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A4LD Torque Converter Lock Up

Joined
February 13, 2005
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City, State
Wichita, KS
Year, Model & Trim Level
1991 XLT
Hi All,

I have a 91 4x4 that I purchased with a rebuilt transmission and rebuilt torque converter. My problem is that I don't believe that the converter is locking up. I can be cruising down the highway at a constant 70 mph and the engine rpms will go from 2300 to 2900 with no apparent "shifting".

The check engine light does not come on and it does shift into fourth gear. I have replaced the TC lockup solenoid and added the transgo shift kit.

Is the lockup on the A4LD just exceptionally smooth? I can definately tell that my AOD in my 5.0 T-Bird is locked up in 3rd and 4th.

I've heard there is a diode in the system. Is this true? If I had wired it backwards, wouldn't that trip the computer?

Thanks for reading!
 






Joined
February 13, 2005
Messages
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City, State
Wichita, KS
Year, Model & Trim Level
1991 XLT
I should also mention that I have a Wells TPS (replaced the stock Ford unit)
 






Glacier991

EF Tranny Guru
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City, State
Sacramento, CA 95827
Year, Model & Trim Level
1992 XLT
Hmmm... let's see.... 2300 vs 2900... I'm able to confirm that would be about the difference between OD and no OD, but cannot confirm that lockup would be that much. You SURE you have 4th gear? When you changed out the tcc solenoid did you check the 3/4 shift solenoid?

And yeah the A4LD shifts generally benefit from some of the transgo mods, like drilling out the pucks and separator plate. Otherwise they can be pretty mushy.... although some like em that way.

There is a diode, but you cannot "wire it backwards" so relax on that one. The two solenoids share a common power supply is all.

It definitely sounds like an issue with the solenoids. A place where hooking up a trans tester would tell you a lot (sigh)... you could run the trans independent of the computer and isolate the problem as trans or input. At the moment it is somewhat difficult to tell.

lack of lockup COULD be coolant temp sender, vss, etc in which case the trans and solenoids are fine. It could also be something in the wiring or the solenoids.... altho the TCC solenoid is undoubtedly fine.

So to ramble... IF it is the TCC not locking up (and you KNOW the OD is staying locked up (I am skeptical) then it is probably inputs or wiring. If is is the 3/4 shift not staying in OD (4th) then it is likely solenoid first off, and if not then wiring or inputs. Generally VSS problems will affect BOTH TCC and 3/4, Coolant Temp sensor will affect TCC and MAF will screw everything up. TPS can be a problem but sounds like you have that covered.

Not sure if ANY of that helps.
 






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