How to remove and re-fit a complete GS3 Shift Actuator unit

This information is also available as a video here.

When a GS3 unit is in a vehicle, there is a pneumatic air feed into the pressure regulator, an electrical connection from the clutch actuator and an electrical connection from the vehicle wiring harness in place. These will need to be removed before any work is carried out.


The first step is to remove the 15 x 13mm headed bolts; the order you undo these in is not important.

removing gs3 actuator unit bolts

The bolts at the front end of the housing are longer than ones at the rear end; we recommend that you keep them separate for ease of fitment later.

To make the re-fit easier, remove the lid from the bottom half of the Shift Actuator so you can see three out of the four location pegs you need to hit when refitting it.

To remove the lid from the bottom half, take out the two T30 Torx screws in the centre of the shift actuator. Put these safely to one side.

how to remove gs3 lid from bottom half

gs3 actuator pressure regulator

Lift the pressure regulator towards you and slot the lid into the holes provided on the side of the unit.

ZF GS3 actuator unit lid lifting

Two ribbon connectors will be revealed. Gently and carefully rock these connectors out of the plugs. This releases the upper half from the lower half; you can now place this upper half to one side.

removing the GS3 ribbon connectors

Lift the lower half of the Shift Actuator out of the unit.

how to lift the lower half shift actuator

Fitting the service exchange shift actuator

When you purchase a Shift Actuator from Ecodrive Transmissions, the pistons could be set in any position. Prior to fitting then, you need to align all of the pistons correctly.

There are four locations that you need to align accurately when fitting the GS3 (first image below). They correspond to keys inside the gearbox (second image below).

how to fit the ZF GS3 shift actuator

actuator keys inside the ZF gearbox

Lay the new Shift Actuator on a flat surface (on the left in the image below). Set the splitter, the main gear box and the range change pistons to reflect the positions of the corresponding pistons on the failed unit (right).

splitter,  main gear box and  range change pistons reflect positions of the corresponding pistons on the failed unit

To do this, measure the height of each piston on the failed unit and match this on the pistons in the new unit. The range change piston will be the hardest one to move as it is the biggest piston.

how to move the range change piston

The central piston should be set in the neutral position; you can actually feel the neutral position as you push it in and out. This is key to certain vehicles being able to start once fitting is complete – if it is in an in-gear position the vehicle will not start.

central piston must be in neutral

ensuring the GS3 is in neutral before refit

Carry out a visual check to make sure all pistons match. The replacement actuator should fit straight onto the gearbox now.

Fitting replacement shift actuator onto gearbox

Back to the gearbox: next we recommend that you place a couple of studs into the housing. This will help you to align the gasket to the housing when fitting.

aligning the GS3 actuator gasket

Put the gasket in place. All GS3 Shift Actuator products purchased from Ecodrive come with new gaskets.

positioning the GS3 shift actuator gasket

Make sure that you’re in the neutral position.

putting th shift actuator into neutral

Place the shift actuator down onto the main gearbox with the aid of the studs.

positioning the shift actuator onto the gearbox

Press down on the rear of the housing (which is spring loaded) to check that the two housings meet and that you have hit all four positions correctly.

ensuring the two actuator housings meet

It is best not to assume that you have aligned it and then tighten the bolts; you can actually break housings and crack parts.

Now that the housings are aligned, place the intermediate gasket into position with the help of the studs. Again, new gaskets are supplied with the unit when purchased from Ecodrive.

positioning the new intermediate gasket for the shift actuator

Slot the upper half of the Shift Actuator, which houses the brain, into the holes on the side of the unit and then reconnect the two ribbon connectors.

replacing the upper half of the shift actuator

reconnecting the shift actuator ribbon connectors

With the aid of the studs, carefully lower the upper half onto the gearbox.

repositioning the upper half on top of the gearbox

Put the two T30 Torx bolts into position to hold the gasket in place so that it doesn’t move. Do not torque these.

position the actuator gasket before torquing

Put the 13-head bolts from before into position; as mentioned earlier, the longer ones go in the front end of the GS3 Shift Actuator and the shorter ones go in the rear.

Take the two positioning studs out now that you have most of the 13-head bolts in place, as the gasket will not move. Put the two remaining bolts in their place.

Tighten the 13-head bolts – because the housing is spring loaded, we recommend that you tighten the bolts on diagonally opposite corners to start with, then follow with the rest. The upper half will lower down into position.

tighten the ZF gearbox head bolts diagonally

Now that the GS3 is secured, the next step is to torque all bolts up to the relevant setting. The 13-head bolts are torqued up to 23 Newton metres; again, we recommend starting with the corner bolts.

final torquing of the head bolts

The two T30 Torx bolts only need to be torqued up to 10 Newton metres – do these last so that the main bolts are responsible for the lowering into position of the housing.

The GS3 is now secured back on the gearbox.

If the unit is in the vehicle, you will need to reconnect electrical connections to the vehicle, the clutch actuator and the pneumatic air feed into the GS3 air pressure regulator.

If you are changing the complete unit then you may need programming relevant to the vehicle. If you are just changing the bottom half, that is the original off the vehicle so it will not need programming.

For parts or further advice from our expert team, please get in touch on 01204 701812.