TorqueConverter locking up Late-any Ideas?

[rockylaurence]

OK, my trany shifts fine and works correctly, except, the T/C wont lock up until 45 mph. It doesn't matter if I'm cruising around town or going down a dirt road, light throttle doesn't matter. The problem leads to high temp. in the trany because of all the slip allowed by the T/C. I understand also that if under heavy load or Wide Open Throttle that it won't lock-up. Lastly, I read in the manual that under normal circumstances it should lock-up around 30mph--at what speed does all of U-nnns T/C lock?.

 

[MrShorty]

I think the slowest I notice mine lock is about 40 mph.

 

[rockylaurence]

I would think that inorder to increase gas milage the X's T/C would lock up sooner. Most residential areas are 25-40 mph which means that all that gas is being wasted while tooling around town. I dont know-maybe it's because the X is so heavy and that it needs to stay unlock to prevent Lugging the engine?
I was hoping that a Ford/tany tech would have an answer or tell me not to be concerned about it.
Thanks:redexp:

 

[Speedfreak]

With my A4LD the torque converter always locked up at 80 KPH. I could set a watch to it it was so constant. I think that converts to about 45MPH, so that would seem normal to me. I never had an overheat problem from this.

I wouldn't be too worried about excess slippage unless your torque converter is bagged though. A torque converter at coupling point is about 98% effecient. (Coupling point is the point where the converter impeller and the turbine speeds are matched.)

 

[MrShorty]

speedfreak, you seem to know a bit about torque converter clutches. mine doesn't lock up like I think it should. electronically, it works normally -- the computer is telling the TCC to engage, and it does -- sort of. There still seems to be a lot of slip when it's engaged. When I tap the brake to disengage the TCC, the engine speed jumps by only 50-100 RPM. On my brother's '98 explorer, the TCC made a difference of several hundred RPM. Any thoughts?

 

[Speedfreak]

Sorry about the late reply, I was trying to find a hydraulic schematic for the A4LD but came up empty. To my knowledge the A4LD uses a clutch in the torque convertor to lock the turbine and the impeller together for direct drive through the converter. This would mean that this system would be where you would want to look to find your problem. First the clutch is controlled by an electonic solenoid that diverts oil pressure to the clutch when told to do so by the computer. This pressure then goes into a piston in the torque converter and squeezes the clutch plate causing the converter to lock up. Now to figure out where the problem is you would have to do a couple of things, first find out how much pressure 'is' going to the clutch and second how much pressure 'should' be going to the clutch. If the clutch is seeing the right amount of pressure then chances are that the clutch is gone and you need to replace the torque converter. If the pressure is lower then it should be then there are a few areas, internal leakage, bad control solenoid or bad signal going to the lock-up solenoid.