240sx right rear wheel occasionally locking and making clunk sound

[hgrewal]

I have some questions regarding rear wheel occasionally locking and making a clunk sound on the 240sx. Unfortunately the right rear wheel started locking up right after I pulled the car off the trailer last week at the track. That was my second time ever at the track and was excited to run the car in that HPDE but because the wheel started showing signs of locking up and occasionally making a clunk sound, I didn't run.

I thought it was the wheel bearing so I opened up the rear axle housing and took out the wheel bearing with flange and the wheel hub. I tried turning it with hand back and forth but it seemed like the bearing is fine. There is no noise and it wasn't locking or turning roughly.

Now I am not sure what might be causing the wheel to lock up. Also, before anything else, the wheel was only locking when i drove it in a circle to the left and the right rear wheel would lock up. Could this be caused by the Nismo Mechanical Locking Differential case that is installed in it? I am not sure about this because I thought that with the Nismo lsd the wheels should not lock like that when turning (or driving) in a tight circle like it would if the differential was welded.

I am just looking for some info about this as I am just a little worried because while on the track I was feeling a minor but somewhat abnormal vibration from the right rear that I never noticed before. I also heard an occasional clunk sound too. I am also not sure if it is normal for the Nismo Mechanical locking differential to lock up the outside wheel like that when turning in a tight circle.

Any info is greatly appreciated.

Thanks,

[Joe Harlan]

I have some questions regarding rear wheel occasionally locking and making a clunk sound on the 240sx. Unfortunately the right rear wheel started locking up right after I pulled the car off the trailer last week at the track. That was my second time ever at the track and was excited to run the car in that HPDE but because the wheel started showing signs of locking up and occasionally making a clunk sound, I didn't run.

I thought it was the wheel bearing so I opened up the rear axle housing and took out the wheel bearing with flange and the wheel hub. I tried turning it with hand back and forth but it seemed like the bearing is fine. There is no noise and it wasn't locking or turning roughly.

Now I am not sure what might be causing the wheel to lock up. Also, before anything else, the wheel was only locking when i drove it in a circle to the left and the right rear wheel would lock up. Could this be caused by the Nismo Mechanical Locking Differential case that is installed in it? I am not sure about this because I thought that with the Nismo lsd the wheels should not lock like that when turning (or driving) in a tight circle like it would if the differential was welded.

I am just looking for some info about this as I am just a little worried because while on the track I was feeling a minor but somewhat abnormal vibration from the right rear that I never noticed before. I also heard an occasional clunk sound too. I am also not sure if it is normal for the Nismo Mechanical locking differential to lock up the outside wheel like that when turning in a tight circle.

Any info is greatly appreciated.

Thanks,
[/b]

What gear lube are you running? The nismo diff will chunk lightly dependng on how tight it is setup and what fluid you are running.

[Tristan Smith]

Also check your rear brake calipers. Any signs of premature brake pad wear? I had a rear brake caliper not release properly and although it never locked up, it did drag sufficiently. How about your half shafts? Are they in good lubbed condition? Like Joe said. Is your LSD set up properly? Does the clunk happen after you were previously backing the car up? Or all the time? Lots of areas that you can look at closely.

[Joe Harlan]

Oh I did for get....CV joints?

[hgrewal]

CV joints seem fine and the caliper and pads look ok too... no signs of premature wear.

i am not sure if this was caused by towing the car on a dolly with the rear wheel on the pavement (had the fronts up on the dolly). i towed it like that 3 times for about 150 miles each time. but after the first 2 time it was running fine and i noticed this problem after the 3rd time it was towed on a dolly. i am not sure if this caused any damage to the driveline



btw- since then i have bought a trailer to tow it on, just could find a good deal before so my second option was to tow on a dolly and hopefully thats not the culprit here :(

[Tristan Smith]

Towing like that on a tow dolly usually just affects the transmission, not the rear-gear at all. I have been told if you are going to do that to disconnect the drive shaft. So that shouldn't have caused the problem. I think I would pull the LSD and make sure that it has been installed properly and how tight it is set up.

[John Herman]

I have been told if you are going to do that to disconnect the drive shaft.
[/b] That is for automatic transmissions, as the fluid is not flowing/lubricating when a RWD vehicle is being towed with the rear wheels on the ground. Towing a manual transmission (obviously in neutral!) with the rear wheels on the ground is ok as the fluid is still moving around doing its job.

[brandonb]

John, a couple of questions that might help find the culprit. Did you or a crew member actually see the wheel "lock" when pushing it around the pit or did you hear and feel the clutches engage which makes it tough to turn in a tight radius but doesn't completely drag the outside wheel. Also, this may sound funny but was the sound a cluck or possibly more of a snap? and Finally what kind of suspension are you running in the rear?

The reason i ask is that you may be connecting two semi-unrelated events. It would make sense and be fairly common that you could feel the clutches on the diff engage as you push the car around the paddock. It sure does make the car tough to push around but i doubt it's a diff problem as that would most likely manifest itself equally for both sides. Meaning, it would cause the problem in whatever wheel was the outside wheel for that corner, not just the right rear as you mentioned. Also, if you run a ground-control set-up with the standard rear springs (7" x 2.5" i think) there is plenty of droop in the rear suspension to unseat the spring from the top perch. If you use the stock rubber in the top perch it also tends to get a tip to it and as the spring reseats you can hear a loud click type sound. Sometimes if it doesn't reseat you can go out on the track with the spring wedged under the top seat and it causes a massive corner weighting problem, and lock-up on that wheel as its essentially been raised about an inch.

On that note if it's only your second time at the track i wonder if you've ever cornerweighted the car with you in it, or tested suspension travel for the track you're running. We've seen it more on the front which has pretty limited travel but if you get the corner weighting off by even 50 or 75lbs it can make it exceedingly easy to lock one wheel.

Finally, have you looked at any preload or binding in the swaybar or suspension bushings on that side? If you put the car in the air, take the wheels off and disconnect one end of the sway bar and take the lower bolt off the rear shocks you should pretty much be able to move the suspension through its whole travel by hand. Obviously this is where spherical bearings have a huge advantage but if they haven't been maintained properly they can bind pretty easily and cause the symptoms you describe.

Good luck and let us know what you find out.

Brandon

BB Racing