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Discussion Starter #1
1996 Thunderbird, 178000 miles

Oh boy oh boy, it's a bad week.
Halfway to work (40 mile drive) I went to take off from a stop sign and the car went nowhere. It revved and revved but wouldn't get in gear. I began to suspect 1st was slipping so I very very gently touched the accelerator to let it engage before I stepped further. Dagnabbit it still wouldn't grab.

I kept trying and trying, getting more and more frustrated. I got mad and revved it again around the 3000rpm range. Holy cow the thing jumped into gear and chirped the tires and I made it to work! I checked the fluid and it was fine. On the way home, I tried nursing it and revving it, trying to figure out what I could do to get it in gear each time I came to a stop. The problem seemed to be getting harder and harder to control.

I got it home and am driving my Mustang instead.
At 178,000 miles a full rebuild is probably a good idea, but is something specific causing this?

I took it back out again today, on a route with no stop signs so I was able to drive it for about 10 miles without stopping. For the first mile, it just crept very slowly. Any further stepping of the accelerator sent the engine revving high with no more power going to the wheels. After that first mile, it seemed to finally grab and I kept it above 25mph until I got it back home. In reverse, it moves just fine. All gears above 1st feel good too. It's just that initial take-off from a stop that's the problem.

This may or may not have something to do with it--
A few months ago, one of the lines for the transmission cooler sprung a leak. It leaked out about 3 quarts (engine running) while in Park, and I did not put it into gear at all until I had replaced the line and topped off the fluid. Could the fluid loss have damaged anything?
 

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Checking The Transmission Fluid On A Thunderbird

You know..Your problem could be something really simple..

Like not having enough Transmission Fluid in your Transmission..

Alot of people make the mistake of checking their Transmission Fluid with the car off..

Here is detailed instructions on how to check the Transmission Fluid on your 1996 Thunderbird..



Checking the Automatic Transmission Fluid

It is preferable to check the transmission fluid
level at normal operating temperature
150°F-170°F (66°C-77°C), after approximately 20
miles (30 km) of driving. However, if necessary,
you can check the fluid level without having to
drive 20 miles (30 km) to obtain a normal
operating temperature if outside temperatures
are above 50°F (10°C).

With the vehicle on a level surface, start the
engine and, while fully applying the brake
pedal, move the transmission shift selector
through all of the gear ranges allowing sufficient
time for each position to engage. Securely latch
the transmission shift selector in the P (Park)
position, fully set the parking brake and leave
the engine running.

NOTE: Your vehicle should not be driven if
the fluid level is below the low cold
reading on the dipstick.

Wipe off the dipstick cap, pull the dipstick out
and wipe the indicator end clean. Put the
dipstick back into the filler tube and make sure
it is fully seated. Pull the dipstick out and read
the fluid level.

When checking fluid at normal operating
temperature 150°F-170°F (66°C-77°C), the fluid
level should be within the hot notched area on
the dipstick. When the vehicle has not been
driven, and the fluid is at room temperature
50°F-95°F (10°C-35°C), the fluid level should be
within the cold notched area.

NOTE: If the vehicle has been operated for an
extended period at high speeds or in
city traffic during hot weather, or
pulling a trailer, the vehicle should be
turned off for about 30 minutes to
allow the fluid to cool before checking..

Courtesy of TheTerminator93




Good Luck!


:thumbsup:





Rayo..
 

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Discussion Starter #3
I checked it before I headed out on my little no-stop route. With engine running it clearly read in the cold range. But when I got back home, and checked it at op-temp, the reading was not so clear, but the dipstick did show fluid in the hot range. I don't really like these goofy dipsticks, but I think it has enough fluid
 

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Any 4R70W/AOD with that many miles would be candidate for worn out forward clutch piston seals, usually the outer causing a slip while in the lower gears.
In most other transmissions, the forward or input clutch is activated at all times in the drive or O/D position, the AOD/4R70W unit applies the forward clutch as soon as the shifter is placed into gear and stays engaged untill O/D or 4th gear is demanded, it is then that the hydralics are dumped from the forward circut and the O/D band is applied, and reapplied when coming out of O/D and back into 3rd.
It is this constant on/off/on that just wears out the rubber lip seals in the forward housing. It is also why the shift timing is so critical on these units, too loose and it will flare between 3rd & 4th, too tight and it will bind or "tie-up" between shifts usually resulting in a burned O/D band.

I think your car is alerting you on it's upcoming failure, so begin preparations for a rebuild/replacement soon.
Good luck,

Kevin.
 

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Discussion Starter #5
Well, I was hoping this particular issue was caused by something accessible, perhaps in the valve body... But I think I'll "bite the bullet" and gear up for a full rebuild.

Any ideas on its remaining driveability before total failure?

...
Did I just say "gear up"...? :rolleyes: LOL
 

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Before springing for a full rebuild, since you don't seem completely sure that the fluid level is good, why not throw a quart or two of trans fluid in and see if it gets any better? If it works, you saved yourself the cost of a rebuild, and of it doesn't work, you're only out a few bucks.
 

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Discussion Starter #7
I'm 95% sure the level is fine. But yeah, I'll check it again.
 

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Discussion Starter #8 (Edited)
Fluid level's good.
I finally got a chance to get it to a friend's house, on a lift. I got started tearing things apart to pull the trans out for a rebuild, and found something interesting.

At the back of the transmission, there is a square wiring connector with about 15 wires. It looked like it was going to the trans and maybe an o2 sensor or 2. When I disconnected it, I found some kind of (oil?) inside; can the fluid travel through the wring to the connector? I also found a brown wire with an orange stripe that had the insulation damaged and only a few strands still holding it together. Inside the connector, a different circuit had a bunch of green corrosion on it- outside the connector, that's a pink wire.

I wish I had taken a picture of it, both wires are at different corners of the connector. Before I go any further pulling the trans out, I want to find out what these wires go to and take care of them. Now I've got myself all prepared for a rebuild, but is there something electrical that is making it so difficult to engage?

That forward clutch being engaged sounds a lot like the very very slow creeping I am able to get out of it. As I drove it to my friend's house, it crept like this for almost a mile while I played with the accelerator, begging it to engage first gear.
Once it finally got into 1st, I felt no slippage whatsoever, and it went through the other gears just fine.


EDIT: Found picture of connector I'm referring to in another thread- Wiring Harness part number ?
The pictures even show the oily substance that I've got too.
 

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If it's only that connector, that would be great! Clean it up real good or replace it if you have to.

From you description, I was thinking clogged tranny filter (or a filter not sealing property where it's seated in the valve body) or weak pump.
 

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I rember when my transmission when i had the same problem the car crept slowly and had to just about slam the acclerator to the floor to get it to move. In stead of a rebuilt i found a police interceptor trans and just swaped the shifting linkage. After the oem trans was out i tore it apart with with help of one of my freinds who know alot more about automatic transmissions and we discovered the thed first gear band was extermly worn. The used trans i got only had 30000 miles on it. If you do a rebuild i would suggest a j-mod it will help slow down the band wear.
 

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Discussion Starter #11
Big thanks to KL Mallender, who happens to be local to my area. My forward clutches were burnt up pretty bad, and we also found the forward piston seal chewed up. (This is a bad combination for 1st gear!) One of the first things I saw, upon pulling the pump, was the retainer snap ring had spun loose, chewing up the thrust washer. No major geartrain damage though.

I've got her all torn apart right now for a rebuild (my first automatic), and will be doing a J-mod even though the previous owner had a kit done. Right now I have lots of cleaning to do while gathering parts. (I'm replacing servos and switching to a Mark VIII TC/flexplate.) The car already has an aux cooler; hopefully the lines will flush clean and I won't have to replace it.

Lots of 4R70W rebuild info here:
4R70W Transmission Rebuild Diary - Ford Explorer Ranger Enthusiasts "Serious Explorations"®
 

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Discussion Starter #12
Finally back on the road! Went on a shakedown run the other day, all is great! My work schedule prevented me from getting it done sooner, but I'm glad I didn't rush anything.

Full soft-part rebuild, including new frictions and OD band, reverse band re-used, new seals and o-rings throughout.
New bushings at pump and tailshaft.
J-Mod (<300hp level), replacing previous owner's shift kit, stock springs re-installed.
New 1-2 and 2-3 accumulator pistons.
New OD and reverse servos.
Mark VIII torque converter and flexplate.
New driveshaft u-joints.
Repaired wiring harness.
Flushed cooler lines.
Brand new filter and Mercon V throughout.

It drives very well now. The previous owner's shift kit and springs slammed 2nd gear pretty firmly, and really wore on the inner teeth of the intermediate clutch frictions. That is fixed now. My favorite feature is the prompt engagement of reverse gear, due to the enlarged reverse servo feed hole. It used to take about a full second or so to engage reverse.
 
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