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

Unless your owners manual is wrong! I discovered the original gear lube my car came with from the factory is much lighter than what the manual calls for. :)

I can give you an extreme example of the benefits of lower viscocity oil:

In air cooled VW drag racing circles circa 1990, for the cars running in Pro turbo, Pro Stock, and Super Street heads up classes, it was a given that your gearbox needed to rebuilt after each event. The ring and pinion set in the type 1 gearbox is notorious for cracking from drag racing starts when putting down about 300hp or more. It was pretty common to see the fastest pass of the day in the final round, even though it is held in the heat of the afternoon. Typically one or both competitors pulled out all the stops, throwing every trick in the book at the car's set up and tune, and drained the transaxle of all the oil just before the final :eek: the word is they'd decrease ET by 1/10th of a second on a 9.70 1/4 mile ET having little or no oil in the transaxle (a 10th is a big difference in heads up drag racing)

**obviously you wouldn't do this in your street car**

Obviously you wouldn't do that in your street car - but it is a great indication of exactly how much of a gain you can get from running lighter oil or synthetic "low-drag" oil in place of your OEM oils.

To add to that - try just changing the fluids... lots of times, they don't get changed for the 140+ thousand miles that are on the vehicle... and while it may not hurt the components on a normally driven vehicle (not beat on), it most certainly will affect FE negatively... crud and gunk build up create more friction in the parts, meaning more resistance to movement...

Even if you don't want to use a lighter fluid, just change it out for the OEM fluid, at least.

i just changed the gearbox oil and i did a hole in cup viscosity test with new and used fluid. the new oil took about half the time to go through the cup 1min 30sec compared to 2min 40 for the used oil.

i used castrol ATF in the end. seamed to be the thinnest in the shop based on shaking all the bottles :)

oh i have a silly question. i spilled some oil, so i didn't have enough to fully top up my box. is it ok to drive 1 mile to the hardware shop on a gear box thats only 2/3rds full?

I would avoid that just in case. You never know if an oil slinger (used to throw oil to desired locations within the case...like to an upper bearing) is not gonna touch the oil it needs and therefore briefly starve a bearing for oil.

If its an auto then definitely don't drive with it low.

To steer this thread a different way...

What is the best brand / type of oil/grease for the motor and the rear end differential?

I have seen hype for redline but then read about people saying it is too light and causes heat problems.

I've read about Mobile 1 some good some bad, Amsoil seems to rate higher but some dislike Amsoil as well.

Then still others say synthetic is a complete waste of money and does absolutely nothing which I disagree with totally, my father changed the rearend lube with some sort of off brand snake oil synthetic back in 1992 on the old 82 diesel suburban, he also put in synthetic tranny oil and synthetic crank oil and our mileage went from 16mpg up to 21mpg and that was with a 3speed auto and a 3.8 rearend! Oil does make a difference but the improvement is many times taken up by the increased cost of oil ah well.

Anyway

I am attempting to get my Dodge Ram 1500 crew cab w/ topper magnum 318 v8 to get the same mileage as my old 350 gas Suburban (which normally gets around 20-22mpg) The Dodge does not seem to respond to any ecomodding attempt, about the only thing that helps somewhat is filling the tires to the sidewall max of 50psi (I go to about 53psi and bounce) Driving 45mph very lightly on a long trip I once hit 18mpg but normally its stuck at 14.5 :(. Sadly my old beaters are falling apart so I will probably have to move into this dodge I am stuck with as a crafting vehicle, nice looking but bad mileage :(

Anyway at the moment I am putting in Amsoil 75w90 synthetic w/ moly and Vacclaisocryptene additive in the rearend (it calls for 90w145 which I cannot locate in Amsoil form at the moment) I am not worried as the truck is generally driven lightly and it is very rare that I pull a trailer though I do load up the back with crafts which are bulky but don't weigh much. So heat should not be an issue.

I am putting amsoil in the crank along with some crankcase moly Vacclaisocryptene additive (yeah, I got the stuff on clearance, its no longer made I think but I have read several dozen posts that it was the only one that worked at improving mpg and at $1.38 I can't do too much so long as it doesn't drop MPG)

So what types of oils for the rearend, crank and transmission do folks think would improve the mileage the most? I am not worried about the wear hype as long as it doesn't cause failure.

The tranny I am afraid to mess with as Dodge made their transmissions to be craptaskic and fail with any improper oil, I am uncertain if there is a synthetic oil for a dodge tranny that would work well but worth knowing for 50k miles from now when I get it changed again.

I also have a little Subaru 360 that I am attempting to fix up and I am curious what manual tranny oil would be the best for MPG, I am probably going to put in Amsoil synthetic and some gear moly since it is a dry clutch. I would consider Redline if it works better for MPG, especially for my fathers electric minivan since at 25mph I would assume lighter than normal oil wouldn't make much difference in wear.

Thank You
Ryan