1Hard ShiftingWhen hard shifting is reported, the first thing tobe inspected is the clutch. An improperly operat-ing clutch will interfere with the shifting of gearsin any transmission. And dont overlook theobvious. Spicer transmissions require the correctlever ratio to shift properly. This ratio is calcu-lated from the fulcrum both up and down. Syn-chronized transmissions require a shift lever ratioof 8 to 1 for proper shiftability.

Next, examine the remote control linkage forproper adjustment, worn bushings, bent rods orlack of lubrication. If none of these are the prob-lem, remove the remote control from the trans-mission.

By removing the remote control and shifting thetransmission into gear with a pry bar, you candetermine whether the transmission is at fault. Ifthe shift rods move readily into position, thetrouble is somewhere in the external linkage. Ifnot, consider these possible causes of hardshifting:

n Worn or bent shift rods or shift rails Replace as necessary

n Broken springs or elongated poppet holes inshift cover

Replace springs, shift cover or bothn Clutch collars tight on mainshaft splines

Check for twisted mainshaft andreplace

n Free running gears seized on either the thrustface or the shaft diameter

Use correct type of lubricant at theproper fill level

n Broken thrust washers or snap rings Replace and check for vibration

n Excessive end play Shim to correct end play

n Loose mainshaft nut Torque to specified rating

n Worn or seized pilot bearing in flywheel Replace worn or damaged components Use correct lubricant

n Oxidized or overheated lubricant Follow recommended lubrication

proceduresn Metal particles imbedded in brass or

GYLON-coated synchronizer ring Replace synchronizer Check lubricant for contamination and

replace Check for other damage that could

result from clash shifting

Gear JumpingGear jumping is caused by interference in theshifting mechanism or some other malfunctionwhich results in the clutch gear or shift rodmoving out of its selected position during opera-tion.

When a problem occurs, inspect the shift leverfirst. Make certain it moves freely and completelyinto position. Also check the floorboard opening,drivers seat or anything that could prevent fullclutch gear engagement. Other potential causesof gear jumping include:n Heavy shift lever extensions

Use a shift lever that doesnt have a top-heavy extension

n Broken poppet springs Replace

n Worn shift rod detents Replace shift rod

n Bent or sprung shift rods or forks Replace

n Worn clutching teeth on shift collars Replace Inspect mating components for damage Make certain the driver knows and uses

proper shifting techniquesn Broken thrust washers

Replacen Broken snap rings

Replacen Worn corners on mainshaft or clutch gear

gearlocks Replace Inspect mating components for damage

S O M E C O M M O N T R A N S M I S S I O N C O M P L A I N T S

2S O M E C O M M O N T R A N S M I S S I O N C O M P L A I N T S

VibrationVibration problems are often difficult to trace andisolate. While the effects of vibration will oftencause transmission problems, the vibration itselfusually originates somewhere else.

Intermittent vibration can be isolated underspecific conditions of engine idle or RPM, gearselection, load and speed. Constant vibrationshould also vary with engine RPM, load andspeed to provide clues to its source.

Some possible causes of vibration include:

n Loose output nut which is sometimes indi-cated by shiny areas on the output shaft(caused by yoke movement)

Tighten nut to specifications Check output shaft for wear

n Rough idling engine Use dampened disk clutch

n Loose or broken engine mounts Replace

Sometimes vibration originates in the driveline.Potential causes include improper universal jointworking angles, out-of-phase shafts, shafts thatarent balanced and excessive driveshaftlengths. If the driveline is the source of thevibration, these conditions must be corrected.

VIBRATION WARNINGVibration can be an early indicator of a problemwith the vehicle driveline. Potential causes ofdriveline vibration are excessive operatingangles, out-of-phase shafts, unbalanced shafts,or excessive shaft lengths. These conditionsmust be corrected immediately. Driveline vibra-tion can cause damage to the transmission andcan also result in separation of the driveline fromthe vehicle. Separation of the driveline from thevehicle can result in serious bodily injury ordeath. In order to avoid driveline vibration, youmust have the vehicle examined immediately bya qualified mechanic who is experienced withproper driveline application and installation.

Heat and LubricationA continuous operating temperature of 250 Fshould be considered as maximum for reason-able drain intervals. A rise in temperature of20 F over 250 F doubles the oxidation rate, thusshortening the effective life of the oil. Shortperiods over 300 F dont indicate a transmissionproblem, but will still affect oil life.

Figure 1Torsional engine vibration could cause wornclutching teeth.

3S O M E C O M M O N T R A N S M I S S I O N C O M P L A I N T SCertain conditions can cause a temperatureincrease and, therefore, make an oil coolernecessary. These include:

n All direct main transmissions behind enginesrated at 400 HP (gross) and above

n All overdrive main transmissions behindengines rated 350 HP (gross) and above

n All main transmissions (direct and overdrive)where vehicle GVW/GCW exceeds 90,000 lbs.

n All auxiliary transmissions where vehicleGVW/GCW exceeds 80,000 lbs.

n All auxiliary transmissions behind overdrivemain transmissions regardless of enginehorsepower

n Vehicle configurations that restrict air move-ment around the transmission (i.e., aero bodyconfigurations, low front bumpers, deckplates, skirting, or an exhaust pipe near thetransmission)

n Any vehicle application that has high transmis-sion shaft speed at low ground speed or runsabove 250 F continuously

n Geographical locations in which the vehicle isto be operated, such as mountains, or in highambient temperatures

n Transmissions running a PTO in a stationeryapplication

LUBRICATION CAUTIONProper lubrication of the transmission is critical tothe life of the transmission and safe operation ofthe vehicle. Lubrication problems can result fromtoo much lubricant, too little lubricant, or thewrong type of lubricant. Improper lubrication canresult in excessive heat and seizure of the bear-ings in the transmission. A seizure of the bear-ings can cause the vehicle to lose power. Inorder to avoid these problems, it is important thatthe instructions for proper lubrication are care-fully followed.

Proper LubricationHelp your lubricant protect your equipment byfollowing these guidelines.

n Always fill Spicer transmissions to theproper lubricant levels. Using too muchlubricant causes it to churn, foam, andoverheat. This prematurely breaks down thelubricant. Too little lubricant allows heatbuildup and prevents adequate coatingand protection of components. The lubri-cant should be level with the transmissionoil fill plug.

n Always follow the recommended gradesand types of lubricant for your Spicertransmission. Never mix and match gradesor types of lubricant: they may be incom-patible. Lubricant specifications are pub-lished in Spicer service manuals.

n Always follow the recommended oil changeschedule for your Spicer transmission.

n Use only quality lubricants.

n When changing oil, check it for contamina-tion. If debrisespecially metal chipsarefound, it could be a sign of internal trans-mission damage. In any case, replacecontaminated lubricant and further exam-ine the unit if it is indicated.

n Check the angle of the transmission. Toosteep an angle could prevent lubricant fromreaching the input shaft pocket bearing.

4Gears and Clutch Collars

As you examine a gear, you may notice hobmarks, or scallops, on the tip and root of thegear teeth. These are normal and acceptablemachining marks. They do not indicate a prob-lem with the gear (see Figure 2).

C O M P O N E N T F A I L U R E S

Figure 2Hob marks are acceptable.

However, over time gear teeth will wear as theymesh with mating gear teeth. When the endur-ance limit of the gear material is exceeded, theresult is pitting (see Figure 3). If a gear withpitting over 50% of its tooth surface is allowed toremain in service, it will eventually fracture.

Figure 3Pitting, scoring and galling can occur when thegear material endurance limit is exceeded. Lubricationproblems can also contribute to these conditions.

Another contributor to pittingas well as toscoring and gallingis improper lubrication.Improper lubrication refers to lubrication break-down, improper lubricant levels, and contami-nated lubrication.

Any breakdown of the lubrication, or reduced oilfilm, can increase the possibility or accelerationof tooth surface distress. More importantly,inadequate lubrication for a sustained period islikely to cause the distress to advance to moresevere stages. Common causes of inadequatelubrication are:n Low lube leveln Inadequate lube viscosityn Use of incorrect luben Use of oil beyond its functional life

This can lead to alternate welding and tearing ofmetal from gear teeth surfaces (see Figure 3).

See LUBRICATION CAUTION (pg. 3).

5As the hardened gear teeth surfaces begin towear away, failures arise. A sudden shockloadfailure shows clean break lines (see Figure 4).

C O M P O N E N T F A I L U R E S

A gear failure that occurs over a longer period oftime has oyster shell or beach marks. Thesemarks look like the pattern ocean waves leave insand (see Figure 5). Generally, bending forceson the gear teeth will create cracks in the toothssurface. Over a period of time, the crack willcontinue to grow, causing a beach mark designfracture pattern. Finally, the tooth is weakened tothe point where it breaks off. The surface of thefailure is generally smooth and will have con-toured lines which show how the failure pro-gressed. A fatigue failure such as this is causedby loading the vehicle beyond its specified grossweight or by abusive operation on the vehicle onrough terrain.

Gear teeth that have rolled over are an additionalsign of heat and lubrication problems. During ateardown, always inspect gears for signs ofpitting, scoring, galling, cracks and rolled teeth.Replace any worn or damaged gears. If one gearshows signs of trouble, also check the matinggears for possible damage. Use a magneticparticle crack detection system to do this.

Figure 4A clean break indicates a sudden shockloadfailure.

Figure 5A beach mark signals a fatigue failure that hasdeveloped over time.

Along with lubrication problems and normalwear, another cause of gear damage isshockload. Shockload failures may occur imme-diately after the initial shock or at a later date.The mainshaft can also be damaged (see Fig-ures 6 and 7).

Figure 6A broken shaft and missing gear teeth indicateshockload.

6A gear tooth that has broken below the root lineis a good indicator of shockload. Usually, matinggears also show signs of the shockloading.Always replace the damaged gear and themating gears, even if they do not look damaged.Also check the rest of the transmission for dam-age from the broken gear tooth traveling throughthe unit.

Common Causes of Shockloadn Starting in wrong gear, too high a gear

Review shifting procedures Driver training

n Starting the vehicle while the brakes are stillapplied

Driver trainingn Popping the clutch

Driver trainingn Overloaded vehicle

Check gross vehicle weightspecification

n Backing into a loading dock Driver training

n Tires spinning then quickly gaining traction Avoid spinning wheels if possible

C O M P O N E N T F A I L U R E S

Figure 7A twisted mainshaft indicates shockload.

A fourth common cause of gear failure is clashshifting. When a driver shifts a transmissionbefore the engine and transmission speeds arematched (or before the synchronizer can do itsjob), a clutch collar is forced into gear. The resultis worn clutching teeth that can lead to thetransmission jumping out of gear (see Figures 8and 9). Gears, collars, or shafts with worn clutch-ing teeth or gearlocks should be replaced.

SHIFTING CAUTIONImproper shifting of the transmission will result inworn clutching teeth, which may lead to thetransmission jumping out of gear. If the transmis-sion jumps out of gear, there could be a loss ofpower. In order to avoid worn clutching teeth,you must: (1) assure that the driver receivestraining and adheres to proper driving tech-niques; (2) inspect the vehicle and replace anyworn gears, collars or shafts.

Figure 8Failure to use the clutch can cause wornclutching teeth, a major cause of transmissions jumping outof gear. Shown here are worn clutching teeth (left) and newclutching teeth (right).

7BearingsThe service life of most transmissions is deter-mined by the life of its bearings. Many prematurebearing failures are caused by vibration orcontamination. If bearings are stored, its veryimportant to coat them with a rust inhibitor andkeep them tightly wrapped to prevent contamina-tion.

Other reasons for bearing failuresinclude:n Lack of lubricant or contaminated lubricantn Improper assemblyn Overloadingn Misalignment

Offset spalling (see Figure 10), is caused bymisalignment of the transmission in relation toother drivetrain components.

C O M P O N E N T F A I L U R E S

Figure 10Offset spalling is caused by misalignment.

Offset spalling is similar in appearance to de-structive pitting, but craters are larger in diam-eter and shallower in depth. Spalling occurs overa short period of time when a bearing is sub-jected to an extreme overload condition.

Figure 9Worn clutching teeth.

To prevent clash shifting:n Make sure the driver is familiar with both the

shift pattern and the required RPM changesbetween shifts.

n Establish correct clutch adjustment to preventinadequate clutch release or dragging.

n In air shifted transmissions, make sure thepressure regulator is at the proper settingusually 55 - 60 psi.

See SHIFTING CAUTION (pg. 6).

8Forks

Clash shifting and over-shifting (going beyondthe shift rail detent position) are two obviouscauses of fork pad and fork shoe wear (seeFigures 13 and 14). A third cause is using theshift lever as a hand rest. Prevent these prob-lems through driver awareness and training.

See SHIFTING CAUTION (pg. 6).

C O M P O N E N T F A I L U R E S

Figure 11Seized bearing.

Figure 13Fork pad wear.

Figure 14Fork shoe wear.

Figure 12Lack of lubrication to the pocket bearingresulted in a bearing seizing to this input shaft (note the ringof metal).

If a bearing isnt properly lubricated, bearingsmay seize (see Figures 11 and 12). Discolora-tion, especially a blue tint, is a sign of heat. Heatis generally caused by improper lubrication. Thiscan mean the wrong type of lubricant, notenough or too much lubricant, using lubricantpast its useful life, or using contaminated lubri-cant.

See LUBRICATION CAUTION (pg. 3).

9A fourth, less obvious cause of fork pad wear is aloose output nut. A loose output nut will allow themainshaft to move back and forth. This motionnot only can damage the shift forks, but cancrack or break thrust washers. To prevent this,always tighten the output nut to the torque speci-fications listed in your Spicer transmission ser-vice manual.

SynchronizersSome of the leading causes of synchronizerfailure include improper shifting techniques,vibration, and lubrication problems.

Starting the vehicle in the proper gear:An empty truck can be started satisfactorily in ahigher transmission gear ratio than when partiallyor fully loaded. If auxiliary transmissions or two-speed axles are used, they must be in the lowerratios for satisfactory starts. Drivers should beshown what ratios can be used for safe startswhen the truck is empty or loaded. Dont letdrivers find out for themselves; they can damagesynchronizers. If the truck is diesel powered, agood rule of thumb for the driver to follow is:empty or loaded, select the gear combinationthat lets you take up the slack and start movingwith an idling engine or, if necessary, justenough throttle to prevent stalling the engine.After the clutch is fully engaged, the engineshould be accelerated to near governed speedfor the upshift into the next higher gear.

When shifting a synchronized transmission, it isimportant to move the shift lever in one motionuntil the shift is completed. Stabbing the shiftlever will result in gear clashing. Another resultwill be worn clutching teeth (see Figure 15) andmetal chips embedded into the brass synchro-nizer ring (see Figure 16). When the synchronizerring makes contact with the desired gear, theblockers automatically prevent the shift collarfrom completing the shift until the gear andmainshaft speeds are matched. At that time, theblocker neutralizes automatically, and the clash-free shift is the result. It must be noted that asteady pressure on the shift lever helps thesynchronizer do its job quickly.

C O M P O N E N T F A I L U R E S

Figure 15Improper shifting techniques cause wornsynchronizer clutching teeth.

Figure 16Metal chips are cause by clash shifting or lackof lubrication.

Another aspect of improper shifting involvesvehicles with power take-offs (PTOs). Never shiftfrom one gear into another while the PTO isengaged. The PTO will act like a brake, slowingcountershaft and input shaft rotation. The syn-chronizer will try to match the mainshaft speedwhile the PTO will work against it.

See SHIFTING CAUTION (pg. 6).

10

C O M P O N E N T F A I L U R E SRefer to the Vibration section of this publication(page 2) for information on causes of vibration.It is also important to maintain proper lubricationlevels. See the Heat and Lubrication section ofthis publication (page 2) for more information.

See VIBRATION WARNING and LUBRICA-TION CAUTION (pgs. 2 and 3).

Shafts

When gears, clutch collars, clutch gear, orsynchronizers show signs of clash shifting,carefully examine shaft gearlocks. If they areworn (see Figure 19), the shaft must be replacedto protect against gear jumping.

Vibration is another big cause of synchronizerfailures. Broken or sheared synchronizer pins area very common sign of vibration (see Figure 17).The brass synchronizer ring may also be pushedoff the pins due to vibration (see Figure 18).

Figure 17Sheared synchronizer pins are a sign ofvibration.

Figure 18Vibration can cause the brass ring to separatefrom the rest of the synchronizer.

Figure 19Worn shaft gearlocks can lead to gear jumping.

11

C O M P O N E N T F A I L U R E S

Figure 20Worn gear locks on the clutch gear can lead togear jumping.

Figure 21Shiny areas on the output yoke splines indicatedend yoke vibration.

Also examine gear locks on the clutch gear.Worn gear locks on mainshaft clutch gearscontribute to gear jumping (see Figure 20). Ifgear locks are worn, replace them. Also checkfor proper clutch adjustment and verify thattransmission lubrication is correct.

Also check the output end of the shaft for signsof end yoke vibration. This is indicated by a shinyarea on the output yoke shaft splines (see Figure21). This problem can be avoided by tighteningthe yoke nut to the specifications listed in theSpicer service manual.

Fretting corrosion is a common type of surfacedamage that occurs when two materials rubwhile vibrating very slightly. Such corrosion iscommon at surfaces of splines and other close-fitting parts that are subject to minute relativemovement.

Gear seizures and discoloration of the shaftespecially a blue hueindicate heat problems(see Figures 22 and 23). Heat problems can betraced to inadequate lubrication, using the wrongtype of lubricant, or not changing the lubricantfrequently enough.

See LUBRICATION CAUTION (pg. 3).

Figure 22A gear seized on this shaft, leaving metaldeposits.

12

Figure 23Discoloration is a sign of heat, which is relatedto lubrication problems.

Improper driveline angles or offset, out-of-phaseuniversal joints will cause torsional vibrationssevere enough to break down oil film. For moreinformation on proper lubrication, see the Heatand Lubrication section of this publication (page2), and review the specifications in your servicemanual.

A third big cause of shaft failures is shockload-ing (see Figure 5).

See VIBRATION WARNING and LUBRICA-TION CAUTION (pgs. 2 and 3).

C O M P O N E N T F A I L U R E S

13

S E A L STransmission seals are the most common causeof problems in vehicle transmissions. If theproblem is not repaired properly, major transmis-sion failure can result. Spicer transmissions haveseals with an improved design that use newsealing materials.

Causes of Seal Failure

n Contamination Dirt Oil Grease Water

n Faulty Repairs Damaged output yoke Incorrect diameter yoke sleeve Seal lip damage during installation Output yoke seal surface not machined

properly Attempted manual repair of yoke with emery

cloth Output bearing wear and / or failure causing

excessive runout or endplayn Improper Installation

Use of improper tools Improper installation of the oil seal in the

bearing cap (seal cocked in bearing capbore)

Installation of damaged yoke or input shaftwith burrs or nicks

n Storage and Handling Damagen Improper storage of oil sealsn Improper protection on output yoke or input

shaft sealing surfacesn Improper method used to prevent sealing

surface from rustingn Excessive Heat

Breakdown of lubrication Use of improper lubrication Use of lubricant not compatible with seal

material

Front Bearing Retainer & Seal

When installing the front bearingretainer and seal in the transmission,

use the red plastic sleeve to prevent seri-ous damage to the oil seal. Failure to usethe seal sleeve will void the seal warranty.

14

Product Warranty

A transmission product warranty covers repairswhen the product proves defective in normaluse.

Normal Wear

All components will wearto a certain degreeunder normal operating conditions. New unitshave an initial break-in period in which compo-nents wear until mating with one another, result-ing in greater contact surfaces. The most impor-tant factor in keeping wear to a minimum isadhering to proper maintenance schedules andincluding an inspection of transmission compo-nents and lubrication. If components with exces-sive wear are found, check and replace them asneeded. Replacing worn parts is less costly thanreplacing an entire unit later.

NOTE: Always use the correct maintenancemanual and genuine Spicer transmission parts toensure a proper repair.

Non-Warrantable ConditionsThe following photos show examples of non-warrantable conditions. These conditions are dueto misuse, negligence, improper maintenance orimproper operation.

N O N - W A R R A N T A B L E C O N D I T I O N S

Lubrication Failure

Pitting, scoring and galling can occur when the gearmaterial endurance limit is exceeded. Lubrication problemscan also contribute to these conditions.

A broken shaft and missing gear teeth indicate shockload.

Shockload

15

N O N - W A R R A N T A B L E C O N D I T I O N S

Worn clutching teeth indicate a clash shifting condition.

Clash Shifting

Vibration can cause the brass ring to separate from the restof the synchronizer. Sheared synchronizer pins are also asign of vibration.

Torsional Vibration

Torsional vibration caused these worn teeth.Fork pad wear is caused by over-shifting and clash shifting.

Over-Shifting Torsional Vibration

16

G L O S S A R YAddendum - portion of a gear tooth between thepitch line and the tip of the tooth

Beach Marks - visible lines on a fatigue fracturethat show the location of the tip of the fatiguecrack

Contaminate - to make impure by foreign mate-rial

Clutch Collar - device used to engage from onegear to another

Dedendum - portion of a gear tooth between thepitch line and the root of the tooth

Fatigue Failure - minute cracks that grow underthe action of fluctuating stresses

Fracture - break or separation of a part into twoor more pieces

Fretting Corrosion - surface damage thatoccurs when two materials rub while vibratingslowly

Gear - mechanical part to transmit motion

Gear Jumping - shift lever movement out of aselected position

Gear Locks - device to keep a gear engaged

Hard Shifting - use of excessive force to movethe shift lever

Offset Spalling - caused by a bearing beingsubjected to extreme overload conditions in ashort period of time

Oil Seal - device used to confine oil to a certainarea

Pitch Line - location of a gear tooth midway upthe tooth

Pitting - resulting marks when the endurancelimit of the material is exceeded

Proper Lubrication - describes a transmissionthat has the proper oil level and recommendedoil type

Root Diameter - innermost part of a stressconcentration, such as the bottom of a groove

Scoring - resulting marks caused by excessiveheat generation in the gear mesh

Seized - condition caused by a lack of lubricantand the presence of high heat

Shockload - violent impact on a gear tooth thatususally causes the tooth to break

Torsional Vibration - twisting action that may beeither reversed (back and forth) or unidirectional(one way)

Failure AnalysisCommon Transmission ComplaintsHardshiftingGear JumpingVibrationHeat and Lubrication

Component FailuresGears and Clutch CollarsBearingsForksSynchronizersShafts

SealsCauses of Seal Failure

Non-Warrantable ConditionsProduct WarrantyNormal Wear

Glossary