1989 defender 2.5TD to 300TDi conversion

I have just bought a discovery 300TDi and im looking at using the engine and box as a replacement for the origional 2.5 TD. i have read a lot about the conversion but it seems a lot of people will codge things in order to get it to fit, being a perfectionist i want it to be as near to perfect as i can get so here goes:
I understand the gear lever housing on top of the gear box needs to be changed from the discovery one and replaced with the defender gear lever housing ?
Also the gear box tunnel needs to be changed from the 2.5TD one to a 300TDi R380 gearbox one so the gear lever sits in the right position ?

I understand the engine mounts will need to be repositioned but what about the TD gearbox mounts to take the R380 gearbox ?

will the exhaust manifold need changing so i can use a standard defender downpipe ?

I would be very gratefull for any help on this conversion and advice on problems i might come across. i want my land rover defender to be as close to an original defender 300TDi as i can get it and i would rather pay for the parts to achieve this rather than bodging bits and pieces just to fit it in. thanks.

i assume u will be using the rad from the disco 300tdi, if so the mounts for the rad will need to b modded slightly....You will need to cut the lower rad mounting brackets and lower them as much as you can. Be careful not to cut them too much as the rad pin mounts on the underside of the rad will hit the chassis. You will also need to weld some pins to the top of the rad, then you can use the Defenders own top mounting brackets. you may also need to elongate virtually all of the piping but dnt quote me on that!!
you should be able to use the wiring loom from the 2.5td and only have to make minor adjustments....i think...
The best thing to do with the mounts is fit the mounts to the disco tdi and then drop the beast into the empty 2.5td bay get some one to help u and get them to mark where the mounts are on the chassis. If memory serves me correctly the orrigional mounts of the 2.5td on the left hand side of the engine should be ok for the 300tdi but u will have to change for other side and also for the box and tranny...what tranny(transfer box) r u using??

let me know how u get on and im more than happy to help you out if u PM me i can give u my number.
also wait and see what some other people say cous some fellas on here are all knowing!!!

hope thats of some help to u

If you are fitting the box and engine complete then the existing mounts should line up. 300tdi's have their engine mounts further back on the block then the TD, but the R380 bellhousing is longer so it pushes the engine right up to the rad - so you dnt need to stretch the pipework.

Fitting the disco box will need a Defender R380 transmission cover, as they are different shapes. To make the sticks come up in the right place you will need to swap the linkage from the top of the boxes over - no-one seems to know how to do it, but a few people have said they have 'had it done'.

Use the 300tdi engine mounts from the disco chassis - the mounts are stronger than the old ones. Weld them in place.


If you are seriously considering spending this much on it to make it original like, surely it would be better to sell it and buy a 300? In all honesty, theres quite a lot of work making it fit anyway, let alone making it fit like LR made them fit outta the factory.

I did a thread on my conversion somewhere, i used my current LT77 box though. search for 300tdi upgrade if you want!

thanks for the info, that has helped a lot. i have put a new bulkhead on the defender changed the rear tub and had the usual rotten bits on it removed and new ally welded in so its like new now, its had three brand new doors the later smooth roof and glazed sides, oh and i cut out the alpine holes and fitted alpine windows. ive changed a lot of the shabby and worn out stuff and given it a full respray. it looks like a new one so thats why im not keen on selling it. i could buy a later one with the 300TDi in it but i think its better the devil you know.
Ive just bought a Defender R380 transmission cover off ebay and a defender gear lever housing. im planning on dropping the engine and box in compleat so the help about the gearbox and engine mounts has been very helpfull. i will cut what ever i need off the discovery in order to make the job as good as i can. once again thanks for taking the time to help me out, it appreciated.

good plan! Sounds like you have a nice LR.

heres whast i would do:

take engine and box outta disco, seperately.
replace clutch, reinforce the clutch fork.

Fit linkage to gearbox, and install the box to the defender.

Cut out the engine mounts from the disco chassis. Bolt them up complete to the engine.

Drop the engine in, and while it is still on the crane, bolt it up fully to the gearbox. you should then find that the existing mounts are in the way. Cut them out.

As your disco mounts are now fixed to the engine, drop the engine to the correct level height, and weld in the mounts. Then remove the crane.

Then look at fitting the rad etc, and all assorted pipes!

Have a good read of my conversion as it shows which pipes to use etc. You will probably be able to buy the correct pipes now, as the engine will be in the right place, but as you can see from mine it takes half an hour to make up the fuel lines and modify the rad pipes to fit, and they look proper and smart anyway, much cheaper.

I used the disco filter housing for the fuel filter, and you will also need to buy a 300tdi air filter housing and pipework, and wing side vent for it

Hope this helps!

brilliant thanks.

ive just added a few pics some where on here in an album titled: defender 90 project. guess its gonna get stripped down again now im going with the 300TDi.

hi all new to the site just been reading the posts above and and doin the same conversion just wondered if the 2.5td loom needs any modifications to it if so could anyone tell me what? cheers andy

hey all just thought this might help.......to convert a disco r308 for a defender you need this

Ashcroft Transmissions - Selector Rail Adapter & Yolk

or you buy a defender quadrant and selector shaft, and use a defender remote top housing...

simples