LT95 oil

**Meccles** · 4th October 2020, 06:05 AM

Well putting some miles on white truck and cold shift into first more difficult than i recall it used to be. I know its harder as my wife who was regular driver can't get it in at all. Running Castrol GTX 20w-50 in both gearbox and transfer case. However see that Penrite recommend their trans gear 75w-80 GL4 oil. Reviewed previous threads and see that as long as oil doesn't have additives that can damage white metal and bronze then viscosities etc are ok with the modern GL4 oils.
Does anyone have current experience/recommendation on oil for both LT95 gearbox and also transfer case? I used GTX 20W-50 30 years ago but oils ain't oils anymore so there may be better alternatives. Bearman care to comment?

**Bearman** · 4th October 2020, 07:18 AM

Have to say that I have never used anything other than 15/40 diesel engine oil from engine to transfer case. Others have had good results with Castrol syntrans and Penrite synthetics but I have never had to need to try them. If you have synchro engagement problems it might be worth a try.

**Red90** · 4th October 2020, 07:52 AM

20W-50 is crazy thick. Anything lighter would be better.

**Homestar** · 4th October 2020, 07:55 AM

I just use 15W40 Diesel engine oil too - mainly because I have heaps of it lying around. My current box has always had 1st gear engagement issues as the PO ran gear oil in it but I just lived with it.

I have a shiny newly rebuilt box that was supposed to be in the 101 by now for my big trip - which didn’t happen, so it’s still on the pallet under my bench...

**Phil B** · 4th October 2020, 07:57 AM

If you are having difficulty shifting to 1st when cold try shifting to 2nd first and then up into 1st.
Works for me.
I also use 15w40 on the engine, gearbox and tc

**Meccles** · 4th October 2020, 08:24 AM

Thanks i always go to second then first but even so very difficult to get into first. 20W-50 was recommended oil years ago and is still listed as recommended today. Along with 15w-40, and some of Syntrans type GL4 trans oils. Not heavy gear/diff oils of old. Might have a word with Penrite and Nulon tech departments. Gearbox rebuilt so want to look after it. And any oil that may minimise transfer case whine is always an added bonus

**rick130** · 4th October 2020, 08:34 AM

You could try a dedicated manual trans fluid, somethiing like Syntrans 75w-85.
isuzurover used that in his 110 with excellent results.
The SAE 85 gear oil viscosity is equivalent in kinematic viscosity to a heavy SAE30/light SAE40 engine oil

Manual trans fluid is optimised for good synchro performance, engine oil isn't, and engine oil often foams in gear applications, it usually doesnt have enough silicon foam inhibitors.

**p38arover** · 4th October 2020, 08:43 AM

Where/when did I hear ATF? Maybe back when I got my first RR - an ‘83 with the LT95.

**Meccles** · 4th October 2020, 08:47 AM

Thanks I was thinking of a syntrans type oil as well but will ring and confirm there's no nasties that present a threat to bronze/brass/white metal

**rick130** · 4th October 2020, 09:17 AM

Originally Posted by Meccles

Thanks I was thinking of a syntrans type oil as well but will ring and confirm there's no nasties that present a threat to bronze/brass/white metal

Most synchros are bronze, and GL4 oils usually achieve 1A copper corrosion test result, ie. no discolouration on the strip test.

Even most diff oils are buffered so the the sulphur isn't reactive and achieve a 1B test result.

FWIW the copper corrosion test range goes to 4C

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