LT95 gearbox oil .... again.

**steveG** · 25th June 2014, 11:19 AM

I've only done 40K kms with mine since a partial rebuild so can't comment on gearbox longevity, but almost all of that has been done with Castrol Syntrax 75w-90 in the main gearbox, and Penrite Pro-gear in the transfer. Only reason for running Penrite instead of Syntrax in the transfer was to try and standardise across the "fleet" as my wife and daughter's cars run the Penrite (and I needed to drop the transfer oil to fix a speedo drive issue). Penrite will also go into the main box when I change it soon.

My reasons (valid or not) for not running engine oil were:
- I HATE changing gearbox oil, and the idea of changing it every 5K kms nearly makes me convulse
- I'm running the truck twin filter setup on the 4bd1, so using 10K engine oil change intervals. With doing a fair bit of towing I wasn't convinced the engine oil was still going to be OK in the box for those k's
- Being turbo'd there is a lot more power going through the transmission than would have been the case with the original engines the LT95 was designed for. To me that places additional stress (mechanical and temperature) on the lubricant and likely shortens its service life.

I really don't mind what anyone chooses to run, but those were my reasons.

I'll also comment that some of you who are avid engine oil supporters are referring to history of standard vehicles, so it stands to reason that unless Landrover got it wrong, it will do the job.
IMO once you move away from that (eg tweaked 4bd1t's) those examples aren't valid.

For a slightly different twist, the one-owner Isuzu County that my daughter has just bought with 500K on it has been running full synthetic ENGINE oil since it was rebuilt at about 180K. With over 300K since that rebuild its one of the tightest LT95's I've driven.
Its still NA, but was used mainly as a tow vehicle for a small caravan and the original owner was very fussy about oil changes. Interesting that it needed a rebuild early on (running engine oil), but is still great now.

Steve

**rick130** · 25th June 2014, 12:33 PM

Originally Posted by joel0407

I'm not saying it will suit everyone but I like Redline Shock Proof oils. It doesn't look much like oil. Probably if you weighed up the cost of the stuff, it'd be better to use a cheaper oil and rebuild the box after many years. I came across it as it, like engine oil in the LT95, is know to work very well in the WRX gearbox. Apparently with a few mods, the amount of power a WRX will make created too much pressure between the teeth of the gears and they would just push each other apart. The Redline Shock Proof maintained enough lubrication under extreme pressure to prevent them failing as often yet it still flowed thin enough to allow the box to shift nicely. I doubt I needed it in the LT230 and my diffs but it's quietened them down all them same.

Happy Days

Shockproof works well in the LT230, a number of LR workshops use it to beat mainshaft and diff shim wear, but I personally wouldn't use it in a synchro gearbox, and you don't use it where there's any filtration going on (admittedly usually only race car diffs with coolers and pumps) as it removes the colloidal calcium.
Apparently you also need to be a little careful with moisture and Shockproof.

FWIW I thought Motul Gear 300 or FF 75W-140, or NEO 75W-90RHD were the 'fixes' for WRX STI's ?

Modern MT fluids like Castrol Syntrans and Syntrax, Motul Gear 300, Valvoline Duragear, etc. are IMO much better suited for manual gearbox use compared to engine oils or ATF's as they have the correct additives to protect gears better while having the right friction modifiers for better synchro engagement.

Engine oils tend to have a decreased coefficient of friction as rotational face speeds drop whereas the correct action is for the coefficient of friction to increase as speeds decrease so the synchro clutch and hub match speeds and allow dog engagement.

**circlework** · 27th June 2014, 10:55 AM

Originally Posted by rick130

That'll be fine, although I'll be interested to hear how it shifts *snip*

It's a little stiff, but nowhere near as impossible as with the 20w-50 and improving every run. The only slight problem is still the 3-2 shift, but I'm confident that it will come good with time, occasionally it won't go in without shuffling. Beginning to wonder if I might have a lockout detent sticking.
All other changes are very good.

A Question of the knowledgeable if I may ....
What would the change intervals be for the Penrite Pro Gear 75W-90?

Thanks,
Daryl.

**Mick_Marsh** · 27th June 2014, 11:20 AM

Originally Posted by isuzurover

You know the perenties have the TR bearing case???

Yep. My Stage 1 hybrid has too, now.
But my 101's don't. I'm sure there are a lot more LT95's out there that don't than do.

**isuzurover** · 27th June 2014, 11:24 AM

Originally Posted by Mick_Marsh

Yep. My Stage 1 hybrid has too, now.
But my 101's don't. I'm sure there are a lot more LT95's out there that don't than do.

The OP was asking about oils for the perentie LT95 he owns. To me your comments seemed misleading...

**101RRS** · 27th June 2014, 02:19 PM

Originally Posted by circlework

It's a little stiff, but nowhere near as impossible as with the 20w-50 and improving every run. The only slight problem is still the 3-2 shift, but I'm confident that it will come good with time, occasionally it won't go in without shuffling. Beginning to wonder if I might have a lockout detent sticking.

As mentioned I use engine oil and I have no issues changing gear - smooth as a baby's bum. If you are having problems changing then there are likely to be other issues in the box not related to the oil.

Garry

**mick88** · 28th June 2014, 06:19 AM

Is there an overdrive available for this gearbox (4 speed on the ex military Isuzu) and what engine rpm are they doing at 100kph?

What is their comfortable/sensible highway speed?

Cheers, Mick.

**87County** · 28th June 2014, 07:29 AM

Originally Posted by mick88

Is there an overdrive available for this gearbox (4 speed on the ex military Isuzu) and what engine rpm are they doing at 100kph?

What is their comfortable/sensible highway speed?

Cheers, Mick.

Mick, there was an overdrive for the LT95, and while some people have used them behind a 4BD1, it is generally considered that it wasn't robust enough to cope.

As far as speed/rpm goes I look forward to reading other's posts.

IMHE, we solved this problem by having a turbo installed (KLR) and fitting larger tyres on D1 rims - it will cruise comfortably at any legal speed (and the speedo reads closer to the real speed that we're driving as a bonus). It doesn't notice hills any more either.

**mick88** · 28th June 2014, 07:59 AM

It's no doubt just that they are a noisy engine/vehicle and they seem to be revving a fair bit.
So are D1 rims 18 or 19 inch and approx. what height are your tire profiles overall?

Cheers, Mick

**Mick_Marsh** · 28th June 2014, 09:15 AM

Originally Posted by mick88

Is there an overdrive available for this gearbox (4 speed on the ex military Isuzu) and what engine rpm are they doing at 100kph?

What is their comfortable/sensible highway speed?

Cheers, Mick.

By all reports, most people think their 4x4 Perenties cruise happily at 100km/h. The 6x6's are a different matter as they have different gearing in the diffs.

Thread: LT95 gearbox oil .... again.

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