Thread: Nulon 75W-90 full synthetic gear oil.

Hi all,

just had a new Ashcroft's gearbox and transfer fitted to Chaffy my TD5 D2 with all the options ticked. HD bearings, sleeved case etc, etc hopefully making it as strong as it can get. My transfer already runs the extended finned sump, which was transferred to the new transfer and had a $$ATB fitted.

After a lot of research my mechanic (landrover D2 TD5 owner as well) decided on running Penrite Progear 70W-75 full synthetic in the gearbox for the quality shifting and resistance to shearing in the heat.

still in the running in phase with only about 600km on the gearbox transfer combo so far. Gearbox shift has been a bit stiff especially into third. Box has been adjusted a couple of times and with some km getting put on it now it appears to be shifting better.

I'm inthe NT and do a lot of high speed highway km between Katherine and Darwin @120-130 km hour with air temps up to 40 degree ambient especially with the build up happening.(God knows what the temp coming off the road will be, probably at least 60 degrees)

Heading down to Katherine in the morning when it's cooler the gearbox temp peaked at 94-95degrees. On the way back to Darwin in the afternoon on another day gearbox temp peaked at 100 and touched 101 for a little bit.

I dont recall call my gearbox temps getting that high on my old gearbox ( not sure what oil it was running ).

I can't find anything on the net regarding specific heat range for the 70-75 and I am hoping it will be more than fine been a fully synthetic. Obviously a bit concerned with temps hitting 100 after spending so much coin on the new gearbox and transfer.

going to change out the oil around the 1000-1200 km mark to get of any build swaff/bronze.

Should I be concerned about the temps the box is reaching seeing as I don't recall my old box getting that hot. Once we have some additional km on the box would I be better off running the PROGEAR 75/85 or 75W/90 as it specifically mentions consistent high temps and shock loads. Obviously I want to maintain quality shifting characteristics.mRemember I am in the NT availability can be an issue. However the Penrite range seems to be well represented up her.


Rick 130 would really like to hear your advice.


Cheers, Chris

Chris, my personal preference fort the R380 is Motul Gear 300.
The shift quality is superb, and you don't get the bearing and gear rattle that oils such as Castrol Syntans 75W-85 can exhibit at high ambients.
Don't let anyone tell you it's too thick/high viscosity, it works well to below 0°, something you won't need to worry about.

If you can source it, that is my go to, just be prepared for sticker shock.

The work BT50 with the MT82 is now filled with Pro Gear 75W-90 and the shift quality when cold has suffered when compared to the Mazda factory fill.

Has anyone asked Ashcroft for their recommendation?

Originally Posted by incisor

it maybe "ok" but it definitely isn't anywhere near as good.

seen it too many times now.

once gear changes start to slow down using the nylon, change to syntrans and after a couple of weeks the difference is obvious.

have yet to see it not improve a box running nylon..

always prepared for a first time tho

Hmm,have to agree,noticed in the cold weather,shifting while cold is not good,once hot perfect.

I spoke to the guy at the dealer,his comment was go back to mineral oil in the Vans,and all will be OK.Every synthetic oil they have tried has caused customer complaints.Strange the original synthetic OEM oil,with very long drainage intervals was fine,but it is not available,even from the dealer.

Originally Posted by donh54

Has anyone asked Ashcroft for their recommendation?

MTF94 or equivalent

Originally Posted by donh54

Has anyone asked Ashcroft for their recommendation?

Originally Posted by rick130

Chris, my personal preference fort the R380 is Motul Gear 300.
The shift quality is superb, and you don't get the bearing and gear rattle that oils such as Castrol Syntans 75W-85 can exhibit at high ambients.
Don't let anyone tell you it's too thick/high viscosity, it works well to below 0°, something you won't need to worry about.

If you can source it, that is my go to, just be prepared for sticker shock.

The work BT50 with the MT82 is now filled with Pro Gear 75W-90 and the shift quality when cold has suffered when compared to the Mazda factory fill.

Thanks Rick, appreciate your insight and experience.

Donh54, Ashcroft website still states MTF94. I have sent them an email asking the question.

Cheers, Chirs

Originally Posted by 4runnernomore

Donh54, Ashcroft website still states MTF94. I have sent them an email asking the question.

Cheers, Chirs

Texaco in the UK still make it, just that Caltex stored importing it a few years. ago

Castrol Syntrans 75W-85 is excellent, but at high ambients and under high load it starts to get a little thin and you can get shift baulking and gear rattle, as does Redline MTL and the MTL/MT90 brew I used (before Redline released their 75W-85.)

Originally Posted by rick130

Texaco in the UK still make it, just that Caltex stored importing it a few years. ago

Castrol Syntrans 75W-85 is excellent, but at high ambients and under high load it starts to get a little thin and you can get shift baulking and gear rattle, as does Redline MTL and the MTL/MT90 brew I used (before Redline released their 75W-85.)

It's certainly a minefield out there and the more you read the more confused you get.

it will be interesting to see what Ashcroft replies with.

I am a little worried that the 70w/75 may be to thin for the temps up here and that is why I am getting high gearbox temps. Will keep an ear out for gear rattle as well. It will be interesting to see what the oil is like after pulling it out at the 1000-1200 km. I suppose whilst running in the box the claimed quick full pressure flow at start up will be beneficial.

I already have the 70/75 to replace the existing oil in the gearbox as Repco had a AANT 30% sale on this weekend.

I will have to investigate how easily available the Motul Gear 300 is up here.

Cheers, Chris