General Motors 6L45

Transmission general data

The Hydra-Matic range 6L45 - ... 6L90 is the second generation of modular-type 6-speed automatic transmissions, used for RWD vehicles. The 6L80 and 6L90 were the first automatic gearboxes of the Heavy-duty class designed in 2005. Next year 6L50 \6L45 gearboxes of the Medium-Duty class (with a lower torque) up to 450 Nm replaced BMW gearbox, which was popular in repair services. The 6L45E (GA6L45R) is a constructively modified 5L40 (which was actually replaced by the 6L45E in 2007 ). Mainly used with budgetary BMW-3 and X3 with engines 2.5l - 3.0L. 6L50, 6L80 and 6L90 transmissions may be considered as quite reliable RWD 6-speed gearboxes of GM series. European modifications 6L45 /R have been used since 2006 on BMW Х1, Х3 of 1-st 3-rd and 5-th series and manufactured in Strasbourg, France. These gearboxes mainly differ in electrical components.

These gearboxes usually get in repair services for scheduled ATF change, replacement of the filters with the pan gasket. ATF gets contaminated because of aggressive accelerations and wear-out of the lock-up clutch. It is recommended to change ATF in accordance with its contamination level, but no later than after travelling 80 thousand kilometers.

Typical problems

The problem detected on the 6L80 (manufactured before 2008) is related to the design of the pump cover and cranking of filler rings resulting in problems with shifting from the 2-nd to the 3-rd gear and delays in switch-on of Forward or Reverse gears.

In case of the overhaul, it is recommended to check the leak integrity of the drum 555. There may be some hidden cracks leading to the operation pressure losses in packs causing problems when shifting gears 2-3 and Reverse. Overheating is dangerous for all pistons, which have to be fully replaced. It is the problem inherited from its 5-speed predecessor 5L40E.

All pistons and retainers are replaced quite frequently (kit of pistons 6L45-50). Problems with the torque converter (TC) may also occur in these gearboxes. The wheel-hub early gets out of order. Rare and complicated cases of the overhaul show some vulnerability of the pack (4-5-6 Clutch), which in neglected cases leads to burning of all frictions, including steel discs and pistons. The reason is often related to wear-out of the TC bushing and TC itself.

The torque converter is often considered to be a soft spot in American gearboxes. After 100-150 thousand kilometers (depending on engine and driving style), it is recommended to test the TC seal for leaks. When there are leakages in the seal or ATF gets rapidly contaminated, then it is desirable to get TC in repair services to prevent problems with the pump or the valve body. This measure particularly should be applied when automatic gearboxes operate jointly with motors (with maximum torques).