Torque converter won't unlock

[Boxcars]

Replaced my transmission with a BRF unit out of an 86 T that has been out of service and on the shelf for about 10 years. I was told it worked fine when I bought it a few years back. It looked clean inside and remaining fluid was a good color, so I put a new filter on it, and added a super servo, my original D-5 converter, and installed it. Fortunately, it shifted through all four gears on the test drive, but the torque converter is always locked, never unlocks. I have a couple new lock up solenoids in stock so I plan to change out the old one tomorrow. Question: is there anything else more basic I might check first that's causing it to stay locked? Another: I saw a post where it was suggested the valve above the solonoid could be stuck. Can I access that valve to acertain if it's free? One way or the other, I'm installing the solonoid tomorrow, but just looking for some affirmation that I'm not overlooking anything. TIA!

 

[Nick Micale]

The solenoid may be stuck or there could be a wiring issue, so remove the electrical connector from the side of the trans to check if it is an electrical issue?

 

[Boxcars]

Thanks Nick. Are the plugs on all TRs wired the same? I would think they are but don't know for sure. My car is an 87, but the replacement trans is an 86 BRF. The trans I took out, there were no issues with the lock up. It worked perfectly. So you mean the wiring from the plug to the lock up solenoid? Usually, if you remove the plug from a working unit, no 12 volts so it won't lock up. Right? In this case it won't unlock so I suspect the solenoid is stuck, and therefore bad. I'll look it all over. The worst that could happen is the new solenoid won't fix it.

 

[Boxcars]

 

[achalmersman]

Easy test to see if it's electrical vs mechanical is to hit the brake pedal while the converter is locked. ASSuming your brake switch is operational and the TCC does not disengage you have a mechanical problem most likely bad lockup solenoid.

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[achalmersman]

The brake switch opens the B+ side of the circuit. Very fast electrical diag. If it DOES unlock when you hit the brake pedal than you need to diagnose why it's staying electrically comanded ie short to ground on ecm side of the circuit

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[achalmersman]

By the way, TCC is not hydraulically available in 1st gear so you should only have symptoms in 2nd through 4th

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[fastblackracing]

Replaced my transmission with a BRF unit out of an 86 T that has been out of service and on the shelf for about 10 years. I was told it worked fine when I bought it a few years back. It looked clean inside and remaining fluid was a good color, so I put a new filter on it, and added a super servo, my original D-5 converter, and installed it. Fortunately, it shifted through all four gears on the test drive, but the torque converter is always locked, never unlocks. I have a couple new lock up solenoids in stock so I plan to change out the old one tomorrow. Question: is there anything else more basic I might check first that's causing it to stay locked? Another: I saw a post where it was suggested the valve above the solonoid could be stuck. Can I access that valve to acertain if it's free? One way or the other, I'm installing the solonoid tomorrow, but just looking for some affirmation that I'm not overlooking anything. TIA!

When your changing the solenoid out you can pull the valve assembly and clean/check it. You will need a smallish set of snap ring pliers for inernal rings to pull the ring out and then you can pull the valve assembly.

 

[gunzandgearz]

just curious, why do you think the converter is locked up, if it was locked up it would kill the engine as soon as you put it in gear, also it would want to kill engine when coming to stop. you can check the sol. by pulling it out and touching the two wires to battery and seeing if sol clicks, good luck.

 

[TurboDave]

By the way, TCC is not hydraulically available in 1st gear so you should only have symptoms in 2nd through 4th

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I was wondering when someone was going to point that out!


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[Boxcars]

Thanks all for your input. All very helpful. The symptoms are, when it shifts into second, immediately the RPM drops as the TC locks, and then shifts the rest of the way through third and fourth feeling kind of under load. When coming to a stop it bucks some as it downshifts back to first. So I guess it doesn't stall because as mentioned, there is no lock up in first. I'll post back with the results, and thanks all again!

 

[gunzandgearz]

Yes this is correct I was thinking about 700-4l60 as they are applied in first if sol is energized, not the 200 . and you obviously are experiencing lockup problems with those symptoms as nick said check your wiring and sol operation as I stated above but valves are also bad about sticking when sitting around for long periods.

 

[RmvBfrFlght]

you can check the sol. by pulling it out and touching the two wires to battery and seeing if sol clicks, good luck.

If anyone does this make sure to get the polarity correct. Red wire to + terminal, black wire to ground. Reverse them and the kickback diode in the solenoid goes poof. In that case need a new solenoid.

RemoveBeforeFlight

 

[Boxcars]

Again, thanks for all the input. I installed the solenoid -- I didn't mess with the valve above it -- I didn't have the right snap ring pliers anyway, so I took my chances. Fortunately, the solenoid was the problem and the trans and lock up now work perfectly.