Transmission Repairs
For satisfactory and successful transmission repairs, the greatest possible care, cleanliness and proper tools are important requirements. Naturally, the basic safety precautions also apply to repair work.
A series of general instructions that apply to individual procedures (otherwise listed many times in many places in the Repair Information) are summarized here. They apply to this Repair Information.
Special tools and workshop equipment required
For a summary of the special tools used in this repair information.
Transmission
- If oil pan is removed or if transmission is not filled with ATF, do not tow vehicle or let engine run.
- When replacing an automatic transmission, check and if necessary correct following fluid levels: ATF in planetary gearbox ATF LEVEL, CHECKING , gear oil in front final drive. Refer to the appropriate Service Information. Capacities and specifications starting on → Planetary gearbox .
- When removing the transmission, secure torque converter to prevent it from falling out.
- Thoroughly clean connecting points and their surrounding areas before loosening.
- When installing transmission, check installation position of torque converter TORQUE CONVERTER, INSTALLING .
- Before installing transmission, make sure alignment bushings are correctly seated.
- Place removed components on clean surface and cover. Use foil and paper. Do not use cloths that leave lint.
- Carefully cover or close components that have been opened if repair will not be carried out right away.
- Install only clean components. Do not remove replacement parts from packaging until immediately before installation.
- Rules of cleanliness for working on automatic transmission AUTOMATIC TRANSMISSION, CLEAN WORKING CONDITIONS .
O-rings, seals and gaskets
- Always replace O-rings, seals and gaskets.
- After removing seals, check contact surfaces on housings and/or shafts for burrs or damage caused by removal.
- When installing seals, apply thin coat of Vaseline (petroleum jelly) on outer circumference and on sealing lip of seal.
- When installing O-rings, apply thin coat of Vaseline to prevent pinching O-rings during installation.
- Always use Vaseline only in small quantities. Other lubricants lead to malfunctions in the hydraulic transmission control.
- Open side of seals face fluid to be sealed in.
- After installing, check and if necessary correct fluid levels of affected components: ATF in planetary gearbox ATF LEVEL, CHECKING . Gear oil in front final drive. Refer to the appropriate Service Information. Capacities and specifications Planetary gearbox .
Circlips
- Do not overstretch circlips, replace if necessary.
- Circlips must be properly seated in base of groove.
Bolts, nuts
- Loosen bolts in opposite order of tightening sequence.
- For covers and housings that do not have tightening sequence, loosen and tighten bolts and nuts diagonally in stages.
- Always replace self-locking nuts.
- Clean threads of bolts that have been installed with locking compound using wire brush. Coat bolts with AMV 185 101 A1 before reinstalling.
- Tightening torques are specified for unoiled bolts and nuts.
Bearings
- Install needle bearings with inscribed side (thicker metal) facing installation tool.
- Depending on installation location, lubricate bearings with gear oil or ATF when installing.
- Do not interchange outer and inner races of same size bearings.
- Always replace tapered roller bearings on same shaft together as a set and use bearings manufactured by the same manufacturer.
- Before installing, warm inner races of tapered roller bearings to approx. 100°C (212°F). When installing press up to stop without axial play.
Shims
- Measure shims at several locations using micrometer. Different tolerances make it possible to obtain exact shim thickness necessary.
- Check for burrs or damage. Use only perfect shims.
Valve body
If shifting elements are burnt, the valve body should be replaced.
On Board Diagnostic (OBD)
Before beginning repairs on an automatic transmission, the cause of the malfunction should be determined as precisely as possible using On Board Diagnostic (OBD).