Thread: 85/ 140 gear oil sooo much better!.

Originally Posted by Brian Hjelm

'phone their technical reps in Mlbourne and ask. They say
Syntrans for the gearbox and VMX80 for the transfer.

There is better stuff than Castrol around, I wouldn't waste the money phoning them

Originally Posted by rick130

.........
FWIW, I nearly burnt the skin off my hand one day when I just touched the Sals after a hard run, I should have put a thermometer on it just to see how hot it was, whereas the front diff I could hold my hand on easily.

Interesting point, and relevant to the comments in other threads lambasting Landrover for sticking to spiral bevel diffs rather than using hypoid gears - as well as having a larger tooth contact area (everything else being equal), the hypoid diff has more sliding action, and hence more severe lubrication requirements, and loses more power, and gets hotter. Maybe Landrover has some reasons for sticking to the spiral bevel?

John

Originally Posted by JDNSW

Interesting point, and relevant to the comments in other threads lambasting Landrover for sticking to spiral bevel diffs rather than using hypoid gears - as well as having a larger tooth contact area (everything else being equal), the hypoid diff has more sliding action, and hence more severe lubrication requirements, and loses more power, and gets hotter. Maybe Landrover has some reasons for sticking to the spiral bevel?

John

Spot on, JD. Hypoid gearing was developed to lower the driveline in passenger cars so a smaller driveline hump was causing less interference with passenger space as cars got lower in the 1930's. The converse is amboid gearing in which the pinion contacts the crown wheel above the centre line. This is, to my knowledge used only in some heavy truck tandem drives to reduce driveline angularity as the intermediate shaft exits the power divider on the forward diff and drives the rear diff. Hypoid/amboid does have more sliding friction than spiral bevel which in turn has more friction than straight cut bevel gears. The reason for spiral bevel gearing was to reduce the noise made by straight bevel gears which emit an annoying whine in service.

It also produces a stronger diff for the same given size.

Originally Posted by Slunnie

It also produces a stronger diff for the same given size.

Precisely! But as I comment above, you don't get something for nothing, and the penalty in this case is more friction, making for lower drive efficiency, more critical lubrication, and higher operating temperatures.

A design decision that the manufacturer has to make, influenced, no doubt, by what they have on the books, what they need in other applications, what their available tooling can make, etc etc.

John

The other thing that I had wondered about hypoid diffs, is as they become more like screws, do they also increase what would seem to be an engine braking effect as the crown wheel loses its ability to drive the pinion during overrun.

well there is more friction involved as this is what generates the heat, so probably.

It's worth noting that the pure race transaxle manufacturers in the world, eg Xtrac, Hewland, Emco, etc., if using a longitudinal gearbox use a spiral bevel CWP.
So all your Formula Fords, Formula Three, GP II, F1 and Champ cars, etc, use a spiral bevel diff.
More power transfer/less heat.

Originally Posted by Brian Hjelm

<snip>
The converse is amboid gearing in which the pinion contacts the crown wheel above the centre line. This is, to my knowledge used only in some heavy truck tandem drives to reduce driveline angularity as the intermediate shaft exits the power divider on the forward diff and drives the rear diff. <snip>

the front diff on a few 4WD's, inc Nissan's GQ and GU Patrol and Toyota's 78/79/80/100 series solid front axles use this, as did Ford in a couple of years of the F100/150 ('78/'79 ??) with a Dana 44 and you can get some Dana 60's in high pinion, too.