Oil leak on the 70 differential

[Chris H.]

The pinion oil seal, where the drive shaft enters the diff, is leaking on the 70. Can I fix it with the differential in place, by just removing the drive shaft and putting in a new seal, or do I need to drop the differential?

Thanks, Chris

[Joe L.]

Re: Oil leak on the 70 differential

Chris-----

You can replace it without removing the differential unit, but it's tricky for the inexperienced. To do it, you must first remove the driveshaft. Then, you must remove the pinion (companion) flange. This may be difficult in the car without the proper tools and a means to hold the companion flange while the pinion nut is removed. Tricky part: measure the break-away torque required to remove the nut.

After you remove the companion flange, it's rather simple to pry out the old seal and install a new one. Then, after lightly greasing the seal surface on the flange, reinstall the companion flange and pinion nut.

Now for the real tricky part: you must torque the pinion nut to the pre-existing torque, plus a few pounds. This is necessary due to the crush sleeve type bearing adjustment. Since, you're not replacing the crush sleeve in this type operation, you must "re-crush" the sleeve, but just by a very small amount.

[Joe L.]

Re: Oil leak on the 70 differential

Chris-----

You can replace it without removing the differential unit, but it's tricky for the inexperienced. To do it, you must first remove the driveshaft. Then, you must remove the pinion (companion) flange. This may be difficult in the car without the proper tools and a means to hold the companion flange while the pinion nut is removed. Tricky part: measure the break-away torque required to remove the nut.

After you remove the companion flange, it's rather simple to pry out the old seal and install a new one. Then, after lightly greasing the seal surface on the flange, reinstall the companion flange and pinion nut.

Now for the real tricky part: you must torque the pinion nut to the pre-existing torque, plus a few pounds. This is necessary due to the crush sleeve type bearing adjustment. Since, you're not replacing the crush sleeve in this type operation, you must "re-crush" the sleeve, but just by a very small amount.

[Clem Z.]

Re: Oil leak on the 70 differential

you can do it but you must scribe a line on the pinion face,pinion nut and pinion yoke so when you put them back you tighten the nut to the very same place. you will need a air impact wrench to remove the nut because it is torqued to very high poundage. take note how far in the orignal seal is installed and install the new one the same depth

[Clem Z.]

Re: Oil leak on the 70 differential

you can do it but you must scribe a line on the pinion face,pinion nut and pinion yoke so when you put them back you tighten the nut to the very same place. you will need a air impact wrench to remove the nut because it is torqued to very high poundage. take note how far in the orignal seal is installed and install the new one the same depth

[Duke W.]

Re: Oil leak on the 70 differential

The shop manual also instructs to use a sealer on the companion flange/pinion splines. I belive some leaks are caused by failing to accomplish this step.,

Duke

[Duke W.]

Re: Oil leak on the 70 differential

The shop manual also instructs to use a sealer on the companion flange/pinion splines. I belive some leaks are caused by failing to accomplish this step.,

Duke

[Chris H.]

Re: Oil leak on the 70 differential

Thanks Joe, Clem, and Duke...........

My only concern now is if I can do this without pneumatics...

Chris

[Chris H.]

Re: Oil leak on the 70 differential

Thanks Joe, Clem, and Duke...........

My only concern now is if I can do this without pneumatics...

Chris

[Bill Clupper]

Re: Oil leak on the 70 differential

A good breaker bar will suffice, in my experience (done it twice) the biggest problem is keeping the flange from rotating.

[Bill Clupper]

Re: Oil leak on the 70 differential

A good breaker bar will suffice, in my experience (done it twice) the biggest problem is keeping the flange from rotating.