushings, etc... gl!

[HashiriyaS14]

HASH! u have the FSM!!!!! come on, man! LOL

matchmarks between the diff flange and the driveshaft so u can reinstall it the same way (to avoid unbalancing issues, is my guess)

reading more about carrier bearing: isn't search wonderful?

zerothread?id=36530

zerothread?id=5505

so after all that searching for you, it may not be the cause... but good to check anyways, along w/ your brakes/rear suspension subframe bushings, etc... gl!

LOL, yeah, I know, I suck. My FSM is on loan at present, and I didn't feel like waiting to get it back to satisfy my curiosity.

I've already got brakes coming in the mail, and I plan to do a full set of energy bushings (suspension and subframe) at some point or other (already did the tension rods out of necessity).

In regards to the searching, I had been searching for "center bearing", which I suppose is why I didn't find those two threads, as the phrase doesn't appear to be in either of them.

Thanks for the info