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Overdrive removal

Posted: Thu Jun 27, 2019 11:31 am
by cannonball
Last night I was under the car yet again to remove the gearbox side plate with a view to replacing the three oil seals and I noticed that the overdrive unit is dripping oil from every nut and bolt also.
Is it possible to remove the unit from the gearbox whilst the gearbox is attached to the engine or do I have to take the whole lot off yet again? :(

Overdrive removal

Posted: Thu Jun 27, 2019 11:41 am
by philipmasonfrance
That's (almost) thought transfer (spooky!). I was about to post somewhat shamefacedly (does that exist as a word?), to ask about overdrive maintenance. My overdrive and gearbox on the GTC leak like a sieve too. I top it up every two or three months, which I suppose is good for the box - nice fresh oil..... Just what maintenance is needed/possible on the overdrive unit? Shame-faced because I've only had my second GTC 20 years and never touched the overdrive!

Overdrive removal

Posted: Thu Jun 27, 2019 11:45 am
by cannonball
The thought of crawling underneath regularly to top up is a bit daunting.

Overdrive removal

Posted: Thu Jun 27, 2019 11:52 am
by philipmasonfrance
No need! Undo the filler plug; feed down a bit of garden hose with a funnel at the back of the open bonnet, push into the filler and gently pour fresh oil down into the box. OK, you will always lose a little bit of oil, but surprisingly little. Fastest pit-stop so far about 6 minutes!

Overdrive removal

Posted: Thu Jun 27, 2019 12:01 pm
by Rev Light
I have been told that it is difficult to get to the bolts at the top that connect the overdrive to the gearbox.

But you might be able to do it if you remove the gearbox mount so it hangs down a bit ????

Just a thought. I am hoping to replace mine soon.

Overdrive removal

Posted: Thu Jun 27, 2019 12:15 pm
by cannonball
Don't know if I could access the filler plug without pulling the carpet out and cutting a hole in the tunnel,

thought of letting the box lower after removing the cross member then supporting it with another jack then removing the overdrive unit if possible.

if only we had eight foot arms with numerous flexi joints with interchangeable ratchets on the end.

Overdrive removal

Posted: Thu Jun 27, 2019 12:27 pm
by Oldconn
I don't know about a GTC (Cologne engine, distributor at the back), but on a GTE you can disconnect manifolds and radiator pipes , also the heater water pipes, then support the gearbox with a trolley-jack, remove the cross-member, and slowly lower the box, tilting the whole unit until a cylinder-head is resting against the bulkhead(cushioned with a piece of plywood). This allows you to access the overdrive from underneath . However IMHO it is easier to remove the gearbox and overdrive together because separating them is tricky, and you have to engage the drive cam correctly when re-assembling.