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Hey everyone,

I think I have some issues with my C4. So I got it out of the shop a few weeks ago, and it ran fine. Shop wasn't working on transmission - originally - they were doing suspension work and fixing overheating issues. They did tell me that the previous shop I had taken too apparently didn't reinstall the kickdown. So they put that on, dropped the pan & make sure everything was ok. Then they put it back together and I picked up the car.

Well, I drove it once or twice and it was fine. Then, on a beautiful Friday (sunny, about 80 degrees, nice day really), I drove the car around town & it was fine. That evening, the wife & I went to see a movie. So we jump in the car and get about 500 feet from my house and it comes out of gear. The gearshift was still in drive, but there was no go. I put it in reverse, no go. I put it in every gear, no go. I shut the car off, wait about 2 minutes, cut it back on and boom it goes into gear and goes forward about 100 feet. We repeated that maneuver until I got home. Went to the movies in my Jeep.

Ever since, there's been a hell of a leak under my car in the area of the transmission. Like a lot. So I cleaned that up, and checked the transmission fluid today. I let it idle in my garage till it got hot, then put it in reverse, neutral, D, 2, 1, then back to park. It didn't engage on any gears, however (and I can't explain it any other way than this) I did feel something almost like a grinding in every gear. Then I left the car running and checked the transmission fluid.

Another part of this fun is that after I left the car off for a few minutes, I cranked it back up and put it into gear and it went into every gear. Then I put it back in park and back into gear but that second time it didn't go into any gear.

The pictures below show the state of the transmission fluid. Can anyone tell me what's going on? Is the transmission hosed?

Also, there's a new leak under my rear axle. I just noticed that today. Was definitely not there in previous times I was under the car.

I'm kind of getting to a point with this car that I'm not sure whether or not I want to move forward with it anymore. I've dropped some serious coin on it so far, and I'm not 100% sure I want to continue to do so or if I want to find another car that's in a bit better shape. I'd like to make that decision before I ship it off to the body shop to get some metalwork done and before I spend $$ to swap it over to a manual.
 

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Shifting issue might just be a bad vacuum modulator. They're cheap and easy to replace. The leak might be a separate issue.
 

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Why is the fluid so high up on the stick? If it's overfilled, the fluid could be aerated and causing all sorts of havoc in the hydraulics.
 

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Discussion Starter #4
Shifting issue might just be a bad vacuum modulator. They're cheap and easy to replace. The leak might be a separate issue.
Are there any signs of when these are going bad? Or do they just go bad and then you can't drive anymore - even if you've been driving that day?
 

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Discussion Starter #5
Why is the fluid so high up on the stick? If it's overfilled, the fluid could be aerated and causing all sorts of havoc in the hydraulics.
I have absolutely no idea. With how much that has been leaking out, I'm actually surprised it's reading that much fluid.
 

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I had a similar situation a few years ago. I finally pulled the valve body and removed and polished the "piston\valves" .
Problem never happened again . I have to assume there was a burr or something that caused the piston\valves to stick .
Not fun to have no forward gears at 50 mph on a 2 lane hiway with a narrow shoulder.
 

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With a C4, Especially the '64-'66 "Green Dot" Tranny, You have to make sure that you are using the right Pan Gasket. It has to be a perfect rectangle...and cannot have any side "notches" in it or it will leak. You can find the correct ones on ebay. You'll never find them at any autoparts store. See the pic below of the correct gasket(s). If your gasket is different from the ones below, You're using the wrong gasket. Also, As already mentioned, Check or replace the Vacuum Modulator first.

:eek:)

Tony K.
 

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Are there any signs of when these are going bad? Or do they just go bad and then you can't drive anymore - even if you've been driving that day?
Two components to the modulator: the valve, and the pin. When the modulator goes, it just goes. The pin is another story. When you pull the old modulator out, there's a pin in the "straw" end that goes into the tranny. Sometimes it stays in the tranny, sometimes it comes out with the modulator stuck inside the straw. YOU NEED THE PIN. If you lose it your tranny will shift just fine - 1 & 2, but it'll never go into 3. There are 3 lengths the pin can be. The longer the pin, the longer it takes to shift between gears. Back when I had a C4 I lost the pin once. I made one out of a 16-D nail using a Vernier Caliper and a grinder to get the correct length.
 

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Discussion Starter #9
I honestly don't know what the gasket looks like b/c I didn't put it on.

I'll order a new vacuum modulator and see if that fixes it.

Kinda struggling whether to keep moving forward with this one or to buy something else.
 

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RDU, the fluid level is really important on a C4. If there's too little, OR too much fluid, you are going to have serious problems with engagement. Too little, and you're sucking air, so there's not enough fluid pressure or lubrication to make everything work right. Too much, and the fluid rapidly becomes foamy. Foamy fluid compresses, unlike normal fluid, so again, you don't have proper pressures to shift gears. You need to figure out what the fluid level *really* is, by starting the car and checking it with the vehicle in park and idling.

If it's not between the marks, then you'll have to get some fluid out, or put some in until it is.


If your leak is spilling quarts of fluid on your floor, then you really need to get that resolved too, obviously!

My advice to you is this: Don't let your Mustang intimidate you. Most of its maintenance and fixit stuff will be very simple, and easy to do. Shops will be eager to charge you big bucks for fixing little things that you can do yourself better, and with a lot less fuss. It can sure be frustrating when things aren't working right, but it inevitably comes down to some small detail that isn't too hard to resolve in the end. For the most part, these cars are very fuss-free, but once in a while, given their age, something may go wrong. You have to decide for yourself whether you'd rather have a brand new car that you can just throw money at to keep maintained, or if you're willing to put in some thought and work to keep your beautiful old Mustang going. My love for mechanical things, and for classic cars makes this an easy choice, but I can also understand that not everyone feels the same way!

Keep in mind, the average price for a new car now is about $35,000. How many little problems like this would you have to fix in order to come up to that mark, even if you're paying some swindler mechanic big bucks to do it? If it were me, I'd just get it fixed, and keep enjoying my car. =)

Best wishes.
 

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Discussion Starter #11
Oh I'm not thinking of buying a new car. I have a 2015 Wrangler that I love and is my daily driver.

What I'm considering is:
1. whether or not to continue repairing this car, or
2. Buy a (classic) car in better condition.

I need to have some metalwork done and since I don't have any skills (nor location) to do welding, so I'll be having a shop do that. Maybe I'll just convert it to manual while they're doing metal work. I want a manual transmission anyway.

Part of me wants to go the route of #2, but I do like being able to bring this car back to life. Wife is supportive either way, so that's awesome.
 

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Even looking at it from that point of view, you've spent a lot of time getting to know this ride! If you fix all the stuff that needs to be fixed, you should be left with something you can enjoy for a long time. Or, start over with an unknown that may be as bad or worse!
 

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Before you do that though, get it good and hot and see what it looks like.

I've been spending a lot of time looking at my transmission lately (there's a thread around here somewhere) and I've noticed that the fluid level changes depending on just how hot it is.

If I just drive it to the store and back (~4 miles) it reads way high. But if I drive to my Dad's house (~19 miles) it reads just fine. I'm not sure what in the time / temperature / speed / distance changes the fluid level but it's a distinct difference.

So if you can, get it good and hot first and check it before draining too much out or it might end up low once it warms up.
 

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It seems odd that the leak and the shift problems did not for the first few trips after the pan was off.
The fluid level usually reads higher when cold after the fluid drains back from the rest of the trans.
The modulator controls the up-shift from low to higher gears. Modulator failure symptoms usually do not affect low or reverse. Sometimes they leak fluid into the vacuum line and make the exhaust smoke.
Does the trans fluid smell sweet or pungent? Type F fluid usually has a sweet smell to it. The fact that the problem occurred after the pan was removed makes me want investigate whether the correct fluid was replaced.
What is color of the new leak towards the rear of the car? Is it dark and thick or is it thin and red? If it is trans fluid then it may have been blown rearward when driving and simply needs to be cleaned up.
 

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You can make the checks as others have said but frankly, it's overhaul time which you probably have already figured that out.
 
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