Stock converter not locking up.

[robertf]

I've recently bought back my GN I sold 18 years back. I immediately noticed on the highway lockup isnt working.
Car has Alky setup and Razor chip tune. Could this be deleting my lockup or do I need to dig further? I'm not sure if some tuned chips will do that. Nonetheless, I'd love to have that extra 200 RPM's on the freeway. Any ideas where to start? Thank you.

 

[larrym]

Check the switch on the pedal make sure it's set up properly it's a normally closed switch has to be pressed against the pedal it disengages lockup when you tap the brakes

 

[mikestertwo]

Are you sure the trans wasn't converted to a NL converter? Tie "A" to "F" on the ALDL and see if the converter locks. Check to see if there is +12v on pin "F" of the ALDL connector. If there isn't it could be the brake switch or other electrical issue or the car has been modified for a NL converter.

 

[robertf]

Still the Lockup unit. Previous owner was a close friend. Thanks guys. I have somewhere to start.

 

[Boxcars]

May be the lockup solenoid in the trans pan needs replacement.

 

[GNRick]

Are you sure the trans wasn't converted to a NL converter? Tie "A" to "F" on the ALDL and see if the converter locks. Check to see if there is +12v on pin "F" of the ALDL connector. If there isn't it could be the brake switch or other electrical issue or the car has been modified for a NL converter.

If you have voltage at the aldl then check for volts on the harness plugged into the drivers side of the transmission.

 

[earlbrown]

The Solenoid needs power and ground to engage. The hot side comes from the brake pedal switch. If ti's ratcheted away from the pedal arm the car will think you hit the brake so there won't be any lockup.

On the ground side, there's two N.C. switches on the valve body. One for 3rd and one for 4th gear. If you have a powerlogger look to see if it indicated 3rd and 4th gear when you get up to speed.

 

[robertf]

Ok one quick question. Does the same switch on the brake pedal that cuts the cruise, cut the lockup? My cruise works perfectly.

 

[RmvBfrFlght]

CC is split between the two switches. The switch with the vacuum hose is for 1/2 of the CC. That same switch also handles the power to the TCC solenoid. That will be the connector with two PNK/BLK wires in one terminal, and a purple wire in the other terminal.

The other brake pedal switch is for the electrical signal to the CC module. Along with operating the brake lights.

RemoveBeforeFlight

 

[robertf]

Just a thanks to all who chimed in. Yes it turned out to be the CC switch was pulled back just enough for the Lockup to stay disengaged but still allowed the cruise to work. I appreciate everyones help.

 

[Tom Kelly]

I have an 86 GN. Along with recent engine rebuild I changed to a 2800 converter with lockup. However I can't get a positive indication that it is working. I have tried the "tests" in posts on this site but can't get the right results. So I checked rpm's at 60. I have 27.2 inch tall tires (255/60/15) and at 60mph scanmaster shows about 2,050 rpm/s in overdrive (I do feel the shift into 4th) Not terrible but according to various online computers, rpm's should be at just under 1,800. Does this discrepancy indicate lockup not working? I found the switch to be not working and fixed it so cruise is now working so it's not the switch ( I think cruise and lockup are same switch). Thanks for your replies.

 

[earlbrown]

Get up to about 60mph at a steady cruise. Then push the brake pedal with your left hoof and listen to the engine.

If your clutch is working right it'll feel and sound like you downshifted

The switch only controls the hot side of the TCC. The ECM sends a ground that it gets from the 4th gear lock up switch in the pan. Every one of those components have to be working right for lock up to take place.
The easiest way to test the ground side is to jump out the ALDL port with a ground lead. (AKA 'lock up switch)

 

[Tom Kelly]

Get up to about 60mph at a steady cruise. Then push the brake pedal with your left hoof and listen to the engine.

If your clutch is working right it'll feel and sound like you downshifted

The switch only controls the hot side of the TCC. The ECM sends a ground that it gets from the 4th gear lock up switch in the pan. Every one of those components have to be working right for lock up to take place.
The easiest way to test the ground side is to jump out the ALDL port with a ground lead. (AKA 'lock up switch)

Thank you for your reply. I have tried to get results from the "brake" test as well as listening for that extra "shift" after it goes into overdrive. Neither test shows results so I was wondering if the fact that my 60 mph speed is about 250 rpm's more than the online calculators makes it reasonable to assume lockup I not working.

 

[earlbrown]

Sounds like it. When the TCC works correcty it's plain as day when it unlocks and locks.

Stick a wire in the top left slot in the ALDL connector and get up to 60 again. Ground that wire and see if the converter locks up.

If it does, you've narrowed it down to the ECM or the 4th gear pressure switch.

 

[GNRick]

My method is to stick a wire in top left spot, and another wire in top right spot. At 45-50 mph touch the wires together. That should lock the converter.

 

[fubar2.5]

How are you measuring speed? Use a gps and try that to see if the calculation works out.

 

[Tom Kelly]

Sounds like it. When the TCC works correcty it's plain as day when it unlocks and locks.

Stick a wire in the top left slot in the ALDL connector and get up to 60 again. Ground that wire and see if the converter locks up.

If it does, you've narrowed it down to the ECM or the 4th gear pressure switch.

How are you measuring speed? Use a gps and try that to see if the calculation works out.

digital dash speedo which agrees with scanmaster which agrees with police radar read outs which we have all over here. I’m gonna look into electrical suggestions Tuesday and I’ll update if I make progress. Gonna have the GN Dyno-tuned at Decordre automotive in Spring City PA. I’ll report back on that experience also. Thanks for all the input.

 

[fubar2.5]

Sorry how does the speedo know you changed the tires Id be willing to bet when the speedometer is reading 60 you are actually doing about 65. Try a gps or some phones have gps built in. Try your calcs using a 26 in tire size cause that's what the speedo thinks are on there. Did you change the speedo gears?

 

[Tom Kelly]

Sorry how does the speedo know you changed the tires Id be willing to bet when the speedometer is reading 60 you are actually doing about 65. Try a gps or some phones have gps built in. Try your calcs using a 26 in tire size cause that's what the speedo thinks are on there. Did you change the speedo gears?

Yes good point. I had calculated that with new rear tires I was actually doing 62.4 mph when speedo said 60. A minor difference which would account for approximately 70 rpm. Still leaving me well short of the 1850 I would expect. I’m showing 2050.

 

[Tom Kelly]

Update. Thoroughly researched the problem at Brandon Automotive in Spring City PA. Must say Brandon is very knowledgeable. Spent the entire day with the GN on the DYNO. Will put my thoughts together on that and make a separate post. But regarding the lockup, we were able to confirm it was not engaging and by trial and error an "jumping" the appropriate connections we found all the components to be fully functioning but not working when needed. So there is a loose/broken wire somewhere under the dash which, being the end of a long day, I decided to search for on another day. But now I know none of the components are faulty, just a bad wire somewhere. I count that as a success.