303 tractor hyd oil in a manual transmission

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well about 2 weeks ago i bought a used 94 ford ranger, very well used and needing all sorts of stuff, when i checked the manual transmission fluid, it had 80w90 hypoid oil in it (can tell by the smell) i knew this is a major problem and it should have atf in it, i drained it out, had only about 2 qts in it, which means it was also low on oil. i went to my oil supply and found i had only 1 qt of atf, but i had over half of a 5 gallon bucket of 303 tractor hydraulic fliud. now since atf is pretty much a hydraulic flid itself and this in a manual transmission, i figured it might be safe, they both seem about the same viscosity and when you consider the heat and loads that a farm tractor is under, than 303 should be more than good enough for a old ford ranger 5 speed. ive searched online just out of curiosity and all ive seen others do with 303 as far as automotive usage is to run them in drag race automatics. so far after 500 miles ive not had any issues with my ranger transmission, at least its closer to the right fluid and its now full, any damaage that was done by being low on oil and being the wrong oil has already been done, but i am curious, any reason why 303 tractor hydraulic fluid shouldnt be used in a light-duty 5 speed manual trans? i know that hypoid oil is bad because of being too heavy and not "yellow metal frendly" which can eat up syncros. trans does have input shaft bearing noise, had it when i got it, and of course its not going to fix itself no matter what oil might be used. vechicle has high milage but not sure how high, shows 44K but its anyones guess how many times its rolled over, im sure its at least 144k but could be 244K. any thoughts on 303 oil and if i should dump it for the atf as soon as possible to avoid a future problem? granted it might not be a "yellow metal frendly" oil, i have no idea, considering tractors dont have sycros (to my knowledge) it wouldnt nessasarliy have to be good for sycros. ive not had a issue with it going up through the gears or downshifting either one. (yet)
 
I'd put a real manual transmission fluid in it, not some GL5 smelly sulfur stuff that is far too slippery for the synchronizers to work,
not automatic transmission fluid as specified by Ford and definitely not tractor fluid.

What the big three sometimes did was to use the same fluid in both automatics and manuals in some vehicles to eliminate an additional expensive UAW employee in the pit.
There were/are strange rules you cant phantom unless you've had a high dollar union job like I do.

Retired Chrysler manual transmission guru ex[plains it here:
 
Originally Posted By: skyactiv
I'd put a real manual transmission fluid in it, not some GL5 smelly sulfur stuff that is far too slippery for the synchronizers to work,
not automatic transmission fluid as specified by Ford and definitely not tractor fluid.


That transmission isnt too picky.

I like redline MTL in those. Another good choice is the ford full syn gl-4 gear oil.
XT-M5-QS IIRC.
 
303 is a John Deere spec that hasn't been around since the 60's.

I don't think it has any decent anti-wear or extreme pressure additives.

REAL tractor fluid (for the kind of tractors with powershift and wet brakes) makes an excellent auto trans racing fluid. it also cost several times more per gallon than the junky "303" oil.

I see no reason to worry about your trans
 
If you can find Pentosin FFL-4 or Redline DCTF Dual Clutch Transmission Fluid (8.1 cSt)
they have the correct viscosity and friction modification for MT's speced for fluids of the ATF viscosity.
 
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