1999 4r70w p0782 problem - TCCoA Forums
 
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post #1 of 5 (permalink) Old 05-06-2011, 08:51 PM Thread Starter
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1999 4r70w p0782 problem

I have been running into some problems with my wife's Mustang. It does fine cold, but when it warms up the car will downshift erratically once it is up into 3rd gear. It does it much less or not at all with very light throttle. At first I though...MLPS. So I put one in. The symptoms didnt go away. So I replaced it with another Standard brand sensor, with no luck. I have double checked the adjustment on the MLPS twice by putting the shifter in N and lining up the marks on the sensor. I have checked the TPS data and it is smooth and in range (~1-4.5 v). If I watch data while it does this, it shows the PID for TRrange moving from OD to MAN2. I have tried bumping the shifter while driving to cause a blip and nothing.

Just for fun and on the off chance that the 2-3 accumulator was leaking, I did the JMod last night with new pistons and a large 01 truck lower spring. The stock mustang one was broken, hence the tire chirping 1-2s it already had. I am just glad I had a broken 4r70w sitting right there . I drove the car, it shifts awesome. Once it warms up though, the symptoms are back, although the jerking in and out of gears is much more spirited. Let me know if you guys have any idea.

I am thinking that it may be something like a bad wire between the MLPS and the PCM. I have tried wiggling the trans harness, but no such luck as far as making the MLPS data change. I havent gotten close to the PCM yet. Thanks in advance.

-Rob
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post #2 of 5 (permalink) Old 05-07-2011, 03:24 PM Thread Starter
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I just knew I was going to find a bad wire or something, but not yet. I checked the resistance of all 5 wires that run back to the PCM. 4 for the signal and 1 for signal return. They all read less than 1 ohm, which is good. I am not in a good mood about this or the 10mm snap on socket that I lost into the body rails just below the PCM. Today is not a good day. If someone has any ideas, post it up. I cant imagine why the data keeps changing like it does. I am just going to put it back together and take it for a drive.

-Rob
RIP '94 Amber Fire Pearl Metallic Thunderbird on Bullitts [email protected]
96 Sport '02 Explorer PI with ported heads, 90MM LMAF, DirtyDog Marauder TC, Lasota tune, Jmod, Magnaflow mid-mount with X, no cats. Urethane drivers motor mount. HIDs!
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post #3 of 5 (permalink) Old 05-07-2011, 05:15 PM Thread Starter
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Well I havent seen the P0782 yet while driving it, but the crazy shifting symptoms remain. Just for reference, I hooked the scanner up in the bird and took it for a drive. In the bird, the trans range voltage moves from 5v or so in P to 0.6v in man 1. In the mustang they start out at 0v, go to 1.66v in R, N, D and back at 0v for man2 and man1. I think I am going to cut the ground wire (grey/red) from the MLPS connector and ground it somewhere on the transmission case. This is getting ridiculous. Also, I was able to get the socket out of the body by using a long telescoping magnet after some very hard braking . Wish me luck and if anyone has any good ideas, let me know. Thanks

-Rob
RIP '94 Amber Fire Pearl Metallic Thunderbird on Bullitts [email protected]
96 Sport '02 Explorer PI with ported heads, 90MM LMAF, DirtyDog Marauder TC, Lasota tune, Jmod, Magnaflow mid-mount with X, no cats. Urethane drivers motor mount. HIDs!
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post #4 of 5 (permalink) Old 05-07-2011, 05:58 PM Thread Starter
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Well, grounding it on the case didnt make a difference. I did notice that sometimes when I pull the shifter into D, it will say MAN2. I could let off the brakes and apply them very quickly and it would affect the reading (it would actually go back to OD). I am wondering if some of those 4 wires that go back to the PCM are shorting on each other intermittently. That could explain why giving throttle makes a difference. Also, these symptoms were there before but got much much worse after I put in new transmission and motor mounts. 2 of the 3 mounts were bad. I am thinking since the motor is sitting straight now, some wires may be rubbing in ways they had not before. I think I've had enough Mustang for one day though.

-Rob
RIP '94 Amber Fire Pearl Metallic Thunderbird on Bullitts [email protected]
96 Sport '02 Explorer PI with ported heads, 90MM LMAF, DirtyDog Marauder TC, Lasota tune, Jmod, Magnaflow mid-mount with X, no cats. Urethane drivers motor mount. HIDs!
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post #5 of 5 (permalink) Old 05-08-2011, 03:02 PM Thread Starter
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Well guys, I just got another reminder that you should always check out TSBs for anything unusual. After a minute of looking at the transmission tsbs, I found a Recall for a rerouting of the transmission harness on the 99 Mustang. I checked my car and the wires had been melted onto the EGR tube. I am going to straighten this out so wish me luck. Hopefully I can close this thread with a happy ending.

EDIT: PROBLEM SOLVED I finally get the full effects of the shift kit since now it will always start off in 1st. It is very mild and wont chirp unless you go WOT. The 1-2 is not very jerky using the yellow lower 1-2 spring from a 01 truck. I decided to not put the smaller spring that was in the middle of the larger spring because we werent going for stock here. This should be great for my wife!

-Rob
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96 Sport '02 Explorer PI with ported heads, 90MM LMAF, DirtyDog Marauder TC, Lasota tune, Jmod, Magnaflow mid-mount with X, no cats. Urethane drivers motor mount. HIDs!

Last edited by Rob; 05-08-2011 at 03:54 PM.
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