The Triumph Dolomite Club - Discussion Forum

Hello All!
Our 1500HL. Had a new overdrive unit fitted, it works fine except the first 2 or 3 miles from cold when it will drop in of its own accord ! Without flicking the switch! I’ve even disconnected the overdrive wiring and it still did it. We called the overdrive supplier and They mentioned cleaning out the breather hole on top of gearbox, which I did but still have this issue. It seems pressure related ie once the oil starts to warm up it works normally! Any thought please ??

Roy .

Have you checked the oil level in the gearbox ? , or maybe the solenoid is sticking ?

The oil is fresh and correct level, I’m now wondering if the solenoid struggles when the oil is cold with the extra pressure ?? Once it’s done a couple of miles it starts working normally.

Are you saying the O/D engages without being activated by the switch or with no power going to the solenoid at all?

Mart,
Yes, from cold I can pull off the driveway, then as I change into 2nd gear and apply power it drops into overdrive! Does this as I go up the gears for about the first 3 miles, then it starts working normally .
Last week I disconnected the overdrive wiring loom plug and it still did it so it’s not electrical. Feels like the extra pressure from cold gearbox oil is pushing past the solenoid??

Based on theory of operation here.... https://static1.squarespace.com/static/ ... Part+I.pdf (See page 6)
I'd say the relief valve is the likely issue? If the relief valve isn't opening until a higher pressure than it takes to activate the pistons with cold oil? Or maybe the operating valve (solenoid) ?

If the O/D is engaging in 2nd, I would be very careful about using reverse when it's cold (or at all).

I can't see it being the relief valve, I would say it is some sort of blockage or maybe the solenoid is stuck? Did you install the solenoid or was it already installed?

Where did you get the O/D from and was it new or reconditioned?