Thread: lt85, 5th gear growl

The Lt85 is well known to damage one of the main bearings (someone else might clarify which one) if the vehicle has been driven a lot under load in 5th gear. The turbo 4BD1 will make this more likely to happen if not driven carefully in 5th.
This may not be your problem, just thought I'd mention it as I went through this with my Lt85.

Cheers, Murray

Thank you for the info. The previous owner had a recent, complete rebuild, but you stated my concern too, but I haven't driven it under load at all and it just started while on this trip.

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

Thank you for the reply The previous owner (2nd owner) was is a retired rover employee and I believe he had it done by a certified/qualified shop based on our discussion. Even before I purchased it he discussed the LT85 and need for conservative 5th gear loading, so I've been extremely cautious, using it only for highway speeds on near flat or only slight, short inclines of less than ~10 degrees. Nothing has been towed since I've owned it, only camping gear inside and a few kayaks strapped to the roof a few times.

I've not heard about routinely gearing down to 4th, though it makes sense. The sound only occurs in 5th with acceleration. There is not any perceptible change in performance, though I am concerned that will come in time.

I am using a synthetic currently, AMSoil 75w90 'severe gear', in the transfer case (lt230) and gearbox. If it is the gearbox, is there anything 'preventative' I could / should be doing at this point rather than waiting for it to get worse over time?

I am not too sure about that oil in the gearbox, especially if you are in a cold climate. The original oil specification for the box was, I think, engine oil or ATF, and higher viscosity is likely to cause failure of the oil pump with cold starts - which will not become apparent until further problems develop.

John

OK that oil is too viscous for the LT85.

I use this: Castrol Syntrans 75w-85 | Castrol Australia | Manual Transmission Fluid - Car Products | Castrol Australia | Car - Motor Oil & Lubricants | Castrol Australia | Products | Castrol Australia | Castrol - Motor Oil, Engine Oil, Synthetic Oil, Diesel Engi

It pours like water - i.e. it has a low viscosity at low temperatures.

This type of oil is the best oil for the LT85.

To compare my oil to yours: The syntrans has a 40% lower viscosity at 40oC and over 4x!! lower viscosity at -40oC.

Originally Posted by isuzurover

OK that oil is too viscous for the LT85.

I use this: Castrol Syntrans 75w-85 | Castrol Australia | Manual Transmission Fluid - Car Products | Castrol Australia | Car - Motor Oil & Lubricants | Castrol Australia | Products | Castrol Australia | Castrol - Motor Oil, Engine Oil, Synthetic Oil, Diesel Engi

It pours like water - i.e. it has a low viscosity at low temperatures.

This type of oil is the best oil for the LT85.

To compare my oil to yours: The syntrans has a 40% lower viscosity at 40oC and over 4x!! lower viscosity at -40oC.

X 2 - amd synchros function very well with it -

While it is expensive it has a very long life - with my doing 10000km p.a. possibly it will see me out.

Originally Posted by 87County

X 2 - amd synchros function very well with it -

While it is expensive it has a very long life - with my doing 10000km p.a. possibly it will see me out.

I noticed a slight deterioration at 60k km and changed mine.


back on topic:
tc-s1 - change to a more suitable gear oil ASAP

The problem is you are in the US, so castrol syntrans isn't available. Are there any 75W85 synthetic gear oils available, or are they all 75W90?