LT95 gearbox noise

[fcnutter]

Hi All,
need a bit of help with my perentie LT95 noisy gearbox. When sitting in idle with clutch out there is an unusual noise coming from the gearbox. When the clutch is engaged while idling the noise disappears. I have changed oils to no avail. I am taking the rig around Oz and want to get it sorted before I move on. I am in Vic at the moment heading to W.A. on a very flexible year holiday. Would much appreciate advice/help.


Cheers.....Adrian.

[isuzutoo-eh]

Hi Adrian,
That sound is normal. They rattle. Someone posted the reason recently, but it is not at all detrimental to the vehicle's operation or longevity.
Enjoy your trip and post lots of photos!

[spudboy]

Hi Adrian,

Seems to be a normal thing with the LT95.

See this thread:
http://www.aulro.com/afvb/coil-sprung-military-land-rovers/188180-change-engine-sound-when-idling-clutch-out-normal-isuzu.html

and this thread:
http://www.aulro.com/afvb/coil-sprung-military-land-rovers/189125-castrol-super-rx-vs-vmx-80-lt95-real-world-report.html

[JDNSW]

I gather by clutch 'out' you mean with your foot off the pedal, and by 'engaged' you mean with your foot on the pedal (in other words, the opposite to the normal use of the words).

If I am correct in my interpretation of your meaning, this is perfectly normal. The engine accelerates and and decelerates twice per revolution due to the large cylinder size, high compression and relatively light flywheel with only four cylinders. As this happens the free play on the constant mesh gears flops back and forth twice per revolution, creating the noise you hear.

The effect can be minimised by increasing the idling speed slightly, better by fitting a hand throttle so that it can be increased as necessary for different temperatures and degrees of warming up.

John

[isuzutoo-eh]

Hi Adrian,

Seems to be a normal thing with the LT95.

See this thread:
http://www.aulro.com/afvb/coil-sprung-military-land-rovers/188180-change-engine-sound-when-idling-clutch-out-normal-isuzu.html

and this thread:
http://www.aulro.com/afvb/coil-sprung-military-land-rovers/189125-castrol-super-rx-vs-vmx-80-lt95-real-world-report.html

Also happens with factory LT85 equipped Isuzu Landies.

[spudboy]

Also, apart from the oil change stuff in the 2nd link in my previous post, I got great improvement by increasing the idle slightly.

Just 100 or so RPM higher and the gearbox rattle was significantly improved, especially when hot.

[Bush65]

A very common noise issue with the LT95 comes from the "finger" of the Hi/Lo selector. It should have a plastic sleeve on the finger, but they break up when they age. Without the sleeve they produce considerable noise rattling in the selector fork.

All that is needed is a piece of oil and heat resistant plastic tube pushed over the finger.

[85 county]

if you look at the back of your injection pump, there are TWO big nuts

thay are actualy covers. inside the bottom one is the idle ajustment screw. best to use this and not the cable

[Bush65]

if you look at the back of your injection pump, there are TWO big nuts

thay are actualy covers. inside the bottom one is the idle ajustment screw. best to use this and not the cable
That is the idling spring adjustment, not the idle speed adjustment. the idle speed adjustment is on top of the governor.

The idling spring adjustment is for the governor to maintain the idle speed when the load changes, eg air con compressor clutch engages/disengage, or the road grade changes up/down.

The stock idle speed is on the low side and the torsional vibration will be improved if the idle speed is increased, via the idle speed setting screw on top of the governor.

[85 county]

That is the idling spring adjustment, not the idle speed adjustment. the idle speed adjustment is on top of the governor.

The idling spring adjustment is for the governor to maintain the idle speed when the load changes, eg air con compressor clutch engages/disengage, or the road grade changes up/down.

The stock idle speed is on the low side and the torsional vibration will be improved if the idle speed is increased, via the idle speed setting screw on top of the governor.

ok so what have i been doing and what should i have done??

[spudboy]

... the idle speed adjustment is on top of the governor.



Do you have a diagram/photo to explain this a bit more?
Thanks

[County3.9]

That is the idling spring adjustment, not the idle speed adjustment. the idle speed adjustment is on top of the governor.

The idling spring adjustment is for the governor to maintain the idle speed when the load changes, eg air con compressor clutch engages/disengage, or the road grade changes up/down.

The stock idle speed is on the low side and the torsional vibration will be improved if the idle speed is increased, via the idle speed setting screw on top of the governor.

Can you please explain more on what this can do. By adjusting this will my engine better maintain a set idle when the air con kicks in?

[fcnutter]

Hi Adrian,
That sound is normal. They rattle. Someone posted the reason recently, but it is not at all detrimental to the vehicle's operation or longevity.
Enjoy your trip and post lots of photos!
Thanks very much, was concerned that I may need to refurbish box and out lay big bucks. I had a 300Tdi and was comparing against that.

[fcnutter]

Hi Adrian,
That sound is normal. They rattle. Someone posted the reason recently, but it is not at all detrimental to the vehicle's operation or longevity.
Enjoy your trip and post lots of photos!
Cheers, may have saved me a trip to the funny farm.......!

[Bush65]

fcnutter,

This post from John is spot on.


I gather by clutch 'out' you mean with your foot off the pedal, and by 'engaged' you mean with your foot on the pedal (in other words, the opposite to the normal use of the words).

If I am correct in my interpretation of your meaning, this is perfectly normal. The engine accelerates and and decelerates twice per revolution due to the large cylinder size, high compression and relatively light flywheel with only four cylinders. As this happens the free play on the constant mesh gears flops back and forth twice per revolution, creating the noise you hear.

The effect can be minimised by increasing the idling speed slightly, better by fitting a hand throttle so that it can be increased as necessary for different temperatures and degrees of warming up.

John
The advice in some of the other posts that it is normal and not detrimental are misguided.

The 'normal' remark while largely correct, you should understand it is only normal because of some issues that are well documented. I strongly encourage you to not continue to live with this 'normal' condition.

The 'not detrimental' remark, I most certainly don't accept. The LT95 is a strong gearbox and has greater success than lesser gearboxes from the torsional vibration.

Increasing the idle speed is a simple adjustment that will improve the vibration and its affects.

[Bush65]

This diagram is a cutaway assembly of the RLD governor, the type used on the Isuzu 4BD1 and 4BD1T.

https://www.aulro.com/afvb/

The 'Control lever' is drawn a little different to what is actually used on most 4BD1 but otherwise it is good enough.

The 'Idling set bolt' shown in the top right corner of the diagram is used to adjust the idle speed. Turn it in toward the control lever to increase the idle speed.

Some governors that have not been serviced since leaving the factory, may have a tamperproof shroud over the 'Full speed set bolt', hiding the end of the screw and its locknut. There is no shroud over the idling adjustment.

Both of these screws simply limit how far the control lever can travel, either to minimum or maximum speed position.

The 'Idling spring' adjustment is shown at the bottom right of the diagram. This spring pressure setting affects the governor action during idling, to return the engine speed if it rises because load has reduces or if it slows because load has increased.

Some of the RLD governors do not have the hexagon caps over the idling spring and governor spring adjustments, as shown in this diagram. They have welch plugs.

[85 county]

This diagram is a cutaway assembly of the RLD governor, the type used on the Isuzu 4BD1 and 4BD1T.

http://www.aulro.com/afvb/attachment.php?attachmentid=71327&stc=1&d=1389836085

The 'Control lever' is drawn a little different to what is actually used on most 4BD1 but otherwise it is good enough.

The 'Idling set bolt' shown in the top right corner of the diagram is used to adjust the idle speed. Turn it in toward the control lever to increase the idle speed.

Some governors that have not been serviced since leaving the factory, may have a tamperproof shroud over the 'Full speed set bolt', hiding the end of the screw and its locknut. There is no shroud over the idling adjustment.

Both of these screws simply limit how far the control lever can travel, either to minimum or maximum speed position.

The 'Idling spring' adjustment is shown at the bottom right of the diagram. This spring pressure setting affects the governor action during idling, to return the engine speed if it rises because load has reduces or if it slows because load has increased.

Some of the RLD governors do not have the hexagon caps over the idling spring and governor spring adjustments, as shown in this diagram. They have welch plugs.


So turning the idle spring out weakens the spring tension making it harder for it to return to idle speed?? if that’s what I have done DUH

[spudboy]

Thanks for that diagram Bush65. Very useful.

As luck would have it, I did adjust the correct screw to raise my idle :)

My Full Speed Set screw was wired in a fixed position, so no accidentally changing that one.

[Bush65]

Can you please explain more on what this can do. By adjusting this will my engine better maintain a set idle when the air con kicks in?
This is from the injection pump manual.
http://www.aulro.com/afvb/attachment.php?attachmentid=71331&stc=1&d=1389840531

This is the data for the 1986 on 4BD1 from the Isuzu 4BD1 4BD1T engine manual. The diagram superimposes the full load and idling performance curves.
http://www.aulro.com/afvb/attachment.php?attachmentid=71332&stc=1&d=1389840649

These two both from the injection pump manual for the adjustment of points on a typical idling performance curve.
http://www.aulro.com/afvb/attachment.php?attachmentid=71333&stc=1&d=1389841077

http://www.aulro.com/afvb/attachment.php?attachmentid=71334&stc=1&d=1389841261

[mark2]

My engine has a noticeable difference between cold idle speed and hot idle speed (faster, less gearbox rattle). Adjusting the cold idle to something reasonable results in it being a bit fast when hot. Is this 'normal'?

[spudboy]

Wouldn't you just use your hand throttle until it warms up?

[Blknight.aus]

on some engines yes, this usually means that either a spring is starting to get weak inside the governor or as the engine heats up its running correctly as compression returns. If you have a whitish smoke coming out the exhaust after about a minute of idling then you are starting to run out of compression

[Blknight.aus]

Wouldn't you just use your hand throttle until it warms up?

why would you warm it up?

Start it, once the oil pressure light is out and the idle is close to stable (as in not hunting after startup) get in in gear and get it working...

[spudboy]

'Cause it rattles around terribly when cold at idle (cold idle is quite a bit lower than warm idle).

At our place, it's start car; drive 30m to front gate; get out to close gate; drive off. Hand throttle is good to keep idle respectable until it warms up.

[Blknight.aus]

thats entirely different to "letting an engine warm up" which is how your post it open to being interpreted.

[The Cowboy]

VERY relieved to find this thread, as my recently acquired County has precisely the same noise at idle with foot off the clutch, also strikes me as being a very slow idle rpm presently so I shall follow the advice and increase. Only other thing to add is that the box is definitely more noisy 1st through to 3rd and then 4th is quiet, I was starting to get concerned by this - should I be??????? I am an LT95 virgin, having owned in the region of 40 Landies previously, but all sII and III :-)
Cheers
Cowboy

[steveG]

VERY relieved to find this thread, as my recently acquired County has precisely the same noise at idle with foot off the clutch, also strikes me as being a very slow idle rpm presently so I shall follow the advice and increase. Only other thing to add is that the box is definitely more noisy 1st through to 3rd and then 4th is quiet, I was starting to get concerned by this - should I be??????? I am an LT95 virgin, having owned in the region of 40 Landies previously, but all sII and III :-)
Cheers
Cowboy

Can you describe the extra noise that you're hearing in 1-3?
4th is a direct drive from the input to output shaft, so no load on the layshaft or other gears, and less load on the main input bearing.
Plenty of people on here with more LT95 experience than I have though...

Steve

[The Cowboy]

Cheers Steve, yes lay shaft bearings is what concerns me! It's a little difficult to describe, but I guess I am just aware of an increased note that is definitely NOT engine derived, I wanted to say it sounds like a 'spinning up' noise but it isn't quite that! A light whirring I guess!

[JDNSW]

From my experience, input bearing.

John

[landrover dave]

VERY relieved to find this thread, as my recently acquired County has precisely the same noise at idle with foot off the clutch, also strikes me as being a very slow idle rpm presently so I shall follow the advice and increase. Only other thing to add is that the box is definitely more noisy 1st through to 3rd and then 4th is quiet, I was starting to get concerned by this - should I be??????? I am an LT95 virgin, having owned in the region of 40 Landies previously, but all sII and III :-)
Cheers
Cowboy
The gearbox being noisier in the intermediate gears is a sure sign that layshaft bearings are on the way out. It can only get worse! Your gearbox will need to rebuilt.

[Bearman]

The gearbox being noisier in the intermediate gears is a sure sign that layshaft bearings are on the way out. It can only get worse! Your gearbox will need to rebuilt.

I would go for layshaft bearings as well but it would be advisable to rebuild the lot while you are at it!

[The Cowboy]

Thanks guys'


After taking advise from a few folks infinitely more experienced than I am, the concensus does indeed point to layshaft. Although both the parties (LRV mechanics) whom listened to it advise that it is not "bad" for a 95, and that it is a large bearing that is renown for being a little noisy??? they both are saying not to panic just yet! Having said that, I intend on keeping this vehicle indefinitely so WILL rebuild it as soon as the finances permit. Was wondering what costs I might expect to incur from your collective experiences???
Thanks again for your help - it is MUCh appreciated

[inside]

Time for this quote again maybe?

The Haynes Manual has a quotable quote which is particularly applicable to this gearbox.

Note: It is sometimes difficult to decide whether it is worthwhile removing and dismantling the gearbox for a fault which may be nothing more than a minor irritant. Gearboxes which howl, or where the synchromesh is worn but double declutching can overcome the problem, may continue to perform for a long time in this stage. A worn gearbox usually needs a complete rebuild to eliminate noise because the various gears, if re-aligned on new bearings, will continue to howl or begin to howl when different wearing surfaces are presented to each other. The decision to overhaul therefore, must be considered with regard to time and money available, relative to the degree of noise or malfunction that the driver can tolerate.

i.e. if it ain't *really* broke, don't fix it.

[landrover dave]

As mentioned earlier, it will only get worse, not better.
The cost of a rebuild all depends on what needs replacing. Most of the needle roller bearings and needle thrust bearings in the main box will be re-usable. If your mainshaft or layshaft are through the case hardening, there is a large expense, unless you can find good s/h parts.
Input shaft bearing, mainshaft bearing, layshaft bearings and seals are parts I always replace.
The intermediate shaft may need replacing and high range gears are another part that is a high wear item.
Most gearboxes I rebuild cost around the $3000-3500 mark.

[The Cowboy]

Cheers again guy's. I am going to have to live with it in the short to medium term, as I simply don't have the $$ to repair it. I have no difficulty at all selecting any gears and having driven a mates LT95 equipped Rangie over the weekend have come to the conclusion that it really isn't THAT noisy, and lefy Matty very indignant when I asked him how bad his box was :-) Deffo going to re-build it when the funds permit as I concur with the logic that it is only going to get worse!

[jackz]

Not wanting to cause you too much stress, BUT, my LT95 was a little noisy under load in 1st,2nd and 3rd. Turned out to be due to the bearing cage on the rear layshaft bearing falling apart, allowing all the balls to congregate on one side of the bearing. The rebuild uncovered quite a few other issues and ended up requiring half the gears in the box being replaced due to the hard-facing chipping off, reverse idler and shaft due to wear and a broken tooth, a complete centre diff, the input gear and high gear in the t/case, and a front output shaft due to the flange being seized on. All up around $5500.