Reply With QuoteUnless you are using Motul Gear 300 I wouldn't use a 75w-90 in the R380.
Shifting will be quite baulky when cooler.
I prefer a 75w-85 to a 75w-80, (eg Castrol Syntrans) less bearing and gear rattle at high loads/ambient
going to do a total oil change on the old girl,and i see the diffs and transfer box take 75-90 gear oil (from Auto barn On line vehicle )
and the gear box takes 75-80
question
would it make much difference or harm to use 75-90 in gear box as well ,then only will have to buy one oil
Moderator
Unless you are using Motul Gear 300 I wouldn't use a 75w-90 in the R380.
Shifting will be quite baulky when cooler.
I prefer a 75w-85 to a 75w-80, (eg Castrol Syntrans) less bearing and gear rattle at high loads/ambient
Thanks for info much appreciated, will get some 75w-85, is any better than others, and is it a full synthetic?
Motul Gear 300, what makes this oil better that others
Moderator
My go to for a 75w-85 is always Castrol Syntrans 75w-90 as it's a really good fluid and widely available. Just beeare there's a few flavours of Syntrans.Originally Posted by david7307
I've never used the Penrite equivalent, but IIRC Justin Cooper, who is a very well respected Land Rover tech uses it and likes it in clients cars.
The R380 can be idiosyncratic, some people prefer the shift characteristics of an ATF but i used to find Syntrans thinning too much, the gearbox displaying to much gear and bearing rattle at high ambients and loads with increasingly baulky shifting in my use.
I've trialled a lot of fluids and witches brews and they are my two fav's.
Motul Gear 300's viscosity index is the widest I've ever seen on a manual trans/diff oil.
It's 222.
The best syn fluids are normally in the 160-180 range.
What this means is that it acts like a very thin 75w oil at low temps, but has the viscosity of a mid range SAE 90 at 100°.
It's thinner at 0° than excellent fluids like Castrol Syntrans 75w-85.
And the shifting characteristics seem to take suit the R380.
It also doesn't seem to shear in use, something that most full syn fluids appear to suffer by around the 20,000km mark.
It's my favourite fluid in that 'box, and most people find it as probably the best fluid they've used in their gearbox.
Just be prepared for sticker shock on buying!
If you have an ATB fitted in the t/case and/or diffs it's my go to fluid there, too.
It's thin enough to flow into the pockets and innards well, as well as having good frictional characteristics for that application.
YarnMaster
Supporter
Looks to be about $32.00 a litre from a quick Google.
Interesting. I'd like to try this then at my next oil changes. What is the benefits though? My understanding was, perhaps mistakenly, that due to the design the ATB's did really have any components that experienced wear?
I think I have Penrite in there at the moment as when I purchased in 2014 Dave Ashcroft told me:
From the Ashcroft Transmissions website:Just use the normal 75W90
Ashcroft TransmissionsThe ATB's work best with a good quality Mineral based oil, we do not recommend synthetic oils, friction additives / modifiers and not required.
Moderator
Most 75w-90's have LSD friction modifiers added, Gear 300 doesn't, at least the non LSD version doesn't!
LSD friction modifiers increase slip % in a controlled way to reduce LSD clutch chatter.
If you've ever used a non LSD fluid in a clutch pack LSD they chatter and lockup fairly harshly.
The FM's in a manual trans fluid are optimised for manual gearboxes, their friction coefficient increases as rotational speeds approach each other, the opposite of an LSD fluid and for that matter engine oils and Dex II/III ATF's
The ATB relies on the helical gears in the pockets friction increasing to bias torque, whereas an LSD additised fluid will try to minimise that friction.
YarnMaster
SupporterOk, thanks. So if I understand correctly with an ATB and/or gearbox transmission we are looking for the opposite effect, in terms of slip as LSD wants additives to increase slip in a controlled way to reduce clutch chatter while manual transmissions want to have increasing friction coefficient as rotational speeds approach each other.Most 75w-90's have LSD friction modifiers added, Gear 300 doesn't, at least the non LSD version doesn't!
LSD friction modifiers increase slip % in a controlled way to reduce LSD clutch chatter.
If you've ever used a non LSD fluid in a clutch pack LSD they chatter and lockup fairly harshly.
The FM's in a manual trans fluid are optimised for manual gearboxes, their friction coefficient increases as rotational speeds approach each other, the opposite of an LSD fluid and for that matter engine oils and Dex II/III ATF's
The ATB relies on the helical gears in the pockets friction increasing to bias torque, whereas an LSD additised fluid will try to minimise that friction.
Therefore with ATB if in doubt use manual gearbox oil and avoid LSD oils.
Noting that you said most do, are you aware if the Penrite 75W-90 have LSD additives added?
EDIT: just checked the Penrite website and they not have four offerings in 75W-90 Gear Oil now:
Trans Gear 75W-90 TRANS GEAR 75W-90 (Semi Syn.) | Penrite Oil - semi synthetic
Outback Hardened 4X4 75W-90 OUTBACK HARDENED 4X4 TRANS GEAR 75W-90 (Semi Syn) | Penrite Oil - semi synthetic
Pro Gear 75W-90 PRO GEAR 75W-90 (Full Syn.) | Penrite Oil - full synthetic
GL4 Pro Gear 75W-90 PRO GEAR GL-4 75W-90 (Full Syn.) | Penrite Oil - where all the above are GL5. I believe that GL5 is specified for our D2 purposes - see below for difference for anyone interested.
In regards to LSD additives, of the three GL5 variants:
The TransGear 75W-90 semi synthetic states:
Outback 4X4 75W-90 doesn't mention anything about LSDs.For Limited Slip Differential applications, a dose of Penrite Limslip Additive is required to be added to the oil.
Pro Gear 75W-90 full synthetic states:
It seems therefore, if sticking to the Penrite range, which is much easier to source and price friendly compared to Motul, that TransGear 75W-90 is the one suitable for the ATB. I think I may need to drain my front and centre diffs as they might have the ProGear 75W-90 full synthetic fluid in them despite running ATBs. I can't recall what I put in there but fairly sure that's what I had on hand.Pro Gear 75W-90 is already dosed with the correct amount of friction additive for use in Limited Slip differentials, no extra additive is required, nor should it be added as seal degradation may result.
Any thoughts on the Outback 4x4 product range? It's only available through Supercheap Auto Stores - is is just a marketing ploy gimmick for them to target sales to the 4x4 customers or does there Outback Hardened Additive pack have a value to it?
Price wise it's almost equal to the Pro Gear 75W-90 rather than the TransGear 75-90 that is probably based on.
I also notice that it meets less specifications that the TransGear 75W-90 and has none in addition to.
According to The difference between GL-4 and GL-5 explained - Rymax Lubricants the difference between GL4 and GL5 is:
The main difference between GL-4 and GL-5 gear oils is the amount of EP additives. Sulphur/Phosphorus containing products are used as EP-additive. This additive has the purpose to prevent the occurrence of micro-welds on the gear flanks at the local high temperatures which prevail in EP circumstances (temperatures well in excess of 800℃!) GL-5 has roughly twice the amount of EP additives compared to GL-4, which is why it is often used in high-pressure circumstances such as in a front axle and rear axle differential. Sulphur/Phosphorus additives however have an unfavourable property: they can react aggressively towards bronze and copper. This can be disastrous for the synchromesh rings of a gearbox. Therefore it is not recommended to use GL-5 in a gearbox unless the manufacturer allows this.
To conclude:
• GL-4 is suitable for hypoid gear service when they are under severe service but are without shock loading.
• GL-5 is suitable for hypoid gear service under severe service and shock loads and not for use in a gearbox.
I recall that I've learnt this previously as I had to drain out and refill my Mazda once after a gearbox oil change because I had used GL5 and it's harmful towards the bronze inside the gearbox.
Apologies to the OP that the thread has gone so far away from the original question. I believe Rick answered your original query and it's too good of an opportunity to extract more knowledge from him.
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