Another MTF Thread.

[Dougal]

So what brand and grade of MTF will have similar viscosity to a 5w30 motor oil?

I reckon 40C would be a good operating temp, so the 5 will be more relevant than the 30.

[rick130]

DP

[rick130]

So what brand and grade of MTF will have similar viscosity to a 5w30 motor oil?

I reckon 40C would be a good operating temp, so the 5 will be more relevant than the 30.

Anything between 10 and 12 cSt @ 100*C Low Viscosity Manual Transmission Lubricants
A couple of other oils that JB doesn't have listed include 'normal' Oz Syntrans at 11.9 cSt @ 100*C and Penrite SIN Manual Trans which is a very light xW-40 at 12.5cSt

The 5W part only refers to pumpability at -30*C so it isn't really applicable above 0*, the oils viscosity index is more appropriate.

If you want to know what an oils viscosity is down to around -5 to maybe -10*C, this calculator is good Viscosity and Viscosity Index (VI) Calculation All you need is either temps at 40* & 100* or one temp and the oils VI.

FWIW I've seen over 75*C, and 'normal' appears to be 65* just running around on the R380. (temp taken with thermocouple on external transfer pipe)

[Dougal]

Cheers.
This is an Isuzu box rather than a leyland so the temps should stay somewhat lower. I've never felt it hot but I've never been looking either.
3 litres of 5w30 is the factory fill, it had done 250,000km in a 4 ton truck before I got it and it's still both tight and smooth.

[rick130]

Japanese gearboxes are generally very good. Our Patrol one has over 300,00km now and it still changes like new.
I kept an eye on the R380 temps today, just a 30km run up the highway from Scone to here and it sat on 75* cruising @ 100km/h.
No wonder most of them use an oil cooler for hard use.

[Dougal]

So just to revisit this thread before I spend any money.

According to this page you've linked up:
Low Viscosity Manual Transmission Lubricants

My 5w30 engine oil at 100C has similar viscosity to castol VMX80 at 10.5cST?
http://www.castrol.com/liveassets/bp.../AU_VMX_80.pdf

This is about 50% thinner than the EPX80w90 I use in the LT230 and axles at 100C, but the 80w90 is twice as thick at 40C.
http://www.castrol.com/liveassets/bp...s_B1716_04.doc

[rick130]

Yep.

If you want something thicker @ 100*c but thinner when colder for acceptable shifting during winter, you'll need Motul Gear 300 75W-90 with a VI of 222.
Specs are 15.2 cst @100*c, 72.6cSt @ 40*C, 425cSt @ 0*C, which is thinner than VMX80 and Syntrans 75W-85 at 0*.
I preferred the shifting of Syntrans over VMX80 in my R380 too, but if the factory fill is a 5w-30 engine oil I'm sure VMX80 or the more exotic brews like Redline MTL would be fine.

Be prepared for major sticker shock with Gear 300 though.

[Bush65]

Cheers.
This is an Isuzu box rather than a leyland so the temps should stay somewhat lower. I've never felt it hot but I've never been looking either.
3 litres of 5w30 is the factory fill, it had done 250,000km in a 4 ton truck before I got it and it's still both tight and smooth.

FWIW, the sticker on my Isuzu says 4.0 L of 5W30.

[Dougal]

Yep.

If you want something thicker @ 100*c but thinner when colder for acceptable shifting during winter, you'll need Motul Gear 300 75W-90 with a VI of 222.
Specs are 15.2 cst @100*c, 72.6cSt @ 40*C, 425cSt @ 0*C, which is thinner than VMX80 and Syntrans 75W-85 at 0*.
I preferred the shifting of Syntrans over VMX80 in my R380 too, but if the factory fill is a 5w-30 engine oil I'm sure VMX80 or the more exotic brews like Redline MTL would be fine.

Be prepared for major sticker shock with Gear 300 though.

Cheers, I haven't had any shifting problems with the 5w30 or even 15w40 when cold, so I'll save my pennies and go for VMX if supercheap has it.

My original Isuzu 5 speed asked for 15w40, the one I have now was made around 1991 and asks for 5w30 and is exactly the same series box, just 3rd gear ratio differs.

Just rechecked the stickers, my gearboxes only call for 2.5 litres.