lt85, 5th gear growl

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Originally Posted by Vern

What about vmx80?

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Vmx80 is fine, and what Mal Story recommended. I ran that for a while but found syntrans better and longer lasting.

Thank you all for the input. There is a line of gear oil here called 'Red Line' that makes 75w85, and there are some good and bad reports on them, so I am still looking for an alternative.

Here the AMSoil was recommended from a trusted Rover shop that uses it more often than not specifically for the LT230 transfer case (which is leaking a bit and I'll be sealing soon). They have seen very good luck with it but there is almost zero experience here with the LT85 gearbox, so we'll go with those of you who speak from experience - thank you for sharing your knowledge.

After a ~3000Km trip to the Great Lakes and Canada I'm now facing full fluid and filter changes and also having challenges finding compatible full and bypass oil filters, air/safety filters, etc. I used the AULRO parts list (awesome) but am still coming up short as a lot of the models/brands available there aren't common here. I've even rung up Isuzu NPR shops with limited success, so I am considering importing from there some bulk stock to keep my 4BD1 going without having to run into this time and again.

Any suggestions for sources there to purchase compatible fluids, filters (oilx2 (full flow and bypass), airx2 (safety and main), fuel filter, etc.)? I really want to enjoy this in the current configuration for many years to come without having to modify or change the engine, etc. I absolutely LOVE this 3.9L 4BD1.

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Originally Posted by isuzurover

Who did the rebuild?
When my LT85 was rebuilt the mechanic shipped the box 800 km to get it rebuilt as there was only one person in Australia (Mal Story / Maxi-Drive) that he trusted to do it properly. This involved a new mainshaft and 5th gear mod. Many years later and it is still holding up fine to my 4BD1T.

Nevertheless Mal advised changing down to 4th regularly on the highway to let 5th gear re-oil itself.

I also run a synthetic low viscosity gear oil.
e.g. in the US something like Mobil Delvac Synthetic Gear Oil 75W-90

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To close the loop on this point, the shop that did the rebuild there was 360 gearboxes in Victoria.

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Originally Posted by tc_s1

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looking for ideas as to what it may be. Any input from experience that might be helpful would be greatly appreciated.

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Wouldn't be surprised if the small pin that is pressed in to the 5th gear itself has sheared off.

Think it's called the 'Anti rotation pin'. Keeps a sleeve rotating at the same speed as the main shaft. When this shears it allows wear of a washer (stop plate) which then creates 'slop' in the gear (axially) and you'll get a 'whiring' buzz in 5th gear.


Happened to mine so I bought a spare box to do up while I wasn't sure what was wrong with mine. The spare box had the same issue - sheared pin.

My fix for this box was to drill out the hole (or actually a second hole, as the pin was sheared in the first) to a bigger size and install a pin double the diameter. The sleeve had a big enough slit to take the larger pin.

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Originally Posted by tc_s1

Thank you all for the input. There is a line of gear oil here called 'Red Line' that makes 75w85, and there are some good and bad reports on them, so I am still looking for an alternative.

Here the AMSoil was recommended from a trusted Rover shop that uses it more often than not specifically for the LT230 transfer case (which is leaking a bit and I'll be sealing soon). They have seen very good luck with it but there is almost zero experience here with the LT85 gearbox, so we'll go with those of you who speak from experience - thank you for sharing your knowledge.

After a ~3000Km trip to the Great Lakes and Canada I'm now facing full fluid and filter changes and also having challenges finding compatible full and bypass oil filters, air/safety filters, etc. I used the AULRO parts list (awesome) but am still coming up short as a lot of the models/brands available there aren't common here. I've even rung up Isuzu NPR shops with limited success, so I am considering importing from there some bulk stock to keep my 4BD1 going without having to run into this time and again.

Any suggestions for sources there to purchase compatible fluids, filters (oilx2 (full flow and bypass), airx2 (safety and main), fuel filter, etc.)? I really want to enjoy this in the current configuration for many years to come without having to modify or change the engine, etc. I absolutely LOVE this 3.9L 4BD1.

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A good filter shop (not NAPA or ISUZU) will be able to cross reference the part numbers for you. I have contacts at WIX/Purolator, so can help out if you struggle. Just give me the PN's that you have.

As for oil. look at the spec sheets.
AC Delco 75W85 looks like an option: [ame]http://www.acdelco.com.au/PDFs/Specs_ACDelco_75W85_SelectPlusSemiSynth-gearoil.pdf[/ame]

Thank you for the 5th gear idea. That makes perfect sense and seems to match what I'm experiencing. We'll be pulling the transfer case to seal it up as it's leaking and while in there may pull the gearbox to see if this matches. I'm not overly excited about opening the gearbox though as I've not done anything with similar internals before. When I do this I'll report back, though I'm not yet sure when that will be.

On the oil filter side, while I've found stores that can cross reference, I haven't yet found any that can supply. We'll be turning to Isuzu NPR part suppliers next to see if they can provide although here many of them don't seem to work with individuals. Amazon and eBay are other options where I've found some (though not a bypass filter yet).

I was thinking I should be running GL-5 but the ACDelco (and many others) are GL-4. No significant issues? I found a comparison of them (posted) and am wondering if there are strong preferences one way or the other?