How much free play should there be on the drive shaft in neutral?

[Bigham]

I am trying to isolate the last noise from the rear of the vehicle.

When the car is in neutral I have approx 3/4" of rotational free play when rotating the drive shaft. The shaft will also move a small amount front to back as well. The play may actually be in the rear differential. Is this normal?

 

[deweyville65]

I am trying to isolate the last noise from the rear of the vehicle.

When the car is in neutral I have approx 3/4" of rotational free play when rotating the drive shaft. The shaft will also move a small amount front to back as well. The play may actually be in the rear differential. Is this normal?

3/4" of rotational play, or slack measured at the outside edge of the u-joint flange? I would say that is fairly normal, but if you are having noise from the rear end, I would be pulling the cover off and have a look inside. Remember, it could be coming from a worn wheel bearing too. How much up and down play at the rear wheels, any gear oil leaking from the ends of the axle? How much up and down play at the differential flange?

 

[Bigham]

I did have a leak from the left side at the wheel. Would the rear bearing going bad make a whining noise, or a grinding noise like the front bearings when they go bad?

 

[deweyville65]

Quite possibly. Every bearing seems to make a different noise. If you had a leak and did not repair it, you may be low on gear oil in the rear end. The bearing rides on the axle, not a race. there are axle saver bearings for that. Since you seem to have noise, better check the oil level at least. If it were mine, I would pull the cover and see what you have. If there are big pieces of metal laying in the housing, then you have a bigger problem than a bearing. If there is quite a bit of metal filings in the oil, at least change the oil, replace the offending bearing, and you will probably buy yourself a bit more time. If there is a loud whining noise, or a lot of vibration, then I would plan on replacing the rear end. Probably cheaper to get a used one from the local wrecking yard than rebuilding the rear end. Good luck.

 

[Bigham]

thanks. the rear has been making that high pitched whining since they replaced the gasket and added new oil. I chalked it up to thinner oil but it is loud enough to be annoying at certain speeds/frequencies.

WHat are the cost estimates to replace or repair?

 

[Bigham]

Another interesting thing happened today-I had about 700 pounds of mulch in the back and it did not whine nearly as much. Probably an 80% drop in the volume of the whine. Also the car rode smoother. I had an extra leaf spring added to the left side of the car to combat the gas tank droop. I noticed the car does not spring side to side as much with the extra weight and it was kind of nice.

 

[deweyville65]

The weight affects the driveshaft/pinion angle. Could be the pinion bearing is going bad. How much up/down and side to side play is there in the pinion shaft?

 

[SoNic67]

^ +1 for the bearing.

 

[corkey]

time for the real info,,

the driveshaft should only have about 1/16 to 1/8 play if at all possible,,
the fact that yours has 3/4 of an inch, and can move back and forth is a pretty good sign of something being real wrong,,
i wouldn't even drive it if it was like that, let alone put 700 lbs of stuff in te back of it,,

I would say the pinion bearings are already done for at this point and in need of repair,,
it may be spendy,, another option is a junkyard axle that is tight , and you can use your brakes, e brakes and all the lines from the one already on there,, you shouldn't even have to disconnect the calipers to change it even,,

 

[Bigham]

I have been driving around with it whining for well over a year now. Dont jinx me. Today the ABS light came on.

 

[corkey]

i don't mean to jinx you,,

pull the abs sensor out of the top of the rearend pumpkin, and see if it has metal debris on it,, it's a magnetic sensor, if there is debris , you found both your problems at once ,,

 

[Bigham]

Will do. Where is the sensor located?

Also, would these potential issues cause a scenario where when I am driving down the highway the car suddenly would swerve/veer to one side? It almost feels like a sudden gust of wind blows the car to one side or the other.

 

[corkey]

the sensor is located in the top of the rear differential,, it has 1 bolt that holds it in place,

if the pinion gear goes, it will just not be able to push itself,, it should stay in a straight line on the road,,
unless the pieces blow up the carrier,, in which case an axle could walk out of the tube ,
but it would take way more than a pinion gear going bad to do that