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How can I tell if I have a Disco gearbox?

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Hi all. I have a 1991 Defender 90 with a 200tdi engine and by identification number lookups I also have an LT77 gearbox and LT230 transfer box.

But when I bought it, the previous owner mentioned it had a Disco gearbox fitted.

Is there any way to tell? And what's the benefit?

I've got a leak that I'll need to fix, so I'm interested from a parts perspective and if there's much difference.



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Welcome !

If reverse is left of 1st gear you have an LT77 main gearbox.

If reverse is right of 5th gear you have an R380 main gearbox.

Transferbox (bolted behind the main gearbox) can be a number of things.

With luck, you'll find a sticker stating the ratio. Otherwise, find the serial number and have a look online.

The ratio of a Disco 1 transferbox is "higher that makes for somewhat higher cruising speed but a bit less pulling power."


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Thanks for the replies.

My gearbox is definitely LT77 based on reverse position and the ID stamped on the case.

And transfer box is 22D prefix, pointing to a defender LT230 + has the 1.410 ratio sticker there too.

Sounds like the previous owner was telling porkies...no bother!

Next job is to find the source of the gearbox leak. Any common sources to check? It's not easy to make out after going for a drive.

Cheers all

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The disco lt77 has a bell housing around 8" long, the defender lt77 only about 4". Lt77's generally leak via the output seal, however the input seal for the transfer box is next to it they also leak. This is where the gearbox and transfer box meet. As above to work out which oil therefore which seal. If it not there then you need to track it down I'm afraid. 

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On 9/17/2021 at 5:16 AM, 92a said:


I did this last week whilst changing my clutch... What a difference- no leaks!!!! I also finally got round to changing my gearbox mounts to Glencoyne ones and the vibration has halved. Well worth the effort.

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  • 4 weeks later...

Later update than planned, but after a thorough clean and a drive, one of the leaks looks to be coming from the diff pinion seal.  The oil seems to get blown back to the transfer box when driving.

New seal and flange kit + new nuts and bolts on order.

Can anyone confirm if they a 14mm nut? That size spanner seems to fit, but slips where someone has thoroughly chewed them up in the past, so they they'll likely need cutting off...


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8 minutes ago, reb78 said:

I hate mine Mo ^^^. I spend more time turning the props to get the socket on than it takes to undo it with a spanner!

I love mine - one of the best tools I have ever bought. Attached to the little battery impact wrench and you can get in prop off easily in a couple of minutes. Well worth having to turn the prop a bit to get access

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