TRANMISSION - LOCK UP TORQUE CONVERTER

[greydbj]

Recently I have encountered a problem with the operation of the lock up on the torque converter; it seems to work fine up to 60-70 kph and as soon as you ease up on the accelerator, it unlocks and stays that way until the vehicle stops. The problem is intermittent as well. It all seems to work the way it is supposed to until the engine warms up.

Does any one have a description as to how the TH350C is supposed to operate? I have seen one somewhere, but don't remember where or when. Does anyone have a diagnostic grid that I can use to trace the possible cause. Seems to me it could be a sensor or vacuum issue as opposed to anything inside and I would just as soon start on the outside and work my way in, if you know what I mean.

Thanks a ton.....greydbj ;help

 

[Sensei]

The tranny has a 4 pin electrical plug on the driver's side. I'd have to go look up which pin, but one of them supplys 12 volts to the converter. Basically, that 12 volts should be there all the time except when the brake pedal is depressed. You could start by checking that. If the 12 volts is there and the converter is not locking up, or is not staying locked up, the problem is internal in the tranny.

God bless, Sensei

 

[22229stingray81]

It's a known problem with the '81's TH-350. Many people add a switch in the cockpit to turn the lock-up on and off as they see fit. I think the fix is pretty complicated. Forum member "Nut" did the mod; perhaps you could shoot him a PM for more information, and any possible fixes.

-Tatortot

 

[Evolution1980]

Recently I have encountered a problem with the operation of the lock up on the torque converter; it seems to work fine up to 60-70 kph and as soon as you ease up on the accelerator, it unlocks and stays that way until the vehicle stops. The problem is intermittent as well. It all seems to work the way it is supposed to until the engine warms up.

Sounds like it's working exactly how it's supposed to. 60-70kph = 38-44mph. That's about the point where it will kick on. If you let up off the gas within that range, it will likely disengage regardless if you hit the brake or not. Otherwise it would be like coming to a stop with the clutch still engaged.

If you just slow down and then get back on the throttle, it may not immediately kick back in until you reach the upper end of it's normal engagement range.

If what I've described doesn't accurately reflect your problem, then it's probably electrical. Replacing the solenoid isn't a hard job, just a messy one because you have to drop the transmission pan. Unless you have an aftermarket pan with a drain plug, then it's only not-quite-as-messy. Replacing the solenoid is probably the best place to start. Easy and cheap. Plus, they do go bad. Mine did.