Do you have problems with your square body K5 Blazer or truck automatic locking, Autolocking Hubs? A lot of people have issues with them sticking and not engaging. Some people have trouble getting them to disengage. I’ve had issues where one or the other of them would engage occasionally on their own. When this happens it creates a situation where one of the front axles is turning the front differential and at highway speeds it creates a vibration like a wheel out of balance.
I’ve followed incorrect advice on cleaning and lubricating the automatic locking hubs in the past and continued to have problems with them. This time I did a considerable amount of research (I read the service manual and and found another document on servicing these autolocking hubs) on the right way to clean and lubricate K5 Blazer autolocking hubs. These hubs were used on some Ford Broncos as well, and the 2nd PDF mentions that as well.
The instructions mention using a special grease (GM 1052750, Darmex Lubricant 123LT) on the “Brake Band” which is a coil spring which wraps around the “Drag Sleeve” (#75 in service manual PDF). Nowhere had I read this before. All the other instructions and posts I’d read said to clean the entire automatic locking hub assembly in parts cleaner and then lubricate with a light oil. I found the MSDS sheet for this grease and emailed it to Royal Purple and confirmed that I could use their Ultra Performance Grease instead. I did purchase a tube of the GM 1052750 Darmex 123LT lubricant off of eBay but it’s pretty old and I didn’t want to use it.
The proper way to service the autolocking hubs:
- Remove the assembly from the vehicle.
- Remove the “Drag Sleeve” assembly – do not remove the “Brake Band” spring from the Drag Sleeve.
- Clean everything in parts cleaner.
- Lubricate the “Brake Band” with high performance grease.
- Soak the rest of the assembly in automatic transmission fluid and let drain.
I also purchased two of the large rubber flat o-ring type seals (part #53 in the service manual pdf) from NOS (New Old Stock – meaning never used old stock) off of eBay. Look for part #’s GM 15664156, and GM 14038036. I ordered GM 14038036 and they fit perfectly.
I wanted to find a part # for the little o-rings on the hub cover torx screws, but I didn’t.
I made a video of the process:
- Automatic Locking Hub Pages from 1987 Light Duty Truck Service Manual
- Automatic Locking Hub Service Cleaning and Lubrication Instructions
- GM 1052750, Darmex Lubricant 123LT MSDS Manufacturers Safety Data Sheet
I can report that I’ve been driving the vehicle for a couple of weeks now after performing this “correct” method of cleaning and lubricating the autolocking hubs and they have worked great.