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Discussion Starter · #1 ·
1996 Taurus GL Vulcan AX4S trans...

I just finished rebuilding my transmission and reverse gear works, but when I put it in drive it doesn't engage. It doesn't work in Overdrive, Drive or 1, but reverse works perfect. Throw it in Drive and the engine revs up a couple hundred rpm in anticipation of engagement and nothing happens. After screwing with it, I found these two weird things that happen though:

1 - With the wheels off the car and it on jack stands, I can rev the engine in reverse and get the axles spinning at about 10 mph, then if I throw it in drive, (and the computer recognizes about 10 mph, second gear territory) it engages in SECOND gear. If I hold the brakes to add resistance it will accelerate as it should, but once it drops down below 7 mph or so when it should shift into first gear, it acts like its in neutral from then on, unless I do that reverse thing again. In short, it seems to be missing first gear but second and the others seem to be ok...

2 - If I unplug the transmission wiring harness/solenoid plug, the white one on top of the trans, and then put it into drive from a stop, it engages.

I'm suspecting a bad shift solenoid as the reason it won't engage into first gear when I put it in drive. I am almost completely sure I did everything right with the trans, and have already taken the whole thing apart again and put it back together to try to find problems and couldn't find any. There is no engagement in drive at all, and no check engine codes unless I do that thing with disconnecting the trans connector.

Any ideas as to why it won't engage in first gear?! Thanks for your help... I'm just at a loss as to what to do next. It just seems weird to me that the solenoids would go bad at the same time as I do this rebuild...

Btw I did the rebuild because of a broken forward clutch piston wave spring. It and the forward clutch piston was replaced during the rebuild.

Thanks!!!
 

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Yeah it could be one of those solenoids I suppose... I just rebuilt mine and thankfully it works. Thats crazy how it engages without that connector plugged in. Anybody else have experience with this situation???
 

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It uses different hydraulic circuits if the PCM is disconnected. It also uses full (not modulated) control pressure. Measure the solenoids for correct resistance, if they check out OK you may have a stuck valve in the valve body.
 

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Stuck valve in valve body or low/reverse one-way clutch malfunction.

Without the PCM connector, most likely it is engaging third gear in limp mode.
 

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Another thing to remember is that the valvebody gasket material likes to shift during assembly and this can cause a "No drive issue". Another thing to check if the solenoids are correctly reinstalled.
 

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Discussion Starter · #6 ·
Alright guys thanks for the info. I'll check the solenoid resistance tomorrow. Does anybody know where I can find a wiring diagram for that 9 pin connector on top of the trans for the solenoids? Or am I better off removing that side pan and testing them that way?

I'm pretty sure the valve body gaskets aren't to blame. The first time I assembled it I admit to reusing the old gaskets on the valve body because I thought I might screw up the valve body but the second time around I used new gaskets and spent the time to remove the old ones. Same problem both times and I really spent a lot of time making sure everything was aligned correctly.

Makes sense that its probably in 3rd gear without the connector... I went out to mess with it again and its definitely not in first gear. And it seems to kind of bang into gear without the connector... probably because of full pressure.

Two last questions though... is there supposed to be a click from the solenoid when I put it into drive? There isn't one. And which piston is responsible for first gear? The forward clutch piston or the intermediate piston??? Thanks for the info guys. I haven't been this stumped on a car repair in a long time and I fix cars all the time :(
 

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Discussion Starter · #9 ·
Does anybody have any other advice?! That connector isn't for my generation transmission... the pin layout is different. I'm really at a loss at to what to do. I love this car and don't want to replace it but I can't figure out why its not working!!!

Should I buy a whole new valve body? What should I be doing to test the solenoids or anything else that may be busted? Is there a way to manually force it into first gear with the solenoid wiring to test the piston function? Thanks for the help guys...
 

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The only way to manually get first gear is to pull the shifter all the way down.

Do you get reverse? If not, there may be issues with the pump.
 

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Discussion Starter · #14 ·
Yes I have reverse and it seems like I have the other gears as well. With the wheels off I can get the axles spinning at about 10 mph in reverse and then throw it in drive and it engages second gear. BUT it won't engage first if its stopped... it just does nothing.

If I remove the side cover and just connect a positive and negative wire to each of the solenoids can I test them that way by listening for a click?! Thanks!!
 

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I had the same problem after doing some work on my 05 transmission. My problem was I did not get the chain cover gasket on right, it was sucking air. It appears that the reverse takes less oil flow then forward. I would look for a leak causing low oil pressure. I spent a lot of time checking solenoids and checking the valve body when the problem was oil flow.
 

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Discussion Starter · #16 ·
Thanks Eric I'll fully inspect my chain cover gasket. The only reason I don't think that is the case is because when I disconnect the trans connector it slams into 3rd gear really hard... as if somebody is just dropping the hood on it. But I'll check it for sure thanks man. I torqued the bolts to 20 ft/lbs... is that the proper torque?!

Today I'm going to remove that side cover and screw around with the solenoids and see what I come up with. (After checking for leaks at the timing chain cover) If I don't find anything I'll get a valve body from the junkyard and install that and see what happens tomorrow. Its time to bring Black Beauty out of surgery.
 

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Discussion Starter · #17 ·
Update-------------------------

Update...


Hey guys I just pulled the side cover and checked the solenoids by running 12 volts through each of the three on the side there and they all worked fine... a solid click from each every time 12v went through them. So seems like the solenoids aren't the problem.

I also looked at the chain cover gasket but it seems fine... I torqued the bolts to 20 ft lbs so I think that should be adequate right?!

So at this point I guess I should try to replace the valve body assembly... doesn't that seem like the next logical step? Or should I do something else!?

Thanks for the input.
 

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im sure u fixed it already but i can help

Hello i see this is a old thread and probably taken care of but to put out info incase someone else reads this thread or if you still have issue the reason why it goes to 3rd gear when u disconect the bulkhead connector is the 3rd gear shift in these transmission is when all 3 SS are off so when u disconect them the are all of releasing plungers. What u wana check first is run a rattail wire from pin number 2 wich is a red wire on the 3 post side of the conector and a rattail from number 3 wich is the one next to it in the corner of the conector opposite side from the missing connector helo since its a 8 pin there is a missing spot as u know. put a volt reader possitive side on the red wire pin 2 rattail negative to the other shift into drive that SS should read 12.5 to 13.2 volts its the second SS the only one thats used for first gear. If u need more help and or info let me know i just faught with a ax4s problem of simular nature and althought before my adventure i would say i knew very little about transmission operation and electronics but now i feel i am very knowledgeable. Best of luck to anyone reading this.
 
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