CH42 automatic transmission and transaxle service STUDENT VE

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Chapter 42

Automatic Transmission and Transaxle Service

• Proper identification is essential but can be difficult

• Pan shape can sometimes be used

• Best method is to used the ID numbers

stamped on the case or on a metal tag

• Many use bar codes for quick ID

Fluid Check

• Check on a flat level surface

• Follow manufacturers service guidelines to accurately check fluid level

• Low and excessively high fluid levels can cause aeration

• Examine the fluid carefully

Transmissions Without a Dipstick

• Checked similar to a manual transmission

• Done to prevent overfilling and causing

damage

• Some transmissions use a fluid level sensor

to alert the driver

• Change at normal operating temperature.

• Inspect the pan for deposits and particles

• Follow all service procedures for fluid and filter changes

Sources of Transaxle Fluid Leaks

Checking Mounts

• Engine and transmission mounts are

important to transaxle operation

• Inspect mounts for looseness and cracks

• Watch the torque reaction when applying power in forward and reverse

Diagnosis of Noise and Vibration Problems

• Many noise and vibration problems may be caused by:

Checking the Torque Converter

• Problems may include:

– abnormal noises

– poor acceleration in all gears

– normal acceleration but poor high speed

performance

– transmission overheating

Testing for a Plugged Cooler

Pressure Tests

• Connect gauges to test ports and route so that they can be seen on a test drive

Typical Pressure Test Specifications

Common Problems

• Valve Body

– Thoroughly disassemble, clean, and inspect – Freeing and polishing valves may correct the problem

• Servo Assemblies

– Check inner and outer parts of seals

– Clean, dry, and inspect seals, pistons, springs, and guides

• Many problems can be associated with

incorrect linkage adjustments

• Gear selector linkage:

– The manual shift valve must fully engage the selected gear

– Poor gear engagement, slipping, and excessive wear can result from misadjustment

Throttle Valve (TV) Linkages

• TV linkage may control downshift valve and TV

• Throttle pressure is used to indicate engine load

• Influences shift timing

• Can cause early upshifts or harsh delayed upshifts

TV Circuit

Kickdown Switch Adjustment

• Used on some transmissions to indicate WOT and force a downshift

Transmission Overhaul

• Before removing the transmission:

– Inspect the torque converter bolts and TC

– Index the flexplate to the converter

– Remove the battery ground cable

– Disconnect linkages, cooler lines, and wiring – Remove the dipstick tube

Transmission Overhaul (cont’d)

• Inspect the flexplate for cracks or damage

• Inspect the TC drive lugs, check for

ballooning, check balance weights, pilot

and drive hub

• Check flexplate and converter drive hub for runout

Transmission Overhaul (cont’d)

• Replace TC if any doubt of its condition.

• Inspect drive chains for stretch and side play.

• Check all pumps, valve bodies, and cases for warpage.

• Keep parts absolutely clean.

• Use correct size thrust washers.

• Soak friction plates in clean ATF before

installing.

Transmission Overhaul (cont’d)

• Always use new gaskets and seals

• Ensure all wiring is connected

• Flush the transmission cooling system

• Use only lint-free cloths

• Check alignment dowels and holes

• Make sure pilot hole in crank is smooth

• Make sure pilot hub is smooth and lubricated

• Flush the converter

• Check converter endplay and height

• Pour one quart of ATF into the TC before

mounting to the transmission