Mercon V and Mercon III - backward compatible?

Another thread elsewhere morphed into this discussion. I posted something and somone PM'd me based on that post and I was politely requested to start a new thread in this forum so we, here in this highly regarded forum we might explore <g> this more deeply, where more people might see it and chime in. The questions was (indirectly as the previous thread as it morphed) "Can you put Merc V ATF into a Merc III ATF designed tranny?". Some of us said..."no, don't"... and were fairly questioned why we felt that way. In reply I posted what follows below ... now mind you.. like I said in that post (and as you read below) I cannot claim any high ground but this may deserve some airing ... so this forum can have a reasoned position. Soo....Have at it guys!

We start...Hang onto your funnels....

What I posted:

"The issue of dual compatability and Mercon ATF backwards compatibility has been long debated. I do not claim to have the "only right answer" but will share my thoughts, for what they may be worth.

First before I forget here is link to a similar thread on a sister site, FORD TRUCK FORUM

http://www.ford-trucks.com/forums/s...&threadid=93464

Anyway here goes, in sort of numbered "bullets":

1. Mercon V has some different characteristics than Merc III. There are different friction modifiers for one thing. While you think of oil as a lubricating fluid, in a "wet clutch" setup, what happens at the molecular level at the clutch plate/friction surface is apparently a pretty wierd complicated thing. When it's wrong you get shudder, excess slippage etc. If you use Merc III where you should use Merc V those are common complaints.

2. I believe, but am not sure, that friction material for use with Merc V may be different in characteristic than in the transmissions designed for Merc III. The transmissions using Merc V, as a rule (to my knowledge) tend to use modulated solenoid activation of some clutch aspects (like torque convertor). I think the clutch material was adjusted for the microscopic slippage that is built into these things (yes the computer actually not only allows, it programs some slippage!).

3. Some Merc V does not meet the differing specs for Merc III (!) [Most does].

4. Dual compatability fluids like synthetics can be used both places. (!)

5. The manufacturer has recommended against using Merc V in transmissions designed for Merc III.

Ok all that said... knowledgeable folks have said that using a Merc V that also meets Merc III standards should not cause a serious problem. I do believe any problem would be at the fluid/clutch/steel interface level and manifest itself in excess slippage or grabbiness, I do not know which.

So, with all this confusion..... WHY would you want to take any chances?

Hence my advice, do NOT use MERC V is a transmission designed for MERC III. If you want the (semi) synthetic benefits of Merc V, go with a full synthetic that says it is useable in a Merc III application.

I hope this adds something of value to the discussion and doesn't just add to the confusion."

[Some edits for clarity to the previous post were added. No words were harmed in the process]

I recall a posting from a Ford engineer who said that the specs for Mercon V and III were different enough that you could not have one product that meets both specs.

Not to get too off of the topic, but what about the older types of Ford fluids, like types "A", and "F" I think they were called. Somebody once told me that they were used on the very old models before overdrive, and computer control. There is also something that is only used in Hondas. I'm sure that there are differences in all of these. I wonder if there is some sort of camparison chart from a fluid manufacturer, or auto manufacturer.

"F" is very "sticky" I am told, and is not anything to use in especially the computer controlled trannies, and not recommended at all in the Merc III trannies. I do not know about A.

I think A and F's current use is tractors and heavy equipment. Monster Allison trannies.

What about the Honda specific fluids? Is the thicker "F" fluid used to prevent excess friction in the severe duty transmissions? What do you think about the B & M Hot Shift racing fluid. I've used this for many years on the A4LDs until I switched over to synthetic fluids.

Well. we skated out onto thin ice when we changed this thread from Merc III vs Merc V and on to Type F. I honestly do not have the knowledge to answer your question. Anyone else ?

That link above came up as an error message. Maybe that page was removed from their website.

Glacier991 said:

3. Some Merc V does not meet the differing specs for Merc III (!) [Most does].... do NOT use MERC V is a transmission designed for MERC III. If you want the (semi) synthetic benefits of Merc V, go with a full synthetic that says it is useable in a Merc III application.

Click to expand...

This is interesting because I was forced to think about this issue a few days ago.

Originally, I had a tiny, tiny "shudder" when shifting into 5th gear. However, a few days ago, I was far away from home and lost a significant amount of transmission fluid (story below). The only thing this one little garage/gas station had in stock was Merc III so I had no choice but to fill it with Merc III. So topped the transmssion off (about 5 quarts added) and when I got back on the road, the shudder was gone <- interesting.

Anyways, you guys dont have to read the rest but this is how I lost the fluid in a very short amount of time:

I took a break from my exams so I was like heck yeah, 22 degrees fahrenheit, I'm gonna go hit the slopes. So packed my board and it was a perfect day - snow falling - ultra nice. So afterwards, I must have been too hyped up over the perfect snow because I was going a little too fast and, upon coming halfway through this one turn, I see a very, very large plow truck - the type that plows highways (but it was operating on a local narrow roads which was I found odd). Anyway, after all the commotion, I was either going to hit the plow or a lamp post and I chose the lamp post.

The impact bent and pushed the bumper back a little which severed one of the rubber transmission lines right under the transmission cooler. So the white snow quickly turned blood red from the leaking transmission fluid. There was no way of reaching behind the bumper and reconnecting the severed transmission line so luckily, I had a pair of pliers and bypassed the filter (by connecting the two metal lines via one of the rubber hoses). I then drove the vehicle about 2 miles to a local hardware store I saw on my way to the slopes. However, a significant amount of fluid must have leaked out between the impact with the post and when I bypassed the filter because there were large "flares" between shifts. Anyways, I took it very easy and when I finally arrived at the hardware store, I was able to remove the bumper, remove the bypass, and finally reconnect all of the transmission lines. After which, I then went to the local garage/gas station described previously and filled it with Merc III .

Here are some links to information on different types of transmission fluids: http://www.checkthatcar.com/new_check/transmission fluids.asp
http://www.nationaltransmission.ca/pdf/Type_of_Fluids.pdf
http://www.tccoa.com/articles/tranny/merconv.html
http://www.tccoa.com/articles/tranny/trfluid.html

ATRA says that type F was used in the early 70s on a transmission called the Cruizematic that had bronze clutches. Type A was used on pretty much everything else, until they came out with other fluids, like Dexron, Mercon, etc. The Honda fluids go under the category of HFM, or highly friction modified. They have other friction characteristics in comparison to DexronIII/Mercon. Here is one list:

Type F — Introduced by Ford in 1967 for their automatics. Also used by Toyota.
Type CJ — Special Ford fluid for C6 transmissions. Similar to Dexron II. Must not be used in automatics that require Type F. Type H — Another limited Ford spec that differs from both Dexron and Type F. Can be replaced with Mercon.
Mercon — Ford fluid introduced in 1987, very similar to Dexron II. OK for all earlier Fords, except those that require Type F.
Mercon V — Ford’s newest type, introduced in 1997 for Ranger, Explorer V6 and Aerostar, and 1998 & up Windstar, Taurus/Sable and Continental. Must not be used in 1997 or earlier Fords.
Dexron — General Motors original ATF for automatics.
Dexron II — Improved GM formula with better viscosity control and additional oxidation inhibitors. Can be used in place of Dexron.
Dexron IIE — GM fluid for electronic transmissions.
Dexron III — Replaces Dexron IIE and adds improved oxidation and corrosion control in GM electronic automatics.
Dexron III/Saturn — A special fluid spec for Saturns.
Chrysler 7176 — For Chrysler FWD transaxles.
Chrysler 7176D (ATF +2) — Adds improved cold temperature flow and oxidation resistance. Introduced in 1997.
Chrysler 7176E (ATF +3) — Adds improved shear stability and uses a higher quality base oil.
Genuine Honda ATF — Special ATF for Honda automatics.
Toyota Type T — Special formula for Toyota All Trac vehicles and some Lexus models.

Here is another application chart from another website with additional information:

Type F -- Introduced by Ford in 1967 for their automatics. Also used by Toyota.
Type CJ -- Special Ford fluid for C6 transmissions. Similar to Dexron II. Must not be used in automatics that require Type F.
Type H -- Another limited Ford spec that differs from both Dexron and Type F. Can be replaced with Mercon.
Mercon -- Ford fluid introduced in 1987, very similar to Dexron II. Okay for all earlier Fords except those that require Type F.
Mercon V -- Ford's newest type, introduced in 1997 for Ranger, Explorer V6 and Aerostar, and 1998 & up Windstar, Taurus/Sable and Continental. Must not be used in 1997 or earlier Fords.
Dexron -- General Motors original ATF for automatics.
Dexron II -- Improved GM formula with better viscosity control, and additional oxidation inhibitors. Can be used in place of Dexron.
Dexron IIE -- GM fluid for electronic transmissions.
Dexron III -- Replaces Dexron IIE and adds improved oxidation and corrosion control in GM electronic automatics.
Dexron III (H) – Improved version of Dexron III released in 2003.
Dexron III/Saturn -- A special fluid spec for Saturns.
Dexron-VI – For 2006 GM Hydra-Matic 6L80 6-speed rear-wheel-drive transmissions, can also be used in earlier transmissions that require Dexron III and III(H).
Chrysler 7176 -- For Chrysler FWD transaxles.
Chrysler 7176D (ATF+2) -- Adds improved cold temperature flow and oxidation resistance. Introduced 1997.
Chrysler 7176E (ATF+3) -- Adds improved shear stability and uses a higher quality base oil. Required for four-speed automatics (do NOT use Dexron or Mercon as a substitute).
Chrysler ATF+4 (ATE)– Introduced in 1998, ATF+4 is synthetic and replaces the previous ATF+3 fluid. Used primarily for 2000 and 2001 vehicles, it can also be used in earlier Chrysler transmissions (except 1999 and older minivans with 41TE/AE transmission). ATF+3 should continue to be used for 1999 and earlier minivans because of the potential for torque converter shudder during break in.

NOTE:Chrysler ATF+4 Must always be used in vehicles that were originally filled with ATF+4. The red dye used in ATF+4 is not permanent. As the fluid ages it may become darker or appear brown in color. ATF+4 also has a unique odor that may change with age. Therefore, do not rely on the color, and odor of ATF+4 to determine if the fluid needs to be changed. Follow the OEM recommended service interval.

Chrysler ATF+5 for 2002 and newer models.

IMPORT APPLICATIONS:

BMW LT7114l or LA2634 -- Special forumla for BMW transmissions.
Genuine Honda ZL ATF -- Special ATF for Honda automatics (except CVT applications).
Mitsubishi Diamond SP-II & SP-Ill -- Special formula ATFs for Mitsubishi transmissions.
Nissan J-Matic --– Special forumla for Nissan transmissions.
Toyota Type T, T-III & T-IV -- Special formula ATFs for Toyota and Lexus transmissions.

Here's a review on Lubegard in the product review section: Dead Link Removed

My trans builder who has 35+ years experience building Ford autos and goes to the update or new tech training classes every year still ( to keep up on all the new units, updates, do's dont's) told me:

"Don't do it!" He stated the same thing as bullet item #3, Mercon V will not meet all the requirements of Mercon III

Good enough for me

so my Mercon III transmissions get Mercon III with a bottle of the Mercon Lube guard, which is the same thing my Mercon V transmission gets....so Ironic!!

interesting read there, thanks Brooklyn

I am more confused then ever now....but the mercon III with lube guards seems to be working...

On End of Summer Run 2 years ago I got a trans leak, because Ford never tighned the t-case when they replaced the trans. Anyhow I had to add some fliud, and all we could find was Mercron III. Added about 2 or 3 quarts, and has been in there for about 30k now. no problems. However I do plan to take the truck over to ford to have the fluid changed in the next month or so. My waranty on the trans runs out in Dec. Want to make sure everything is in good shape. Oh and freak them out with a full width solid axle under it.

When I was into drag racing and rebuilding trannies in the late '70s early '80s Type F was the preferrred tranny fluid to use for hard quick shifts in any brand auto trans. Of course this was not reccomended by the OEM. It was a hot rod trick which worked very well for it's purpose.

I occasionally ran B&M fluid back then. It did provide firmer shifts than even the Type F. This was in a Mopar Torqueflight 904.

Rick said:

When I was into drag racing and rebuilding trannies in the late '70s early '80s ..

Click to expand...

Ouuu -- a side of Rick I didn't know about

I'm anxiously waiting for Rick to write an M5OD rebuild diary whenever he gets to rebuilding his old one that is in the garage. Somebody else started to write one, but didn't finish. The information that they provided up to a certain point is still useful, especially the part with the home made gear puller.

I was waiting for him to finish! I never rebuilt manual trannies except when I was in automotive school in 1980...

Iz, check out this page: Dead Link Removed