Hi Forum members .
Have the GV now behind my John Cope CTR-4 for 2 years.
Have had same issue for last 2 years.
After driving a total of about 2000 miles the GV disengages by it self when activated on highway.
It's not a temp problem.
2 years ago had issue first time. Changed fluids and cleaned filter.
Problem gone. Now last year again same issue.
Have momentary switch on Cheetah shifter and select on moment always above 50mp/h.
Strange thing is that it's never first drive after winter of when cold or very hot.
Always in august . 2016 and 2015.
Have called GV tech line and have had very good test instructions but was wondering if anybody have had this also.

After driving 2000 miles Id be ready to disengage too. So what's the problem.

Ive almost bought one before, got all the literature on it and stuff, and as I remember. The engagement and disengagement was controlled by electric solenoids. Will have to dig it back out to really give any input on it for you. One would think once its engaged electronically that it would stay engaged unless there's a connection problem.

Are you running a relay on the circuit.. it
sounds like the you have it hooked up to a
switch... the solenoid could be drawing a
bit too much causing heat.. if you turn it
off then back on does it engage.. it wont
have anything to do with the month

Ok, back when I was looking at them, the switch was either on or off, that's it. Now, they have Much more complicated controls for them if needed, with there Own controller box . They can even tie in with your electric lockup vert,vac etc for more precise control of the gear vendor unit. How complicated is your setup. Now there can be Much more to consider then just the on off of the engagement solenoid.

MrPbody , It's like the GV makes the oil dirty after about 2000 miles and this causes the GV to not have enough oil.
When I stopped and let the oil cool for about 1 hour it didn't work.
Drove for about 500 miles more and then it worked again for some days.
After changing oil and cleaning filter the issue was gone for 3 moths till winter and first 5 months of next year.
Then again the GV turned off every now and then.
And stopped again after 400 miles.

Sport440 , The GV is 2 years old and besides "stock" set-up like in manual the only difference is the momentary switch on the Cheetah which is connected like the supplied footswitch.

Not really clear in my head if it's not the wear of GV , like the tech line said , why the issue is gone for 1 year if you change the oil and clean filter.

The Gear Vendors is a much strengthened version of the overdrive that was used in Volvos in the '70s. Back then it was called the Laycock de Normanville. It has an internal pump to compress a clutch pack for the overdrive to function. This clutch pack looks just like one in an automatic transmission.

The OD depends on oil pressure to operate. Many years ago I helped a friend on his 245 Volvo when it wouldn't stay in O/D. Took off bottom pan, cleaned up the filter, and put it back together. That worked for a long time after.

So here's what I think about your situation:
1. Something is causing the oil pressure to lessen its pressure on the clutch pack. It could be faulty clutch disks that are making debris.
2. Pressurized oil is routed to the clutch pack by a normally closed solenoid valve. When energized, the solenoid valve opens and you get O/D. If for some reason the solenoid isn't working properly it could allow the valve to close.
3. It's possible that the solenoid coil has an internal short, or for some other reason it is heating enough that current flow is reduced and the valve closes.
4. It's possible that the oil is leaking past the piston rings or through porosity.

Even though it is an American made item, you should be able to find a mechanic familiar with the Laycock overdrive.

R.

Uh-uh, it's a cone clutch.

Our gear vendors behind a Hemi 4 speed has similar problems with randomly switching out of OD. Dave at GV said if the power to it goes below 12.7 volts, the brain will turn it off. With our car, it could be an RF issue
when the electric fans turn on & off or an issue with a custom switch we installed. Should know by end of this week & will pass it on. Have you tried calling GV tech support?

Dogdays : Thanks for the input. Heat should not be issue as it has only happened on highway and not after stopped or slow driving.
And the heat does not change after the 2000 miles. Had even higher temp outside and GV still worked. It's deffinitly a distance/time related issue.

Triggerfish : Have called tech GV and they said it's power issue .
Something like battery to low or too high. Have changed 1 wire alternator for other type last winter and issue did not change.
Perhaps some issue like leaking pressure and this causes slippage like bands in 727 but then in GV and this makes oil dirty.

Tech GV have given me some tests to do and need to get back to them after this BS weather is gone in The Netherlands and I can give the Hemi a nice beating.

Dutchrunner, I could be wrong but I don't think it is a momentary switch. It is either off or on and the GV "remembers" whatever the last value was. Turboaction sells a GV switch for their shifters (I have one) that may work for you. Could your switch be bad?

I experienced something like you are a while back. It turned out to be one of the connections to their controller had worked itself loose from the G forces from hard launches. I reset them all and it's been fine since.

Preddy , Thanks for input.
Above could be possible but still does not answer questions why GV works again okay after oil/filter cleaning.

GV Techkies said Volts issue but why only happening after long driving months and is gone after new oil.
In my point of view it's like loose band in 727 but then in GV unit.
Slip causes material to make oil dirty and clogs filter and GV switches of.