Hi All,
For anybody who ’ needs ’ to fix the 5/ Rev shift stiffness, the bad news is you will have to get your box looking like the pic below at least if you suspect the following applies. The well meaning suggestions regarding weakening the heavy spring and plunger combination in the bottom of the box can prove fatal to the box, particularly if you are going to use the vehicle a great deal. The easy spring/plunger/washers etc. fix is equivalent to a good friend suggesting you fix your flat tire by drilling another hole in it – to let more air into it.
You can leave the ‘lock plate’, lever and shims bolted to the box, remove select. shaft as per manual. I use a 1/4 drive deep reach socket of appropriate dia. to retain the spring and ball in the ‘‘lock’’.
The excessive force usually applied to shift 5 or Rev. tends to mangle the lever pivot and it’s corresponding drilling in the lock plate. If the retaining circlip is mangled and bent out of shape, chances are the drilling and pivot won’t be in great shape either. The ''5 Speed PSD. ‘’ offers a fix for this but I will only address the main issue here.
Once the works are removed, the first thing I do is check is the ball ended sliding lock key that lives in the ‘‘lock’’ which is the irregular shaped casting you will have driven the selector shaft out of. This slider (key) looks like a machined shaft with ball bearing at each end. This slider should fall effortlessly from the lock when you invert it or during dismantling process.
If it does not, you have probably not seen it yet because it is seized, partially or completely, inside the lock body. There is only one way out of the lock for this component, unlike the spring loaded ball next to it.
My experience is this sliding shaft can be seized to varying degrees between bad and nightmare.
The latest box I fixed with this fault is one of my own, purchased on Ebay. Two hours of tapping, levering and heating and it was still tight to the last 1/4 inch.
The following pics are two slightly different angles of what you will see when this component is seized.
These two pics were taken after the slider was freed so the left hand ball is as it should be when seated in it’s D-dent in the shaft.
A slightly different angle showing the gap that opens up around the ball where it emerges from the lock body.
When the sliding key is seized in the lock, slightly more of the dome is visible than seen in the left hand lock.
Sliding the lock body along the selector shaft should be not quite effortless but easy bearing in mind that the only drag that must be overcome is the pressure of the spring loaded ball, housed in the hump closest to the camera. When slider is seized, pulling the shaft from the lock can be very difficult depending on how bad the seizure is.
The left/H ball position is common to all gears except when 5 is engaged and the ball emerges to lock the selector in that gear and eliminate the possibility of Rev. being engaged. The R/H lock mech. shows the slider at the highest point of travel, when it engaged with the notch in the lock plate control rail and 5th gear is engaged.
The following is a combination photo/drawing with the lock body ‘ghosted’ to show what is going on at the top of the key shaft and it’s bore.
The coloured area indicates the ‘moat’ that appears when the ball is at it’s lowest point. This acts as a collection area of oil and the metal particulate content of same. When 5 is selected and the ball face is forced upward, any particulate which is not small enough to pass down the sides and back into the box, is pressed and compacted into the wall of the bore by the curved face of the dome. This happens to the entire circumference of the bore and as the bore/slider clearance decreases, the smaller particulate also becomes impacted to the bore wall.
At this point those not interested in how and why this insignificant component determines the shift quality of 5/Rev. and do not wish to join the ‘Gearbox Academy’, get the slider out, clean the bore down with a neatly rolled strip of emery paper ( 180 grit is good )clean it all and nail the thing back together and get back on the road.
For the academics, a photo layout of the actual components should help.
In this photo all components are in their horizontal position at Neutral. The lock key ( shown suspended above the lock ) is actually buried in the lock immediately below it and precisely South of where it appears. The bottom dome of the slider is resting in his D in the shaft ( gravity contact only ). It should also be noted that the spring loaded ball housed in the hump on the r/side of the lock is engaged with his own D in the shaft providing a ‘‘soft lock’’ on the selector shaft we are all familiar with.
When engaging 5 from this position, the rod, A - C, is pulled through the lock body by the pivoted lever on the left. The lock itself is prevented from moving with the shaft or rod, by a limiter on the downward facing control track of the lock plate. The slider key is forced out of its’ D in the shaft and upward so that the upper ball end locates in the notch which can be seen on the L/side of the lock plate control track.
The above pic has a second selector shaft added at the bottom to show where the D-dents are situated inside the lock body. In 5th, the slider is resting on the high land of the shaft, forcing the slider upward. The D immediately to the right is never visited by the slider, it is exclusively used by the ‘‘soft lock’’ spring loaded ball when N and Rev. are selected.
In normal operation, effort at the top of the pivoted lever would have to overcome the resistance offered by the ‘‘soft lock’’ ball, negligible friction in the lock and bore of the box casing, the heavy D-dent spring and plunger in the bottom of the box and the engagement of the sychro hub and 5th gear.
If the sliding lock key becomes seized, it takes a position somewhere midway between the upper and lower travel limits. It will not lock properly or release properly. Basically noman’s land.
Depending on how solid the seizure is, the slider will be applying considerable ‘grip’ on the shaft when the shaft should pull through the lock with little effort. This will translate as a noticeable difficulty engaging and disengaging 5th gear.
Refer to pic above.
To disengage 5th and move to N, the green highlighted part of the shaft must be pushed back through the lock body until the 5th gear release D-dent is under the slider and it can disengage its’ upper end from the notch in the lock plate control rail by dropping into the D in the shaft. Until this occurs, the lock body will be held in position where you see it in the pic. Once the green highlight section of shaft is pushed through the lock body, the lock body and shaft are free to move to the right of the photo to engage Reverse gear.
The above pic shows R engaged. The lower Shaft has been added to show the extent of travel from N and to assist orientation.
The L/H side of the lock plate control rail is now exposed and the lock notch can just be seen to the L of the lock body.
Unfortunately or fortunately, the clearances of this design are relatively huge and allow the partial jamming of the 5/Rev. mechanism when the slider key seizes. If these components were precision machined and the slider even started to seize, 5 and Rev. would have become immediately unavailable and nobody would have started talking about shimming out the main 5/Reverse positional spring and plunger.
This box needs the tight location it came with. You only need to down shift from 5 a bit too enthusiastically a few too many times and get those ‘‘dog tooth’’ Rev. gears kissing each other at 3 or 4,000 rpm to find that out. Get it badly wrong just once and you will wish you had drilled a hole in your flat tire.
For convenience I will repeat an earlier pic from above.
The casement drilling for the 5/R selector shaft is in relatively soft alloy and no hard bearing surfaces. It is designed to sustain light stress location of the shaft A-C. B is not designed to act as a fulcrum, only to guide, lightly support and allow the shaft to access the tailshaft housing where it operates the 5th gear sychro. Since both A and C are both effectively unsupported, B will act as a fulcrum when any up and down or sideways force is applied to A or C. The drilling is only designed for fore and aft movement of the shaft.
When K is seized in the lock body in a position which is neither ‘lock’ or ‘release’, the clearances of the mech. allow the lock body to be forced along the lock plate control rail while the sliding key is still only halfway between lock and release condition. This expands the distance between the control rail and the upper surface of the shaft because the ball ends of the slider are both ‘riding’ the high lands of the components they are in contact with. The lock plate is solidly bolted to the side of the casing and so, the control rail at the bottom of it can be considered immovable. When the expansion occurs, halfway between A and the casing at B, the result is considerable downward pressure on the A end of A - C forcing B to act as a fulcrum, which it was not designed for. Since the lock plate and control rail are immovable the only component with the necessary ‘give’ in it is the unsupported A end of A - C, the selector shaft.
Adulteration of the main 5/N/R location plunger and spring may give the impression of easing the 5/R shifting but it only really serves to encourage continued use of the car/g-box despite the true malfunction. Any side or down thrust on ( A ) will produce excessive wear and distortion of ( B ) over an unknown mileage or time.
It may be useful to remember that if and or when, the casing at ( B ) gives way, what happens at ( A ) will be inversely expressed at ( C ), which carries the selector fork which needs to be parallel with the sychro hub to make a clean engagement.
If you have a ‘‘trailer queen’’ with the 5/R tough shift, I’d just leave it but if serious mileage is on the cards …
I don’t know any easy way of doing the above fix or any ‘sure-fire’ way of confirming if that one small component is indeed seized, without stripping the box. No intent to depress anybody here just a possible fix and a little warning.
Sixty years ago I had an engineering tutor who got fed up with a string of my easy fix solutions to mechanical problems, he said ‘’ If we’re gonna talk about the s–t, we’re gonna talk ‘bout the s–t the way the s–t REALLY is, anythin’ less and we’re just sitt’n here gett’n older fer nuth’n.‘’ Sounded good to me then, still does.
Satyr Icon
) for the closer ratio B4BP but with a longer 5th, but in reality it really is good in standard guise. It’s agile, small and gives all the thrills without the need for massive horsepower. I have a V6 Exige which puts out much more power, but around the Alps it does not come close to the Elise. What does let it down a bit around the Alp, is that with two fat guys, a full tank of fuel and luggage it doesn’t pull half as well up the slopes, similar I guess to what you mentioned earlier. But still, a great car.