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Type F with Dexcron Mercron

6K views 24 replies 11 participants last post by  krp 
#1 ·
I have got a Th350 trans... and i have been told that if you put type F Trans fluid in it, it usually makes it shift a little harder. But i need to know is if i change my trans fluid, how do i get the trans fluid out of the torque converter, if not can i mix a little Type F and dexcron mercron?
 
#3 ·
My old 1954 hydro had a drain plug in the fluid coupling can so I can do a complete fluid change. Modern torque converters don't. The two fluid systems THEORETICALLY take different approaches to provide soft shifts for Ma and Pa. GM's approach is to drill large orifices and use Dexron fluid which has the property to get 'slipperier' as clutch speed slows down on engagement down to soften shifts. Ford on the other hand drills small orifices and uses type F fluid which gets "stickier" as the clutches slow down but get soft shifts due the the orifice restrictions. Thus if you use type F in a GM tranny, the large orifices and sticky fluid should result in quicker clutch apply and less slippage. In fact, B&M's SlickShift is basically Type F fluid with some magic elixir additions and a different dye color. Use Dexron in a Ford, on the other hand, and the slick fluid and small orifices supposedly results in exaggerated clutch slippage and quick demolition of the tranny.

We had this conversation on this board last year and 4 Jaw Chuck commented that he used to work for a company that formulated both Dexron and Type F fluids and all they did was take the same hydraulic fluid base, dye it to meet the buyers color preference and put the same exact fluid in every can. Food for thought.
 
#4 ·
thanx alot you guys i think that i will just drain it, fill her up with some type f. run it for a while then change it again in a month er so and re fill it with type f...

P.s. Willys, are you saying that basically i can use any hydraulic fluid... if so which do you prefer...?
 
#10 ·
You can buy a decent shift kit for under $100, which when installed will really wake up your tranny. You can, if you are careful, install it yourself. Just follow the instuctions, to the letter. A tranny shop will probably install it quite cheaply, if you are not sure of yourself.
 
#12 ·
My mistake.......

One would think. If you have a manual valve body in a tranny, you would also have a shift kit, amounst other stuff, and it would be hitting pretty hard as is. Unless something is slipping in there to make it "slushy"

Just my thoughts.....I may be wrong. I was ONCE before.
 
#15 ·
Depending on the guy who built the tranny there may or may-not be accumilator springs in the tranny.

Some check balls are required in the forward shift pattern FULL manual valve body.

in a reverse shift pattern vb the check balls usually are all removed.

I have used Dexron fluid for decades.

Type F has fewer friction modifiers in it. Some folks think the Ford fluid provides firmer shifts.

This is a discussion that has been going for years.
 
#16 ·
Crosley mentioned the spring in the accumulator, if it still has a spring, remove it. This will give you a firmer 1-2 shift.

Is this the same tranny that you posted about shifting too soon?

If so, with that manual valve body just move the selector a little later when you want second.:p
 
#17 · (Edited)
Thanx again you guys.... i have rebuilt a few th350's roughly 5-6 and all of them were for my buddies mud trucks.. of course all of them were full manual... mine is my daily driver with a full manual and a rachet shifter in my chevy truck...but i took a class just before i graduated in a college which taught me just the basics.. so i had a shop rebuild my first one i told them what it was going in and they had it hitting so hard it made my 400 hp 350 feel like it was going to lift the front tires off the ground.. of course it chirped through all gears.. ever since then i haven't been able to find the guy who built my trans of find out how he did it... i have experimented a few times and most were good but i had some bad ones... i was just wondering if the type F would make the full manual hit harder through the gears.. if not what can i do to make it hit harder.. drill the holes in the seperator plate bigger for more press... or what? can you guys help me out...

Hey.. BstMech i don't know but i had a guy tell me that if you put a bolt in the accumulator a little shorter than the spring that would make it hit harder from 1-2 but it seemed to not make any difference....but if i was to take the spring out you think this would help 1-2....? And Yeah its the same tranny i just changed it to full manual.. it had a stage two B&M in it when it just wasnt cutting it for the mud so i put the full manual one out of the transpack in there and seemes to work much better.... but doesn't hit.. like some of the trannys i had before with manual valve bodys
 
#18 ·
Since there are 2 accumilators

I recommend leaving the springs in on any tranny used for full or part time street use. It makes for longer life on parts.

Even on some full race stuff used off road I use the springs.

Reducing the fluid feed to the acc works well.


BstMech said:
Crosley mentioned the spring in the accumulator, if it still has a spring, remove it. This will give you a firmer 1-2 shift.

Is this the same tranny that you posted about shifting too soon?

If so, with that manual valve body just move the selector a little later when you want second.:p
 
#19 ·
Well, I wasn't talking about the intermediate accumulator, but the one on the side of the tranny. It seems to only effect the 1-2 shift but I'm not sure if it's a 1-2 accumulator only.:embarrass

I have just gone through my th-350 to convert it to a long tail. It was rebuilt back in '97 and the guy that rebuilt it left the spring out of that particular accumulator. I drove it that way every day to work twenty miles each way for about three years. When I tore it apart to make it a long tail I went through it pretty thoroughly looking for any tell tale signs of damage. I found none, to the case or otherwise (that I knew to look for anyways). That motor/tranny sat for about two years and I have recently put them in a truck and started driving it again, no problems to this day (knock on wood?).

I guess I have a question and that is, what should I be looking for as far as damage from running one like this? I know there's issues with having a lot more overlap between gears as opposed to going with a quality shift kit, is that part of the problem?
 
#20 ·
the acc in the side of the T-350 tranny case is the intermediate accumilator.

It seems to be better to have a spring in there rather than the piston slamming back and forth. An aluminum rod will restrict the movement of the piston with little long term damage.

You can also restrict the oil flow with a rod inserted into the gallery under the plug next to the accumilator. A 5/16 bolt cut off is a close fit.



BstMech said:
Well, I wasn't talking about the intermediate accumulator, but the one on the side of the tranny. It seems to only effect the 1-2 shift but I'm not sure if it's a 1-2 accumulator only.:embarrass

 
#25 ·
SAE requires all fluids to be compatible, and can be substituted if necessary when one or another is not available. In a stock trans, type F can cause your shifts to be a little firmer,,, if you like the change,,,,,, or harsher if you don't. If you have a fresh trans and a good quality shift kit use whatever fluid you like, but the fact is you won't find much difference in the shift. Gil Younger recommends dexron. He's been in the business for a long time and has fixed a lot of trans. I think his opinion should account for something. Either way, any fluid should be fine.
 
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