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Easy Question - What Transmission Fluid

MoparHusker

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Judging by the multitude of threads and posts, does not seem to be a straight forward answer. I will apologize up front for the long post.

I just joined up yesterday and am hoping to get an answer to this.

I have a 1973 Charger with a 69 440 and a 727 transmission that has not run or been driven since 1996. I am in the process of collecting parts, so I can get it back on the road and driving again, Phase 1 of the project.

One of the questions I had is what type of transmission fluid to use. In 1993 I pulled the transmission out and had a mechanic from work tear it apart and do the work I did not have tools for. I swapped in a clutch housing that was from a tranny that was behind a hemi, so could take 5 clutch discs instead of 4 (memory may be failing me, so please let me know if I am incorrect). Additionally I put in a Turbo Action shift kit and a 5.0 kickdown. I also had an additional 3 springs added (can't remember what the part is called) bringing it from 9 springs up to 12. My goal was to get a firmer and crisper shift.

I have done several looks through quite a few threads on the fluid type to use and it seems like there are several choices. I figured out that back in 1993, I put in Dextron III / Mercon. I was at Firestone yesterday and asked the manager there and he said I needed to flush out the transmission and put in ATF +4. His reasoning was that his brother had put in Dextron in his Charger transmission and it ended up burning it up. At the time I did not think about the fact that his brother's car is a newer Charger, so may be irrelevant to the discussion here, but it did scare me until I started doing some looking again.

I have seen a number of different answers on here and am still not 100% clear what direction I need to go. I will probably be draining the Transmission anyway, so there will not be a better type to switch types if that is what I want to do. I think I have seen a number of posts that say you can stay with the Dextron III and that it is a little more slippery than the Type F and the ATF +4. I also saw someone say that you can mix the Dextron III and Type F to whatever blend you want to firm up your shift however much you want. Others have said that ATF +4 is great and that is the way to go. Would I be correct in assuming that the Type F has a firmer shift and is less slippery than the ATF +4? At this point I am thinking I will probably move away from the Dextron III, but not sure between these other two. Also, need a little firmer answer on whether these can be mixed. I would probably drain the tranny, fill up the new Torque Converter and put it in and then fill up with the new fluid, so assuming there will be some of the old stuff in there yet if I do not flush it.

I will probably try calling a transmission shop locally as well, but hoping there will be a definitive answer from someone on this forum.

Thank you!
Allan
 
Trans fluid is usually forward compatible, meaning ATF +4. Is ok. Dex/merc turned into "ATF"

I just run ATF. I did run type F a few years ago, and it did firm up the shifts, but people like it or dont. My only concern going to a synthetic fluid is because the molecules are the same size, leaks can happen. Ive had that happen w syn motor oil
 
Jmho , but dex 3 , type F , no matter what you use the main thing is to keep the fluid cool and clean. Myself I prob would not switch a trans to synthetic that had been using dex or F.
There will be guys that know way more than me give you some ideas and advice.
 
Don’t switch now. This is what I always use.

91FBE14A-7AAA-4311-80F9-9A64F4E85E3D.jpeg
 
Look up the specs on these fluids and you will see the Mopar ATF+4 is superior.
Mike
 
Look up the specs on these fluids and you will see the Mopar ATF+4 is superior.
Mike

I have run type f since 1969 or so , in race cars and street cars , still using it today , like the previous poster sad, cooling is where its at .
 
I have run type f since 1969 or so , in race cars and street cars , still using it today , like the previous poster sad, cooling is where its at .
Hell, I have used type F for 40 years in my 66 SW but after reading the specs I went straight to ATF+4 for my 65 Coronet. I will use it in my 540 Belvedere also.
Mike
 
From what your describing I would just use type F. The +4 is better, it also has a healthy price. If you want a synthetic go w the +4. We will likely switch to the +4 on our bigger hp tranny builds. I would not use dexron in a mopar.
 
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ATF +4

Easy to find and relatively cheap at wal-mart.
 
Here is the page from the 1969 and 1970 factory service manual. DEXRON is the fluid the folks who build your Car say to use. There is no letter T in dexron.

Non of the factory chrysler books mention type F

Type F has the worst lubrication quality of any ATF. If you want firm shifts then build the trans to suit.

E153A538-A249-43DB-B56E-AB88BA6C2899.jpeg A63426C2-3051-48F5-A905-CD2CD02574B9.jpeg
 
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Here is the page from the 1969 and 1970 factory service manual. DEXRON is the fluid the folks who build your Car say to use. There is no letter T in dexron.

Non of the factory chrysler books mention type F

Type F has the worst lubrication quality of any ATF. If you want firm shifts then build the trans to suit.

View attachment 1138106 View attachment 1138112

Tom Hoover said a bunch of chrysler racers were using type f fluid w/ great success , at a chrysler drag racing seminar once in OKC . We/I have run it ever since .
 
I’m aware the racing folks love type F. They are running for a few minutes and shutting it off.

I don’t see a need for it on a street driven car running down the road for hours at a time. Not what it’s designed to use, and has Poor lubrication qualities.
 
I'm surprised the ol' "executive that didn't wanna spill his coffee during transmission shifts" story hasn't been posted yet....:p

I switched to ATF+4 awhile back, for it's better heat protection driving the higher-stalling custom converter around on the street.
 
Huge thank you to all that have replied. I definitely think that no matter what option I would choose, I can't go wrong as it seems that all of you have had success with what you are using. It looks like there probably are 4 responders that favor Type F, 4 that favor ATF+4 and 3 for staying with what I have. So, about evenly split.

Today I called three different transmission shops and the service department of one of the local Dodge dealers.
1. Parts guy at Dodge dealer did not seem to know very much about the fluids, so passed me back to the service department. That guy said the ATF+4 was a good fluid and did not see any issues in switching. He also looked and said that they the ATF+4 and Dexron III were compatible, so I would not need to flush the old fluid out.
2. First Transmission guy said to stick with the Dexron III and that I probably didn't need to switch to anything else.
3. Second Transmission guy seemed extremely knowledgeable (Fort Dodge Transmission, Fort Dodge, IA) and said that he will be using the ATF+4 in his Chevy transmission he is building. He said the detergents are good and overall should perform well for me. Also said I would not need to flush the system, just drain everything out that I can and fill with new fluid.
4. Third Transmission guy also was extremely knowledgeable (Rocket's Transmissions, Ames, IA) and said the ATF+4 is a very good transmission fluid. He took some time and asked a lot of questions, so I very much appreciated the discussion. He said that he did not think the ATF+4 would change the shift at all over the Dexron III and was not sure how much of a difference the Type F would make. Could be noticeable, but maybe not by that much.

I do hate calling places, just to get information, but in the long run it also helps me get to know some of them, so when I do need to have something serviced and can't do it myself, I know where I will turn to.

I additionally asked questions about installing a transmission cooler as I had some engine overheating issues when I last had the car on the road. With the higher stall converter that is in there currently (2800 stall, getting replaced with stock type converter purchased from Fort Dodge Transmission), it probably was spinning up some extra heat. It was too long ago for me to remember if this was happening before the Converter upgrade or did not start until afterwards. It was very good information and I think at this point I am going to stick with not doing an external cooler and see if I still have overheating once the car is running again. If it is, I will try to track that down and it may end up that I get a new radiator (3 or 4 core) and then we will see if that may be the issue. Possibly could look at electric fans, could be that my timing is off too much one way or another that could contribute to the overheating.

Anyway, too much information. My decision on the fluid type is that I am going to switch to the ATF+4. I ended up purchasing the Valvoline ATF+4. In looking at prices, seemed like Amazon, Wal-Mart and a few others were at $6.64 per quart and then I found the best price at Menards of all places. They had it for $4.97 per quart and they are doing their 11% off right now, so final price will be $4.42 per quart.

Also, got the back rims today, Cragar 342 Black D Window, 15 x 8. The fronts are supposed to be here tomorrow. My daughter says the car will look "sick" with those rims on there. Must be a generational thing as I am not sure whether "sick" is good or bad.

Cragar342.png


Thank you again for all of your help on the Transmission fluid!
Allan
 
If the trans has not been used since 96, I would plan on at least a reseal and/or rebuild in the near future.
If the car has sat for that long plan on replacing all rubber items and fluids and anything that the fluids reside in that have seals. Hoses, water pump, thermostat, heater core, radiator, Soft plugs if not brass, wheel cylinders/calipers, hoses, and on.
Remember that the Service Manuals were written in the sixties for the most part, and the fluid/seal technology then was no where close to todays stuff.
 
I’m aware the racing folks love type F. They are running for a few minutes and shutting it off.

I don’t see a need for it on a street driven car running down the road for hours at a time. Not what it’s designed to use, and has Poor lubrication qualities.

how do u account for the fact that I have been using it in all my mopars for over 50 yrs. , no lubricating related problems in street or race cars , curantly have it in my 505'' barracuda street car ---------------end of story.
 
Oh the type F works, and it won’t kill the trans. Many use it. But it’s not this great thing. You didn’t gain anything, except it made you think you were “upgrading” because racers do it.

At least atf+4 is an improvement for the lubrication and heat capabilities of the trans.

so use what makes you happy.

I’ve never used any of the type F in Any of my 60+ mopars or customers cars and they work great and don’t slip. None of our mopars EVER came from the factory with type F. How do you account for these 2 happenings?
 
The main thing about type F vs ATF is:

Don't mix them.
 
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