As always when working underneath a Car make sure that it is well supported.
A Scimitar landing on you will give you a sense of humour failure.
While the information contained in this page is mainly about improving the Gear Linkage there is information that will help with the existing Gear Change. See below. All pictures are expandable by clicking on the thumbnail image. As there are connections to the Overdrive Inhibit Switch and the Reverse Light Switch it would be a good idea to disconnect the Battery.
The design of the Gear Linkage leaves a lot to be desired. It must be one of the worst Gear change designs to come from Ford. Changing Gear is more like stirring a bowl of porridge with rocks in it. Some have changed the Gearbox to a five speed but I like the Overdrive so I thought I would try to improve the design. This idea has been done by others who have used Rose Joints but I "acquired" some Ball Joints and Clevises for nothing so I have used them. The result is very pleasing, so much so if I had of known how much of an improvement it would be I would have done this a long time ago. The work required may seem a lot but it is definitely worth the effort. The Ball Joints and Clevises came from RS. The RS part number for the Ball Joints is 689-423 and the RS part number for the Clevis is 312-0270. The threads of these joints and clevis's are M10. The rods were made from M10 threaded studding that can be purchased from normal DIY stores like B&Q. At first I thought that the rods were not going to be stiff enough but they have proved to be O.K. I had some heatshrink sleeve so I used it to cover the threaded rods to make them look better. You could get some rod and cut your own thread but personally I don't think it is worth the effort unless of course you have stuff in your garage that you can use. Obviously if you are using other types of linkages like rose jointed both ends the thread size will determine what you use.
They look like this.
As well as replacing the Selector Rods it is a good idea to remove the Gear Lever assembly and tighten things to remove any wear as a small amount of wear at the bottom of the assembly will show in a large amount of movement in the Lever. Removing the Gear Lever assembly is not an easy job as it requires the removal of the center console ( The bit inside the car that has the arm rest ). ( Make sure that the Gears are in neutral before removing the Gear Lever ). This will require the removal of the Ash Trays and the screws holding the console in place. To remove the center consol it is quite likely that you will have to remove the handbrake cables where they attach to the levers that come out of the rear brake drum backing plate. This will then enable the Handbrake Lever to be lifted high enough to enable the console to slide off. ( The joys of working on a Scimitar ). Once the console is off there are three bolts that hold the Gear Lever assembly in place on the transmission tunnel. It is best if two people are available as when you try to undo the bolts as the bottom screw will turn and so someone will need to be underneath the Car to hold the screws. You can do it by yourself by using a Mole Wrench holding the upper bolts while you undo the bottom nuts. It may seem like more work but if you remove the Propshaft you will find working in this area a lot easier. Removing the Propshaft is easy as there are only four bolts holding it at each end. I believe that there are some propshaft's that bolt onto the differential and the Gearbox end slides into the end of the Gearbox. If this is the type you have take care as when you slide out the Propshaft from the Gearbox ( Overdrive ) there will be a release of oil so have some rags at the ready to "stuff" into the gap. If you do remove the Propshaft you will get a better view and easier access. As you remove the three bolts that hold the Gear Lever assembly in place you will find that the rear one is holding the Overdrive Inhibit switch in place. Take note of it's position before removing as it is not obvious how to refit. Before removing the Gear Lever assembly you will need to remove the selector rods. They are held in position by some clips that need to be pushed in the direction of the rod pin. These clips have oval holes that when in place engage in a grove in the rods. It can be a bit fiddley but once you have the first one off the rest will be easy. When the clips are removed the Gear Lever assembly can now be removed from inside the Car. You should now see this. Note, the pictures show the plate is broken where the shaft goes through. This is a common problem. The unit I fitted was a different one and not broken.
The pin as shown will have to be removed so you can slide out the shaft. Once this shaft is removed you will see this. Note the position of each lower lever before removing the shaft as they are different lengths and have different bends.
You will now be able to see how the assembly works. As the Gear Lever is moved from side to side the pin in the shaft locates in one of the lower levers. As the Gear Lever is moved forwards or back it pushes the lower lever forward or back so pushing the rod and moving the selector lever on the Gearbox side plate and so engaging the selected Gear. See here.
There is not a lot you can do with this assembly except tightening the pin that holds the Gear Lever to the shaft and ensuring that the shaft has as little "Play" as possible. Reassemble the Gear Lever assembly and refit to the transmission tunnel. When refitting the Gear Lever assembly remember to refit the Overdrive Inhibit Switch. Adjustments will need to be made ( Twist the Switch ) to ensure that the arm locates on the shaft. When 3rd/4th gear selected this shaft slides outwards and so pushes the lever of the Overdrive switch. When 1st/2nd gear selected this shaft slides in and the Inhibit switch lever moves and so turns off the voltage to the Overdrive solenoid. If you are clever a bit of gentle bending of the Inhibit switch mount will enable you to have the switch adjusted so overdrive can be engaged on all four forward gears ( If you want to, not everyone agrees that Overdrive engaged in first and second is a good idea ). The most important thing is to make sure that the switch is not adjusted so Overdrive can be engaged when selecting reverse. Reversing the Car with Overdrive engaged will "Kill" the Overdrive. Now remove the Rods from the Levers on the Gearbox side plate. It is easier to remove the 1st/2nd and 3rd/4th levers to get access to the clips that hold the rods in place. Once the old rods are remove you can use them as patterns to make the new ones. Unsure if the dimensions of the Old rods will be of any use to anyone but they can be seen here.
The new Rods I made can be seen here, complete with heatshrink sleeve.
Once fitted adjustments will need to be made. Even if not fitting new Rods this adjustment can make quite a difference. On the bottom of the Gear Lever assembly there are holes that allow you to slide in a rod to align. A 5.5 mm drill bit can be used. The only problem I found after fitting the new Rods was the was too much play even when using the drill bit to hold levers in place. This resulted in the Levers not quite being aligned and so when the Gear Lever was moved side to side there was not a smooth movement as the pin on the shaft was catching on the misaligned lower Lever. Not a problem but when aligning the Levers feel the grove in the Lower Levers where the drill bit slides through and you will feel the misalignment, only requires a small adjustment of the Rods. To check move Gear Lever between 1st/2nd and 3rd/4th, it should slide easy, if not more adjustment required. To see this area click here.
Once all adjusted you can now refit all what was removed, Console, Propshaft ( If any oil did escape you will need to check the Gearbox Oil level ). See here.
You should have a nice looking Gear linkage like this.
Once all back together off for a test drive. Take care as if you have been used to changing Gear with a sloppy linkage you will find Gear changes very different. I realise that the above work seems a lot but the improvement to the Gear change and the overall improvement to the drivability of the Car is well worth the effort. If required I have included an exploded view of the Gearbox side plate assembly.
An additional improvement can be done by moving the position of where the Selector Rods fit to the selector levers is also a worth while modification. New holes will need to be made in the levers that are connected to the gearbox. The holes are nearer the shaft into the gearbox meaning that less movement of the gearlever is required to give gear selection. This means a bit more of a "Push" required when changing Gear but gives a much better Gear Change as there will be less movement of the Gear Lever required.
Click on Picture below to see Gearlinkage Modification.