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ah crap, help me diagnose my transmission?

H

hbar

Member
All that useless talk about engine swaps, my C4 just started acting funny. Figures. Driving home last night, I felt like it might've been shifting wierd, like maybe it couldn't find 2nd or 3rd or something. On the back stretch of my neighborhood, I got it up to around 60, but never really felt it go into 3rd, but then again I wasn't convinced it wasn't going into 2nd way too early...disguising what I thought was the 1-2 shift as actually being the 2-3 shift. But I don't mean to speculate.

This morning I idled through the neighborhood. The at around 15-20mph the engine was idling way higher than normal (sorry, no tach), like it really needed to shift. I gave it a little gas, and it finally did shift. Through a few stop signs, same thing. When I got it out on the street and actually gave it some gas, I think it would try to shift into 2nd (a bit too early, I think), but it kinda missed or something, because it would have that "hesitation" (I use that term loosely here) as it is shifting, but then the RPMs wouldn't drop...indicating that the shift never really happened. Then at higher speed it would actually complete a shift. But I don't know if it actually made it into 2nd there, or if it went straight to 3rd. I couldn't get it up beyond 45 mph on my way into work, but I never did feel that last shift. Maybe it already happened, maybe I missed it. Something seems amiss.

Geez I hope that description made sense. Maybe I'm just low on ATF??
 
Did you check your fluid?

Maybe all it needs is a service, you know new filter and new fluid???

I have one laying around in my garage, so if it is bad...???

Anyway, I am not an auto guy, don't like them. I find if you want to see if it is shifting, you should be stopped, then start out and feel for each shift. A C4 will only switch gears two times. Thus the 3 spd. You can manually shift it so you can feel it and then do it again in drive. Then you will know if it is shifting.

Get a tach on it to see when it shifts. Then we all will be able to go from there.

It really doesn't sound too serious to me.

Mel
 
"guruatbol" said:
Did you check your fluid?

Maybe all it needs is a service, you know new filter and new fluid???

I have one laying around in my garage, so if it is bad...???

Anyway, I am not an auto guy, don't like them. I find if you want to see if it is shifting, you should be stopped, then start out and feel for each shift. A C4 will only switch gears two times. Thus the 3 spd. You can manually shift it so you can feel it and then do it again in drive. Then you will know if it is shifting.

Get a tach on it to see when it shifts. Then we all will be able to go from there.

It really doesn't sound too serious to me.

Mel
Click to expand...

Thanks. Checking the fluid level is the first order of business when I get home. I did notice like 2 drops under there a few days ago. The car sat for 3 years right after a transmission rebuild, and there wasn't a drop under the car in that time. Maybe there were drops I never saw that dried up before I noticed. What is the current preference on what ATF to use?
 
Use Type F fluid. Look around the rear seal of the transmission and the shifter areas for common leaking problems. Also, pull the hose to the vac. modulator and see if it is wet with fluid. If fluid is good, it could be an adjustment problem but that is doubtful. Sitting with no activity is worse than beating on them.....
 
"gotstang" said:
Bad modulator due to sitting so long? At least that's a cheap/easy possiblity.
Click to expand...

It sat for three years, but the last 2 months has seen me put ~500 miles on it. No issue until last night.
 
vacuum tubing can dry-rot in that time. Sounds a lot like a vacuum related issue to me. Check the rubber line on the back of the intake and the rubber line at the modulator valve. As said, could be the modulator valve itself.
 
"hbar" said:
It sat for three years, but the last 2 months has seen me put ~500 miles on it. No issue until last night.
Click to expand...

I'm glad you said that, because I was going to suggest that after sitting 3 years after a rebuild, your internal seals may have dried up and are now leaking.
 
"sigtauenus" said:
vacuum tubing can dry-rot in that time. Sounds a lot like a vacuum related issue to me. Check the rubber line on the back of the intake and the rubber line at the modulator valve. As said, could be the modulator valve itself.
Click to expand...

Check the vacuum line coming off the rear of your engine and make sure it's making a good connection to the transmission's modulator. A new modulator is ~$10 and available at most local parts stores.
 
Dumb question...I haven't checked the fluid level on this car before. I was always taught that you check it while running, but e-How says to do it while the engine is cool on a C4.
 
"AzPete" said:
Pull the tranny dipstick....should tell you idling in park....
Click to expand...

This is what I thought.

If you can't trust the internet for information, who can you trust.
 
"hbar" said:
If you can't trust the internet for information, who can you trust.
Click to expand...

Yep, I also always believe all the things I read on the internet..... :shrug
 
Re: ah crap, help me diagnose my transmission problem?

Ok, fluid looked good, right color, right level. Must be something else. Haven't checked the vacuum line yet.

I feel dumb that I didn't mention this earlier, but the problem happened shortly after something weird happened. I was coming out of a red light, and I was giving it some gas. It shifted before I wanted it to, so I gave it a little more gas.....it downshifted, but revved higher than I had ever heard it rev before, so I took my foot off the gas, and then everything seemed ok. Now I don't recall if that high rev was paired with acceleration, or if it was more of a neutral-rev.

So does that change anyone's diagnosis?
 
Have you tried changing your shift points via the modulator? Remove vacuum line from modulator and slightly dial it counterclockwise with a small allen wrench. Very little, say from 12:00 to 10:00.
 
Yay, another frustrating Mustang project.

First off, the hose at the modulator has no evidence of any ATF in it, which probably doesn't mean anything, but I was hoping to see some so I'd know the modulator was bad. I replaced the upper hose, haven't done the lower one yet.

Secondly, there's no way I can get that modulator off. My 3/4" wrench is too fat to fit in there. I don't know who designed that awesome setup, but I'd like to thank them in my own special way. I tried a few other techniques to extract it.....if it wasn't broken before, it almost certainly is now. Is there some special tool I should have for this? I'm thinking it wouldn't even be any easier with the transmission out, so I must not be doing something right.
 
I used a bench grinder to my a cheap wrench thin enough...This was a very long time ago when I had an auto (80s) now only manual trans for me.

Mel
 
"guruatbol" said:
I used a bench grinder to my a cheap wrench thin enough...This was a very long time ago when I had an auto (80s) now only manual trans for me.

Mel
Click to expand...

Something tells me Ford didn't have a team of people grinding down wrenches so the transmission assembly team could torque down vacuum modulators.
 
No they had the correct tool which was a wrench that was thinner.

IIRC you just need a thinner cast tool...

Mel
 
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