Hi all. I am a new Mark 2 owner and was wondering about filling the 4 speed w/od transmission. My OD isn't working, but it is getting power. I'm thinking I might be low on fluid. Can I check and fill it from inside the car, or do I have to do it from underneath the car? Also, I will be topping off with 30wt non detergent fluid. Is this correct?
Thanks,
Walter

 

Walter, Your car is from 1961. Does it have it's original Moss box, no synchro on bottom gear and reverse forward and adjacent to first? You fill the gearbox via a plug on the side reached from under the car. Fill till the oil reaches the level of the hole. As you wrote, Jaguar indicated a 30 grade engine oil. There are several suggestions as to what might or might not work better, but none of that has consequence for the failure of your overdrive. You say the overdrive is getting power. Is the solenoid moving?

 

The overdrive operates on two main principles. Oil pressure & solenoid adjustment. If the oil pressure is too low it wont engage. The pin in hole adjustment of the solenoid is hopeless & seldom works. You really need to ensure engagement by trial & error or on the work bench.

Another issue ~ if the OD has not been used for a long time the cone clutch gets stuck. There are two solutions. A hard blow from a rubber faced hammer at the thick gasket/spacer between the Gearbox & OD or stripping the OD if not successful. The OD can be removed with care from the rear of the gearbox without taking the Engine & GB out. Just loosening the stabaliser & rear mounting & lowering the rear of the gearbox a little.

BTW ~ the OD pressure feeds the gearbox from it's pump. Once you have filled the gearbox to the filler hole. Drive the car and then top up again as the level will drop due to filling the OD.

 

Hi. The car has been sitting for some time. I will fill the gearbox with oil and hopefully have a working OD -- I'm hoping it is just stuck or low on oil. The solenoid is getting power when the switch is activated, but it is not moving. Also, the speedometer cable is not attached -- it is on order -- will oil leak out from where the cable goes in?
Thanks,
Walter

 

If the plunger isn't moving when volts are applied to the solenoid, is it free to move or blocked? If it's blocked, it can burn out. I think the solenoid should have a resistance of 15 to 20 ohms when the plunger has moved to the on position. When It's not switched on (or when it's initially excited), the resistance is low, less than 1ohm. If the solenoid is burnt out, you'll see open circuit.

 

I checked the solenoid and I got negative (-) 6 ohms. That was just with my voltmeter attached to ground and the solenoid wire.

 

6 ohms sounds odd. I'll see if I can get access to one of mine tomorrow to measure.

 

Far better test. The OD solenoid draws 20 amps engagement current then backs off to 1 amp holding current. The mechanism is under the black cover on the rear of the solenoid. If it does not do this it burns out & will give all sorts of crazy readings. As said before. Pin in hole adjustment is usually wrong.

Example:




Moss gearbox installation.

 

The cable drive has a seal on it so oil should not leak if the seal is good. An O ring seals the whole speedo mechanism into the hole in Gearbox or Overdrive if fitted with a pinch bolt.

Inner seal.


O ring 83. Pinch bolt 84.

 

Should that read 0.6 ohms? That's about the correct value for the high current and low current coils both connected (switch off).

 

And one important item to remember. Do NOT cut the inhibitor switch out of the circuit. If you engage reverse with the OD switched in you will smash the one way roller clutch in the OD causing awful damage.

 

That didn't quite works as I planned. The solenoid is missing from the overdrive that I bought years ago for spares. So I crawled under my car to measure there. It served to show the the high current winding on that one has blown. I have another, or will sometime next week, and can check that when I bring it home.

 

I will recheck the ohms reading and update. The switch is on the car that only allows OD use in 4th gear. I will top off with fluid and hope that the seal for the speedo cable is good
Thanks for all the replies.
Walter

 

Good ~ leave it that way! (Inhibitor switch). People get clever & want OD on other gears.

 

If you don't have the Jaguar service manual, the attached pdf may be helpful in explaining how the Laycock od works, its adjustment and repair.