How does my 727 trans lock up

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maca

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Hey guys I have a 727 transmission that locks up automatically in 3rd gear. In the past I have run the 46rh / A518 transmissions which you have to supply power and an earth to get them to lock up via a solenoid.
However this one just locks up on its own and only in Top gear. Does anyone know if it's the converter that losck it up or the valve body. I'm chasing a vibration and would like to try another valve body but I only have one out of a non lock up 727 to try.
 
Converter Lock-up on a 727 is controlled by the lock-up module on the valve body. In the module there is a so called Fail Safe valve which only allows lock-up when the direct clutch is fully engaged (3rd Gear). It also provides a quick Lock-up clutch release in the event of a kick-down situation. The lock-up on a 727 is purely hydraulically controlled, eliminating the need for a solenoid as in the 46RH.
 
Thanks guys. That's great info.
I'm chasing a vibration and wanted to try a different valve body. Could I just try a non lock up valve body as they look identical.
 
maca said:
Thanks guys. That's great info.
I'm chasing a vibration and wanted to try a different valve body. Could I just try a non lock up valve body as they look identical.
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Everything I've read said the valve bodies don't interchange. Someone with more trans experience may chime in. I made a brass plug for mine and blocked the circuit.
 
Lock up and non lock up Valve body will not interchange, the main case and valve body are different passages in front of rear servo area.
 
I've seen a lot of case differences in that area right in front of the rear servo area, but the only vb differences I saw were ptk and non-ptk.
 
What would be the main reason to get rid of the lock up. Would it be because of horsepower and performance?
 
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