1995 2500 4x4 desil.. I had some leaking of gear oil out the ends of the drive shaft by the tires..

I just replaced the breaks and rotors and such a few days ago and probley damaged the seals in side..

I have the dif cover off .. but cant figure out what size that pinion shaft lock bolt is to take out the unit..

any ideas.. Im thinking its a allen key of some size.. but have tried both metric and sae.. but neither take..

what is that thing so I can finish the job.. lol