Maintenance Q&A - October 2018

Replacing clutches and flickering lights

October 2018

Paul Abelson

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Q. A good friend of mine trucks locally doing construction work. He’s home every night and has an 80-foot-long garage for his tractor-trailer out back, complete with a grease pit and an oil pump. He buys in bulk and pays for it by doing oil changes and minor work for me and other local truckers.

I run long haul. He does my oil changes and inspections. It’s a good deal for him, and it saves me money compared to my dealer or a truck stop. My problem is my clutch. I have a 2014 Pete with a Cummins 550 and a Fuller 18-speed manual. The clutch is an Eaton Solo XL. With synthetic oil, I change quarterly or around 30,000 to 35,000 miles.

At my last oil change, my friend said the use indicator tab showed I had to replace the clutch. I had it replaced right after my last change, about 32,000 miles ago. The heavy work was done at my Pete dealer. They said they replaced part for part, all factory new, so I shouldn’t have any off-shore crap. Is my dealer ripping me off? Did Eaton have a problem? Please advise.

A. Replacing a clutch is a major undertaking requiring specialized tools, proper procedures and the right supplies (bolts, gauges and so forth). You were wise to have your authorized dealer and his trained personnel do it. Yes, 32,000 miles is way too soon for a clutch to be worn out, but there are other things that can affect wear and the indication of wear, including linkage and the Solo mechanism itself. To check, you must go beyond the wear indicator tab in the inspection hole.

First and least expensive, check the clutch linkage for any signs of damage – anything like bent rods or stiff joints that would inhibit clutch travel.

If the friction plates don’t separate completely or evenly, they will wear excessively. But that still should yield more than 32,000 miles. When I called for more details, you admitted to bumping a few docks “faster than usual,” as you put it.

When you’re in reverse and the clutch is engaged, the indicator tab can be jarred out of position to show that your clutch needs replacement when it doesn’t. Solo clutches self-adjust by having two plates with beveled ramps facing each other. When the clutch disengages, pressure causes these ramps to move and readjust their position relative to one another. The ramps force the friction plate out to compensate for wear, thus self-adjusting the clutch. The ramps are angled to allow this in a forward direction. When jarred, the wear side with the visible indicator tab can shift to indicate more wear than has actually occurred.

Your clutch was removed and measured for actual wear and found to be good to go. It was a costly way to find that you needed to improve your driving habits, but at least you didn’t need a new clutch.


Q. I have a problem with flickering trailer lights. I’ve been pulled over several times in the past few years, but thankfully the boys in tan saw fit to just give me warnings. I got so disgusted with paying to have my trailer checked that I finally sold it. I couldn’t afford to replace it, so now I’m pulling company trailers for less money. But the problem is still there. It seems as if every second or third trailer I pull has flickering lights. For all I know, it may be every one because drivers don’t seem to use the CB like they used to. With all the new LED lights and super-duper harnesses, this isn’t supposed to happen. What’s going on? Can you help?

A. I hate to tell you, but you may have been premature selling your trailer. Your problem likely lies in your seven-pin connector cable or your tractor pins. Studies have shown that the cable is almost always disconnected at the trailer, rarely at the tractor. Since all cables and junction boxes are designed to Society of Automotive Engineers standards to ensure interchangeability, tolerances must allow for variances in manufacturing processes.

Resulting gaps can range from 0.3mm or 0.016-inch on up. This is more than enough to allow water containing corrosive road salts to enter the assembly.

When plugs are disconnected and reconnected, normal wiping action removes corrosion in its early stages, but at the tractor end this self-cleaning doesn’t happen. TMC Recommended Practice RP159 suggests periodic inspection of the tractor-trailer connector cable and the SAE J-560 connector sockets and plugs at either end. I would suggest switching the cable ends every month in winter and every two in summer. Every truck parts store sells terminal brushes designed specifically for J-560 connectors. There are two types: a male wire brush to penetrate the socket holes on the cable assembly and a female wire brush to clean the prongs on the tractor or trailer nose box.

TMC’s recommended inspection starts with the cord. Make sure it’s abrasion-free. Check the “pogo stick” or springs to make sure cables are carried high enough that they won’t chafe. Being exposed, the cable will eventually have ultra violet degradation. If it’s hard cracked or brittle, replace it. Watch for excessive sag.

Inspect all terminals for dirt and corrosion, and clean as needed using a compatible cleaner. TMC RP155 covers corrosion prevention materials. When reconnecting always use a dielectric grease, but use it sparingly to prevent hydraulic lock that could prevent complete closure.

Latching devices need to be checked. Even if corrosion-resistant metals or engineered polymers are used for the bodies, springs are still made of steel. If they are weakened, they could allow the connection to loosen allowing corrosive liquid to enter.

Maintaining your cord should help solve your lighting problem. LL

Read more of Paul Abelson’s work here.

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Paul Abelson, senior technical consultant, is a longtime contributor to Land Line. He’s a member of the Society of Automotive Engineers and a member of the Technology and Maintenance Council. In 1995, TMC awarded him its Silver Spark Plug award. In 2006, he received the Lifetime Achievement Award from the Truck Writers of North America. Although he’s “retired,” he still makes a popular contribution to Land Line readers with “Maintenance Q and A.”