Refitting The Hydraulic Gear Selector (aka the 'Gear Brain')

The hydraulic gear selector (aka 'gear brain') is back on the car. 

The 'gear brain' on a bvh car

Fitting is a little fiddly but otherwise simple. Setting it up - as part of the fitting - requires a bit more attention. Instructions can be found at Operation Dh.334-1 in volume 2 of manual 814.

 

The first task is to 'lock' the brain in the 'first gear' position. This is done by aligning the hole through the slide valve with the hole on the body of the selector.

Hole for the gear brain setting pin

The slide valve is locked by inserting a pin through the hole - Citroen tool 2429-T. 

 

The mythical 'tool 2429-T'.....

The manual says this pin needs to be 3.94mm in diameter. That's pretty precise! I found that a 4mm twist drill was too big but given the tolerances in drill bits, you might find one that fits. Don't be tempted to use some thing of a smaller diameter as you need to set the slide valve as precisely as possible. You dont want to jam a pin in, but you want it to be as snug as possible.

Setting Pin. The red tape indicates 3cm depth

For the correct setting, the pin needs to disappear about 3cm into the body of the selector. It's possible to have the slide valve hole lined up BUT the slide valve rotated 180 degrees out. If this is so, the pin will fit partly only through the valve  - apparently 'locking' it - but internally, the grooves/ channels in the valve will not line up as they need to.

The slide valve is a complex piece of engineering (setting hole indicated)

Setting pin correctly located

The setting hole is on the underside of the gear brain, so once confident that I had the slide valve set in first gear position, I used a bt of copper wire to keep my pin in place.

I used some wire to stop the pin dropping out during fitting

 The gear brain bolts through a tunnel piece - that passes through the bulkhead - and onto the gear wand/ changer mechanism. I had already repainted and fitted the tunnel. 

The 'tunnel' piece being repainted.....

The gear wand had only been loosely fitted to the dashboard shelf at this point.

 

Gear 'wand' mechanisms (photo credit: Faullksy)

I had cleaned off the old grease that had accumulated dust and dirt and re-greased it anew. I had cleaned up the starter switch and contacts - making sure they were in good condition.

I cleaned the gear selector (wand')

I checked and cleaned the starter switch

Before presenting the gear brain, I hooked the end of the operating rod for the auxilary clutch to the auxilary clutch valve. Because of the hook end, and the diameter of the hole the rod passes through, it's not possibe to fit this rod after the brain has been fitted.

Hook on auxilary clutch control rod

I had my hands full with the next bits as you need to work on both sides of the bulkhead at the same time. The operating rod for the auxilary clutch was threaded through the tunnel and through the trunion on the clutch lever.....

Auxilary clutch control rod and trunion

 .... at the same time that the slide valve of the brain was threaded onto the gear wand mechanism - hidden away inside the tunnel.

 

 The brain is held in place by two bolts. The tips are pointed. There is a reason for this! Once the brain is presented to the tunnel piece, it becomes very difficult to locate the nuts on the bolts. Pointed bolts helps to get the theads located. 

Hard to see: the fixing bolts are hideen away deep in the tunnel

That's great in theory, but what you are battling is gravity: the nuts fall out of the socket before they reach the bolts. I used a little Blutak to hold the nuts in a socket on a long extension bar. 

 

With the gear brain bolted home, I tightened the bolts securing the gear wand to the dashboard shelf and 'tunnel' part.

Fixing for the gear wand mechanism

The special pin holds ther gear brain in 'first gear' position, and so the gear wand has to be in the same 'first gear' position too - before the bolts joining them together are tightened. I had to dig out the 'gate' from my dashboard top to remind myself where the first gear position was.....

Working out 'first gear' position......

With first gear selected, the two bolts joining the selector rod on the gear wand, to the slide valve on the gear brain were tightened from above and the special pin (tool 2429-T) was removed. 

Access to the bolts to secure the selector

The last job was to set up the auxilary clutch lever and rod. The hooked rod (and so the auxilary clutch valve in the gear brain) are pushed FORWARD, and the little lever under the dash is pulled BACKWARDS. The square-headed screw on the trunion is then tightened to secure the rod.

The rod is pushed forward and the lever pulled back.....

 And that was it for now.