I would like to know the thoughts, opinions and experiences on the tranny fluids that are availible. This is for a 700R4. Ive seen Dextron/Mercon 4 and now they have 5 I believe. Also synthetic Mobil 1, Royal Purple and others. Also there is the B&M stuff. I useually get Valvoline or AAMACO brand regular stuff. Im doing this rebuild/upgrade myself and want to do it right and get the best I can. Ive used B&M one time along while back, but didnt notice any differences with it. Not as claimed anyway. Is it just expensive junk and a wallet lightener or is there a hidden benefit. Educated answer on that please..no bottle readers. I can do that myself. What are the ins and outs of the synthetics. Better, just an enviromental thing or bad if you have a hi-po setup? Any input is appreciated and experiences are best. Thank you all!!

I'd stick with regular Dexron.

B&M Trick Shift is cheap Ford Type-F fluid with a blue dye added so that they can charge more. It has different friction modifiers for the asbestos-backed clutches in old Ford transmissions, which makes it "grab" quicker on a GM paper clutch.

Well thats interesting info! So which Dexron was used in 1991? Thats the tranny year but its been rebuilt. I think there is only one now availible right? 4 or 5 or 6..something like that.

personally, I stick with standard dexron/mercon III. I've had to many issues with sythetics to run them in anything other than my harley, which I do because of the heat(and I'm still undecided on that).

I had a trans that I built for a buddy of mine in a 95 4wd tahoe. He was running a synthetic atf. It kept having slippage problems. I ended up pulling the trans and checking everything. I couldn't find a problem, so I re-assembled it. All same parts. Put it back in the truck with regular dexron/mercon III, not problems in over 30k now.
- My opinion, the slickness of the sythetic wasn't allowing the clutches to grab fully. Those who like synthetics may argue otherwise, but that was the only thing that changed and it works fine on regular fluid. FYI, all pump pressures were check before and after and all remained constant, just under/at peak reccomendations from the ATSG manual.

Mostly, just change it and the filter every 30k. Too many people are still running on factory trans fluid and factory gear lubes with way too many miles. There is a service life to all oils, after which they begin to break down and many become caustic.

It doesn't matter. All the Dexrons are compatible with earlier versions.

If you want the best use Lubrication Engineers Monolec 7500

Mikz86TA, I have tried just about every brand of ATF in the past 40 years and never seen any difference between any of them. I have found that the 2 best things to do for an auto trans is to run a trans cooler in addition to a deep trans pan with extended pick up. I have never had trans problems in any car I have done that with. The turbo 350 in my `74 El Camino has well over 200k miles on it and it still shifts hard and reverse works just as good as it did 10 years ago. I also change the fluid and filter every year regardless of mileage and add 1 can of Trans-X. I always buy the least expensive fluid I can find. An old time 40 year GM mechanic told me about the Trans-X 30 years ago and I have used it since.

Dexron III in my tranny but then I also change it at least once a year. Dexron III in my daily driver and it's been in there for a few years now.

Tranny oil and filter should be changed every 5 years or less. Change it regularly like you're supposed to and it doesn't matter what tranny oil you use.

What does your owners manual say for changing the tranny oil. How old is your diff oil, brake fluid, antifreeze? All these need to be replaced regularly not just engine oil.

Since I live by the motto 'Maintenence is cheaper than repair' you can tell that I regularly service everything on all my vehicles. Nothing from a PCV valve to the wheel bearings get overlooked. I just did the diff a few months back. The tranny fluid isnt but a year old. But my recent issue with the band is resulting in a pull out and fix. So, I just wanted a few opinions. Seems like there wasnt much past debate on it. DM3 is whats in it now...or was. Its Valvoline. I had Aamco in it B4 that. Most of the time I stick with conventional and Valvoline. The Trucks motor oil, the previous trans fluid in the TA and the gear oil in the TA is all Valvoline. The TAs engine oil is Mobil1 synthetic. Just what I did after the 355 was built. Just curious about what others have experienced. I see now that the B&M is B&S which I thought it was anyway. But the other day the D6 cought my attention and raised awareness to learn all I can. THX

I used Wal-Mart brand Dexron the last time I serviced my 700r4, and it shifts just as good as it did when I used the more expensive, brand-name stuff the time before. I have to agree with the other guys who said the most important thing is just to make sure to change the fluid and filter at regular intervals. As for B&M, they've been quite successful in the snake oil business over the years. Lol. My 700r4 has 238k on it, and it still shifts quick and firm. All I've ever done is service it regularly, not abuse it too much, and I did install B&M's 3/4 shift valve about 8 years ago.

stick with the dexron the b&m stuff or the type F will only reduce the life of your clutches. as stated obove it grabs the clutches faster but not necessarily better. I even run the dexron in my 68 mustang shifts are smoother but still firm.

I dont know about the 700R4, but I know on my last board, a few people swapped their DexIII for the new DexVI with really good results on the 4t65e. I guess the dexron 6 has better friction modifiers and better hydraulic properties, along with a longer life. Plus, it is officially backwards compatible to be mixed with / added to, and or refilled into a DEXIII tranny. They said they felt firmer shifts, and all the actions of the tranny like going into gear ect. were quicker.

If I were completely rebuilding a tranny, I would use the new dex 6 and change it at a 30-40k mile interval. If i was just doing a pan drop / filter, I would stick with Dexron III. Just my $.02