Damage inside differential, what to do next?

I bought my truck a couple months ago, and have been doing all the fluid changes and routine maintenance stuff. When I went to change the differential fluid, I found some strange damage inside. The cover has a deep dent from the inside, and one of the pinion teeth is chipped (pics in next post). There were no chunks of metal inside, which makes me think this happened a while ago and a previous owner removed the pieces. I hadn’t noticed any strange noise from the rear end while driving, but the truck is very loud so maybe I just didn’t hear it. The fluid did have a metallic sheen, but no gritty particles that I could find. What do you guys think I should do? I haven’t filled it back up yet because I hate to waste $60 of gear oil if I’m going to have to tear it open again in a month. Does this need a total rebuild? Could it last a while as-is?

Fill it and drive it. In the mean time, be sure your AAA towing in paid up. Your just another recipient of no one sells a good running vehicle.

Looks like the differential cross pin walked out at some point. PO probably “fixed” it. If it’s not making and abnormal sounds, I’d say run it. Change the gear oil again in 5-10k miles and reassess. In the mean while keep your eyes open for a decent deal on another rear end. That will probably be the most cost effective solution if it does let go.

Double ditto!

I think you guys are right. I don’t have much choice right now but to fill it back up and drive it for now. There seems to be a pretty constant supply of people parting out their trucks around here, so it shouldn’t take me too long to find another axle. Thanks.

I agree, you probably have it back together by now, but if not, just make sure that the differential cross pin is secure before putting it back together.

Here's a sampling of the availability and price in Ohio for these rearends. I picked a 4.10 ratio.

The damage was done by a broken spider shaft (maybe just a broken end), it has been repaired. If the scrapes bother you, replace the cover with a clean one. If the chipped pinion makes noise, consider a replacement rear end. Those chips were probably made by the broken shaft when it popped out of the housing. Nice photos!

Thanks for the help guys. I was glad to see that axles are plentiful and relatively inexpensive. Does anybody know if a 93+ axle (with the long pinion) will bolt right up to my driveshaft? I know the yokes are different on long and short pinion rear ends, but do they use the same u-joint? If it’s not a hassle I figure I might as well get one of the long pinion axles.

I think it's unusual that when I plugged in a 1989 f250 on www.car-part.com above, that it listed those later rearends fitting. They usually only list direct interchange. Like you, I would have thought you would need a shorter driveshaft or something like that.

The main change was on the pinion and yoke, not the housing. The yokes are different in that they reach farther into the housing with 1/2" longer splines. I believe that the shaft length is the same, as is the U-joint.

That’s what I thought too, that either one would bolt up to my driveshaft. I took the truck for a fairly long drive today, and I didn’t notice any noises from the rear end. I do think the clock is ticking on those bearings given the metallic sheen of the old gear oil, but hopefully I have time to shop around for a good deal on a long pinion axle.