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Thread: Oil Recommendation for LT95 4 speed box and Isuzu 4bd1

  1. #11
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    Yeah but we all know DNSDC Stands for

    Dont kNow sh** Dont Care

    Dave

    "In a Landrover the other vehicle is your crumple zone."

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  2. #12
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    JDNSW is offline RoverLord Silver Subscriber
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    The engine is not particularly fussy (the turbo is a bit fussier) - any reputable diesel oil, grade depending on where you live, but this time of the year probably 15W-30. I use RX super as this is what the local agent sells, and have for the last ten years or so.

    The gearbox uses engine oil, I use the same as the engine, but the gear change may improve with synthetic engine oil. Do not use anything heavier than engine oil.

    The transfer case is remarkably unfussy about what is in it as long as it is oily, and the manual for my 110 says the same as the engine and gearbox. A good reason for using the same as the gearbox is the tendency of the oil to move between the two boxes. There is no reason for using an EP oil in this box.
    John

    JDNSW
    1986 110 County 3.9 diesel
    1970 2a 109 2.25 petrol

  3. #13
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    most modern GL5's have de-activated sulphur as the EP component, although the cheapo oils can still cause discolouration.
    If you can source a TDS for an oil it should have a copper corrosion test #.

    I really dislike engine oils in synchro gearbox's. They have the wrong charcteristics in terms of friction modification for the synchro's and have to be changed frequently as they shear quite badly in a gearbox. They were used as they had the vicosity characteristics the designers were after, these days there ar dedicated manual transmission/transaxle oils that are designed for a manual gearbox that wren't available when these gearboxes were designed.
    A 15W-40 engine oil is roughly equivalent to a 75W-90 manual trans fluid in viscosity and a 10W-30 equal to a 75W-85.


  4. #14
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    So is TDI saying that a dedicated non EP gearbox oil would make the sycros work better or last longer, or make the oil last longer?

    What do you mean by shearing badly (don't know much about oil), i guess this damages it?
    84' 120" ute - 3.9 isuzu.

  5. #15
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    generally speaking, a dedicated manual gearbox fluid, eg Castrol's Multitrax, VMX-80, VMX-M, Syntrans, Syntrax, etc are formulated with friction modifiers to enhance synchro performance, engine oils aren't. (This isn't an add for Castrol, all the manufacturers have dedicated manual gearbox oils, it's just that I'm familiar with Castrol's ones)
    Remember that a GL5 lube isn't necessarily a bronze killer (eg. Multitrax and Syntrax above are GL5 rated for use in hypoid diff transaxles but are copper safe) but a dedicated diff/final drive lube isn't usually suitable for a gearbox.

    this is taken from a Redline Oil's paper.
    The time this process takes depends on how easily the
    synchro ring moves and the rate of frictional energy
    transfer between the two synchronizer surfaces. Higher
    viscosity lubricants slow the sliding of the synchro ring on
    the input shaft and require a longer time for the oil to be
    squeezed out from between the mating synchronizer
    surfaces. After the lubricant is squeezed out, the
    coefficient of friction of the lubricant determines the rate
    of frictional energy transfer between the two surfaces.
    Slippery lubricants such as hypoid gear oils can take too
    long to synchronize the gears, which promotes
    synchronizer wear. Red Line MTL and MT-90 has a
    coefficient of friction which is greater than conventional
    oils, allowing a quicker transfer of frictional energy. The
    graph below shows the desirable friction curve
    demonstrated by Red Line MTL compared to
    conventional lubricants. Note how the coefficient of
    friction is greater for the MTL than all others except the
    motor oil. Some motor oils have an adequate dynamic
    coefficient of friction, but most have problems with the
    static and low velocity coefficient of friction which can
    result in clashing.
    Clashing of the gears (actually clashing of the
    synchromesh gears, since the drive gears are always in
    contact) can occur if excessive shift effort is used in
    order to shift the locking ring into place before the
    surfaces have achieved equal speed. It may also occur
    at the end of a reasonably smooth shift if an instability
    exists in the coefficient of friction, causing stick-slip to
    occur. In this form of clashing, the ring slides on the
    mating synchro gear, but a sudden slippage causes a
    grinding of the gears. In order to prevent stick-slip from
    occuring and the gear clashing which results, the
    coefficient of friction should inflect downward as the
    relative speed drops to zero.

    Shear means that the oil literally breaks down losing viscosity (becomes thinner)

    The reason that many manufacturers have made
    recommendations of motor oils or ATFs is that petroleum
    80W gear oils frequently do not shift well at low
    temperatures. Motor oils and ATFs are much more fluid
    at lower temperatures and they are not corrosive toward
    synchros, but they provide very poor gear protection.
    These lubricants provide almost no extreme-pressure
    protection. In addition, petroleum multigrade motor oils
    and ATFs have very poor shear stability. The shearing
    action by a manual transmission on thickeners is much
    worse than in an engine or automatic transmission.
    Within 5,000 miles the thickeners can be rendered
    ineffective and the transmission will be operating on a
    much reduced level of protection, as shown in the graph
    below. In hot weather these transmissions will whine
    and rattle because of poor vibration dampening and
    metal contact. Red Line MTL and MT-90 provide the
    excellent gear protection of a GL-4 gear oil in a synthetic
    lubricant which spans hot and cold temperatures and will
    not shear or oxidize with use.

  6. #16
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    the gear box and transfer case (lt95) is an integral unit. the two are basically 2 parts of 1 unit with separate oil galleries. they must have 15W40(visco 2000) or 15W50 for castrol.
    a couple of years ago, a reputable "land rover expert" on sydney's northern beaches (narrabeen), serviced my ute and being the experts they are, they put gear oil in both my gearbox and transfer. i didn't find out until i did the next oil change myself.
    if you want it done right....do it yourself
    LAND ROVER;
    HELPING PUT OIL BACK IN THE GROUND FOR 70 YEARS
    CARS DON'T GET ANY "GREENER" THAT.

  7. #17
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    Quote Originally Posted by Blknight.aus
    Yeah but we all know DNSDC Stands for

    Dont kNow sh** Dont Care

    Comment gotta come from a .....I wont say it......... things only went to s#$t when Tenxtoll took over there were a lot of good mechs in the workshop
    don't know about the stores side of the place mind...

    The LT 95 gear box and T/case are all in the same casing but are two separate containers...G/B engine oil T/C gear oil
    yes the oils do migrate time to fix the box....

    There are a lot of differant opinions on what oil to use where and the owners hand book isnt allways right............but LT 95 gear oil in the T/C

    Tony

  8. #18
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    Quote Originally Posted by rick130
    most modern GL5's have de-activated sulphur as the EP component, although the cheapo oils can still cause discolouration.
    If you can source a TDS for an oil it should have a copper corrosion test #.

    I really dislike engine oils in synchro gearbox's. They have the wrong charcteristics in terms of friction modification for the synchro's and have to be changed frequently as they shear quite badly in a gearbox. They were used as they had the vicosity characteristics the designers were after, these days there ar dedicated manual transmission/transaxle oils that are designed for a manual gearbox that wren't available when these gearboxes were designed.
    A 15W-40 engine oil is roughly equivalent to a 75W-90 manual trans fluid in viscosity and a 10W-30 equal to a 75W-85.
    Agree 100% Rick. Proper gear oils are MUCH better than engine oil. I use VMX80 in my LT85, and am 100% happy (Mal Story - Maxi-Drive - also recommends this oil).

    In the 4BD1 I use any good quality diesel engine oil - Castrol RX-Super, Penrite Diesel, etc...

  9. #19
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    Interesting, I run motor oil in my LT95 and once hot sometimes experience 'clashing' once past the syncro. I always thought the sycro had done its work and i was selecting the gear. But i realise that what TDi described is right as the LT95 is constant mesh.... Has got me thinking. Next oil change i think i might go to a proper gearbox oil.

    The gearbox makes a terrible clatter when hot and idleing on the Isuzu (neutral and clutch engaged), would a gearbox oil reduce this?
    84' 120" ute - 3.9 isuzu.

  10. #20
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    Quote Originally Posted by wovenrovings
    But i realise that what TDi described is right as the LT95 is constant mesh.... Has got me thinking. Next oil change i think i might go to a proper gearbox oil.

    The gearbox makes a terrible clatter when hot and idleing on the Isuzu (neutral and clutch engaged), would a gearbox oil reduce this?
    The gear changes (especially when cold) in my LT85 got a lot smoother when I switched to VMX80. I don't think it made a difference to the clatter in neutral - I think this is an ISUZU thing...

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