Dexron

I had a brand X front wheel drive car that were know for trans failures. So I changed the ATF once a year, the trans is still working fine.

and don’t just pump it out the cooler lines, remove the pan and clean it out. Have you ever noticed that gray film inside a trans pan? Isn’t that contaminating it? Yes can/will/does.

For those who say they don’t get contaminated, have you ever taken some apart and looked in all the “corners” of the trans and see what kind of crap “can” accumulate in there?

bottom line is change the fluid and drain the converter.

Lots of folks seem very zealous about changing fluid in their automatic transmissions so I decided to consult the factory service manual. The 1974 manual I was looking at stated, "Fluid and filter changes or band adjustment are not recommended for normal passenger car usage." That's in the Lubrication and Maintenance section up front if anyone would like to see it. Section 0

Like the time I put 20% gasoline in my 300D. Mercedes mech says, "You're friggin nuts". I show him in the factory owners manual; the recommendation by MBZ to add gasoline to the diesel. And what did he say? Deer in headlights!~! I NEVER change my trans fluid. If your trans fluid needs changed, then your trans is toast. Nothing wrong with changing the filter, but if the fluid is nice, you can save $50. These ripoff shops that suck out the fluid thru the dipstick tube and just add new fluid are doing a disservice cuz they're leaving in the old filter and adding fresh high-detergent fluid that going to clean out all the nooks and crannies and clog the old filter. Guy just paid over $100 to have the f&f changed in his C6 cuz his fluid was BLACK...hahahhahaha. Folks bring their transs in with it and the converter all filled up with new fluid...another $50 I just made; cuz that chits goin into MY car! My brother is constantly changing the oil in his BMW; 100% SYNTHETIC!! I say, hey I might be able to find a use for that....Somebody stop me...

RustyRatRod said:

If the fluid in the converter really bothers you , you can disable the ignition, remove a transmission line and spin the engine over with a drain pan under the line.

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A seen a feller who once did a flush by opening the trans line at the radiator and filling the trans as the line drained out...engine running. Disclaimer I am not recommending this, just saying I watched someone do it once...

CudaFactHackJob said:

Like the time I put 20% gasoline in my 300D. Mercedes mech says, "You're friggin nuts". I show him in the factory owners manual; the recommendation by MBZ to add gasoline to the diesel. And what did he say? Deer in headlights!~! I NEVER change my trans fluid. If your trans fluid needs changed, then your trans is toast. Nothing wrong with changing the filter, but if the fluid is nice, you can save $50. These ripoff shops that suck out the fluid thru the dipstick tube and just add new fluid are doing a disservice cuz they're leaving in the old filter and adding fresh high-detergent fluid that going to clean out all the nooks and crannies and clog the old filter. Guy just paid over $100 to have the f&f changed in his C6 cuz his fluid was BLACK...hahahhahaha. Folks bring their transs in with it and the converter all filled up with new fluid...another $50 I just made; cuz that chits goin into MY car! My brother is constantly changing the oil in his BMW; 100% SYNTHETIC!! I say, hey I might be able to find a use for that....Somebody stop me...

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Ok, tell me about the 20% gas. Been thinking along those lines of increasing the cetain level in the diesel for my truck. Also I read that same thing about trans fluid back IN 73 and earlier.

CudaFactHackJob said:

Like the time I put 20% gasoline in my 300D. Mercedes mech says, "You're friggin nuts". I show him in the factory owners manual; the recommendation by MBZ to add gasoline to the diesel. And what did he say? Deer in headlights!~! I NEVER change my trans fluid. If your trans fluid needs changed, then your trans is toast. Nothing wrong with changing the filter, but if the fluid is nice, you can save $50. These ripoff shops that suck out the fluid thru the dipstick tube and just add new fluid are doing a disservice cuz they're leaving in the old filter and adding fresh high-detergent fluid that going to clean out all the nooks and crannies and clog the old filter. Guy just paid over $100 to have the f&f changed in his C6 cuz his fluid was BLACK...hahahhahaha. Folks bring their transs in with it and the converter all filled up with new fluid...another $50 I just made; cuz that chits goin into MY car! My brother is constantly changing the oil in his BMW; 100% SYNTHETIC!! I say, hey I might be able to find a use for that....Somebody stop me...

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true. the propwer way is to use a flush machine, flush the trans, then drop the pan and change the filter. You use alot of fluid and it would be costly but thats how Id do it.

I think most know we use trans fluid to get heavy black dirty grease off our hands it’s a good cleaner by itself, motor oil does the same. If the filter ain’t broke there should be no trash inside trans so if you’re having a hard on about it change em both and feel better

Gas in the diesel fuel was a common practice in cold weather to prevent gelling.

Ceedawg said:

Ok, tell me about the 20% gas. Been thinking along those lines of increasing the cetain level in the diesel for my truck. Also I read that same thing about trans fluid back IN 73 and earlier.

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Ceedawg said:

Ok, tell me about the 20% gas. Been thinking along those lines of increasing the cetain level in the diesel for my truck. Also I read that same thing about trans fluid back IN 73 and earlier.

Click to expand...

Unless your truck is "old-school diesel" with mechanical injection pump and none of the super-high-pressure common-rail or Unit Injector systems, I would NOT put ANY gasoline in with the diesel fuel. Newer diesels are very sensitive to fuel lubricity and if that gets too low you'll destroy your injection system which is sometimes more expensive than replacing the entire rest of the engine. Just get one of the additives they sell at parts stores, I've used Stanadyne fuel additive and Power Service Diesel Supplement with good effects in my brother's 2005 VW Passat TDI, they both contain cetane boosters for better cold starts. Also the quality of diesel fuel varies widely compared to gasoline, I tell my brother to always fill up at our local Cenex station near our house, they sell "Roadmaster XL" premium diesel which has improved lubricity and cetane versus "regular" diesel fuel and it's not much more expensive.

For ATF, last drain/filter/fill I did on the 904 in my Duster I just used O'Reilly brand universal synthetic ATF, I think it's Dexron-based. And there was still a few quarts of fluid in the converter I didn't drain which was mostly Lucas universal ATF; I was only replacing fluid because my valve body cracked and I had to swap it out, fluid was still clean and clear with no bad smells. That was summer of 2020, since then I've put a few thousand more miles on it and beat the hell out of it at multiple track days with no issues. Fluid type on the old Torqueflites really doesn't matter much IMO. Similar story for the 727 in my D200 pickup, it was a few quarts low when I got it and had no idea what fluid was already in there so I just topped it up with the same O'Reilly universal stuff. Also put solid ~5000 thousand miles on that since topping up the fluid and even towed my Duster to the track 120 miles away and back up and down the steep grades of I-25 along Colorado's front range; again, zero issues. YMMV but that's what's worked for me so far.

Kinda interesting side-story, when my VB cracked I lost about 95% line pressure in the trans; I managed to baby it almost 20 miles to my house from work on the freeway and everyone here was saying my trans was probably toast. Well to my surprise I dropped the pan and everything looked completely normal. I think it came down to just having a basic understanding of how auto transmissions work; I knew since the line pressure was low there was very little force to apply the clutches. So I was verrry ginger with the throttle and watched the tach like a hawk; if I noticed the RPMs rising (trans slipping) at all I'd let off the gas then gradually get back on it. I also found that as the RPMs went up thus spinning the front pump faster as I slowly accelerated there was a bit more grab from the clutches and the trans slipped less/not at all as there was more fluid flow and thus slightly higher line pressures. Overall I was very lucky but I am pretty confident my basic understanding of what was going on helped it survive to some extent.

I think it was in a 1973 MBZ 300D Owner's Manual that recommended the gasoline in the diesel. OEM manufacturers' recommendations for adding gas are based on new vehicle operation; lubrication. An old diesel that's getting blowby has lower compression so it needs more combustibility to perform/start as it did when new.