Thread: Identifying problems with LT85 in an Isuzu County?

If the noise goes away in 4th gear its the lay shaft bearings.

Do you get it in high and low range?

What about when you are going down hill and place the box in neutral?

What about put the clutch in?

The early type 230's were quite noisy.. but if its a new noise....

Thanks Flagg.

The noise is worst when in 4th. e.g when it started to be an intermittant noise it was after a period of cruising on the freeway, when I lifted-off to approach the off-ramp in 4th the noise was noticable.

I'm not sure about low-range. I will test that.

Don't know about downhill with box in neutral. I occasionally stick it in neutral when I'm coasting slowely to a stop at lights but haven't noticed any noise (but the isuzu clacking the gbox would drown it out anyway!)

I believe there is no noise with the clutch in - it's definately when in-gear on the overrun.

I'm well-tuned to all the noises my landy makes, and this is definately new.

Cheers

Don't discount t-case, propshaft or diffs. Many problems that sound like they are the gearbox end up being somewhere else, and the nouse is transmitted to the box.

Check all the propshaft UJs first, and diff pinion play and backlash. Then drain a small amount of oil from the box and t-case into 2 clean containers and check for shiny bits.

If there are shiny bits in the t-case oil you can pull the inspection cover off the bottom to see what the problem is.

Thanks Ben,

Rear diff and both propshafts have just been rebuilt with an air-locker and maxidrive flanges. I'm pretty confident that the driveline is fine all the way through except for the gearbox.

I'm going to check the oil for metal. Would anything show in the oil if the bearings are worn? I guess some fine silver bits?

Nick

Originally Posted by isuzurover

If there are shiny bits in the t-case oil you can pull the inspection cover off the bottom to see what the problem is.

Just on that bit: I'm not sure I'd know what to look for. Wear on the gears should be easy to spot. What about the bearings, can I inspect in-situ?

Rear diff and both propshafts have just been rebuilt with an air-locker and maxidrive flanges. I'm pretty confident that the driveline is fine all the way through except for the gearbox.

Even more reason to double check - if the installer has stuffed up the pinion preload etc... I also had a grease nipple rattle out of a UJ once, which caused a rapid failure of the UJ after a few water crossings.

Originally Posted by McBrain

Just on that bit: I'm not sure I'd know what to look for. Wear on the gears should be easy to spot. What about the bearings, can I inspect in-situ?

First check what colour the particles are and if magnetic (though your case should be an LT230T (T=taper roller bearing intermediate shaft). Gear wear would most likely be seen as pitting on the tooth faces. Bearing wear would show up as play (e.g. side-side play you can find with a tyre lever or pry bar), the weakest part of the t-case is the centre diff. That could also be wearing, but shouldn't make noise when going straight ahead. (does the noise change with the CDL locked or unlocked? What about in low range - is the noise still there?)

Noise is there in low range, but only noticable in 3rd/4th gears. Again, this could be due to the engine noise at lower gears.

Next step is to test with the diff lock engaged and drain the oil and inspect.

There hasn't been much mention of the main gearbox. I assumed the most likely problem was a bearing in the LT85 due to use of 5th gear? Is this less likely? Or is it easier/cheaper to check the transfer box first?

Nick

I can't see why it wouldn't be in all gears if it was the transfer case, unless it's speed related.
Having had 2 LT85 Isuzu gearboxes in pieces recently, my money would be on input bearings starting to play up, but, again, it should be in all gears.
I assume you are throwing the clutch at speed when you say it goes away with the clutch depressed?