Hello, I am new to jag lovers forum. I find myself with an issue that I could use some help with. Reverse gear doesn’t want to work. I initially thought that it might be a gear selector problem as I seemed to be able to drive forward ok. I had a little look at the gear selector mechanism and it looks ok so I decided to try and reverse out of the garage. Reverse could be selected and I got halfway our and it seemed like the clutch was slipping. I couldn’t smell burning friction material, which I would expect from a slipping clutch. Does anyone have any ideas as to what the problem could be? Thanks
Hi , I have never come across the problem , if you think it’s the clutch , put the hand brake on , select 3rd and try and pull away , engine will stop or the revs will go up and your not be moving .
May be clutch , not sure if the brakes may bind going in reverse , if they are could show a clutch problem
If you can select reverse and it moves , sounds like the clutch more then a gearbox problem ! ,
Thanks, I have been fettling with it for most of today. I have had times when reverse has engaged and allowed me to get onto the drive?? Then it stopped working. No problems at all with forward gears. Very strange. I found a fault diagnosis section in a manual that I have and it suggests you can get clutch slip in reverse if there is a blocked restrictor jet in the operating valve of the overdrive??? Any ideas anyone? Ta. Harry’s Jag.
Someone has kindly confirmed that I have an overdrive issue, now all I need to know is how to fix it. Being a bear of little “mechanical” brain. Is this an easy mechanical fix? Or does it require a specialist and gearbox, which I think means engine too, out?
which is #67 in the drawing above. It is possible that the shift appears to move (or sometimes actually does) the gears into reverse, but may slip at other times.
Is there any chance you are operating it with the wrong viscosity oil? SAE 90 or 80W90 perhaps?
I believe it is supposed to be SAE 30, still commonly used in air compressors.
An oil change couldn’t hurt, might clear it up.
We need to clarify, Moss gearbox with overdrive or full syncro box with overdrive? Per Jaguar Service Bulletin F.9 of December 1964 SAE 90 Hypoid Oil is to be used in the full syncho box/overdrive. Workshop manual supplement for the later OD unit also states “Clutch slip in reverse or free wheel in condition in OD could be caused by a) solenoid operating lever out of adjustment, b) partially blocked restrictor jet in operating valve, c) worn or burnt inner clutch lining.” Earlier units with the Moss box did call for 30w oil.
It is definitely a moss box, no synchro on first. Reverse is left and forward which I believe indicates a moss type gearbox. It’s a 64 car but from a dim and distant memory my dad bought the car in the ‘70s from his mate because the gearbox had broken. So who knows what happened. I’m not sure when ‘all synchros’were fitted as standard in place of the Moss?? But I definitely have a Moss box fitted. Maybe that was fitted in place of the original in the ‘70s?
Ok, since it is a non-synchro first, try changing the oil and put in SAE 30 or 10W-30 or 5W-30 motor oil.
Give it time to drain, rotating the driveshaft if you can.
If there is SAE90 or 80W-90 gear lube in there (which is correct for later boxes but not yours) it will have a distinctive smell.
Tony, if your car is manual gearbox with overdrive may be overdrive is ligthly engaged , I had a similar trouble with my mark 1 and actuacting valve of overdrive dont seat properly…with it engage , in reverse, gearbox may be seriusly damage
