P1800ES strange overdrive issue
 

I changed my gearbox oil today hoping it would solve my overdrive issues but it hasn’t made any difference. Only half a litre of oil came out.

I emptied it with the rear jacked up high and filled it with the front up in the air. It took the required 1.6 litres so I was confident it filled correctly and I filled it very slowly.

For the first few minutes of driving it behaves perfectly, engages and disengages quickly when I flick the lever and only in 4th gear. After a few highway miles it stops working in 4th gear and seems to engage itself when I pull away in 1st.

This suggests the wiring and solenoid is fine, but I can’t figure out what’s causing this behaviour when it’s up to temp. Has anyone got a clue what might be happening?

I’m at a loss now. Only thing I can think to try is cleaning out the strainer and filter??

I'm surprised there isn't a safety system that stops engagement in lower gears - sorry I haven't been playing with Volvo overdrives just yet but this PDF looks like it might help a little =>

https://volvo1800pictures.com/docume...20shooting.pdf


...

HI , Check your wiring underneath :-) I recall that the overdrive is wired in series to the solenoid i.e wire from engine bay to switch on top of gearbox (this switch only enabled when in 4th and then passed current to solenoid which is earthed to the overdrive body ?
Hope this helps
:-)

Thought I'd update this as I had an interesting call with Overdrive Spares today.

They recommended the first thing I try is to drop the inspection plate, clean out the filters and most importantly clear out the bleed port between the solenoid and valve closest to it. There is a hole less then 1mm and when that blocks it causes my symptoms. Fingers crossed it just all just needs cleaning out.

I'm not looking forward to doing this job. It's going to be intricate, messy and very awkward under the car.

Whatever you do don't run the car in reverse with the OD engaged as it will destroy parts in either the GB or OD or both.
As the GB and OD share the same oil it's a good idea to check the level after you have run the car for a few miles. When you drop the GB oil it leaves some in the OD. Dropping the sump on the OD will clear that. Good advice from Overdrive spares re the small tube. If this is blocked it can't relieve the pressure to drop the OD clutch out of engagement even though the solenoid is switched out.

Isn't an inhibitor switch fitted to prevent inadvertent operation of overdrive when in any other gear but top?

Yes there is, but that seems to be the problem.

See post #1

“ After a few highway miles it stops working in 4th gear and seems to engage itself when I pull away in 1st. ”

I thought I'd update this as I have now sorted the problem.

Today I got under the car and the first thing I noticed was the back half of the solenoid was lose. It is clamped on with a strange bracket and it was lose. The solenoid was also lose in the housing and so i removed it all and also the bottom plate and filter.

The filter was clean and I also tested the solenoid and cleaned it out with mystery oil. I reassembled everything correctly and tightly and took it for a long drive. It performs perfectly now and no longer engaged on its own.

It was definitely the solenoid causing my issues and reassembling properly resolved the issue.

Very happy days indeed :)

I'm pleased you managed to fix the overdrive problem yourself - always rewarding.