J Type o/d question

[hilly10]

When cruising at 60mph overdrive engaged when slowing to 40mph does the O/d  disengage automatically at the lower rpm.

[Graham C]

Hello

The overdrive will only engage or dis engage when you operate the switch. So the answer to your question is no. Generally the engine revs will increase (dis engage) or decrease (engage) by about 500 rpm. 

Graham

[NonMember]

Yes and no.

There's no mechanism to disengage the overdrive at low revs but as the speed drops the oil pump that provides the hydraulic pressure also slows. Depending how old/worn/hot/low on oil you are, sub-40mph might be too slow to maintain enough pressure to engage it.

[hilly10]

8 minutes ago, NonMember said:

Yes and no.

There's no mechanism to disengage the overdrive at low revs but as the speed drops the oil pump that provides the hydraulic pressure also slows. Depending how old/worn/hot/low on oil you are, sub-40mph might be too slow to maintain enough pressure to engage it.

 

8 minutes ago, NonMember said:

Yes and no.

There's no mechanism to disengage the overdrive at low revs but as the speed drops the oil pump that provides the hydraulic pressure also slows. Depending how old/worn/hot/low on oil you are, sub-40mph might be too slow to maintain enough pressure to engage it.

Makes sense 

[Pete Lewis]

j types like all  rely on the gearbox oil levels being  correct, 

the gearbox and OD have a common oil level they  are not seperate units   one level plug does all.

If the levels are ok     all A D J  types can al, drop out  if the 1st 2nd inhibitor switch needs some small adjustments 

try holding the gear stick towards you to the  right when in 3rd or 4th  does it  hold in better ?

and a little more J types can have a real mind of there own, if the solenoid is playing up

you need an1"thin AF  spanner to easy unscrew the solenoid assy, you may loose a cupfull of oil 

dont unscrew by gripping the body , you can wreck it..

The sol is sealed to the body with O rings these can fail, but in the end is a 10mm circlip, pop this  out the plunger inside should be free to 

clatter back and forth , if stuck or Small O ring failed it will engage and disengage to suit itself  

All easy   DIY able

Pete