matt formula

I've searched the forum and have been unable to find anything that matches my exact problem. The problem I'm having is with my 2000 Z28 when I'm just cruising in OD around 50-55mph for any extended period of time, if I hit the gas to speed up my RPM's shoot up but my speed doesn't change. You can feel that there isn't that resistance on the motor that you normally feel and the only thing I can think of is that my converter is unlocking for some reason. Now when this happens all I need to do is tap the brake and BAM the converter seems to lockup and I'm back in action. Now the transmission seems fine mechanically and has no issues shifting or anything like that. Is this some electronic issue? If so what can I do to fix this? Also I'm not throwing any codes. Any help is greatly appreciated.

FirstYrLS1Z

sounds normal/as it should be to me.
cruising in overdrive(4th gear) with convertor locked and giving it gas to speed up will unlock the convertor due to the increased torque demand to accelerate/speed up. Convertor lock-up clutch is designed/set for relatively steady cruising.
tapping the brake unlocks the clutch(which already is) and that removal of foot from brake pedal allows the lock-up circuit to re-activate.
going up hills,erratic front/head winds,very wet road surface will cause clutch un-lock.
wet roads will cause more effort for the tires to 'squeeze' the water out of the way thereby increasing torque demand.

Rear gear also influences/affects locking/unlocking. 3.73s'(for example) gives the powertrain a greater advantage over the vehicles' weight and inertia compared to 2.73s'(for example). When I was running 4.56s',even going up hills didn't influence the convertor to unlock because of the great advantage the powertrain had.
For example if the vehicle needed 20 more ft,lbs. of torque to the rear tires to accelerate,having 2.73s' would require 7.3 more ft.lbs. of drivetrain torque before the gears to supply that 20 ft.lb. demand,3.73s'-5.4 ft.lbs.,4.56s'-4.4 ft.lbs.

matt formula

Thanks for the response! I understand what you're saying and I feel better knowing that I may not even have a problem. Something just felt weird to me but perhaps I was overreacting.

zachisageek

You might have a tuned PCM. My 1998 z28 was tuned from the factory to unlock at 100% throttle position. Tuning recommendations said to reduce this value to avoid burning up the lockup clutch if your car is modified.