Overdrive not engaging in 4th, but does in 3rd

[mazfg]

Just been out for what will probabaly be the last spin  of the year. Was fine on the drive out but on my way home, I found that I couldn't get overdrive in 4th. Goes in (slowly) with 3rd, if I then select 4th it comes out of overdrive?  If i'm in 4th and then select overdrive, I get nothing?  Relay is working ok/ clicking ok
Could it be the solenois or something more sinister?

I'm about to take the whole thing out anyway and get it refurbed (again).

Any help appreciated.

[mazfg]

Just to add to that..taken it out again and found that it will engage in 4th but as soon as i go over 40mph it goes in and out (judders) and then stays out. Obviously the higher speed is causing it to disengage?

[Paudman]

Is your oil level alright? Top it up and try again.
Failing that it may be wiring chafing or loose; at higher speeds wind resistance or vibration may stress the wiring and cause it to lose connection.

[mazfg]

I'll check the oil, but never had a problem with the level. Been driving it all summer and this is the first time it's done this. I'm removing at the moment anyway, so i'll see how much oil comes out???  Otherwise will re-check the wiring continuity. Thanks

[mazfg]

Checked the oil and it's at the right level.

[John Bonnett]

Well worth checking that the cable that passes through the centre of the gear lever hasn't worn through the insulation and intermittently earthing.

[RobPearce]

If it's an original Vitesse installation there is no wire through the gear lever - the switch is on the column. You can still get problems with the wire but they're not usually gear-sensitive.

[mazfg]

I have the lever on the steerign column. This all seems to work ok..

[Nick Jones]

With hydraulic problems, usually the problem goes the other way.  If you push on to higher speeds in third does it drop out then too?

If it does, possibly the strainer is blocked.  The pump is driven by the mainshaft and varies with road speed.  At lower speeds it may be able to just draw enough oil through.  At higher speeds it will be trying to draw more but perhaps failing to overcome the increasing losses and drawing air from the top/cavitating.

Would be a reasonably easy fix though the question of what was causing the blockage and why would arise......  Black "fur" from the clutch linings is the usual culprit.

Nick

[mazfg]

Thanks for that Nick.  I did clean the strainer out in the OD back in February. it was quite gunked with that silvery grey liquid..
I'll have another look tomorrow.

[mazfg]

Just checked the strainer. .not clogged up.....oil again was quite silvery grey tthough.

[Matt306]

silvery oil sounds like something is breaking up in the OD.

The OD works on a Cam on the Mainshaft driving a pump, when the solenoid engages it lifts a ball bearing and lets the fluid into two pistons pushing them forward against springs and pulling the cone clutch forward.

A low pressure may cause this, and this can be shimmed, could be your pump on its way our which to replace could be done from under neath.

The manual talk of a special tool..... however i botched something with a 1/2" pipe union to remove mine.

I would check the solenoid and electrics first.

[Pete Lewis]

Do the simple first  this sounds a classic case of inhibitor switch adjustment
theres no conection between gearbox selection amd overdrive operation
other than wires down the gear stick (not in this case) and the 3rd 4th inhibitor switch
Bet if you   side load the gear stick you will make this worse or better
so remove a shim  washer from under the switch and retest if  the switch is bracket mounted it may need some gentle adjustent
Pete

[mazfg]

I've buzzed through the cable and will try the switch again whilst jiggling the gearstick.....but it seems to look all good

[Pete Lewis]

this switch can give lots of interrupted if not making good plunger pressure , its only a bell push inside  and they can be quite corroded
if its a simple crimped case you can disassemble and clean but some later ones are sealed for life  what ever that gives.
the fact it plays up differently in 3rd to what happens in 4th is got to be selection related not overdrive related
the OD doesnt know what gear youre in
Pete

[mazfg]

The switch has been thoroughly tested/ checked and all good.

[Pete Lewis]

was that on the gearbox being operated by its cam or  switch on bench ?
Pete

[mazfg]

Quoted from Pete Lewis

was that on the gearbox being operated by its cam or  switch on bench ?
Pete

Gearbox operating the switch. Once continuity was flowing I moved the gearbox aroundo,  rolled it, bumped it and all stayed good.

[nang]

Don't know... have trouble with my TC not engaging . Recent gearbox and o/d overhaul. Will engage when cold but that's about it.After 2 or 3 km''s gives up. Sure it's not electrics, checked everything out. Replaced the relief valve assy with no improvement. This morning I thought I'd found the problem. Removed the pressure filter, plug was loose and filter was full of crap. Cleaned it out best I could. Better but still not right. Ordered a new filter from Rimmers. We'll see what happens. Costing more on oil than anything else. (huh)
Tony.

[Pete Lewis]

mazfg is Dtype on the 2000 its J type,  i found the inner piston in the solenoid was sticking , needs a thin 1"af spanner to undo the sol,
dont grip its case you can wreck it,  and remove the small  10mm  circlip inside and pop the piston out for a good clean and all intermittent mind of its own solved  dont need to drain the oil either .

mazfg,  have you tested the holding coil  current should pull in at 10 amps and the switch to 0.5 amps , theres a switch mechanism in the end of the solenoid can be very corroded over the years   ( some  later ones are solid state you cant service the contact)

[nang]

I now convinced my problem is not electrical, I've stripped the solenoid (J type) cleaned it up and replaced the O rings. I'm sure that it's working as intended and my problem is hydraulic. I'll see if the new filter improves things. At the moment it changes normally for the first 5 minutes or so and then stops working.
Tony.

[RobPearce]

nang,
Is it the same in both 3rd and 4th? I had a problem on a Stag where it would work when cold but not when hot, with different sensitivity depending on gear. It turned out a previous owner had fitted too many washers under the inhibitor switch. I removed one and the problem disappeared.
Hydraulic problems that cause it not to work when hot are usually down to leaks and/or low oil pressure. They generally go through a phase of being very sluggish with a very soft engagement before finally giving up. The problem I had on the Stag wasn't like that - it worked great then suddenly it did nothing.

[mazfg]

Quoted from Pete Lewis

mazfg is Dtype on the 2000 its J type,  i found the inner piston in the solenoid was sticking , needs a thin 1"af spanner to undo the sol,
dont grip its case you can wreck it,  and remove the small  10mm  circlip inside and pop the piston out for a good clean and all intermittent mind of its own solved  dont need to drain the oil either .

mazfg,  have you tested the holding coil  current should pull in at 10 amps and the switch to 0.5 amps , theres a switch mechanism in the end of the solenoid can be very corroded over the years   ( some  later ones are solid state you cant service the contact)

It pulls in  fine and holding current is 0.95 amps. It's rock solid and won't move at that and is in the correct position

[Pete Lewis]

Not much more I can dream up , it still has all the snags of inhibitor messing up ,
how about you make up a bypass lead and toggle switch to prove its completely eliminated
Just dont use it in 1 2 or reverese with the od engaged

Nang did you remove the  J  solenoid inner plunger, it should rattle if you  the shake the sol  firmly.
they only seem to supply O rings for the outer body not the piston valve one hidden inside
just a thought

pete

[nang]

Pete, I managed to get suitable O rings for the inner bits and yes the thing rattles !
I'm waiting for a new filter to arrive before I go into the pump plug. Present filter was full of that looks like clutch lining bits and yes, the o/d was rebuilt recently.
Although I've cleaned the filter the best I can, I'm still not sure it's enough as the gauze is quite fine.