Best ATF?
Thread Starter
Melting Slicks
Joined: Aug 2000
Posts: 2,961
Likes: 1
From: Sealy Texas
Cruise-In III Veteran
Best ATF?
I've completely rebuilt my 700R4 in the '82, going so far as to not only replace any part that could possibly break, but also mic out each and every steel and clutch to make sure I have my tolerances within spec. I installed the Transgo shift kit as well as a special cooler setup I have that's right up front, underneath my new (universal) AC condensor. I have a brand new converter with a higher stall than stock, and I'd like to know what the best ATF to put in it is for longevity.
The motor I've built will have about 300hp peaking around 5000RPM. It's still a CrossFire so it'll be quite torquey. After that it's into 3.23 gears I'm putting in the back and 275/50R15 tires.
I'm thinking synthetic?
The motor I've built will have about 300hp peaking around 5000RPM. It's still a CrossFire so it'll be quite torquey. After that it's into 3.23 gears I'm putting in the back and 275/50R15 tires.
I'm thinking synthetic?
Race Director
Joined: Nov 2002
Posts: 12,142
Likes: 54
From: Taylor Michigan
B&M has a fluid called "Trick Shift" used in all there performance transmissions. [GM Ford Chrysler] I was on contract with them several years ago, and it`s in reality "Ford type 'A' ATF" that I used in a B&M Torqueflite 727. Shifts hard and solid . 
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
The heavy duty truck automatic manufacturers (Allison, ZF) all know that synthetic fluid is lightyears ahead of organic oil when it comes to reliability. My 36 year-old THM-400 has never been out of the car and has always had Dexron in it (and I'm not about to change that now). That being said, if I ever have to pull it and rebuild it, it'll have synthetic fluid but into it.
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Thread Starter
Melting Slicks
Joined: Aug 2000
Posts: 2,961
Likes: 1
From: Sealy Texas
Cruise-In III Veteran
OK So I was pretty well sold on synthetic in the first place - so I guess the next question is, which brand, and which TYPE? I've seen Mobil 1 at Wal-Mart and Autozone so far, but only seen the MERCON (which I thought was for Fords) carried. However I read the label and it said for 2005 and earlier GM cars/trucks, it would work also. For 2006 and later, to use the Dexron version. Any thoughts?
Race Director
Joined: Jul 2004
Posts: 12,706
Likes: 329
From: Scottsdale Arizona
I have a slightly different view.
I'm a great believe in synthetic oils. They certainly last longer and some of them (Mobil 1 in particular) clean better, From seat of the pants testing in my own cars, I believe that the engines pull better on synthetics, I would assume by reducing friction. That's certainly what the sales research says. I like to use synthetic lubricants in everything EXCEPT
Automatic transmissions. I did try the trick, synthetic fluid in a TH350 and was never happy with the way it felt. Remember that ATs work by having clutches and steels rub together while the gears are switching to allow the gear to gradually engage. I found that with the synthetic fluid, the tranny slipped too much and then engaged a little too hard when the clutches finally locked. I would immagine that the parts, bushings in particular, will last longer but not sure if the higher temperature stabililty buys you anything. The internal seals will be damaged by the heat, regardless of the fluid type.
I'm with Marshrat. I like simple Dextron III from Castrol and change it rediculously often.
I'm a great believe in synthetic oils. They certainly last longer and some of them (Mobil 1 in particular) clean better, From seat of the pants testing in my own cars, I believe that the engines pull better on synthetics, I would assume by reducing friction. That's certainly what the sales research says. I like to use synthetic lubricants in everything EXCEPT
Automatic transmissions. I did try the trick, synthetic fluid in a TH350 and was never happy with the way it felt. Remember that ATs work by having clutches and steels rub together while the gears are switching to allow the gear to gradually engage. I found that with the synthetic fluid, the tranny slipped too much and then engaged a little too hard when the clutches finally locked. I would immagine that the parts, bushings in particular, will last longer but not sure if the higher temperature stabililty buys you anything. The internal seals will be damaged by the heat, regardless of the fluid type.
I'm with Marshrat. I like simple Dextron III from Castrol and change it rediculously often.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Allison has a product they call "TranSynd" which is the synthetic they recommend. I don't know what company makes it, but if you call up a Detroit Diesel service outfit, I bet they can steer you to the source. I have no knowledge of whether it "acts" differently than other synthetic ATF's, but I know Allison was very concerned about clutch frictional behavior differences and settled in on TranSynd.
