LH overdrive overhaul

[David Ramsbotham]

Hi Everyone,
As part of my on going refurbishment of my 1975 MGB I am now tackling the overdrive unit. I am following guidance from the University Motors videos but sadly real life is not quite the same as car maintenance on line!

I need to undo the none return valve plug but it is stuck tight and requires the 2 pronged special tool 18G1118 to free it up.

Does anyone know where I can buy, hire or borrow afore mentioned tool or have some great diy invention to take it’s place?

As always many thanks in advance, cheers, David.

[Peter Cresswell]

Hi David
I had my overdrive done by ODSpares in Rugby. The reason is you can't test it after you have done any work, and as you have discovered you need a fair few special tools to do it dismantle and rebuild it.
In my case the Overdrive had been functioning on low oil for around 1000 miles as we carefully drove it home following the loss of the oil through the hole where the wire goes into the casing for the solenoid. Ever since I bought the car the OD had been lazy to engage when hot and similarly to disengage. It never stuck in OD though so I just put up with. ODSpares stripped it down, replaced the seals and filters, checked the clutch lining, replaced the solenoid and tested it. They found the pressure was way too low (about 250psi) and corrected that to 430psi. The bill - just £80 including VAT. They even fitted it to the gearbox when I went to collect it.
A highly recommend company and really not worth messing with an OD yourself.
See here for details: http://www.odspares.com/

[David Ramsbotham]

Thanks for the reply Peter, but not a feasible option I’m afraid as car in pieces including gearbox drained and overdrive solenoid and pressure relief valve already out!

[David Ramsbotham]

Since my search for tool 18G1118 has been fruitless I decided to make my own tool using a piece of bar steel and 2 small nuts, bolts and washers. Careful measuring and bingo I have a tool that works and plug is now easily unscrewing!

[Peter Cresswell]

Hi David,
If you need any parts for your overdrive, ODSpares have them all - and probably cheaper than anywhere else!

On another thought, did you mark how the gearbox cross member goes together? There are something like 36 combinations of how all the parts fit together. I didn't but managed to work it out using one of the University Motors videos, and I cut two 1inch holes through the cross member to allow access to the nuts on the mounting, but I still spent 3 hours lying on my back trying to get the 4 cross member bolts into the chassis rail and the 2 bolts (which were by far and away the worst to get in) that hold the lower bracket to the centre of the cross member. A real pig of a job!!!!

[David Ramsbotham]

Hi Peter,
As the overdrive was working before taking the car “off the road”, all I’m doing is effectively servicing it in line with the University videos, hence no need to remove unit or crossmember.
Actually found things to be remarkable good considering age of unit, some swarf on wire filter screen and slight wear to plunger valve wheel. I’m replacing wire filter screen and all the O rings and gaskets, thoroughly cleaning and then putting back together. Thanks for info on supplier but I already ordered from Moss as my usual go to source for parts. Not necessarily always the cheapest but have found to be very reliable and speedy.
Getting new oil back in the box will be the next challenge, I have a large syringe but that has max capacity of 200ml so will take some time to fill the 3.4 litres required!
Next stop after that will be front suspension - thinking of renewing all bushes and also dropping whole car down to chrome bumper ride height.
All the best, David.

[Andrew Tilney]

David its a lot easier to fill the box before you fit it

[Charles Farran]

Hi David,
I understand that some clever individuals purchase a cheap pump that they drive using an electric pump & a couple of hoses. (This beats getting under the car for hours with a litre bottle like we used to get for lawm mower oil & the oil drippng down your arm)!
Cheers, Charles

[Vic Butler]

I have a large capacity Draper oil gun/syringe which I use to fill my Land Rover gearboxes, overdrive and axles. I'm not sure of the capacity but I guess it's more than 200ml.
. Vic Butler

[Andrew Tilney]

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