So, it looks like I'll be working on the differential in the 280Z just in time. I have noticed an oil drip from the center/rear area of the car over the past couple weeks, so I put the car up in the air today and rolled under it. I was expecting to see a leak from the rear trans, but upon inspection, it appears as though it is the front diff oil seal. Is this a common seal failure? Within the next two months, I intend to drop the diff and replace it with another unit anyway - how critical is it to keep the diff completely full? So far, there is no noise. The area around the front of the diff is coated in oil, the weight below the front diff mount is dripping, and the driveway has 10 or 20 drip places on it from the past few weeks. Is there anyway to tell when it is getting 'too low'?

Thanks.

It's a common leaking point in the diff. As the diff wears(bearings, pinion and ring gear), the preload on the pinion bearing will change and allow movement in the pinion that will wear out the seal.

Just pull the fill plug on the rear cover to check the level, and if the leak is that bad, I'd leave it slightly lower than the fill plug, perhaps just enough that you have to insert your finger in and bend the first joint of your finger to get to the fluid. If you fill it completely, it may leak even worse.

Originally posted by 2ManyZs

It's a common leaking point in the diff. As the diff wears(bearings, pinion and ring gear), the preload on the pinion bearing will change and allow movement in the pinion that will wear out the seal.

Just pull the fill plug on the rear cover to check the level, and if the leak is that bad, I'd leave it slightly lower than the fill plug, perhaps just enough that you have to insert your finger in and bend the first joint of your finger to get to the fluid. If you fill it completely, it may leak even worse.

Thanks, Keith, at least I know it's a common problem now. This car sat for 10 years (well, it was driven 2000 miles in that time), so I'm having all sorts of interesting seal failures after having driven it another 4000 miles over the past 8 months. I'll top it off and hope it makes it long enough to get me to my diff replacement time.