L3N71B 3 speed w/TCC - Understanding

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ibjman
Posts: 30
Joined: Tue May 12, 2015 5:36 pm
Car: 1986 720 King Cab Z24
Location: Phoenix

L3N71B 3 speed w/TCC - Understanding

Postby ibjman » Sat Aug 27, 2016 8:42 pm

Hi,
1986 720 2.4 L3N71B Transmission.
Original Rear Axel Ratio was: 3.889/1.
Changed to super economy axle: 3.64/1 to achieve lower overall RPM's @ Freeway speeds.
(Perhaps I've overdone it)? In hindsight, on ratio lower might have been better but I really don't want to buy yet another 3rd member.
Because of the extremely high gear ratio.....the engine barely has enough power to maintain the higher road speeds I was hoping for.

Normal ops of the auto trans indicates that shortly after top gear engages, TCC can be felt to engage as expected.

Looking for someone that has a thorough knowledge of the exact working of this transmission.

As far as I can observe, the TCC stays locked up in 3rd at cruising speed even if the wide open throttle kick down switch is depressed...... (As expected, at highway speeds, the kick down switch will not cause a 3-2 downshift).
My transmission shop said that he though it might at least unlock the TCC when the kick down switch is activated.
I think it would be very beneficial if a way could be found to force the TCC clutch to unlock as desired at times for slightly more torque.

It appears from my studies that there is no electrically controlled TCC solenoid even though there is a kick down solinoid.
My guess is that the TCC is mechanically controlled to lock up whenever the 3rd gear(direct) clutches are applied by the valve body.

Is there anyone who could offer a constructive suggestion on any possible way to create a manually controlled override to unlock the TCC to gain some extra highway torque when needed?
Most modern TCC transmissions are made to unlock the TCC when accelerating.
Please post a comment or PM me.
Thanks, Ibjman


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