Hey. New member, and I'll try to make this short. Soon I will tell the whole story of my truck and post some pics, but for now I need help. Got the truck in July 2013. Obviously it had been sitting a while, 1969 F100. Not original drive train, has a 429 and C6 Trans from early 70's. When I got it it would run but not very well, so I drove it around my neighborhood a few miles and it has been at a few mechanics since. That's another story...

I picked it up last week, and it's come a long way. I drove it for a couple of days (about 30 miles total) and Saturday I went to take a drive and had no forward gears. Again automatic C6. I figured out that if I start it and let it get warm, put it in reverse for a few minutes, jiggle the selector in drive, it will start working. I spoke with my mechanic and he said he serviced the trans and put Dex/Merc in. My dip stick specifies type F. He said what he put in was fine. I read the labels on a bunch of Dex/Merc bottles today and they all say "not for F type trans". He still says it should be fine. I spoke with 5 different transmission shops today and they all agree with my mechanic... and they say I need a rebuild. Maybe I do, but would it be worth the cost the remove the Dex/Merc and replace with Type F to see what happens? They all say no, I would be wasting my time and money. Any suggestions? Should I just rebuild or spend some more money (ouch) and try replacing the fluid? Thanks.

 

Any mechanic who performs services and lubricants clearly contrary to the factory recommended specifications should have informed you beforehand what he intended to do AND provided supporting documentation to support his methodology.

To simply state "still says it should be fine." should be highly suspect. In case something goes wrong, then what is your recourse??? Does your mechanic offer a lifetime guarantee that "it should be fine?". I didn't think so.

Go back and tell him you didn't authorize a non-recommended specification to be used and require him to flush the system change it to Type F as recommended. Watch him do it.

I wouldn't go back to that dirtbag... it's not his rig, it's yours and you are paying him good money for quality servicing. Him not telling you about why he used Dex/Merc it is a major foul.

 

type F is a thicker fluid, it will make it act differently, however I don't think it will be that significant. Trying it wont hurt anything and is cheaper than a rebuild.

What exactly is the tranny doing now, and what was it doing before he changed the fluid?

 

Type F fluid has friction modifiers to make it more "sticky" for a lack of a better term. What is happening is now the clutches are slipping until they get very hot, and then grabbing through the fluid. If the trans wasn't bad before, it likely will need a rebuild very soon.

 

Thanks for the replies.

Even though I got the truck in July, it's new to me (been in a few shops since July). So I can't really say how it drove before. But for a few days and about 30 miles it drove fine. Now I have no forward gears until it warms ups and I mess with the selector.

I know the trans may have been bad from day 1. I have no way of knowing for sure. I just don't get why my mechanic and 5 different transmission shops (ranging from national chains to small 2 man shops) All say it should not be a problem to use a fluid that specifically says not to use in my transmission... I've only put about 30 miles on the trans since the change, so I'm hoping if the fluid is the problem that there has not been any damage. When it drove, it drove fine, no slipping.

 

Most techs these days have never heard of Type F since Ford stopped using it in the 90's. Heck, the trick of the day back in the 60s and 70s was to use type f in the GM trannys to give a firmer and shorter shift than the stock tranny fluid

 

Dump it. Your transmission needs either Type F or FA, one or both of which are available at NAPA. You may not have damaged the transmission if you haven't driven it hard, but there is still that chance - plus it may have been tired to begin with and this just finished it off. Unfortunately you now have contaminated whatever was left in there, especially if your 'mechanic' didn't drain the two plus quarts from torque converter. Not draining that TQ is not unusual as it takes extra time and effort to pull the motor plate access cover and the 'verter pipe plug. Dex/Mercon can be used only if the transmission has been rebuilt and only if the rebuilder specifies that ATF. There are some performance builders that do specify that stuff. Good luck!! Let us know what happens (and find another but competent mechanic)

 

Do you know what the fluid looked like before it was serviced? Was it dark red or even black?? Sometimes when you service old or high mileage automatics, they tend to start slipping with fresh fluid. That said, I would of used a multi vehicle trans fluid certified for type "F" and a quality clutch conditioner. In addition to that I would of told you prior to the service the risks and types of fluids you would be getting.

 

1966/76 C6 = Type F ATF / 1977/96 C6 = Mercon aka Dextron II

 

In all my years as a mechanic I have never mixed ATF. Dex/Mer is one thing, Type F is something of another animal all together. the idea of mixing them together is kinda like adding 3 gallons of water to a quart of auto paint so you can make enough paint to paint your truck.

What decides which fluid you use in a transmission is the type of fluid the clutches were soaked in during initial build. Using the wrong fluid will cause excessive slipping of the clutch pack and will cause them to fail in short time. The fact that you have to wait for the transmission to warm up before you have any drive ability, leads me to believe that you have another issue all together. I would guess that your having issues with the front pump. this is possibly why your being told to rebuild the transmission.

 

2X all the above. I was told back in the day by a Ford tranny mechanic that Ford switched to dexron II because it's acidic level creates softer shifts than type F. And yes, when it was originally built the friction discs were soaked in F before installation. Looks like Ford had two different tranny rebuild kits. They are listed as before/after 4/1/76. I am assuming that is the day Ford satarted building the 1977's. As noted by Bill above, 1977 IS the year Ford switched to dexron II. Part of the difference in the F and Dexron II kits is some of the friction discs. So I think the tranny's friction discs were probably on there way out and the wrong fluid finished them. I too would make him FLUSH all the mercon/dexron out and put in F and another new filter. See if you don't get lucky. But even if it does work I wouldn't tow anything with it.

 

Thanks for all of the replies and comments. I think I'll sleep on this for about a week and not drive the truck. What started as a fun project has turned into something else... I'm debating on just getting the thing rebuilt and hoping I'll have a somewhat dependable ride. I have some quotes from $850 to $1,200. Getting the old fluid out and refilling will cost around $185.00, and it may not work. I don't want to go back to the shop that did the work. He disagrees with me on this. They did a lot of engine work, installed headers, and a bunch of other stuff. He cut me a good deal and did a lot of small things that he did not charge me for. I like the guy and his crew. I don't like this, but I'm not ready to burn a bridge over it.

I'd probably feel better in the long run with a re-build. Right now I don't want my wife driving the thing, I'm afraid she will lose drive when she needs it most. She already is not real happy with this journey. When she does drive it, I want her to love it...

Thanks again!!

 

FWIW, I have a nicely built C6 that will fit your engine, but it is out of a car not a truck. I know it will work well and it needs a new home. If you are interested I will make you a sweet deal. It has never been installed and is ready to go. just pm me for the details I will talk with you on the phone and tell you all about it. Send pics too. Good luck.

 

Hey. Thanks. I tried the PM, but I am new and don't have enough posts and have not been a member for at least 10 days, which I need in order to PM. When able I'll shoot you a PM. For now, I'm still up in the air. One minute I'm convinced I'll just rebuild, the next I think I'll try replacing the fluid. For curiosity, I'd really like to see what changing the fluid would do.

 

just my personal oppinion, but I've been working on these things since they were new, changing the fluid is a waste of 185 bux.

Put that money towards a used tranny or a rebuild.