I've researched like crazy online, and got answers ranging from ATF to 50wt gear oil, to 70wt gear oil, and even 90wt gear oil. Figured I would get a more definitive answer here. Anyway, my coupe has a Borg T5 trans, non WC, and I don't know what fluid to use when it's changed. Anybody have experience with this?
If you have a WC (world class) T5 use Dextron III - if not use 50 wt gear oil, (the original recommendation way Dextron II, but that's not available anymore - so 50wt is the next best thing). Hope that helps, Frank
Here's another one that won't die. I was a 3rd-generation GM employee, in Vehicle Engineering. I have read directly from the GM records. I am not trying to sell you something. I am not trying to ruin your transmission. I am not speaking from ignorance, or repeating hearsay. The official answer is 70W API GL-4 gear oil, with cold climates calling for 50W API GL-4 gear oil (50W GL-4 is Ford's original recommendation for all NWC T5's). Note the GL-4. It cannot be any number higher than 4. GL-5 that you find at the auto parts store will erode the yellow metal parts in a NWC T5, leading to premature failure. ATF of any kind does not belong in an NWC T5, as it will lead to premature failure. Higher weights of gear oil will lead to balky shifting, if GL-4. If GL-5, they will lead to balky shifting, and premature failure. Acceptable substitutes are Valvoline Syncromesh (meets API GL-4), and Redline MT-LV 70W/75W GL-4.
The reason why ATF of any kind does not belong in any NWC T5 is the difference between how the gears ride on the shafts. In a WC T5, the gears ride on needle roller bearings, that ride on the shafts. The lubrication requirements are lower. In a NWC T5, the gears ride, metal-on-metal, no bearings, no bushings, but directly on the shafts! The lubrication requirements are much higher. Plenty of people only think that they are getting away with ATF in a NWC T5. They just have not yet driven enough to render the transmission a total loss, and that holds true for those running GL-5 gear oil. GM saw people that did, on both counts. It was ugly, and people were irate. Specifications exist for a reason.
The numerous and various iterations of Dexron are at or around 20W, or less. Running any iteration of it is the fast-track to ruining a NWC T5. People are only "getting away with" running the incorrect lubricant because they are not driving the US average 14,263 miles-per-year. Do that with the incorrect lubricant, and you might be looking at an annual rebuild, if you make it that far.
This post should get a sticky. WTF every happened to Tech Weeks? This post should be in the archives.
Seriously. It is not like an acceptable lubricant is hard to find, or expensive, or needs to be changed that often. Skipping all of those easy steps can cost you up to, and including, a whole viable transmission. I have had people ask me to rebuild NWC T5's that ran the wrong lubricant for far too long. Best case, the yellow metal parts were shot. Worst case, no moving part made of steel, but the shift rail, shifter receiver, and input shaft could be saved. This is the risk of ignoring the specifications.
If these are not available locally: https://www.jegs.com/i/Red-Line-Oil/816/50604/10002/-1 https://www.amazon.com/Valvoline-Synchromesh-Manual-Transmission-Fluid/dp/B071YBH8P1
No, it is NOT still made! The Non-World-Class T5 went out of production several decades ago. Only the World-Class T5 is still in production. They are VERY different inside, and do not have the same lubrication requirements!
Wow! I got that 50wt/Dextron information from the guys at Modern Driveline. Thought they should know their stuff. Thanks for correcting this Gimpy. Frank
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