Lockup Torque Convertors

Lockup Torque Convertors

Bill Amberger
aka Magnumguy
aka Padre Bill

Our beloved Magnums were equipped with (due to government mandates for better fuel economy) not so durable lock-up torque convertors.

One way to delay or totally eliminate them is to go to your local Mopar dealer and ask for a spring that is sprung to lock-up at a speed higher than the 28-33 mph in ’78 and 45 or so in 79.

They sell springs that go from the aforementioned 30 mph to infinity. The spring goes in a passage on top of the valve body. Most “shade tree” mechanics and/or local tranny shops would just place a checkball in the passage to block off fluid to the convertor.

Seems when this is done that little or no loss of mileage is noticed. I’ve got a 79 w/a 318 that has had it disabled, this car delivers around 19-20 mpg’s. And the motor isn’t lugging so much. These cars are geared high, with the highest gear being 3.23. So motor noise isn’t too much of a concern.

I recommend that the spring be used instead of a checkball. I had this done to a 78 GT that I owned. A couple months after the “checkball” procedure the tranny started slipping between 2nd and high. Keep in mind the car had 120K + on it. So maybe the end was near anyway.

Pre-78 904’s, especially with the 360 engine, had a 2.74 (?) low gear set, used to offset the near 2 ton weight and high gears. I believe the pre-lock ups were a more durable unit, although I’ve owned numerous Magnums with the lock-up tranny and have had minimal problems.

So if your considering a tranny switch go that route. If you wish to keep your “number’s matching” tranny, go with the spring thing. I believe that shift kits came with the proper items to disable the convertor. This is second-hand info., so check with your kit’s manufacturer to be sure.

Click the above thumbnail to see the cover to be removed for access to this spring.

 

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