Nothing is more annoying than a nasty oil spot on your clean driveway or garage floor. In this case a newly rebuilt 9" centersection in our project Bronco started seeping oil almost as soon as it was filled with oil.
Here is the annoying spot on the shop floor:
A little investigating led me to determine the oil was leaking out of the pinion or seal area:
I started the process by removing the pinion nut using my 18 volt Craftsman cordless impact wrench. If you have never used a cordless impact wrench, you are missing out because I cannot live without mine:
I had replaced the pinion seal, but I re-used the pinion yoke even though there were a few small grooves in it. It was most likely the culprit. A call to Randy's Ring & Pinion got me a new yoke, pinion seal, and pinion nut. There are repair sleeves for the yokes, but they are only $5.00 cheaper than a whole new yoke, which cost me about $50.00:
I cleaned the splines on the pinion with some brake cleaner to remove any remaining oil:
I next smeared some silicone on the inside of the yoke as I have seen the yokes leak through the splines:
I did the same on the pinion nut:
Some bearing grease was smeared on the sealing surface of the yoke to keep the seal from burning up from being dry:
I didn't replace the pinion seal because it had just been replaced, and the vehicle did not run at all. I placed the yoke back on the pinion and seated it as far as it would go by pushing on it:
The pinion nut was then replaced and threaded on by hand:
There are different ways of making sure that the pinion bearing has the correct amount of pre-load such as counting threads, or turns of the pinion nut. I have a different method: While tightening the pinion nut with the impact wrench, I pull on the yoke to see if there is any play on the assembly. I slowly keep tightening the nut until a slight amount of resistance is felt, and then I go 1/16th of a turn more which is the correct amount of pre-load on the pinion bearing. The cordless impact WILL NOT crush the crush sleeve any further than it is. I have used this method on dozens and dozens of 9" centersections and I have never had one fail yet:
The best part of the whole process is the clean floor.