GTE Overdrive

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2837GT
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Joined: Wed Aug 06, 2014 7:55 am

GTE Overdrive

Post by 2837GT »

My overdrive has (again) stopped working.

Unlike on previous occasions, the fuse has not blown as the wires that were previously shorting are now insulated properly.

When you turn on the ignition (but without starting the engine), place the gear lever in fourth and move the overdrive leaver forwards you can hear an audible clunk which I assume is a relay functioning as intended.

This does not happen in any other gear so I think I can assume the electronics and the safety switch are working correctly. It also leads me to believe the switch on the column behind the bell housing is functioning properly.

As an aside, which I hope is not relevant, back in October I pulled into a garage, changing down through the box from 4th to 1st as normal, but forgot to pull the overdrive leaver back.
I then tried to reverse the car to get to another pump. The car would not reverse. Once I released the overdrive lever, it reversed normally. On setting off again the overdrive worked as normal.
I assume this is a safety feature too ?

Anyway,I drove the car to my local dealer on Monday this week, on the way there I had OD, on the way back I didn't.

I am a little mystified. Looking at one of Tom's blogs from 10/18/2002 he reports a case of the OD relay on the fuse panel clicking but power still not getting to the solenoid. The contacts had corroded. I wonder if this is where I should start to look?

Any thoughts welcome.
tim
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Re: GTE Overdrive

Post by tim »

Greetings... When I pickedup my 330GT the overdrive worked sporadically. It was amazing how much improved it was by filling it. But you did check that, didn't you?

Tim
1964 330GT 5769 -the big yellow taxi 61&66 Morgan +4's Daimler SP250 Turner 950S and some other dull stuff plus a brand Mercedes C300 4matic
2837GT
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Re: GTE Overdrive

Post by 2837GT »

Actually no Tim, though I see I no reason why it shouldn't be full, car serviced regularly and fluids changed.
But, assumption could be dangerous !
How do you check? I guessing under the cover on the drivers side of the transmission tunnel.
I had heard some cars have a common chamber for gear and overdrive, threads on here suggest different fillers for the gear box and overdrive.
Probably time for Tom to chip in :P
tim
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Location: sacramento, ca

Re: GTE Overdrive

Post by tim »

On my car, an early 330GT, there are two fill plugs located behind seperate access panels. I've heard of them sharing fluid but on mine they are seperate. He overdrive access is almost behind the leading edge of the seat.

Tim
1964 330GT 5769 -the big yellow taxi 61&66 Morgan +4's Daimler SP250 Turner 950S and some other dull stuff plus a brand Mercedes C300 4matic
2837GT
Posts: 81
Joined: Wed Aug 06, 2014 7:55 am

Re: GTE Overdrive

Post by 2837GT »

Thanks Tim, I will check soon, though I would be surprised if that is the issue, I am prepared to be surprised.
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tyang
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Re: GTE Overdrive

Post by tyang »

Hi All,

Early overdrives shared the gear oil with the transmissions, while later cars had separate chambers. The way to tell is usually the rear tail section of the transmission will have separate fill plug.

It sounds like the electronics are working as you hear the click, but make sure it's coming from the transmission and not from the relay at the fuse panel. I always say, easy things first. You can access some of the transmission parts through little doors on the transmission tunnel after unsnapping the leather cover. The shared oil fill plug is located just by the parking brake. There should also be another access door by the overdrive solenoid. You may be able to reach the single wire that operates the solenoid and confirm it's getting power. Behind the rectangular box of the overdrive unit is a lever that is pulled by the overdrive solenoid and is adjusted with a clamp bolt. There is a procedure that requires a rod inserted to check for proper alignment of the lever, but I don't think that can performed without removing the trans tunnel. Sometimes the overdrive may go out of adjustment and as things warm up, the OD doesn't engage. Do you see a pattern with failure happens only when warm?

Good luck.

Tom
'63 330 America #5053
2837GT
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Re: GTE Overdrive

Post by 2837GT »

Hi Tom,
Happy Thanksgiving to you, you family and all American Ferrari folk.
Thanks got the reply, I suspect the clunk is the relay by the fuse box.
We will test to see if the wire to the solenoid is getting power.
Certainly before we remove the trans tunnel, as you say, easy things first.
I assume the operation can be tested with the ignition on and the gear lever in 4th without the engine running?
I also assume that the last word in you post should be ‘warm’ not ‘wear’?
That does conform to my drive on Monday, it was working on the way out and not on the way back.
This is the reverse of the headlamp relay which prior to adjustment was not working until the engine bay warmed up.
It has now been adjusted and works properly.
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tyang
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Re: GTE Overdrive

Post by tyang »

Thanks for the Thanksgiving wishes!

Yes, you can test the overdrive with the key on engine off, in 4th gear to see if the solenoid is energized. It will make a distinct click at the tail of the overdrive when the lever is activated.

Yes, warm. I found my personal car can sometimes stop working when things get warm after a long drive. I have not circled back to figure out what was going on.

Tom
'63 330 America #5053
2837GT
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Re: GTE Overdrive

Post by 2837GT »

Well, all the external parts have been checked. The solenoid is powered and working, alignment on the other side is good, tested with a drill bit inserted as per the manual.
So it looks like it will have to come out.
There is a cottage industry in the U.K. dedicated to renovating Laycock units, prices are around £750 to £1000 for warrantied rebuilds.
So it could be worse.
In my years of GTE ownership the overdrive has been the only consistently unreliable part. Hopefully that will now change.
Season’s greetings to you all.
mechaniker
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Joined: Tue Dec 18, 2012 8:18 am

Re: GTE Overdrive

Post by mechaniker »

In Germany is a guy called Volker Herrmann. He alreday did several Ferrari Units.
http://www.getriebe-overdrive.de/index.php
2837GT
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Re: GTE Overdrive

Post by 2837GT »

The overdrive has now been overhauled by Overdrive Spares , Rugby, England.
The company was founded by ex Laycock de Normanville employees.
These units were fitted to a variety of British sports cars in period so they have plenty of work over here.

They seem very switched on and are able to test the units on a bench potentially which saves a lot of time taking the unit in and out of the car to test it.

Their conclusion was simply that the unit was 60 years old.
Much of the clutch lining was gone, explaining the slip that I encountered with the OD engaged.
The operating valve was clogged so oil pressure was not bleeding out on engaement.

Bearings, filters, magnet etc have been replaced.
It looks like the unit was not damaged by the lever remaining engaged when the car was manoeuvred in lower gears and reverse.
I have asked Carrs (who will be putting it back in the car on Friday) to check that the system is disengaging when in the lower three gears. Even with the lever engaged you should hear the solonoid click out when you move the gear lever.
I have no reason to believe this is not happening but its always worth checking these things.

Anyway I am glad all is well and that I resisted the temptation to splash out on the GTO 5 speed modification.
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