Thread: Defender gearbox oil.

Syntrans is cheaper and you seem to be able to buy it everywhere, it's a about $20L and MTL about $30L

Hi guys !

No Paul, I haven't posted on here before, but check out the join date ! 8O I forgot my password, then my handle, then.... :roll:
I actually signed up earlier than that, but for the life of me can't remember under what ?

I'm still cacking m'self that you both ended up lumbered with the job !

Col, Redline is pretty available over there at most race shops, you just might have to shop around for the best price.


Shaun, an oil would have to pretty trick chemistry to get thinner, then thicker the hotter it got. 8)

Check out the SAE viscosity chart on JB's site that Paul linked to above. You will notice that all the fluids thin out substantially as they approach 100*C.
Futher down the page is a chart showing the actual viscosity range vs temp for the different SAE grades.

You are right that synchro performance is governed by the oil's viscosity and its coefficient of friction. It also needs the correct balance of EP and AW additives for adequate protection/life.

Most conventional multigrade lubes start out as a lightweight base stock, to which are added the VII's (viscosity index improvers, which are polymeric thickeners) to ensure oil doesn't thin out too much at higher temperatures. A problem with large amounts of VI improvers is that they aren't very sheer stable, and as a consequence, the oil sheers (thins) fairly quickly. This is why a gearbox feels/shifts better when fresh fluid is used at a 40 000km change.

The beauty of Redline and Syntrans is that little to no VII's are used thanks to the synthetic base stock, so their life is much greater. Syntrans is rated at 300 000km in large truck transmissions !

cheers.

Well it looks as though we&#96;re all here now, Paul I forgot your handle on here but its has all come back now. [img]style_emoticons/<#EMO_DIR#>/laugh.gif[/img]

Yes Rick you escaped that nicely. 8O

This gearbox oil thing has been doing my head in, the way I read it MTL is probably about the best, but even over here it&#96;s not just a normal over the counter thing, but the Syntrans is quite easy to get, and as we do quite a bit of travelling, it is easier to find a local Castrol distributor in most countries if you need to get more for any reason.

Rick your the only person I&#96;ve heard of who has run both oils and from what you have said it seems much of a muchness, depending on your temp.

At the momment I&#96;m still running ATF, as I threw it in when I changed the gearbox to let it bed in, now it&#96;s got a couple of thousand Ks on it, its time for the synthetic oil to go in. We&#96;re driving over to Poland in a few weeks so I want it in before then.

What are you running in your T/X box, I&#96;m running syntrax now, hoping it&#96;ll be kinder to my mainshaft/input gear.

Rick I'm not sure how SAE rateings for given oils are rated against the actual viscosity. A gear oil and an engine can have the same viscosity but different SAE rating I suspect this may be due to the extreame presure aditives, ie a sae 75 gear oil has a similar viscosty to say an sae 10 engine oil, clearly the additive package is quite different because they do different things. It is my understanding that the V-Is are a long chain polymers that un folds/rolls as the temp increases to maintain viscosity from the original base grade I'm not sure at what temp this starts to happen so the rating could fall before it goes up. So if a gear oil has an SAE rating of 75w80 it will be no heavier than SAE 75 at 0 deg and no thiner than 80 at 100deg. However I believe that this means it can be lighter than 75 at 0 or heavier than 80 at 100. This could explain with some oils at high temp give poor syncro performance because there is no garentee that they are 80, they will be no lighter than 80 but could be 90 which would explain why the box would stiffen up. I did a box on a mates Disco where he cooked the oil and it got thick to point where it wouldn't pump and smoked the box. Having said that it was pretty toasted so I'm not sure which came first the chicken or the egg. I know on my own car a V8 disco which has an oil cooler on the box still getts stiff if towing in 5th, clearly this is related to oil temp, I drop it back to 4th every so often if on the highway and the box cools off pretty quickly and shift quality returns. I'm interested to here that MTL also had poor hot shift, I just did a long trip towing the Jayco through cnetral NSW and back up the coast to Brisbane, I considered changing to MTL prior to this but didn't because I was concerned if it leaked it on to the clutch I'd be in trouble. So I just refilled it with Valvoline Dura gear 75/85 which is what I normal use in these, it to stiffens up at high temp however but only when towing.

I can't tell you all how grateful I am for all your advice. I phoned around yesterday and found some Valvoline dura gear 75/85 GL4 in Narrabri,changed the oil and it drives much better now.

A week ago I topped up the box with SAE 80/90,that made it stiff to put into first and reverse.When I changed the oil neither oil had mixed it was dirty of course,as were all the oil's.The oil had that coppery look to it as well so I guess we'll see what the future holds.

Many thanks to you all for your help.
James

I was at Narrabri a couple of weeks ago, we stoped at the caravan park nexted to the pool for the night, went for a drive up Mt Kaputa for a look. We were just passing through for the night.

OK took the plunge today and ordered some MTL at nearly 35 bucks a litre with frieght I hope its worth it, will keep you updated with how it goes.

Haven't posted here before so.....G'day everyone.

Just looking through the posts on this topic and thought I might just chip in.

Firstly I'm no expert on Gearboxes or oils etc... but have a 93 200Tdi which had A/T in for the first couple of years of it's life...very difficult shifting and problems with the 2nd gear synchro assembly early on.

Had the box rebuilt about 3 or 4 years ago and have run various reccommended oils since, but lashed out on the Redline MTL about 2 1/2 years ago.

Initially disappointed at very little change for the huge $$, but after a few thousand K's the box just seems to be getting better and better.

So save up and put in the MTL...you won't regret it.

Cheers,

Mark