Hi folks: I've just installed my third 3-speed trans in my 1952 Chevy 3100 (hopefully this one doesn't stick in 3rd gear like the original started to do or have a bad second gear syncro like the second one I installed). I went to the parts store for 90W oil and the Valvoline 80W-90 gear oil says it's not for use in synchronized transmissions. Don't know why, since it says GL5. Any suggestions on what oil to use? Thanks. Richard
Timely post for me to be on. I'd also like to know if I should "flush" with any certain cleaner before adding the new gear oil in my 4 speed tranny. Rick
?? I've never heard of this . Maybe the GL5 attacking the bronze synchro baulk rings ? . I dunno , I just buy it and pump it in... Synthetic gear oil is the best , it helps old tech synchros shift easier . Flushing is tricky , if you're willing to remove the cover then go for it , use Gasoline or solvent but _not_ kerosene nor Diesel Fuel . Me , I just get it up and driving therm do a hot oil change , let it drip a long time and use a clean drain pan to see what comes out . I also always add a 1/2" NPT magnetic plug to both the fill and drain , don't freak out when you see the SWARF on it ! . : . .
Got me scratching my head on this one. I wonder if there is some new ingredient in the 90W. I can see where there would be a warning on not to use it in new synchro trans as many of these now use ATF but old ones still use 90 wt. I agree, use synthetic in anything without a leak problem. If it seeps or drips with regular then synthetic will run out.
GL5 is designed to lubricate rear ends - the application is very different from a manual transmission with synchronizers. From another forum -- Current MTL GL4 viscosites are: 1. ATF Series - Type; 6.5 to 8.5 cSt (Equivalent ATF viscosity; Note: ATF additive package is weak compared to most GL 4's) 2. Synchromesh Series -Type; 9.3 - 9.5 cSt (such as Amsoils MTF, Texaco's MTL, Pennzoil's Synchromesh, GM and Chrysler's Synchromesh) 3. 75W85 Series-Type; 9.8 to 11.5 cSt ( Redline's MTL, RP's Synchromax LT, Nissan's MTL, Honda MTL, Castrol Syntorq LT) 4. 75W90 Series-Type; 12.8 to 14.5 cSt (Amsoil's MTG, Redline's MT-90). MTL specific lubes we're developed for manual tranny's and transaxles, and not for differentials or industrial gear boxes. A differential lube may not kill your tranny, but it is not the optimum lube for it. A diffy 75W90 (GL5) usually has a higher viscosity than does an mtl in the same advertized weight. ------------------------------------------- There's also a GM version: You might also want to try the GM Synthetic Manual Transmission Fluid, # 12346190. And it IS a real synthetic MT fluid with PAO's and esters and none of the pseudo-synthetic GroupIII oils. http://www.amazon.com/Genuine-12346190-75W-90-Synthetic-Transmission/dp/B000QIR1V2
