Auto Service Professional

OCT 2018

Magazine for the auto service professional

Issue link:

Contents of this Issue


Page 9 of 69

T e c h n i c a l 8 A S P O c t o b e r 2 018 Lock your lift It may be hard to fathom, but many shops are not in the habit of lowering their above-ground lis onto their lock blocks be- fore working on a vehicle. A recent release from Rotary Li reminds us about this im- portant safety feature. Not only does lowering a li onto its lock blocks serve as a safety precau- tion (in case the hydraulics fail, the lock blocks prevent the li f rom accidenta l ly dropping), but use of this feature also helps to protect the li from prema- ture wear. Once the li has been low- ered onto its lock blocks, hy- draulic pressure is relieved. Failure to rest the vehicle me- chanically onto the lock blocks and relying only on hydraulic pressure can place stress on the system over time, including the hydraulic cylinder and other li components. Just remember: li it slightly above the intended work height and lower it onto the blocks before work com- mences... every time! Thread lube makes a difference When you're looking up the torque specifications for a criti- cal fastener such as an engine or transmission application, pay attention to the requirements for thread treatment. Clamping value (the reason that a torque specif ication ex ists) ca n be greatly affected due to the con- dition of the threads, whether dry, lubed with oil, a high pres- sure lube or a thread locking compound. For example, if a bolt torque is specified as installed with engine oil and torqued to a value of 30 .-lbs., installing the bolt dry can easily result in under-torquing. Installing with the thread lubed with a super-slipper y assembly lube can result in over-torquing. If the torque wrench was set at 30 .-lbs. but the bolt threads are dry, the friction experienced during tightening can cause the wrench to reach 30 .-lbs., but in reality the bolt may only have been torqued to 20 .-lbs., prov iding less t ha n adequate clamping force. If a low-friction assembly lube was applied and the torque wrench indicates that 30 .-lbs. was achieved, the actual torque may be 40 .-lbs. or more, re- sulting in excessive clamping force. Friction during t hread engagement is a critical factor in torque value. If the instruc- tions (service manual, fastener m a k e r 's i n s t r u c t ion s , e t c .) specif y dr y t hreads, t hreads lubed with engine oil, applica- tion of a threadlocker or the use of a specific high-pressure/ low friction lube, follow those instructions to the letter. Oth- erwise you won't achieve the r e q u i r e d t orq u e v a lu e a nd clamping load. Powerstroke mystery noise If you have a customer's 1999- 2002 Ford F-350 equipped with t he 7. 3L Power s t roke eng i ne a nd automat ic t ra nsm ission, and you hear a mystery rattling noise that only appears at idle, and the noise appears to come from the rear of the engine, sus- pect a cracked flexplate or more likely a torque converter that's on its way out. e noise may appear at idle only, sounding somewhat like marbles in a coffee can. As soon as you give it throttle, the noise goes away. is is a fairly com- mon issue for these vehicles. ■ From lift locks to an annoying 'marbles in a coffee can' sound TECH TIPS Always lower your lift onto its locks prior to vehicle service. The "marbles in a can" noise can point to a torque converter issue.

Articles in this issue

Archives of this issue

view archives of Auto Service Professional - OCT 2018