why is gearbox oil mod listed as large improvement in the 65+ mods
 

hi

why is the thinest gearbox oil mod listed as large improvement in the 65+ efficiency mods where as thinest engine oil mod is listed as small improvement? i read the example thread that gave the large improvement but that was an anomoly where the vehicle had the wrong oil. in most cases i would expect the improvement would be a lot less.

or am i missing something?

well done on the quality of the 65+ efficiency mods section tbw. it looks very profesional now with all the pictures. :)

what temparatures to transmission fluids work at? i bet a block heater would help since there is no heat of combustion helping it.

Gearboxes are more sensitive to oil changes since their components are entirely submerged in the oil. Every moving part churns and has to move the oil around as things rotate. Engine components really don't have moving parts churning oil (to the extent that the gearbox does).

whats the thinest gearbox oil i should go to? its hard to tell viscosity with gearbox oils because they don't have numbers on.

i think i will go to the auto shop and shake all the oils to find out which one is the thinnest :)

The gearbox lubes that I am familiar with are:
ATF
motor oil
75w90 gear lube
75w140 gear lube
90w gear lube

You should use whatever type of lubricant that your owners manual calls for, and using pure synthetic lube of the appropriate weight and type will usually result in reduced friction in your transmission.

Well said Wriley.

If you really wanna push the limits you can always run something thinner and see if it holds up by doing an oil analysis after X amount of miles.

modmonster,I'm going to chime in with Wriley.If you select a synthetic with the same rating as a straight mineral oil your vehicle came with,you're actually getting a lower initial viscosity oil than what is listed with the synthetic(do to a quirk in labeling requirements),but it will protect from asperity or high-point just like your OEM lube.--------------

This lower viscosity is the only thing that will improve your mpg.-------------------

Racing transmissions use low-drag spur-gears (very noisy!)and low-drag spray-lubrication rather than bath-lubrication,to reduce"swimming losses"( not something easily accomplished ),so for typical everyday drivers,the synthetic is about our only direction for MPG.------------------------

Pre-heating all lubes would obviously save fuel,although poses a significant challenge in itself.-------------------------

I would caution you very strongly against using very light oils,as they will not maintain the hydrodynamic separation between reciprocating and rotating parts.Should you have metal to metal contact,the parts will momentarily weld together,then break apart,transferring metal,beginning a cascade of rapid self-destruction and failure.Play it safe!

The drivetrain drag due to thick oils is more pronounced on vehicles such as large 4x4s where you have multiple gear boxes. I put 140wt oil in my transmission, transfer case, and rear end a long time ago. Happened to do it during a real cold spell too. The vehicle would barely even roll down a hill on its own:eek: I went back to the 85-90 wt and it was much better. I suppose switching to synthetic would help even more however I haven't driven that vehicle on the road in several years so I won't bother (in that vehicle at least).

IN my honda hx I used the factory honda MTF (manual transmission fluid) cause that's what seems to work best and is recommended by Honda. That's the only gear oil in the car too...about 2qts compared to about 2 gallons in the aforementioned 4x4.

it all adds up