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GL-4 tranny/gear lube


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Hello all. Long and short I’ve been all over Gods kingdom looking for what I believe is supposed to be used gl-4 gear oil (2L) in my 69’ 521 transmission. Pretty much all of the suppliers have only gl-4/gl-5 all in one and I’m hesitant in using this. Milton Nissan had a Gl-4, wasn’t 80w-90 so I passed and found another place that had Gl-4 75w-85...I think the Nissan stuff was the same, but can’t be sure. I see nowhere on the label that says “yellow metal safe” or the likes on any of the two mentioned. Any idea if these are ok to run in the tranny or should I stay clear of both? I’ve used Ratsun search and google with Ratsun as the end word and am still lost. Could someone point me in the correct direction as to what’s safe and what’s not. I’m in Southern Ontario Canada and don’t have a plethora of scrap yards with 521’s that I can easily replace a transmission or get parts. Thanks, Pidge. 

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Just to be clear...you guys think it should be ok to run the 85w-90. It calls for 80w-90. From what I gather the 85w is a bit thicker. I don’t plan on driving the truck here in the colder months. (Ontario Canada)The Sta-Lube is all I can find that’s not a synthetic oil and I’d prefer to run non synthetic. Thanks. 


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I use Redline MT-90 GL4; it is a synthetic.


For the longest time I used Sta-lube in my 1200 that I race. The only reason I'm using Redline is the place I go to has it in stock.


I wouldn't be to worried about the 85w...…..once upon a time I used straight 90W, it was like pumping syrup into the trans. As long as you don't flog the car from dead cold I wouldn't expect any issues. 


You are correct to be hesitant to use GL4/5; I did that once and the next time I drained the fluid it had a lovely metal flake brass sheen to it. Clearly it was not yellow metal safe. I think I ran one race weekend with it (could have been two).


If you can't get Redline just run the Sta-Lube; it's perfectly fine for your use.

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Just don't run it if near 00 F. Use parking brake and leave in neutral if you do. My Dart, I had to shut off in reverse to get the key out of the ignition. At below zero F I could NOT pull the shifter out of reverse the next morning. 


I survived Ontario winters north east of Toronto in my '72 521 not because of the heater but in spite of it. Heater core is too small and the engine barely keeps itself warm.

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I second what Tom says. Redline MT-90 works well in my transmissions and is readily available here in Canada even if it is a bit expensive.



Edited by datsuntech
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Synthetic tends to seep past old seals. The rear seal is only $5 at NAPA. The GM Delco oil is also available everywhere and at Lordco. About $17  CDN and you need 2 liters. Way better cold shifting and will downshift easier where before it would grind. 

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Ive been using gm synchromesh with good results and derevetives of it. I ran redline shockproof when the syncros were dying and it wasnt good. You could run that delco gl-4 that would be fine. If it shifts like shit get an ebay rebuild kit and put new synchros in your tranny. Oil wont fix grindy gears.

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Thanks Scooter.....ended up finding some Sta-Lube 85w-90 on amazon that’ll ship. Should be here next week hopefully. Can’t believe how many places won’t ship oil to Canada. In good shape now though. Thanks to all for the help. 

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