fast442

wondering if anyone suggests a good Trans fluid to use on my 1969 Cutlass 442 with a turbo 400 three speed trans.

Someone (Chevy guy) said, Dexron 3, but I wasn't 100% on his answer.

Someone else (Mustnag guy) said, use Castrol Mercon V Automatic Transmission Fluid, since it states it's good for Ford and 'other GM cars'. Again, not 100% on his answer.


Lastly, is there a way for me to read/match numbers on the transmission to tell if it's the original?

Allan R

Here's a link that will help you find the trans identification plate, and the recommended fluids on SMT. Look for that under periodic mtc on page 0-13. If you also have your owners manual check that too. I just looked up manual trans in my 72 owners manual - says the 4 speed will take 2 1/4 pints. Doesn't say what fluid, but I searched the web for manual trans fluid and Royal Purple seems to pop up with their Synchromx product. Have a look: http://www.royalpurple.com/products/...mission-fluid/
Not saying buy it. Saying call them and ask if it will work in your 4 speed. Personally I don't see why it wouldn't.

Remember one thing: AT fluid is not the same as MT fluid. So I don't think I'd be adding Dexron 3 to an SMT.

MDchanic

Allan, he said he's got a TH400 .

For a TH400 or TH350, anything on the shelf that says Dextron should be fine.

Dextron III, Dextron IV, Dextron V, Mercon/Dextron, whatever.

All newer formulations are "backward compatible."

The only thing I'm not sure of is whether you could use Dextron I, but I doubt you could find any, so it doesn't really matter.

- Eric

Allan R

D'oooohhhh! Man I need new glasses. Thx Eric. 2 questions, even though the newer formulations are backwards compatible - aren't they more expensive than good ol Dexron 3 products?

Is it worth changing to a fully synthetic tranny fluid?

Rickman48

What isn't??
Just from a month ago!!

Allan R

Ya got me. It's so hard to keep up with things these days. I usually wait for sales and stock up on auto fluids. Last good deal I got was Castrol synthetic oil 5W20 for 5.99/Litre (that's good up here). It seemed to really make a difference with cold starts in sub zero temps.
So, would you change your tranny fluid to synthetic?

MDchanic

As far as I know, all modern ATF essentially IS synthetic - maybe not 100%, but near enough.

Someone with far more knowledge about petrochemicals than I may be able to shed light on this, but I believe that they need to use "synthetic" production techniques to provide the consistency in viscosity that ATF needs through a wide range of temperatures.

All "synthetic" really means is that the base oil is made up of consistently sized molecular strings, rather than the wide variety that results from good old fashioned cracking. You can get this from synthesizing the molecules in a lab, but I believe they just use more modern refining techniques to achieve the same thing from regular old crude oil.

Also, I believe that there is no significant difference between the high-priced brands, like Royal Purple, and the more "normal" brands.

- Eric

fast442

Thanks Allan and Eric! This is all great info. Exactly what I needed to find out. I'm glad I asked before buying and pouring in the wrong fluid.

Funny, when I went to my local Napa, they offered a dozen kinds of Trans fluids, so you're right, Allan, about 'keeping up with thngs'. And don't even get me going on the 23 different kinds of transmission 'additives' they had on the same shelf.

Allan R

I know I talked to you about this last Nov but thought I'd share this with the rest of the forum. One of my neighbors was an HD mechanic in the North and he told me that ATF was the go to fluid for power steering too. He said it has a wider range of fluidity under harsher temperature ranges. Didn't gel like regular PS fluid does in really cold sustained sub zero temps. That would be consistent with your comment. BTW, I don't remember if I thanked you for your help back then. If I didn't - Thank you. You were a great help. Your check should have arrived by now . It's the same amount I paid you for some AC advice

That's different from what I was told. Story I got was synthetic was produced in labs instead of refineries. Hmmmm. Sounds like a scam. I thought labs were a breed of dog.. or a place the narcs raided for crystal meth

Don't let Stacey David hear you talking like that. Although I gotta admit I'm curious to know if you're right

MDchanic

Don't worry, I got it...

Not since the Germans were looking for "alternative fuel sources" about 60 years ago, as far as I know, at least not in any quantity.
My take on it is that its faster, easier, and cheaper to refine it out of actual petroleum than it is to synthesize it from other substances, such as vegetable oils and animal fats.
Remember, most plastics, fuels, and drugs are made from chemicals that are refined from crude oil, as it is the easiest place to get the various hydrocarbon structures needed to make them. On that basis alone, it would be silly if motor oil itself were made from something else.

Like I say, there may be someone here who knows this from experience - I have only a vague knowledge of the chemical processes that would be needed to achieve this (and I know they would be a PIA).

- Eric