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3-4 shift issues, power loss

1190 Views 6 Replies 3 Participants Last post by  Crak88lx
Still working on the Turbo Swap, 88 T,bird into a 90 Mustang. Using an A4LD in the Mustang. I drive it, it shifts fine 1-2 and 2-3, but at about 45mph it acts like it wants to shift again, but will suddenly lose power, not shift and slow down. I can take my foot off the gas, and then speed up slowly and it will shift and I have power again. Also, when the power goes away, the engine light comes on, when the engine light goes off the power is back. At the loss of power the vaccum will go from around 0 to 20 all at once. about 1 out of 10 tries it will shift all the way through and work fine. This is a 2 wire A4LD.

Codes 81, 82 83, 85 and 88.

I am just not sure what is the instigator of this problem. It seems like it is the transmission, but I am wondering if I have some electrical something that is happening that would cause the same problem even if I had a manual tranny in it.

Is there a difference in a modulator valve for a 2 wire vs a 3 wire A4LD?

Any ideas on where to attack this would be great!
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I'm not a transmission genius by any means but check the vacuum lines, I had a car that miss shifted like this found a leak fixed the hose and bam she shifts. Also check fluid (don't mean to sound insulting).

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No insult taken. I am grasping for ideas! I think my fluid is good, but I should check again to be sure. I think I have all the vacuum lines tight, but again worth another look. Thanks for the post!
No problem. Maybe also try some electric component cleaner on the electrical hookups

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youre getting a code for the 3-4 shift solenoid. code 85. Ford OBD Trouble Codes – that is most likely your issue, but it wouldnt hurt to check a couple other things first.
like crak said, check the vac lines, especially the one for the modulator. also, pull the hose out of the modulator, if theres any fluid in the hose then the modulator is going bad and needs replaced. its cheap, like $20 at napa. bad modulator can screw up your shifts in the trans.
also check the vac lines for the egr, and check the egr itself. egr helps feed vacuum to the trans for shifting, so bad egr can starve the trans for air and slowly kill it, and can screw up your shifts if it is bad enough.
one more thing, if you havent changed the trans filter ever, it would be a good time to change it. clogged filter can mess up your shifts too. changing filter is easy, just drain fluid, drop pan, filter is right there. if you have good fluid then its ok to resuse it, but if it is iffy then just put new fluid in there. you will probably only get 4-5 quarts to come out since most of the fluid stays in the converter.
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Really interested in the code 85. I see it says the 3-4 shift, but what does that mean? This has been a long term project in my spare time (ha), so it has drug out over time. I had the tranny rebuilt so feel certain I have a good filter and new fluid. I am not positive whether I have the Mustang transmission in it or the Thunderbird transmission in it. Only after putting all back togeter did I learn about the 2 wire, 3 wire difference. The 2 wire is in the car, the 3 wire is sitting in my garage floor. Could it be the computer is trying to make the 3-4 shift electronically when the 3rd wire is not there and causing some sort of reaction?
I'd think if that were the issue it wouldn't work at all, but as stated earlier I'm not a transmission guy.

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