Hi,
I have just purchased a 1967 240
Great car, but have an issue with getting reverse
When the car is cold it is OK. Needs some force to get it in reverse but not too much
When hot it is very difficult and requires quite a lot of effort and it seems wrong
Any ideas?

 

Strange. The opposite should happen. If you declutch & try again is there any improvement? Presume the clutch is correctly adjusted and disengaging properly.

There is a cross detent adjustment on top of the gearbox that adjusts how hard you have to push the lever to the left to engage reverse. Stops you catching reverse on your 1st to 2nd change. That requires console removal & glass fibre gearbox cover to access. Presume the console is correctly fitted & not impeding the lever.

What oil are you running in the gearbox? Try GL4 SAE 75W-90

Worst condition is a damaged reverse gear idler.

Good luck!

 

Thanks. I had a look at the lubrication chart and sure it said SAE30 for the gearbox oil. Is 75W/90 OK for the gearbox then?

 

SAE 30 engine oil is for the old Moss box that was thrown out in '65 on Mk2's & October '64 on S Types. You have the full synchro Jaguar box with Synchro on 1st gear which requires GL4 90. The multigrade version eases gearchange a little.

BTW ~ is your car fitted with Overdrive? Presume you are not trying to engage reverse with overdrive selected? You will smash the one way roller clutch in the OD if someone has messed with the wiring to the inhibitor switch.

 

Yes it has O/D and it is definitely not engaged. Will the 75/90 be OK with the O/D? . My MGB GT with O/D uses 20W/50 for the gearbox and O/D

 

I'm a tribologist. Will not give you bad advice. The OD is quite happy with engine oil or gear oil. Anyway if you read the updated Jaguar Service Manual & bulletins it makes it absolutely clear that GL4 SAE 90 is the correct oil with the synch 4 gearbox & Type A compact OD which you will have. The synch 4 gearbox requires a mild dose of EP additive (GL4) for proper gear protection.

See here. Do not use GL5. It will damage your synchro cones. GL5 is for axles/diffs. These things were printed a long time ago & lubricants have moved on from that time which can be confusing.

 

Great. Many thanks. Will use this oil but I guess the issue is more mechanical linkage problem. As you say , remove the cover and investigate

 

See above edit from Service Manual.

 

Just a thought but if the car is new to you, the reverse lock-out on the later full synchro box may also be new to you. It may not be intuitive. I have an E-Type with the later box and to engage reverse you need to slap the stick to the left, not just push it. I'm not sure how the mechanism works but mine will only engage with a quick slap. It doesn't need to be that hard. Warm or cold, I can always find reverse. I've had the car a very long time and it has always worked this way so I assume that they all work that way.
Hopefully its nothing serious inside the box.

 

Is the obstruction in moving the lever across neutral to the reverse branch, moving it forward afterwards or in finally engaging the gear? It's important to consider as it indicates where to look for the solution.

 

The issue is moving across the gate not finally engaging it. When cold it is fine although does need a little force.
As it is new to me it is a bit different but cold it is fine. Hot is requires much more of a 'slap' across the gate.
I suspect it is a detent issue. I will have to remove the tunnel cover and investigate.
Any further thoughts would be most welcome

 

That's the cross gate adjustable detent for reverse. (Peter you only move it forward on a Moss. On the Jaguar Synch 4 you move it rearward ~ across & down)

Moss box Fig. 10., Jaguar box Fig. 10A.





Entire mechanism around item 16. Mine was too tight. Now it's too loose. Needs further adjustment. I can just nip reverse if careless on the 1st to 2nd change. What I don't understand is why it's getting worse hot. Don't replace glass fibre GB cover & console until you are absolutely satisfied. Getting it just right is a bit of a fiddle.

 

I’m by no means an expert on the change mechanisms, though I have explored that of the Moss box. One of the biggest problems is that there’s little guidance in the manuals. It seems to be assumed that the function is either obvious or sufficiently simple to require no explanation.

Possibly because of the change from moving the stick forward to moving it back with reverse adjacent to second in the all-synchro box, Jaguar modified the mechanisms that prevent accidental engagement of reverse instead of second. The spring and horizontal plunger that provided most of the resistance in the Moss box were reduced in stiffness, while the ball, vertical plunger and spring lock (or détente), which did very little in the Moss, were significantly stiffened. That's basically why the feel changed from a ‘progressive push’ to a ‘take swing at it.’

My suspicion is that something is close to blocking the movement when everything is cold. The slight change in relative dimensions as everything warms may be sufficient to make things worse. Three parts come to my mind as places to check. The first two are the items I mentioned above. The spring and plunger that provides lateral stiffness and the ball, plunger and spring lock. They need to move freely without hitting any dirt, swarf or ridges that may have appeared due to wear. The third possibility is the alignment of the slot in the selector rod (striker rod in more old-fashioned Moss nomenclature) with the selector finger (the bottom end of the gear lever). At least on a Moss box, both the finger and the slot look to be hand-finished with a grinder to allow a smooth shift. It’s quite possible the work wasn’t perfect and, with years of use, some ridges have developed. If they have, it may be possible to grind them off.

Getting to this stuff in a Moss box is relatively straightforward as it has a change mechanism lid on top of the main lid of the gearbox. Looking at the drawings, for the all-synchro, I’m guessing that you have to take the main lid off and turn it upside down? If access requires a lot of disassembly, it may be easier to buy a second-hand lid complete with all the mechanism. As I said at the start, I’m no expert, but I hope that it helps.

 

Item 16 & all it's adjuster gubbins sticks out of the back of the cover with all it's adjusters below the gear lever. To adjust that which is the common problem does not require removal of the top of the GB. It's external. You might have to remove the top if it is something worse than the adjustment. Buying a new/used lid won't help you unless the lid is damaged. The adjustment is quiet simple. Getting it to your liking, less so. Trial & error. The WSM is about as much use as t*ts on a bull.

The selector rod ends were very well finished on my box. The box is a delight to use correctly adjusted & with new synchro cones. The Jaguar box uses baulk-ring synchromesh on all forward gears. The Moss is highly agricultural by comparison ~ but a tough old thing.

 

That at least makes adjustment easier. It would be ace if it also allows access to the springs and plungers and the slots on the striker rods. It's very hard to tell from the drawings.

 

It allows access to all adjuster bolts, lock nuts, springs & ***** for the reverse selector rod. Trying to find you a representative picture is a sod. Excuse orientation vs diagram. Best I can do without hours of internet searching. I can't find the other side.

 

Actually Glyn, you're one of the few that goes above and beyond, most say "Google is your friend" and some get down right nasty.

 

Most of my habit comes from MBWorld. I talked Benz into allowing us to use the WIS (Workshop Information System), EPC (Electronics Parts Catalogue) & any info & screen shots from their Star diagnostic computers as long as everything is shown in complete form & unaltered. Fortunately each WIS task is downloadable as a pdf. and even tells you what tools you will need & all torque settings.

We also frown upon comments by members of STFF, as mods. Some members would not have a clue what to search for so how much help is that?

 

Although you've discussed lubrication of the gears, there's not been much said about lubricating the change mechanism. Obviously, it doesn't need much and probably some mist gets up from the gears. However, it would be good to have something that ensured a smooth and consistent action.

Any suggestions?

 

Peter. There is what I would like & what is practical & available/available in small packagings.

What I would like is a longlife Polyurea synthetic 5% Moly grease.

What I recommend & will be available & compatible is a Lithium or preferably Lithium Complex 3 to 5% Moly grease. No2 penetration.

Caution: For all those oil canners that usually have engine oil in their oil can. Do not get engine oil anywhere near gear oil & vice versa. You will induce severe foaming/air entrainment in either.