Overdrive Unit

[Ken Nelson]

Little by little I've been getting my LHD P5 3-litre manual transmission car on the road. Yesterday I discovered pleasantly that the little stalk on the right side of the steering cowl actually does something! The overdrive works! However, I've never had one before. It takes about 2 seconds to kick in, and I don't know what it should do when I switch it off. Does it wait until I shift out of gear to turn off? It doesn't go off immediately. Is this working as it should? Any words of encouragement, or things to check on it? Thanks, Ken

[Phil Nottingham]

It sounds like its working OK as long as you can tell its actually engaging/disengaging by change of engine revs

Rover were very thoughtful and did not want a jolt when disenging O/d so they put a lomit switch which only allows disengagement when the throttle is slightly open or at switch off of ignition!

[Ken Nelson]

Thanks Phil, it seems to be working OK then.

[Ken Nelson]

New problem with overdrive control on my P5. I have a Mk IIC 4-speed with O/D and now have a problem with the throttle linkage jamming closed on me. There must be enough slop in the linkages that the cam operating the limit switch for O/D drops below the cam switch button and gets caught intermittently no matter how I seem to set it. Can I just back that switch off so it is always "on" and not hitting the cam and have things work OK? Ken

[Phil Nottingham]

Yes that should OK - its pity you cannot get it working properly though but it better than having the throttle jam open!

Have you followed the book for adjustment

The switch should operate with more than 1/8th throttle opening

[Ken Nelson]

Thanks Phil; I'm afraid I have left the boundary of the shop manual behind me because I fitted the engine from my 1964 saloon into the "keeper" car which is my 1966 Coupe. Regrettably the throttle linkages are slightly different (as was the size of the main journal bearings compared to the later original coupe engine). I had to do a bit of jury-rigging, combining one system with another, but it all works fine except for that one glitch. I tried again today to readjust the linkage lengths, but the diabolical works engineers stuffed all the important bits out of the way underneath the intake manifold and blocked by the servo and a bunch of very hot radiator hoses. I may keep working on it, but it is discouraging to be all dressed up looking good and sitting by the side of the road! Ken

[Ken Nelson]

Further update: The throttle linkage rod was the wrong length and after correcting this, all works well without hanging up. But the tradeoff is, the overdrive unit doesn't engage now! I had to disconnect the overdrive limit switch and reconnect it later. There are only two wires, but could I have screwed something up with this switch that stopped it working. I'll have to start investigating, but any advice on this for me? Thanks.