LT77 Gearbox oil

[adam quantrill]

simon_h said:

On the gearbox front, I spoke to Competition Transmission Services, who rebuilt the box, and they have asked me to try some different oil in it before condemning it. I’ve swapped it already and hope that sorts it as I can’t cope with the prospect of heaving the whole lot out again.

Well I've done a few thousand miles since my gearbox oil flush and change, including the long run to/from BBWF (I don't usually go over 100 miles on a run).

And I can report good news all round, my previous niggle with SMX-S, where after a long run the gearchange would get relucatant to change and crunchy, is gone. And the new oil is Mobil one 0W-40 with a dose of Molyslip.

For the flush procedure read here:

Strange gearbox/clutch problem

[simon_h]

adam quantrill said:

Well I've done a few thousand miles since my gearbox oil flush and change, including the long run to/from BBWF (I don't usually go over 100 miles on a run).

And I can report good news all round, my previous niggle with SMX-S, where after a long run the gearchange would get relucatant to change and crunchy, is gone. And the new oil is Mobil one 0W-40 with a dose of Molyslip.

For the flush procedure read here:

Strange gearbox/clutch problem

Thanks for the info Adam.

I've had the box rebuilt by CTS while I was doing a body off as it seemed like a good idea to do this while it was out. It was fine before, apart from the usual oil leaks, and I was running it on SMX so I thought I'd stick to what seemed to work. On the way to the BBWF and during the run out I found that it was crunching going into 3rd at high RPM unless I let the revs die down before I tried to engage the gear. It's fine going into all other gears and if you double de-clutch coming down through the gears you can go into 3rd without any problems.

It's now filled with ATF as advised by CTS, but I can't say I'm happy about it. I think I'll give it a blast to see what happens and then try the flush and Mobil 1 route as suggested. I'd prefer a decent oil in there rather than a 30 odd year old formulation of dubious lubrication properties.

I'll report back with my findings.

[adam quantrill]

ATF is too thin - I predict you'll have much the same sorts of problems. At least you can drain it out and use it as your "flush" before going over to the Mobil 1.

[honestjohntoo]

adam quantrill said:

my previous niggle with SMX-S, where after a long run the gearchange would get relucatant to change and crunchy, is gone. And the new oil is Mobil one 0W-40 with a dose of Molyslip

Phew! And there's me thinking,'will he ever be convinced?' It's the same with every person who tries it, the success rate with Mobil 1 and Moly is very high.

Being the first, that I know of, to take the plunge around 1996, I had no choice, the LT77 box was virtually useless, so it was simply "do or die".

If your success is long term - like mine - you will still be using the box in 2028. Just repeat the process every 4 years.

[carsy]

yes have to say i cant fault the mobil 1 and molly. Still in my fairly new box and will be staying in. i have tried all the usual oils for the lt77 and this feels the best.

[simonwedge]

Sorry if I've missed it but how much oil does the box take?

[carsy]

Just short of 2 litres.

[Wedg1e]

Maybe I'm just lucky but I find no problems using the recommended ATF.
My car has covered 120,000 miles and it's a D-series 'box IIRC.

[adam quantrill]

I bought a gallon of Mob1 for 30 quid on offer, and it used just under half, so I have some for topping up and another change in 4 years time ;^) and I used half the Moly.

[TV8]

I am doing an oil change on the gearbox (early chim with Lt77) tommorow and putting difflock synthetic in it. The gearbox is in pretty good condition but I think this will be better when it is very hot and hopefully, when cold - but I wont know this until the winter!

[Number 7]

I've used SMX S for years in the Wedge, with regular changes. Last year at Zolder I lost third gear. Had the box rebuilt by the same company that did it about 8 years / 40K miles before, and they said that even that Castrol stuff is too thin, and put a proper gear oil in , 75W 80 I think, which has now done about 800 miles including this years Zolder event without problems. I'll be changing it for some Redline gear oil of similar grade shortly.

[GV]

I went the Mobil/Molyslip route and so far all has been well. I also renewed the entire clutch assembly when I got my rebuilt box back from CTS. However, I cannot emphasise enough how important a properley bled clutch is to the whole process...

[TV8]

Oil change all done and feels good. Oil hasnt got properly hot yet, which will be the real test. Anyone else used difflock?

[TV8]

put a few more miles on the car now and noticeable improvement over the SMX in there before.

I was surprised how thin both the oils are. Especially the old stuff which was very warm when I drained the box.

A great tip from a land rover forum was the use of one of those garden spray things with a pump

[TV8]

Took the car around a track on Monday, with lots of use and one 30 min session which is a long time! If there was going to be any overheating or syncro crunching, that would have brought it on. It didnt.

I am very pleased with this diflock oil!

[adam quantrill]

Good stuff - nice to see an alternative - it'll be interesting to try it in winter too - we both have that final test to do - will it shift OK when freezing cold from startup? I shall resurrect this post on the first frosty day (at this rate, that won't be long....)

Graham, what is the exact brand and type of your difflock oil?

[simon_h]

Well, I promised to report back and here goes. I've swilled out the SMX and replaced it with ATF as advised by CTS. The clutch has been bled to within an inch of its life and the results were about the same. Changing from 2nd to 3rd above 3k5 RPM and it starts to sound like a popular Kelloggs breakfast cereal. At 5K it sounds like there may be some swarf in the bottom of the box as a result of the gear change! So, I'm going to treat the ATF as a flush, dump it and go the Mobil 1 + molly route and see what happens.

[K4TRV]

simon_h said:

Well, I promised to report back and here goes. I've swilled out the SMX and replaced it with ATF as advised by CTS. The clutch has been bled to within an inch of its life and the results were about the same. Changing from 2nd to 3rd above 3k5 RPM and it starts to sound like a popular Kelloggs breakfast cereal. At 5K it sounds like there may be some swarf in the bottom of the box as a result of the gear change! So, I'm going to treat the ATF as a flush, dump it and go the Mobil 1 + molly route and see what happens.

It's been said before, but do try this stuff:

http://shop.difflock.com/difflock-evolution-fully-...

Miles better, but it does not change a crap box into a silk purse, but it DOES all that Mobil one can do and more,...........!

Trev

[simon_h]

Hmm, might just try that before remortgaging the house to buy 5 litres of Mobil one and some moly. I’m struggling to reconcile the effects of a moly based additive and the requirements of the syncro hubs

[TV8]

adam quantrill said:

Good stuff - nice to see an alternative - it'll be interesting to try it in winter too - we both have that final test to do - will it shift OK when freezing cold from startup? I shall resurrect this post on the first frosty day (at this rate, that won't be long....)

Graham, what is the exact brand and type of your difflock oil?

Hi Adam,
It is the oil recommended in the link below your question and this reply. Very pleased with the results of a simple change