94 X when cold auto transmission won't shift into drive

[gmanrocks]

Hi,

I have a 1994 Ford Explorer 6 cylinder Automatic with about 150k. I just started having an odd problem. When I first start up, and shift into Drive, 1st, 2nd, or Overdrive - it won't "catch" meaning I am still in Park or Neutral. Reverse will work fine. After a minute or so it will shift and work fine. If I warm up my truck, like a minute, it will shift fine. I am not used to warming up my truck, usually I start it and go. I don't see any other problems (I do have some pinging, but it goes away with a higher octane.) I do have some vacumm hoses that are popping off the rear of the intake manifold. (I also do lose some oil). Not sure if it is all related.

I am planning on changing the transmission fluid and filter, but I am thinking that this won't fix the problem. Any ideas? (and costs)?

PS - I searched but couldn't find a thread that addressed this problem - if you can please point me in that direction.

 

[Glacier991]

Generally this points to a problem in line pressure. Often it can be as simple as the fluid being low.. It can also be related to a leak somewhere, but the fact it is ok when warm sounds less like a leak to me. Not to insult you but have you checked the fluid level? A bad vacuum modulator can allow fluid to be sucked into the engine and burned and you'd never know you were losing fluid. Let us know what the fluid level is like... you check it warm, in park, with the engine running.

 

[MacGyver]

i had the same problem and my fluid was low (like a quart)i would definatly say to start with that

Thanks Glacier i never knew about the vacuum modulator which must be whats wrong with mine cause i always check for fluid loss and never find any. would you know where to find it?

I hope im not jacking this thread but i think it would help awnser the original question

 

[Glacier991]

It is the bronze looking thing in the pic under the blue bolt. It is on the passenger side of the trannie... follow the vacuum hose....

 

[ohe_boy]

I am having the same problem with my tranny. But I'm also finding trans. fluid on top of my engine. I've done some searches and read about the modulator being the culprit. I'm just confused has to how to get to the modulator. Would I have to drop the tranny or remove the passenger seat and come in from the top.

I have a '94 XLT A4LD thanks

 

[Glacier991]

Shouldn't have to do either. It is in a tight spot... you may have to remove the heat shield to get it out (will have to take off the top bolt in any event since it holds the modulator clamp too)

 

[ohe_boy]

After reading more about the vacuum modulator, it seems that the modulator "piston" could be bad. Is there a difference between the two or are they the same thing?

I'm trying to trace where the problem and getting confused at the same time thanks for your help

 

[Glacier991]

The vacuum modulator consists of 4 parts. The actual diaphragm unit (the diaphragm can tear allowing ATF to be sucked up into the engine. A short "rod", the actual throttle valve, and a small return spring (in this pic I have plaved it on the new version. The only difference here is the one I am using is adjustable. Here's the old and the new, disassembled on the bench, side by side.

 

[Brain]

Those are the parts all right, but what you can't see is inside the factory sealed vacuum modulator unit on the left (which contains the diaphragm). I took an old one and pulled the seam apart and shot some pictures if anybody wants to see the inside "guts" of the modulator. It is pretty simple...two case halves, a diaphragm, and a spring. The adjustable one has another part that regulates how much vacuum is needed, but it is only one or two additional parts (I don't have a picture of those parts).

 

[gmanrocks]

We have a winner and a loser...

Ok - glacier991 - you are the winner. I am the loser for not having enough fluid in the tranny. I figured I should fess up - so that you would know that your troubleshooting abilities were right on. Thanks. I took your advice and have been driving it for two days now - the problem is gone.

Ok - now in my defense. This started happening just as I was talked to my brother about dropping the pan and changing the fluid and filter. So I wanted to ask the question before we did that work, so that I could fix it at the same time. Since I was going to change the fluid - I didn't bother checking the level. Totally newbie of me to not check the level before posting my question on the board. But hopefully someone else will search and find this and it will help them.

Thanks again - since I thought I might need a new transmission or a rebuild.