D1 Gearbox

[SoldierBoy1]

I am a new 92 Disco 200TDi owner and I am having problems with my gear box, 2nd gear to be precise. Dropped the oil out of the box after I got it and quite a bit of crap came out in the way of metal!! However it drove just fine, over the few days I have found it all but impossible to change down from 3rd to 2nd with out doubling the clutch. I’ve spent quite a few years in the ARMY and know only to well the problems the 110s have, but to me the Disco is a whole new ball game.
Can some one tell me what the more common things that go wrong with them are and what is the best option ( Repair or Replace )

Soliderboy1

[ISUZUROVER]

The 200Tdi disco was fitted with the LT77S gearbox. They are about the weakest 5-speed LR made (S stands for "strengthed" - the disco/defender version had slightly improved bearings), but seem to hold up OK in rangies and discos if not abused. Sounds like yours is just getting a bit long in the tooth. The best option would be to wait until it dies and replace it with a later model (300Tdi disco) R380 box. It is not a straight swap, but worth the effort.

[Davidh]

Same thing happened to my 91 Disco about 8 months after I'd bought it.
I was told not to expect much more than 150-200tho klm's out of an LT77 box.
I haven't been able to downshift from 3rd to 2nd in 3 years without crunching!

You just have to shift hard and fast, and put up with the crunch!

[Bush65]

What oil did you use?

[SoldierBoy1]

Penrite Gear Oil 75

That’s what the local Landy expert told me to use.

Davidh, so I take it they will crunch for quite some time before they give up all together!

Soilderboy1

[Davidh]

Gear oil?

There's your problem. They're supposed to run ATF.

I was told initially that the synchro's could last a week or a year.
Mine are still in one piece, just very well worn.

[landy_man]

nope.. LR stopped advising on ATF in the LT77 ages ago.. and now specify Castrol MTF 94 or similar.. Penrite light gear oil is equivalent and cheaper than the LR castrol stuff..

[SoldierBoy1]

So it’s the right oil then. How much to rebuild one yourself, parts only.

And also I after info on things such as Maxi-Drive axles, and the diff conversion using Toyota diff center?? RE what you are replacing and how much of an improvement they are.

Soldierboy

[Bush65]

As landy_man, rover's recommendation changed from auto transmission fluid (ATF) to manual transmission fluid (MTF).

The MTF should meet API GL4 specs (ATF is GL3).

There are a number of GL4 complient MTF's, but some people have had shifting/syncro problems with some and better success with others.

I use and recommend Castrol Syntrans, but there are some others that are good in rover boxes.

If your syncro isn't stuffed, you may find changing to a different MTF will fix the problem.

Your post implies that the problem came after changing the oil.

Don't use gear oil (only manual transmission fluid). These oils are too viscous and can lead to failure of the lubrication pump.

[SoldierBoy1]

It is labeled on the bottle as Manual Gear Oil 75 so I can only guess it's not gear oil but tranny oil?

And no it didn't play up straight away, it took about 6 weeks of driving say 1200klm before it gave me trouble.

[landy_man]

the manual gear oil 75 is fine.. I use it in my LT77s and is on the Penrite site as a substitute for MTF94.. I only started using it after recommendations from other LT77 owners after asking about hard changes to second, especially when cold..

[MacMan]

I use the same Penrite oil and it seems to work fine. This was also on the advice of others who tried a few and settled on Penrite.