Maintenance Q&A
Oil drip, torque control and battery corrosion

By Paul Abelson, Senior technical consultant

I have a 2006 Freightliner with a Detroit engine and Eaton gearbox. It started leaking oil, and I noticed dripping under the truck. The shop said it is gear oil and I need to replace the oil seals. That’s an expensive job because they have to take the transmission down. What do you think about putting in an additive that restores the seals?

Oil companies spend millions of dollars developing and testing lubricants. Those tests include material compatibility with seals from all major suppliers. Some oil additives, often from secondary suppliers, may temporarily swell seal elastomers. The swelling helps them regain function, but the additives may have long-term negative effects on seal life. I recommend them only for short-term emergency fixes followed by a thorough disassembly and repair.

It’s possible that the seepage may not indicate seal problems. As transmissions work, they heat up, building up pressure inside the closed chamber of the gearbox. The air pressure bleeds off through breather values. If the valves are clogged, the air pressure in the box can force oil past otherwise good seals. Have your mechanic clean your 10-year old breathers and drive a few thousand miles before spending any serious money.

I bought a five-year-old Kenworth from a local fleet, mostly because they had good maintenance records and the price was good. I did get some aluminum wheels to replace the steel wheels it came with. That was about a year ago, 92,400 miles to be precise. Recently I started to feel a wobble in the steering. I had the truck aligned and tires balanced but that didn’t help. What should I look for?

We spoke and reviewed your maintenance procedures, including wheel fastening. As far too many shops do, the wheels were mounted with an air wrench. You control torque with a torque-limiting device often called a “torque stick.” They are not very accurate, according to another TMC Recommended Practice. It seems at some point the wheel nuts were over-torqued. Many studs were elongated and the threads were damaged.

Wheels are held on by a clamping force created when studs are stretched within their limit. Tension in the stud creates the clamping force. When a stud (or any fastener) is stretched beyond its limit, it permanently elongates and can no longer exert a clamping force.

Because of inadequate clamping, your wheels were loose. They wobbled against the steel stud threads. Aluminum being softer than steel, the stud holes were worn out-of-round, creating the wobbling. Not only do you need to replace the studs, you must replace the wheels, too.

When tightening wheel nuts, use a calibrated torque wrench and hand tighten to the specified torque. Don’t use an air wrench, and never give it a little more “just to be sure.”

My truck took longer than normal to start so I checked my battery connections and found white powder buildup. It’s on all the terminals but a little heavier on the positive side. I have a normal set of four 650 cold-cranking-amp batteries. Do I have to replace them?

When we talked, you said it had been more than two years since you got new batteries. If they have been in severe service, such as frequent engine-on, engine-off conditions or a great deal of city driving, then probably yes. For normal over-the-road use, there are other things to check first.

Use protective clothing and acid-resistant gloves and disconnect the terminals, negative terminals first. Inspect them and adjacent cables for damage and corrosion. Replace as needed.

Clean the terminals to get rid of the corrosive, acidic powder. For a light buildup, use a battery cleaner spray. Let it sit according to package directions, and then flush with clean water.

Don’t use any soaps or detergent. They could leave a residue. If the buildup is heavy, make a paste of baking soda (sodium hydroxide) and water and apply liberally to the buildup. Let it sit for a while, and then wipe it off with a paper towel or disposable rag. Flush with clean, clear water. Use a brush and added paste on any stubborn spots. Flush again with water.

Remove the batteries, being careful not to spill any acid. Inspect each battery on all sides, looking for cracks, loose terminals or other signs of damage. If any is found, that battery should be replaced.

It’s a good idea to test each battery using a carbon pile tester as described in a Technology and Maintenance Council Recommended Practice. It puts the battery under a load to simulate use. If it fails the test, it should be replaced.

As often as not, perfectly good batteries are disposed of with considerable life remaining. That’s why you should test batteries before replacing them. The work you did cleaning away corrosion will not be wasted.

If you can reuse your batteries, go ahead and thoroughly clean the battery posts and terminals with special “male” and “female” brushes designed for the tasks. When cleaning the terminals, check for corrosion that may have migrated up the cables. If found, replace the cables.

Reinstall the batteries, either cleaned or new, connecting the positive terminal first. Use dielectric grease to protect posts and terminals and, following directions, spray terminals and connections with a battery-protecting spray. Last, wipe any acid residue from your tools. LL

(Editor's note: When sending in questions for Maintenance Q&A, please include the make and model of your truck and your vehicle identification number (VIN) as well as your contact information. Paul Abelson tries to respond to every question, whether it's published or not. Send questions to