Hello all, first time poster here. I’ve used this site for all of the problems I’ve ever encountered with all of my trucks and I’ve always found the answer here. I’m stumped on this one though. This morning I went out and started my 88 7.3 with 88,000 miles on it. Let it warm up for a little while and went on my way. I was doing about 45 on the highway and all of the sudden my rear right tire just locked up and started skidding. Left black marks all over the road. I came to a stop and checked it out, couldn’t see anything wrong. I put it in drive and tried to pull forward, it wouldn’t do it. So I tried it in reverse, and it backed up. So I went back to drive and it seemed to “disengage” it. Then I could drive normally again. I’ve been busting my brain trying to figure it out, and I read some other forums. I checked the e brake and I never use it because it hasn’t worked since I’ve had it. It’s a zf5, and I wasn’t pressing the brake when it happened. I’ve drove it around 5,000 miles since I’ve had it. I’ve never been into drum brakes before so I’m not sure what to expect on that end. I appreciate all of your help.

I was talking to a buddy of mine and he seems to think it’s the rear differential locked up. I put it in reverse when it happened and I was able to back up and then pull forward and drove like normal. Surely if it was the rear differential it would permanently be destroyed if that happened unless a huge chunk of something got wedged in between the gears right?

It is noisy when I’m driving with the windows down. Mostly because of the flat spot that is now on that tire, but I can also hear a slight clicking sound coming from that side. That’s why I’m agreeing more with you than the differential possibility. The linkage would cause a clicking sound of it was loose and flopping around. I felt the differential and it wasn’t hot, but the drum was. It was also covered in a black looking material that I didn’t see there before. The rear anti-lock light has been on since I got it but if you push down on the pedal as hard as you can the light will go off. I tried to bleed the brakes in the back, but the nut is rounded off on the back of the drum. The hard line going into the drum is also rounded off. Maybe I should just replace everything back there and forget about it?

The only noise I could hear was the screech of the tire skidding on the road. That was a low mile tire too. That’s disappointing. But it didn’t make any noise really that was coming from the truck. I mean no vibration, no shaking, no shimmy, it just happened all the sudden. I look behind me in the rear view and I’m leaving a long black trail from the back right tire. It didn’t act like it slowed it down either. But like I said. I only locked up the back right tire. Not the left. But I appreciate everyone’s input. I haven’t had a chance to dig into it yet due to the weather. I’m also leaning towards it being the brake. I’m pretty sure I have the sterling 10.25 with the 4:10 rear end. My dad’s truck which is a 97 has the same rear end I think which I did the wheel bearings on a couple years ago. I’m thinking about just tearing into the bearings and brakes all together to really get a deep inside look of what I have. I bought this truck on an auction and it was an “as-is” buy. Only bought it for 2K though. It sat for around 5-6 years and was only moved by a forklift. Probably should’ve done this from the start. Just glad I wasn’t loaded or anything.