Running my 1968 240, now 3.4, on the car lift to check the O/D operation before installing the interior and I find it is not working, there seems to be a short on the 12v supply wire (green) but I will look at that later, I have hot wired the solenoid directly and it clicks in with a loud click but no noise when the power is cut, is that normal? before refitting the original gearbox I cleaned the solenoid and I seem to remember adjusting the lever, used a rod through a hole? so question is what can I check without removing the unit? can I remove the unit with the gearbox in the car? it does look possible,
The car was last run in 1979 so it has been standing a while! the box has only done around 85,000 miles from new,
Mine clicks when energized but no click when power is cut. This is how it’s been on my 1967 Mark 2 since I purchased the car 35 years ago.
I took a few bits off it today, the arm moves when energised to the position where the holes line up, I do remember adjusting it a few years ago, it was full of EP89/90 gear oil, the big spring looks ok, the plunger , ball and spring were in place, not removed the pump plunger as yet but everything is very clean, no debris, will research more later.
If the electrical circuit is like the one on my full syncho, compact overdrive unit (1965 3.8S) there is an on off switch on the steering column and a switch on the top of the gearbox that permits the OD to only operate in 4th gear. The adjustment of the solenoid is critical as there are two coils involved, one is a high amperage (15 amps?) one that is the pull in coil, then when that is achieved, that coil is disabled and a hold in coil is energized drawing very little amperage. With an accurate dashboard ammeter one can determine if only the hold in coil is operating. I don’t think the operation of the internals of the OD can be checked unless the car is on a lift and the engine run in 4th gear and the operation tested, or on the road noting the drop in RPMs when in 4th gear and the dash switch is turned on.
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I vaguely recall that there is an in line fuse right above the gearbox/overdrive units. Hopefully its that easy peasey.
What do you mean by “not working”? Have you driven the car?
1st thing to check is that you have enough oil and it is correct one.
Too little oil (OD is filled through gearbox) and it will not work.
Too “thin” oil and it will not work. Use SAE30 or similar.
You can try “direct hot wire” in testing but do not use it in normal use,
if you accidentally leave your “hot wire” on while reversing, you will break
your OD. That is why there is a 4th gear switch in original wiring.
In theory you can remove OD without removing gearbox, but getting it back is not a funny job: there are springs between OD and gearbox and getting those back correctly under the car is much more difficult than on a table.
Kopik, There are springs between the overdrive and gearbox on the older unit, but not with the later compact type used with the full syncho gearbox. With that one it is relatively easy to remove it with the gearbox in the car. One will need to remove the center console and the removable tunnel cover to gain access to some of the mounting nuts. When replacing be SURE to remove the OD pump so that the roller wheel does not foul the cam on the mainshaft.
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Same fuse as reverse lamps?
Anyways, loud click means it is not power. Not an electrical problem. Run engine in gear, then stop engine, 4th gear, activate overdrive. Is there an audible engagement besides the solenoid click?
Not quite, anything but 4th has too much torque for the o/d rating. It would slip and break in 1st or second.
The car has no interior installed as yet, the top is off from the tunnel, I drove it for 5-10 mins on the single post lift in 3rd and 4th gear, no change in rear wheel speed or engine rpm when the solenoid clicks in, the solenoid was pulling the arm to the position where the holes line up, there is an inline fuse just under the rev counter, I seem to remember that the solenoid was stuck or sticky when I tested it before I put the engine and box in, I removed and cleaned it, I will check the current draw to make sure it drops when left engaged, I did wonder if the o/d clutch was stuck together after sitting for 40 +years, I have driven it around the garden and it did not seem to be over geared when I pulled away, I have reversed it again in the garden, I will pull out the pump plunger tomorrow when I work out how to, I have removed the plug but nothing fell out, all very clean in there, no sign of rust or water ingress…
And the oil level is good?
The fuse is irrelevant as it seems to work electrically. I had the switch fail before (and it’s not even behind an engine yet!): what if you power the solenoid directly?
I tested it with a powerful battery drill, ran it for a bit then removed the drill and had a few actuations until the accumulator ran out. Mine only works in top gear,
only a click that I can hear, maybe when I put it back together and refill the oil I will have the engine running in 3rd or 4th and hot wire the solenoid whilst I stand under the car, I may hear or notice something.
Testing it with a hot wire to rule out switch, gearbox switches and fuse problems, once it works on a hot wire I will work forwards to make sure all the other bits work correctly, unless I know the o/d actually works it is hard to know when the rest is functioning ok,
And just a thought; has the gearbox and overdrive been separated any time recently? It’s possible to leave the cam off the mainshaft which would prevent the plunger pump from operating and building up any pressure. There is a Churchhill pressure gauge that can be attached to the OD and the pressure measured while the engine is running in gear. Can’t recall the pressure it is supposed to develop but IIRC it is pretty high around 300-400 pounds. When the OD is engaged it drops suddenly then builds back up quickly.
All I did with the tranny was to clean it and replace the input and drive shaft seals, and the gear lever bushes, if it ain’t broke…well maybe it is DOH. not been separated, ever by the looks of things, the clutch had been replaced in 1979 as witnessed by the slot cut into the tunnel to get to the bellhousing bolts! I was thinking about testing the pressure, does anyone know how the gauge attaches? I may have a 600psi gauge somewhere…
If the solenoid is clicking , then the electrics are good , should only work in 4th gear , I would wait and see what its like on a road test .
There is a oil filter in the overdrive unit , mine was very dirty , so that may be worth looking at !
Filter and magnets are very clean, no glass or interior at the moment so really want to get it working before fitting it up,
Seeing the cut out in the pictures above of the tunnel, leads to the question of whether one can replace the transmission and or clutch without pulling the entire engine.
Thanks
The attachment for the gauge on the compact overdrive as fitted to the full syncho gearboxes is on the bottom. Refer to a workshop manual for details. If the gauge has a long enough hose one can have the car on a lift, sit in it and run the engine in 4th and observe the gauge and what happens when the solenoid is operated. Did it once with my 3.8S many decades ago.
From a quick internet search other jaguar forums discuss this and a common thread seems to be that when contacting Dave Twigger at overdrive spares a sticking O/D mechanism is very likely. Having personally dealt with O/D spares over the years I support the idea of giving him a call. If you’re going to spares day on the 17th he will normally be there.