JMOD-now T/C issue-help! - TCCoA Forums
 
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post #1 of 6 (permalink) Old 06-03-2004, 11:42 PM Thread Starter
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Question JMOD-now T/C issue-help!

A friend owns a 1997 Lincoln Mark VIII with 113k miles on it. A "JMOD"(valve body separator plate modification/accumulator piston upgrade/removal of lower 1-2 spring and 2-3 spring) was recently performed to this vehicle. The shifts are perfect. However, an area of concern has come up.

When in park, if he moves the shifter into reverse, there is a delay of approximately 2-3 seconds before the transmission engages reverse. if he touches the gas pedal to raise the rpms up at all, the transmission immediately engages reverse.

At the same time, while in DRIVE, if he lets up on the brake pedal, the car barely creeps forward, but if he presses the gas pedal to accelerate, there is a distinct feeling of "engagement", and the vehicle accelerates normally.

It feels like the transmission is low on fluid, or the T/C is trying to lock up too early. Upon checking the dipstick while on level ground, and at operating temperature, we found the fluid perfectly full. There is Mercon V in the transmission at this time, with no more than 700 miles on it(replaced at time of JMOD, including draining the T/C).

Interestingly enough, when I asked him to leave his left foot on the brake pedal ever so slightly, while accelerating from a stop, there is NO delay, or obvious feeling of "engagement". The car accelerates normally. Also, while cruising in drive(3rd-OVERDRIVE OFF) if he lightly touches the brake pedal while keeping equal throttle with his right foot, the T/C unlocks(you can feel the rpms increase by 100 on the tach-indicating the T/C solonoid is operating)

Could this be a typical TCC problem? If so, will the addition of an aftermarket SCT chip with a re-programmed TC lock-up schedule help remedy this problem?

Of course, we need to isolate, and identify the problem first, which is why I am here. Have any of you who have done JMOD's to their 4R70W's encountered anything like this before? The car is 600 miles away now in 29 palms, Ca. He drove it up to the SF Bay area for me to do this JMOD for him. We drilled to the 300+ hp specs. The shifts are perfect. No driveability issues at all. Just the weird feeling at the touch of the throttle from a stop.

is there an additive he could try? or a friction modifier? or is it best to sort this out first?

BTW, I have a 94 Mark VIII. I did a JMOD to mine 20k miles ago, and it has been flawless since. My shifts are perfect, and there are NO T/C issues at all. Same with another 97 I have done a JMOD to. That owner is thrilled. I am very stumped, and want to fix this U.S. marine's car a.s.a.p.

help, please, if anyone can. I would appreciate it.


Thank you for your time.
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post #2 of 6 (permalink) Old 06-04-2004, 12:31 AM
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The TC is acting just fine. It's supposed to unlock when you tap the brakes.

On my 95 Tbird I had the little hesitation going into reverse, I don't really think it's a sign of anything bad. And both of my cars did the little jerky thing from a stop... I couldnt say for sure, but it's possible a chip could help that problem. You could go over to ModularDepot and see if one of the SCT guys can provide any info. Their tuning is the best for Fords.

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97 Thunderbird 4.6L LX /w Sport Package
24k B&M Cooler, 1" lowered, Steeda UD Pulleys, Dynomax cat-back, J-mod, 3.73's, PI intake, PI cams, 03 GT MAF/Tube, SCT tuned - Gone but not forgotten.
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post #3 of 6 (permalink) Old 06-04-2004, 03:04 AM
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I think the hesitation going into reverse has to do with the Reverse Servo that these cars (atleast my 96) came with stock. We've already got the servo with only one little ring around the bottom, which IIRC is the longer servo, so it takes a little more time to engage the gear. When I had my transmission rebuilt.. they used the shorter servo (the three "ring" design, if I was hearing the Mechanic's broken english correctly.) and the engagement seems a lot quicker now.

The above is entirely speculation on my part. If I'm wrong, so be it. I've got no problem with that. Just please keep the flamage to a minimum.
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post #4 of 6 (permalink) Old 06-12-2004, 06:55 PM
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This may be from left field, but have you checked your IRS bushings? MN12Performance has an article on this, and others have told me if your IRS bushings are bad, it does affect things like shifting into reverse.

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post #5 of 6 (permalink) Old 06-13-2004, 11:37 AM
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I suppose installing the longest reverse servo could speed up the engagements, but there's also a hole in the separator plate that controls that. Check the OD 101 article, it's covered in there.

96 Mustang GT 5spd. w/ 248A Option (GTS). Stock for now until I get the Roush on.

97 Thunderbird 4.6L LX /w Sport Package
24k B&M Cooler, 1" lowered, Steeda UD Pulleys, Dynomax cat-back, J-mod, 3.73's, PI intake, PI cams, 03 GT MAF/Tube, SCT tuned - Gone but not forgotten.
MAMN12 Drag Racing Team [email protected] In need of updated times.
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post #6 of 6 (permalink) Old 06-13-2004, 01:32 PM
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Blackicelsc,

It is NOT possible for the EEC to lock up the TC in first gear. What you are feeling is most likely the forward clutch seal rings are worn and leaking pressure. This will show up as a flare/late movement on take off from a stop. This can be band aided through the EEC via more line pressure, but it's not a fix.

JUST A NOTE:

Some of the 4R70W transmissions came unique cases that required a spacer to be installed bewteen the reverse servo cover and retaining ring. Those transmissions had an orange dot on the bottom of the torque converter housing and/or a yellow sticker on the transmission pan.

The TSB 96-7-11 covered this information.

There are three different reverse servos in production.

- E0AZ-7D189-A has one groove or ring on the bottom and it's 2.936" long.

- E0AZ-7D189-B has two grooves or rings on the bottom and it's 2.989" long.

- E0AZ-7D189-C has three grooves or rings on the bottom and it's 3.043" long.

The shortest servo is obviously E0AZ-7D189-A and it's the one you should use. By using the shortest reverse servo, it reduces the drag in the transmission (slightly, but it does). The longer the piston, the longer the stroke and faster the engagement should be.

The shortest servo should be used with a modification to the main control as PER JERRY'S THESIS. Hole #10 should be opened to 0.089-0.100" depending on how fast you want it to engage. The larger the hole, the faster the reverse engagement. This is because the reverse servo area is huge and needs time to fill before the piston moves forward to engage.

If you want a super fast reverse engagement, open HOLE #10 to 0.110".

A-Train

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