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LT77 / R380 Gearbox Fluid Selection


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#1 Jaroslav

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Posted 15 September 2008 - 02:16 AM

The following posting is buried deep in this thread, but I think it deserves a thread of its own. My summary: using synthetic fluid is a must for LT77 and R380.

"5-speed LT77 and R380 main gearbox (Land Rover 90 & 110, Discovery, Range Rover)

Firstly, lets deal with the somewhat notorious LT77 and R380 5-speed main gearbox. These are famed for a poor, notchy gear change, especially from 1st to 2nd gear.

The notchy gear change is due to a combination of a weak synchromesh and the use of a plain mineral ATF fluid.

ATF was originally specified for the LT77 5-speed gearbox and, theoretically, could be used in the later R380 box. Type DIII is the best grade currently available. ATF was originally specified because of the weak synchromesh in the LT77 and R380 boxes (especially second gear).

ATF has a very low viscosity (rated as 5W20 since it falls below normal gear oil viscosity grades) and so it has minimal drag on the gears, enabling the weak synchromesh to do the best of a bad job.

BUT ATF has several drawbacks which is why it is NO LONGER recommended for use in such boxes. These are:

It is generally a plain mineral base stock formulation (even DIII) and this, coupled to its very low viscosity, means that it is poor at preventing metal to metal wear in manual transmissions.

This is compounded by the fact that the viscosity improvers within (thickeners) are more rapidly sheared down in manual transmissions. Again, this reduces the protective film strength of the ATF in those areas of high pressure contact and also increases transmission noise.

ATF thickens as temperatures drop (increasing that drag on the gears) which is why folks notice that gear changes are worst on cold mornings and improve after a few miles motoring when the ATF has warmed up a little.

So, what are the alternatives?

Land Rover currently has commercial arrangement with Texaco/Chevron that leads it to recommend a Texaco/Chevron MTF94 fluid. From the freeback we have received and read on this Forum and elsewhere, we feel its a little too viscous (5W30 or 70W80) to give the best results. Nonetheless you should use it in preference to ATF if your choice is limited to the two.

However, there are better alternatives such as the fully synthetic MT75D gear oil we have developed. Rather than simply plug our MT75D Ill give pointers to what you should look for when seeking alternatives to ATF or MTF94.

Firstly, the lubricant must have the original 5W20 low viscosity of ATF fluids to give minimum gear drag. However, it MUST also be formulated only from fully synthetic base stocks since these will have a much higher lubricant film strength so as not to be squeezed out of those all important high pressure contact areas where wear might occur. This, and the low viscosity, has the added benefit of reducing friction which lowers transmission noise and improves economy.

It must also be highly shear stable and able to maintain its optimum working viscosity over a very wide temperature range. This and a very, very carefully matched coefficient of friction (probably the most critical parameter) will ensure that it dramatically improves gear shifting in LT77 and R380 boxes (especially from cold).

It is the improved shear stability and higher film strength that enables synthetic gear lubricants to outlast their plain mineral counterparts by up to 5 times. However, we err very much on the cautious side and recommend only a doubling of drain intervals.

Note that unlike engine oils, gear oils do not have combustion by-products building up in them, nor do they suffer the higher temperatures of engines, so extending drain intervals is entirely acceptable if the lubricant is of the highest performance and the increase is modest. The exception to this would be if the gear oil were contaminated, perhaps by water or mud during deep wading, though this is unlikely. If the oil is contaminated in this way it MUST be changed immediately, regardless of its formulation.

LT230 Transfer Box (Land Rover 90 & 110, Discovery, Range Rover)

Thats the problems of the LT77 and R380 boxes solved, but what about the LT230 transfer box to which these are commonly mated?

You should NOT use ATF, MTF94 or MT75D in an LT230 TRANSFER box. It must use a thicker gear oil such as EP90 (monograde), EP80W90 (multigrade which is better for cold starting lubrication on winter mornings) or EP75W90 (typically fully synthetic giving the best lubrication of all). This is the same lubricant that you should use in your axles and you should look for an API GL5 specification for best protection."



#2 Jaroslav

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Posted 15 September 2008 - 03:08 AM

This page seems to be implying that Redline Synthetic Hi-Temp ATF is suitable for manual transmissions.

#3 MudAllOverIt

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Posted 15 September 2008 - 07:57 AM

This page seems to be implying that Redline Synthetic Hi-Temp ATF is suitable for manual transmissions.


IMHO Redline MTL would be a better choice.

RedLine MTL

BTW Land Rover stopped specifying ATF for R380s and LT77 years ago. The Land Rover spec'd oil for these boxes is MTF94.

MTL is direct synthetic replacement for MTF94.
Bill

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#4 FridgeFreezer

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Posted 15 September 2008 - 09:22 AM

Would some Dexron 6 ATF be worth a go I wonder?
Yes*
*No

#5 Red90

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Posted 15 September 2008 - 09:36 AM

IMO, no. An MTF is a much better choice as the friction modifiers are better designed for the synchronizers to function.

#6 tacr2man

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Posted 15 September 2008 - 11:37 AM

Using a fully synthetic of a quality like Redline is a must in Landrover transmissions if subjected to hard use due power, temp, loading etc. as they are all quite limited in specification capability ( mind you there are those that are far worse (eg some jap origin makers) and you are looking for a long working life. JMHO BOE

1986 110 CSW 3.0Tdi6,  1991 90 300tdi auto, 1999 Rangerover 2.5 dse auto,  2001 Freelander TD4 Auto 

 


#7 JimAttrill

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Posted 15 September 2008 - 11:50 AM

I use Redline MTL and we recommend it to all our clients with R380s. At least the box only takes 2 1/2 litres so it doesn't cost the earth. (And never needs changing again).

Strangely enough, one advantage of MTL (apart from the normal advantages of using a Cat 5 polyolefin synthetic as mentioned above) is that it has a HIGHER coefficient of friction than other oils, especially all ATFs. This helps the synchro rings to work better.

You have to be careful nowadays as many oils advertised as 'fully synthetic' are actually Cat 3 highly refined mineral oils and not synthetic at all! Castrol seem to be a bad culprit for this. Of course, the easiest way to tell a true synthetic from a fake one is to look at the price - with oil you do get what you pay for :)
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#8 Jaroslav

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Posted 15 September 2008 - 02:32 PM

Strangely enough, one advantage of MTL (apart from the normal advantages of using a Cat 5 polyolefin synthetic as mentioned above) is that it has a HIGHER coefficient of friction than other oils, especially all ATFs. This helps the synchro rings to work better.


I just bought my truck and I have no idea what kind of fluid is in the gearbox. But I do know that I have difficulties to shift into the 2nd gear, which is kinda annoying.

I thought that using a Redline ATF would fix this problem, but you seem to be implying that the Redline MTF will do just as well? Am I correct? This would be good news because Redline does say that MTF is better in protecting the gear comparing to ATF.

#9 Bull Bar Cowboy

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Posted 15 September 2008 - 03:21 PM

I have tried fully synthetic ATF (Mopar ATF+4) in the LT77S and it is no different to the cheap stuff.

The ozzies seem to really like Castrol Syntrans in their LT77/R380s which is a fully synthetic 75/85 designed for heavy duty use in truck transmissions.

I decided to follow this recommendation, however, Syntrans is not readily available in the UK in smallish quantities the smallest I have seen is 20L at nearly 200.

After some discussion with Castrol UK, they recommended SMS-X which is also a fully synthetic 75/85 but designed for car and light truck use. To be honest it has totally transformed the box with much smoother changes, no more cold 1 2 / 3 -2 issues, and the engagement of reverse when hot is very much smother.

At the same time I also changed the transfer box and diff oils with Morris Lubes fully synthetic 75/90 GL5. This seems to exhibit a lot less transmission drag, however, I need to put it on the rolling road to prove the point.

:)

#10 MudAllOverIt

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Posted 15 September 2008 - 04:49 PM

I thought that using a Redline ATF would fix this problem


It's already been said a few times in this thread but a good MT (manual transmission) oil is what you what for LT77s and R380s. Not sure why people persist with ATF -- LR themselves stopped using it in their manual Defender manual gearboxes about ten years ago.

From Redline's product line MTL is what you want. End of story.

The ozzies seem to really like Castrol Syntrans in their LT77/R380’s which is a fully synthetic 75/85 designed for heavy duty use in truck transmissions.


IMHO you'd need to careful with that in colder climates in e.g. UK and Canada -- don't know about the LT77 but higher viscosity oils than MTF94, MTL etc will cause problems with the oil pump in R380s in colder climates. I've heard of folks in Oz deliverately going to thicker viscosity oils cause MTL in particular is prone to thinning out too much.
Bill

'97 300Tdi Defender 90 - Big Red
'51 Series One - Resurrection Project, Seriously Stalled
My other motoring vices:
'78 Triumph Spitfire 2500 - Much Modified
'76 2000TC Triumph Saloon - Forever Original




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