[TransAmRIP]

As title says, just rebuilt my 4 speed super t10 transmission and was wondering what is the correct fluid to fill it with. I read about so many different types of fluid to use and not to use, So what is the correct fluid.??

Thanks, Bub

[tom s]

I just use reg 90 wt gear oil.Tom

[Murf]

+1with Tom, This is what I use

The part about not harming bronze is supposed to be important.

Murf

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[sp4spd]

I agree with Murf.
Good discussion here about using GL-4 gear lube in our older transmissions.
http://v8buick.com/index.php?threads...t-read.174330/

[TransAmRIP]

The Sta-lube is what I've been hearing is the best for the trans. Just really wanted to double check ...Sta-Lube it is.

Thanks

[Murf]

NAPA keeps it around here.

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[77 Canamman]

I used Amsoil Severe Gear in mine. Quiet and shifts like butter...

[Hesster1977]

Originally Posted by 77 Canamman

I used Amsoil Severe Gear in mine. Quiet and shifts like butter...

Is that a synthetic, and what weight.? Going to change all of my fluids this year. Last time I did the trans fluid years ago I used synthetic, and it did not like it, shifted terrible.
Thanks

[77 Canamman]

Amsoil 75W90 GL4 spec. 2 quarts. Some say stay with Dino oil, but Amsoil is the best for a reason.

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[Hesster1977]

I would think that the Amsoil would may be the best even if it is very expensive, but my personal experience with terrible shifting and all this mixed input I included below makes me want to play it safe with Stay Lube. Maybe I did not use a "good" or correct synthetic, I can't remember as it was years ago.
Then there is GL4, GL5, GL6, and the various oil weights. I don't really drive it enough and bang shift it to worry about my synchro's.

So as with any forum topic, there are many recommendations, just Google what fluid to use in a Super T10, and you will find a whole bunch of various opinions. Some of these links and comments I included here got me chuckling, and I included it in this thread for your enjoyment

FROM:
"There are several threads on gear oil in early four-speeds that you may want to search, but fundamental point is NO on synthetics."

First Article :
https://oldcarmemories.com/muncie-bo...on-oil-change/
"Stay away from synthetic lubricants since there have been too many Muncie, T-10, and Super T-10 owners who have used synthetic lubricants and have had their transmission synchronizers succumb to premature failure. It is believed that the more slippery synthetic fluid doesn’t offer enough protection for the synchronizers in Muncie, T-10, and Super T-10 transmissions"
"Super T-10 units came from the factory with 75W90 conventional gear lube, it is becoming very hard to find 75W90 conventional in the modern era – 80W90 and 85W90 are more commonly found and both can be safely used as a 75W90 replacement.

And 2nd Article from Motor Trend:
https://www.motortrend.com/how-to/hp...-transmission/
"Even though synthetic lubricants are popular and a new option for manual transmissions is now available, anyone that's had to tear down a newly rebuilt transmission only to replace excessively worn synchronizer rings because of synthetic gear lube may very well be convinced that conventional gear lubricant is the only choice for a vintage manual transmission."

TO:
1. "Pure Urban Myth. The thinner Synthetics are better for Syncros than the Thicker "Dinosaur ****" that everybody seems to use. Muncies and Super T10's are pigs to shift when cold, and can actually benefit from a synthetic gearbox oil."
2. First off, a disclosure, I am an Amsoil dealer. Amsoil makes a GL4 rated 75W-90 synthetic manual transmission fluid that I not only sell, but use in the Ford Toploader 4 speed in my "A" roadster. My customers for this oil have reported favorably on it with no problems at all, and my experience has been good with it also. All this crap about "don't use synthetics" is pure old BS if you have a piece of machinery, a transmission, an engine, or an air compressor in sound mechanical condition, that you want to protect, preserve and get maximum performance from it.
3. First Comment: "I use gm 1234589 or something like that is is called syncromesh lube. sk speed told me NOT to run synthetic cause it will cause syncro crash. 2nd comment: I've been told the same thing, but I didn't listen. I put Amsoil synthetic 75W-90 in my Camaro Muncie about 15 years ago, and the same stuff in my daily driver Chevy pickup 4 speed over 20 years ago. Neither one has any issues yet, so I no longer believe the "experts" when they talk about synthetic gear lubes."

So in the end I am going with the following and maybe change it every few years:
2 quarts of Sta-Lube hypoid SAE 85W90 GL-4 (SL24229) gear oil, Amazon, $13.99 ea.

[77 Canamman]

I also use severe gear in the rear diff. Again, fine product. I did put one bottle of GM L/S additive in it and NO chatter.

[turbo69bird]

Moroso climbing gear lube. Use it in most stick transmissions (unless it calls for ATF ) and rear diffs and you’ll be happy forever . In trans that call for ATF I still mix in some climbing gear lube .