Got it. Thanks.

 

Gentlemen,

The striations in the surface of the gears comes from a contaminant in oil or oil that has lost its lubrication properties and started allowing direct metal contact. Judging by the residue coating everything and the burnt smell, the oil has long expired. Was there any leaks? This could cause it to run low and thus create heat, wear, and accelerated breakdown. You will notice the striations run with the direction of the rotation of the pinion in relation to the ring gear. Metal contamination could be the answer. If you haven't wiped down or cleaned out the case, look on the bottom for material that didn't drain out with the oil. This could come from bearings or from the clutch plates inside the limited slip. The clutch material is softer and causes milder wear. I have run into this problem first hand on a pickup truck. The gears maybe salvageable but impossible to determine from just these pictures. Take the driveshaft off if you have not already done so and slowly turn it back and forth and see if you feel any roughness or excess slack. The pinion should not move in and out of the housing. You should not feel any roughness and just a slight bit (aprox 6-8 thousandth of travel) in the pinion to ring gear. If the pinion is truly coming in contact with the carrier, it should have made noise in reverse. The torque actually tries to push the pinion out the front of the housing under hard acceleration which is why the rear pinion bearing is the largest and its bearing race faces the ring gear. The smooth areas on the carrier are factory machined areas to true up the surface. If you are not experienced as you say, take it to an expert you can trust.

James
ASE Master Mechanic

 

Pictures of my differential all cleaned up.

 

It does look like the end of the pinion has been hitting the carrier in one area. But the gear mesh pattern looks OK on lead and trailing side of the ring gear teeth. If the pinion does not have any looseness in it, I would be surprised. But if that's the case, there may be no real damage in the unit. Was there any debris or metallic material in the remaining gear lube in the unit?

 

I will let the experts chime in, but your pinion is definitely hitting the posi case. I think a rebuild is in order. Do you see any cracks in the posi case?

 

Yep, now you can see the pinion has been loose at some time. But all of those old stains cleaned up. Looks to me that the gear is pretty much trashed by the wear and what looks like pitting on the face.

 

It's looks better then I thought it would. Yes the pinion hit the case and the gear pattern looks bad. The case scoring doesn't look too bad and if there are no cracks then it may be reusable. I would grind those spot to blend them in and as long as you're not going to dump the clutch at 5k RPM and drive "normal" you'll be ok. The one in my son's 75 was much worse, really requiring a replacement but I wanted to see how it would how up with a polish and tune and 21 YO driver. well it lasted 8k very HARD miles before it cracked in 1/2. Now even with this worn one, if he had not beatup the car with 200' burnouts, high shifts, then it would still be in the car.
If it were mine I would take it apart, blueprint it with better clutches, polish and tune it and install a new R&P. The RH yoke looks to have more wear in it but that is just by looking at the chamfer on the end.
If it was quiet, no leaks, no hammering, and you want to drive the car for a while then you can put it back and see how it acts just be aware of what you have.
The hit could have come from someone not correctly installing a pinion seal in the past as well.

Those are 308's BTW

 

I would still like to know if there was any metallic debris in the oil. That would be the determining factor on how to proceed IMO.

 

There were metallic debris in the oil. I put a magnet in the bottom and I saw tiny metallic dust moving towards the magnet.



So are you suggesting I should rebuild the rear end?

So what exactly does 3.08 mean other than the ring and pinion ratio?