Transmission Service "A" Flashcards
Trans. slip out
Trans moves into neutral when torque is being applied to the driveline. Caused when sliding clutch and mainshaft gears wear.
Trans. jump out
Tends to occur during normal driving conditions or rough road. No torque on driveline
What are some of the common conditions that contribute to jump out are? (3)
Extra heavy and long shift levers
Excessive movement between the trans and shift linkage (worn motor/trans mounts)
Worn or broken detent springs
Hard shifting
When the operator experiences unusually excessive force to get trans into a gear
Gear clash
Occurs when the speeds are not properly matched between gears when shifting. Clash that occurs while shifting into 1-R is typically due to a clutch issue
Trans whine or squeal
Usually caused by insufficient clearance or backlash. Uneven wear patterns caused by mis-matched gears.
Bearings with insufficient clearance will also cause noise
How many shims can be used when installing a PTO?
Up to 4 - ILM
Up to 2 - Class
Trans growling
Commonly caused by severely damaged gear teeth. Also caused by improper timing or incorrect install of counter shafts
What is considered normal operating temperature of a trans?
100 F above ambient (175-200)
At what temp does trans oil breakdown begin to occur?
250 F
What is first step when removing trans?
Disconnect battery cables
Bearing failures in trans are usually caused by?
Contaminated lube, typically dirt and water in oil
What tends to be the root cause of many other trans parts failures?
Bearing failure
Frosting
Is a form of micro-pitting that appears as a band of off-white discolouration formed in the middle of the tooth. Caused by loading and unloading at pitch line. Normal from mating of gears, is not a reason for gear replacement
Offset-frosting
When frosting appears on one side of the gear tooth and not the other
Healing
As mating teeth wear into each other and frosting occurs, the wear rate will decrease until the point is reached where it polishes itself out and frosting is replaced by a very shiny area
Initial gear pitting
Mildest form of pitting, consists of definite pits that are about pin hole size (.030”)
Moderate gear pitting
About twice the size of initial pitting, when is evenly distributed across face the gear doe not need to be replaced.
When it is concentrated to 50% of pitch line it will make noise and the gear should be replaced
Destructive gear pitting
Pits are larger and mainly deeper than those in moderate pitting. Requires replacement
Gear spalling
Craters are larger in diameter and shallower in depth. Occurs over a short period of time when a gear is subject to an extreme overload condition
Gear scoring/galling
Caused by insufficient oil film between mating gear teeth. High temps result leading to adhesive wear.
Burned gear sets
If blue from teeth going inward, this is due to excessive torque combined with lack of lube.
If blue from centre going outward, can be due to lack of clearance on assembly for lack of lube between mainshaft and gears (towing, coasting in neutral)
Should be replaced
