Eaton Fuller Transmission Troubleshooting Guide

Guide to servicing and repairing Eaton Fuller heavy-duty truck transmission, assistance locating the issue of transmission trouble, analyze the cause and make necessary repairs for 7, 8, 9, 10, 13, 15 and 18 speed Eaton transmissions. For more in-depth assistance refer to your transmission model service manual or give us a call at 877-776-4600. The transmission function is to efficiently transfer the engine’s power, in terms of torque, to the vehicle’s rear wheels. Torque is the twisting or circular force delivered by the engine’s flywheel. The transmission’s gear ratios increase or decrease torque depending on the requirements needed to move or start the load. Gearing also increases or decreases speed. The gear ratios are correctly spaced so that the engine will operate in its most efficient RPM range with progressive speed changes. To meet the vehicle’s requirements, the transmission must have ratios low enough to start the vehicle moving, to maintain movement up-grades, and to keep the engine operating in its peak efficiency range. The transmission, too, must provide an easy method for gear selection.

Troubleshooting Guide for the following Eaton Fuller transmission models:

FR-11210B RTLO-14610B RTLOF-15610B-T2 RTOF-11909MLL RTX-14709A RTXF-14709H FROF-16210B
FR-12210B RTLO-14610B-T2 RTLOF-16610B RTOF-13707DLL RTX-14709B RTLOF-14610B RTLOF-11610B
FR-13210B RTLO-14613B RTLOF-16610B-T2 RTOF-13707MLL RTX-14709H RTO-16909ALL RTO-13707DLL
FR-14210B RTLO-14618A RTLOF-16618A RTOF-14608LL RTX-14710B RTX-13710B RTX-12710B
FR-15210B RTLO-14713A RTXF-15615 RTOF-14708LL RTX-14710C RTXF-13710C RTXF-12710B
FR-9210B RTLO-14718B RTLOF-16713A RTOF-14709MLL RTX-14715 RTXF-14710B RTX-14610
FRF-11210B RTLO-14913A RTLOF-16713A-T2 RTOF-14908LL RTX-15615 RTLOF-14610B-T2 FROF-16210C
FRF-12210B RTLO-14918B RTLOF-16718B RTOF-14909ALL RTXF-16709H RTOF-11607L RTLOF-11610B-T2
FRF-13210B RTLO-14918B-T2 RTLOF-16913A RTOF-14909MLL RTX-15710B RTX-13710C RTO-13707MLL
FRF-14210B RTLO-15610B RTLOF-16913A-T2 RTOF-16908LL RTX-15710C RTXF-14608LL RTX-12710C
FRF-15210B RTLO-15610B-T2 RTLOF-16918B RTOF-16909ALL RTX-15715 RTLO-11610B-T2 RTXF-12710C
FRF-9210B RTLO-16610B RTLOF-16918B-T2 RTX-11509 RTX-16709B RTLOF-14613B RTXF-16710C
FRO-11210B RTLO-16610B-T2 RTLOF-17610B RTX-11608LL RTX-16709H RTOF-11607LL RT-7608LL
FRO-11210C RTLO-16618A RTLOF-17610B-T2 RTX-11609A RTX-16710B RTX-14608LL RTLOF-12610B
FRO-12210B RTXF-14710C RTLOF-18610B RTX-11609B RTX-16710C RTXF-14609A RTO-14608LL
FRO-12210C RTLO-16713A RTLOF-18718B RTX-11609P RTXF-11509 RTLO-12610B RTXF-16709B
FRO-13210B RTLO-16713A-T2 RTLOF-18913A RTX-11609R RTXF-11608LL RTLOF-14618A RTXF-13609A
FRO-13210C RTLO-16718B RTLOF-18913A-T2 RTXF-15715 RTXF-11609A RTOF-11608LL RTLO-13610B-T2
FRO-14210B RTLO-16913A RTLOF-18918B RTX-11610 RTXF-11609B RTX-14609A RT-8608L
FRO-14210C RTLO-16913A-T2 RTLOF-18918B-T2 RTX-11615 RTXF-11609P RTXF-14609B RTLOF-12610B-T2
FRO-15210B RTLO-16918B RTLOF-20913A RTX-11708LL RTXF-11609R RTLO-12610B-T2 RTO-14709MLL
FRO-15210C RTLO-16918B-T2 RTLOF-20918B RTX-11709A RTXF-11610 RTLOF-14713A RTX-13609A
RTXF-14615 RTLO-17610B RTLOF-20918B-T2 RTX-11709B RTXF-11615 RTXF-15710C RTXF-13609B
RTXF-14708LL RTLO-17610B-T2 RTLOF-22918B RTX-11709H RTXF-11708LL RTX-14609B RTLOF-14918B-T2
FRO-16210B RTLO-18610B RTLOFC-16909A-T2 RTX-11710B RTXF-11709H RTXF-14609P RT-8908LL
FRO-16210C RTLO-18610B-T2 RTO-11607L RTX-11710C RTXF-11710B RTLO-12713A RTLOF-12713A
FRO-17210C RTLO-18718B RTO-11607L RTX-11715 RTXF-11710C RTLOF-14718B RTO-14908LL
FRO-18210C RTLO-18718B-T2 RTXF-15710B RTX-12509 RTXF-11715 RTOF-11707LL RTX-13609B
FROF-11210B RTLO-18913A RTO-11607LL RTX-12510 RTXF-12509 RTX-14609P RTXF-13609P
FROF-11210C RTLO-18913A-T2 RTO-11607LL RTX-12515 RTXF-12510 RTXF-14609R RTOF-11908LL
FROF-12210B RTLO-18918B RTO-11608LL RTX-12609A RTXF-16710B RTLO-12913A RTF-8608L
FROF-12210C RTLO-18918B-T2 RTO-11707DLL RTX-12609B RTXF-12515 RTLOF-14913A RTLOF-12913A
FROF-13210B RTLO-20913A RTO-11707LL RTX-12609P RTXF-12609A RTOF-11708LL RTO-14909ALL
FROF-13210C RTLO-20918B RTO-11708LL RTX-12609R RTXF-12609B RTX-14609R RTX-13609P
FROF-14210B RTLO-20918B-T2 RTO-11709MLL RTX-12610 RTXF-12609P RTXF-14610 RTXF-13609R
FROF-14210C RTLO-22918B RTO-11908LL RTX-12709A RTXF-12609R RTLO-13610B RTX-14615
FROF-15210B RTLOC-16909A-T2 RTO-11909ALL RTX-12709B RTXF-12610 RTLOF-14918B RTF-8908LL
FROF-15210C RTXF-14715 RTO-11909MLL RTX-12709H RTXF-12709H RTOF-11709MLL RTLOF-13610B
RTO-14909MLL RTXF-13709H RTLO-11610B RTO-16908LL RTXF-13710B RTOF-11909ALL RTX-14708LL
RTX-13609R RTLO-14610A RTLOF-13610B-T2 RTX-13709H RTLOF-15610B

Common Transmission Complaints


Although the effects of vibration will show up in the transmission, vibration usually originates somewhere else in the drive train. Vibration can usually be felt or heard by the driver; however, in some cases, transmission damage caused by vibration will occur without the driver’s knowledge.

Some Transmission Problems Due to Drive Train Vibration:

  1. Gear rattle at idle
  2. Gear & shaft splines (fretted)
  3. Noise
  4. Fretted Bearings
  5. Repeated rear seal leakage
  6. Broken or loose synchronizer pins
  7. Continuous loosening of capscrews, brackets and mountings
  8. Worn Shaft Spine Wear
  9. Worn universal joints (Not a transmission symptom, but an indicator of vibration.)
fretted splines on transmission

Fretted Splines

Broken transmission synchronizer pin

Broken Synchronizer Pins

transmission input spline wear

Input Spline Wear

Common causes of vibration include driveline imbalance or misalignment, unbalanced wheels or brake drums, rough running engine, broken or worn engine mounts and worn suspension.

Gear Slipout and Jumpout

Front Section
When a sliding clutch is moved to engage with a mainshaft gear, the mating teeth must be parallel. Tapered or worn clutching teeth will try to “walk” apart as the gears rotate. Under the right conditions, slipout will result. Some of these conditions are:

  1. Transmission mounted eccentrically with engine flywheel pilot.
  2. Excessive gear clashing which shortens clutching teeth.
  3. Incorrect adjustment of remote shift control linkage resulting in partial engagement. Also check for loose connections and worn bushings.
Snubbed Clutching Teeth

Snubbed Clutching Teeth

Gear clutching teeth wearing to a taper.

detent spring

Detent Spring

Insufficient pressure on detent ball from weak or broken detent spring.

worn yoke bar

Worn Yoke Bar

Excessive wear on detent notch of yoke bar

Conditions That Can Cause Jumpout

  1. Extra heavy and long shift levers which swing, pendulum fashion, from operating over uneven terrain. Whipping action of the lever overcomes detent spring tension.
  2. Mechanical remote controls with the master mounted to the frame. Relative movement between engine-transmission package and frame can force transmission out of gear. Worn or broken engine mounts increase the effects of this condition.
transmission with jumpout

Auxiliary Section

Slipout in the auxiliary section may be caused by the clutching teeth being worn, tapered, or not fully engaged. These conditions cause the clutch gear to “walk” out of engagement as the gears turn.

Causes of these types of clutching defects are clashing or normal wear after long life. Vibrations set up by an improperly aligned driveline and low air pressure add to the slipout problem.

Jumpout in the auxiliary section usually occurs with the splitter gear set. If torque is not sufficiently broken during splitter shifts, the sliding clutch gear may not have enough time to complete the shift before torque is reapplied to the gears. As torque is reapplied, the partially engaged clutch gear “jumps” out of the splitter gear. Since the gears have torque applied to them, damage will be done to the clutching teeth of the mating gears.

tapered clutching teeth

Hard Shifting

The effort required to move a gear shift lever from one gear position to another varies. If too great an effort is required it will be a constant cause of complaint from the driver.

Most complaints are with remote type linkages used in cabover-engine vehicles. Before checking the transmission for hard shifting the remote linkage should be inspected. Linkage problems stem from worn connections or bushings, binding, improper adjustment, lack of lubrication on the joints or an obstruction which restricts free movement. To determine if the transmission itself is the cause of hard shifting, remove the shift lever or linkage from the top of the transmission. Then, move the shift blocks into each gear position using a pry bar or screwdriver. If the yoke bars slide easily, the trouble is with the linkage assembly. If the trouble is in the transmission, it will generally be caused by one of the following:

  1. Splines of sliding clutch gear binding on mainshaft as a result of a twisted mainshaft key, bent shift yoke or bowed mainshaft key.
  2. Yoke bars binding in the bar housing as a result of cracked housing, over-torqued shift block lockscrew, sprung yoke bar, or swelled areas of the yoke bar.
transmission hard shifting

If hard shifting occurs only in first and reverse, the shift block detent plunger movement may be restricted. This can result from burrs on the plunger, or from overtightening the plunger spring plug. With the plunger blocked in the depressed position, the plug should be tightened until it bottoms out against the spring, then backed out 1/4 to 1/2 turn.
Gear clashing should not be confused with hard shifting. Gear clashing occurs when an attempt is made to engage the clutch gear before it has reached  synchronization with the mainshaft gear.


The transmission operating temperature should never exceed 250°F (120°C) for an extended period of time. If it does, the oil will breakdown and shorten transmission life.

Because of the friction of moving parts, transmissions will produce a certain amount of heat. In most cases normal operating temperature is approximately 100°F (40°C) above ambient. Heat is dissipated through the transmission case. When conditions prevent the proper dissipation of heat, then overheating occurs.
Before checking for possible causes of overheating, the oil temperature gauge and sending unit should be inspected to make sure they are giving correct readings.

Causes of Overheating 
1. Improper lubrication. Oil level too low or too high, wrong type of oil, or an operating angle of more than 12 degrees.
2. Operating consistently under 20 MPH.
3. High engine RPM.
4. Restricted air flow around transmission, due to the transmission being “boxed in” by frame rails, deck lids, fuel tanks and mounting brackets, or by a large bumper assembly.
5. Exhaust system too close to transmission.
6. High ambient temperature.
7. High horsepower, overdrive operation.
8. Coasting downhill with the clutch depressed.

In some cases, an external oil cooler kit can be used to correct overheating problems.

Transmission Oil Coolers are:

  • With engines of 350 H.P. and above with overdrive transmissions


  • With engines 399 H.P and above with overdrive
    transmissions and GCWs over 90,000 lbs.
  • With engines 399 H.P. and above and 1400 Lbs.-Ft.
    or greater torque
  • With engines 450 H.P. and above

Transmission Noise

There will always be a certain level of noise due to the normal transmission operation. However, excessive noise or unusual noise such as a whine, growl, or squeal indicates some kind of a problem.

The transmission itself can be the cause of excessive or unusual noise. Also, noise can originate elsewhere in the vehicle, but be picked up and amplified by the transmission.

1. Knocking or Thudding

transmission gears
  • Gears – Bumps or swells on gear teeth. Such bumps or swells can be removed with a hone or small hand grinder; these areas can be identified as highly polished pots on the face of the gear tooth. Generally, this noise is more prominent when the gear is loaded; thus, the problem gear can be located as the noise occurs in a  specific gear position. Bumps or swells are caused by improper handling of gears before or during assembly.
  • Bearings – Noise comes in at low shaft speeds in any position. It is caused by bearings with damaged balls or rollers, or with pitted and spalled raceways.
cracked transmission gears
  • Cracked Gear – A gear cracked or broken by shock loading or by pressing on shaft during installation will produce this sound at low speeds. At high speeds a howl will be present.

2. High Pitched Whine or Squeal

  • Gear Wear – Result of normal gear wear, including gear tooth pitting from excessive use. In advanced deterioration, a howl will result.
  • Mismatched Gear Sets – Such gear sets are identified by an uneven wear pattern on the face of gear teeth.
  • Bearings –“Pinched” bearings, having insufficient axial or radial clearance

3. Growling

  • Timing Error – Improper timing of the transmission during reassembly, or improper timing due to gear turning on the countershaft. Both conditions  produce an error in tooth spacing.

Causes of Transmission Noise Originating Elsewhere in Vehicle:

  1. Rough idling engine. (see gear rattle)
  2. Engine operating noise.
  3. Clutch driven plates in which the dampening action of springs or rubber blocks has been eliminated by wear set or fracture.
  4. Driveline out of balance.
  5. Unequal joint working angles.
  6. Worn crosses in universal joints.
  7. Loose or worn center bearings.
  8. Worn or pitted teeth on ring gear and pinion of driving axle.
  9. Rear axle bearing failure.
  10. Wheels out of balance.
  11. Worn spring pivot bearing.
  12. Loose “U” bolts.
  13. Brake drums warped or out of balance.

Transmission Troubleshooter’s Guideline

Following is a basic procedure guideline for troubleshooting transmissions:

  1. Preliminary Inspection
    • Personal Observation – look for signs of misuse such as broken mounts, fittings or brackets; check airlines.
    • Question the Owner or Operator – gather information on operating conditions and vehicle use, on the history of the problem, and on shifting characteristics if affected.
    • Gather History of Unit – including maintenance and lubrication procedures, past failures, and mileage or hours of use.
  2. Disassemble Transmission
    • Keep oil sample for impurities, check if needed.
    • During disassembly, check for incorrectly installed parts, missing parts, and nongenuine parts.
    • Clean and inspect each piece closely.
  3. Determine Type of Failure
  4. Determine and correct Cause of Failure

The Troubleshooter’s Guideline Chart is used to locate and correct transmission problems. To use the guideline,

1) Locate the transmission problem in the boxes below

2) Hover over the box to see the possible problem and take note of the numbers next to the possible cause

3) Refer to the list below and locate the corresponding number listed next to the problem. The matching number from the list will tell you the possible correction.

4) There may be more than one possible cause and possible correction for each problem.

Possible Corrections:

  1. Instruct driver on proper driving techniques.
  2. Replace parts (after trying other listed possible corrections).
  3. Loosen lock-screw and retighten to proper torque.
  4. Look for resultant damage.
  5. Smooth with emery paper.
  6. Reset to proper specifications.
  7. Install missing parts.
  8. Check airlines or hoses.
  9. Tighten part.
  10. Correct the restriction.
  11. Recheck timing.
  12. Clean part.
  13. Apply thin film silicone.
  14. Apply sealant.

For Manuals and other free resources please visit our downloads page

transmission manuals pdf

Diagrams, Manuals and Parts PDFs >>>

Any transmission part you need we have it! Same day shipping available, worldwide.