My 9 inch rear end has started to leak. Gear oil appears to be coming from the front flange of the 3rd member where the yoke attaches. What are the probable causes of the leak and can a backyard mechanic (me) do the job without special tools.

Thanks for any suggestions.

 

It's not too bad of a job. The key thing is to figure out whether the seal simply aged out, or if maybe a bearing has enough wear & caused the seal to fail.

Drop the driveshaft and grab the flange & try to move it back and forth...it should be pretty stable. Assuming that all you need is a seal, remove the big center nut from the flange, pull the flange...& take a look at this diagram to see where the seal is.

When you re-assemble it, the torque of the flange nut is important...look up the specs.

 

There is an o-ring on the pinion retainer. Probably shot. that's a cinch to replace. Pop off the 5 bolts once the drive shaft is out and replace the seal.
The pinion yoke oil seal is a little more complicated and will require a large breaker bar, large torque wrench, a large socket to match the retaining nut and in some cases a pinion yoke puller. You have to be careful doing this one as you need to match the rotational torque of the pinion yoke (measured before you tear it apart) when tightening up the pinion yoke retaining nut on re-assembly. Since it's a crush sleeve that's already been crushed, it can easily be over tightened. Pay attention to how many threads are showing past the retaining nut before dis-assembly. Run it back on the same amount and then slowly tighten until you get the same rotational tension of the yoke as it was before. In most cases this (rotational torque) can be measured with a small scale in-lb torque wrench.