Driveline preventive mainte-nance is largely lubricationservice. That doesn’t meanit’s a low-tech service, how-ever, and driveline PM has

taken on new aspects in the pastdecade. Let’s take a look at some of themodern features of these traditional un-dercar services. What you learn herecan help you do a better job for yourcustomers and may help you avoidsome costly comebacks.

Today’s scheduled services for drive-line components are basically fluid ser-vice for the transmission (manual orautomatic), differential (final drive)and transfer case on 4x4s; lubrication

of U-joints and slipjoints; and inspec-tion and lubrication of front-drive CVjoints and boots.

U-Joint, Slipjoint &Driveshaft ServicesUniversal joints on modern rear-drivepassenger cars are largely maintenance-free items. That’s not so, however, forthe U-joints on light trucks and 4WDsport/utes. Many truck drivelines haveU-joints with lube fittings, and some ve-hicles have as many as four or five fit-tings on the complete driveline. Thenthere may be a couple more on thefront axle U-joints of a 4x4. Don’tguess about the number and locations

of driveline lube fittings on any truck or4x4; check the lube charts in a manual.

Because driveline services coincidewith lube, oil & filter (LOF) service in-tervals, it’s easy and efficient to hit allthe lube fittings on a vehicle with thesame grease gun. Watch for the excep-tions, however. For example, GM callsfor a special grease on the driveshaftspline of 2WD trucks and vans. It’s GMPart No. 12345879, Specification No.998530. Similarly, Ford specifies a high-temperature grease that meets specifi-cation ESA-M1C198-A (Part No.E8TZ-19590-A) for most truck drive-line U-joints and slip yokes. Your regu-lar chassis grease may or may not meetthese requirements. Check with yourlubricant supplier to be sure.

CV Joint & Boot ServicesConstant velocity (CV) joint and bootservices for front-drive cars usually fallunder the catchall instruction “inspect.”It’s a good idea to look at the driveaxleboots closely whenever a FWD car is onthe rack for any undercar service. Theaccordion pleats of these boots can hidecracks and tears that will turn into seri-ous leaks and allow the grease to bethrown out of the CV joint by the cen-trifugal force of axle rotation. Check theboot clamps, too, to be sure they’re notbroken or loose. Also look at thetransaxle lip seals at the inner CV jointsfor signs of leakage.

Scheduled maintenance can move in-to the area of “preventive repair” if youfind a cracked, torn or otherwise dam-aged boot or a leaking transaxle seal.

Awash in ATFLess than 20 years ago, your inventoryof transmission fluids could be prettysimple. Ford automatic transmissionsused type F fluid; most of the rest of theworld used DEXRON. Manual trans-missions and rear axles on rear-drivecars were filled with hypoid gear oil, al-though some manual gearboxes andtransfer cases used motor oil or ATF(usually DEXRON). It’s not that simpleanymore.

Today’s automatic transmissions andtransaxles may require DEXRON-II,DEXRON-III, MERCON, MER-CON-V, ATF+3, type F (for a fewdiehards) or type T. Additionally, morethan a dozen vehicle manufacturers

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specify variants of these common fluids,special additive packages or extra re-quirements contained in the manufac-turer’s specifications. Some of thesevariations are “recommendations”; oth-ers are firm requirements. For example,the automatic transmission of an all-wheel-drive Toyota Corolla will die aquick and hideous death if the specifiedToyota type T fluid is not used. No,DEXRON or MERCON is not “okay”;that transmission requires type T fluid,period.

Does DEXRON-III supersedeDEXRON-II in all applications? Maybein the world of GM it does, but not allother carmakers agree. Honda/Acura,Audi/Volkswagen and Mazda are amongthe manufacturers that say not to useDEXRON-III, even in their ’98 mod-els. Nissan and Infiniti say thatDEXRON-III is okay after the warrantyexpires, and Chrysler as yet is reluctantto recommend DEXRON-III retroac-tively for older models that originallyused DEXRON-II. The differences be-tween DEXRON-II and DEXRON-IIIare mostly related to “lifetime” serviceintervals of several recent GM transmis-sions, and it’s likely that other vehiclemanufacturers will require similarchanges as they move toward extendedservice intervals.

Ford, meanwhile, has developedMERCON-V for some 1997 and latertrucks, and it is not interchangeablewith regular MERCON. Chrysler spec-ifies its own ATF+3 for many late-mod-el cars and trucks; and, no, it’s not exact-ly the same as any of the DEXRON orMERCON variations. You can bet thatthe dialogue and debate among carmak-ers and oil companies will continue. Nooil company wants to package differentATF blends for more than a dozen dif-ferent specifications, and you probablydon’t want to carry that kind of varietyin your inventory. The best thing youcan do is to be aware of today’s fluid re-quirements and be alert for the changesthat doubtless will come.

Drowning in Gear OilIf you think the variety of late-modelATF specifications is confusing, look atthe OEM recommendations for manu-al transmission, differential and trans-fer case lubricants. For manual gear-boxes, we still have GL-1, GL-3, GL-4

and GL-5; but there are almost threedozen variations on basic gear oils rec-ommended by different carmakers.Throw in the gearboxes that use motoroil or ATF and you could write a bookjust on transmission, differential andtransfer case lubes. No one can re-member all the variations, but the fol-lowing can help you sort out the OEMrecommendations.

When all the world’s cars andtrucks were rear-drive, the final driveused a hypoid ring and pinion gearset.The design of hypoid gears creates awiping action between the gear teeththat generates extreme pressure andtemperature. Hypoid gear design ledto the development of extreme pres-sure (EP) hypoid gear oils that me-chanics have known for generations.You’ll still find one of these familiargear lubricant (GL) fluids used wher-

ever a hypoid gearset is used. The mostcommon fluids are GL-4 and GL-5.

Limited-slip differentials require afriction-modifier additive in the gear oilfor the differential clutches. Here’swhere the variety starts. You’ll findabout eight or nine different formula-tions or additives specified by carmak-ers such as GM, Ford, Chrysler, Mer-cedes, Mitsubishi, Volvo and others.Without the friction modifiers, clutchchatter becomes a major problem, andclutch life will be drastically shortened.

When all the world used hypoid gearoils in RWD differentials, it was simpleto use the same oil in a manual trans-mission. Even 30 years ago, however,

some carmakers were specifying SAE30 motor oil or ATF in manual gearbox-es and 4x4 transfer cases. Today, mostfront-drive cars do not have hypoid finaldrive gears, so the use of motor oil andATF in manual transaxles has increased.So has the variety of lubricant specifica-tions. Chrysler, Ford, GM, Honda andToyota are among the major carmakersthat call for special lubricant formula-tions, additives or synthetic gear oils inat least some of their gearboxes andtransfer cases.

Watch Out for These PitfallsIf transmission fluid service is part ofyour business, you should be aware ofthe differences in FWD and 4x4transaxles, final drives and transfer cas-es. Many FWD transaxles have a com-mon lubricant sump for the gearboxand the final drive. Almost an equal

number have separate drain & fill loca-tions for the transmission and the finaldrive—and thus different lubricantspecs.

Many Toyotas, for example, havetransaxles with a common lubricantsupply for the transmission (manual orautomatic) and the final drive. Manyothers have gearboxes and final drivesthat are serviced separately with differ-ent lubricants. Toyota 4x4 and AWD ve-hicles may have either separate or inte-grated transfer cases that use fluids thatare the same as—or different from—the gearbox fluid.

The 41TE automatic transaxle inmany Chrysler FWD cars and vans

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The accordion pleats of a CV joint boot can hide cracks that cause loss of lu-bricant. Check the boots carefully anytime you have a vehicle on the rack.

has a common sump with the finaldrive and uses Chrysler ATF+3 fluid.Chrysler’s 42LE auto transaxle usedwith longitudinal engines, on the otherhand, has a hypoid final drive withseparate drain & fill plugs. The trans-mission uses ATF+3, but the finaldrive requires GL-5 gear oil. Do youthink you can remember all these dif-ferences? Probably not; rely on yourmanuals to do the job right.

Maintenance-FreeTransmissionsJust as “permanent” antifreeze dis-cussed in the September issue is a pop-ular topic for discussion, so are “long-life,” “maintenance-free” transmissions.In the past three or four years, GM andother carmakers have produced auto-matic transaxles without dipsticks andno requirement to service the fluid orfilter for 100,000 miles in normal ser-vice. “In normal service” is the catch be-cause GM specifies a fluid and filterchange at 50,000 miles for severe ser-vice. Of course, severe service includesall the common conditions of short-trip,stop & go driving, as well as operationin hot or dusty conditions, trailer towingand mountain driving.

ATF Flush & Fill EquipmentIn the equipment marketplace, ATFflush & fill machines are as hot ascoolant and refrigerant recyclers. A lotof pro-and-con dialogue has been goingon about the merits of these machinesvs. the traditional service of droppingthe pan, cleaning the screen or chang-ing the filter and refilling with freshATF. Much of the debate centers onwhether or not the filter should bechanged.

Transmissions use either a replace-able paper or felt filter or a reusablescreen to remove contaminants fromthe fluid. Asian manufacturers seem tofavor screens, while U.S. and many Eu-ropean carmakers use filters. A screenundergoes a backflushing action whenthe engine is shut off and the fluiddrains out of the transmission pump.Dropping the pan to inspect and clean ascreen is not as critical as it is to changea filter. Some flush & fill machines stillrequire pan removal, but at least theymake the job faster and cleaner.

Three general kinds of flush & fillmachines are currently marketed by ahalf-dozen different manufacturers.All offer some unique features andbenefits:

•Fluid evacuators. A fluid evacuatorhas a suction wand that’s inserted downthe dipstick tube. The evacuator usesyour shop air supply to create an air-as-pirated vacuum that sucks fluid out ofthe transmission. These machines alsowork great on a differential or manualgearbox that does not have a drain plug,and they can remove fluid down to thelast fraction of an ounce. An evacuatordoes not drain a torque converter; butbecause drain plugs went away fromconverters 30 years ago, this method is afast, efficient alternative to the standardservice of changing the ATF in the pan.

•Cooler line flushers. These ma-chines tap into an ATF cooler line nearthe radiator. Most techs use the car en-gine to run the transmission, to pumpold fluid out and new fluid in. Some ofthese machines use about twice the vol-ume of fluid that the transmission holds,to thoroughly flush the system. This alsoflushes the torque converter and cansignificantly clean a transmission thathas been neglected. Other coolant lineflushers use less fluid but do the job inless time. With any of these machines,however, you’ll still have to drop the panto change the filter.

•Fluid injectors. A fluid injector re-quires you to drop the pan, but that’sokay if you plan to change the filter any-way. The machine is connected to thepump pickup tube on the transmissionvalve body and uses the car’s engine toflush and refill the gearbox and thetorque converter. During the process,used fluid drains into your customarydrain pan.

You can expect more flush & fill ma-chines to appear on the market, withadded features. As regulations to pro-tect the environment from chemicalspills increase, the use of this kind ofequipment will most certainly grow.

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