Transmission oil

[durangoroadboss]

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

 

[rix 48]

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

 

[vwnate1]

?? 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 ! . :

.

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[coilover]

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.

 

[ccharr]

I got my last quart at the chevy dealer

 

[RidesWithYah]

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.
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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

 

[Zig]

Thanks, RWY. I guess I think I know what I need to put in my tranny... or at least ask for.