engine and drivetrain 1976 Bmw 2002, Differential Slipping. I Think.

[Jason Dittmer]

I think the differential is slipping or something.

 

When I go around turns at regular speeds sometimes I hear a "clunk" noise. It feels like it's coming from the back left wheel.  But it's hard to tell.

 

I put the car on jacks to try and see the problem. But I'm really just a hack mechanic wannabe. So I have no idea what I'm doing. Any ideas?

 

Edited April 28, 2014 by Dittmer

[Hans]

This has been covered before - maybe search under diff noise, etc. Before attacking the diff, check all attachment bolts for half shafts, rear wheel nuts, etc. Get under car with wheels off the ground, car in neutral. Try turning drive shaft to see if you can replicate.

 

One clunk or clunk - clunk - clunk? 

[Jason Dittmer]

One clunk. Only on acceleration.

 

The car was in first gear when I made the video above.

[peterschop]

The CV bolts take a 6mm allen wrench. To tell if you have an LSD, with car in air and in gear, turn one wheel. If the other wheel turns in the opposite direction, you do not have an LSD. 

[AceAndrew]

To check if the LSD is worn.  Jack up one side rear and try to rotate the wheel by hand (bear hug the wheel like you love it).  If you get it to break away and spin you've got your self a pretty worn limited-slip.

Edited April 28, 2014 by AceAndrew

[oh2fly]

The c/v bolts are 6mm. Looks like your diff input shaft seal is leaking. It doesn't take long to lose a qt. of gear oil. Is there any play in the rear u-joint on the driveshaft? Did you check the 4) 17mm head nuts attaching the shaft to the diff?

[oh2fly]

oops sorry

Edited April 28, 2014 by oh2fly

[FB73tii]

One clunk. Only on acceleration.

Check stub shafts for worn splines. We had a thread on this recently.

[Jason Dittmer]

With the car lifted and in neutral I was able to spin both the CV shafts in the same direction. If I just spin one of the CV shafts the other will go in the opposite direction. Does that mean it's a limited slip differential, but it's worn out or something?

 

Also, I was able to get a look at the stub shaft splines on the drivers side by just removing the hub cap, cotter pin and castle bolt. From what I could see, the splines on the stub shaft do not look warn. I tried to remove the CV shaft so I could remove the stub shaft and get a better look at the splines, but I was unable to get the stub shaft out.

 

I ended up putting it all back together and taking it out for a drive. And it worked great. There was no clunk noise.

 

My plan is to just replace the differential input seal like you guys recommend. Should I also replace the output seal or the seals on the CV shafts?

[Tommy]

Sounds that you have open diff.

 

The way you write how you were able to check the splines makes me think everything over there is not right. Did removing the castle bolt and hub include using 5 foot breaker bar and a puller? If not - that's your problem. The nut was loose and usually that indicates worn out splines on stub shaft. Tightening the nut helps for very short while but it will soon be loose again and catastrophic failure is waiting to happen.  

 

  Tommy

[Jason Dittmer]

It did involve a 5 foot breaker bar and liquid wrench to get the castle nut off. That nut was on there very tight. I took some pictures of the splines with the nut off.

Edited April 29, 2014 by Dittmer

[peterschop]

As Tommy said, you have an open diff, not an LSD. Replacing the input or Pinion oil seal take special tools. You need a crush spacer and measure the preset before and after. It is above my level of comfort. The out put seals are much easier to replace.

 

As far as the diff, I would keep an eye on the fluid level and leave the input seal alone. If the output seals are leaking, they aren't too hard to replace. 

Edited April 29, 2014 by peterschop

[Jason Dittmer]

I'm thinking about just taking the differential out and replacing the seals. Then putting it back. Does that sound like a good idea?

['76mintgrün'02]

Replacing the seals sounds like a good idea if you are trying to stop the leaks, but it won't not solve your clunking issue.  

 

You said you replaced the fluid in the differential... was the fluid level low when you drained it?  If not, the leaks may not be a priority.  

 

What did you fill it with?  

 

"one clunk on acceleration"      Have you inspected your rear sub frame and diff mounts?

 

Might sound silly, but there isn't anything rolling around in your trunk, is there?    

[peterschop]

I'm thinking about just taking the differential out and replacing the seals. Then putting it back. Does that sound like a good idea?

 

I replaced my diff output seals but then again, I had the car in the air and the driveshaft out already and had to slide the diff forward for the new transmission and DS. I will not attempt the pinion seal without the proper tools and more advanced help.

 

If you want to replace the output seals, go for it but leave the input seal alone. If it were me and isn't leaking too bad, I would just keep an eye on the fluid level and leave it alone.