Ins & outs of impeller vanes and weld gaps

Impeller Vanes

The movement of a vehicle relies on the torque converter’s ability to transfer the torque of the engine to the transmission (the beginning of the driveline).

Hydraulically speaking, movement starts with the first revolution of the engine, when the vanes of the torque converter impeller start the oil moving toward the turbine. If the vanes become loose or fall out completely, the impeller loses its ability to move the oil and can no longer transfer torque. Converter rebuilders see the dramatic results of this when they cut open a converter and find the impeller looks like a salad bowl. This is why checking and securing the vanes to the impeller is an important part of a quality rebuilt torque converter.

In the early years of torque converters, the impeller vanes were secured to the impeller by a secondary inner wall. This inner wall was sufficient to hold the vanes to withstand the torque of the engines of the day, but was a nightmare for transmission rebuilders. At that time automatic transmission fluid (ATF) was still in its primitive stages and was prone to shellacking. The fluid would cake up and become deposited in the cavity created by the inner wall. Technicians had to hold their breath every time the fluid was changed because there was always a risk that the new high-detergent fluid would dislodge a contaminant and cause a valve to stick in the valve body and/or governor.

To read the rest of this Technical Article on the Sonnax Website click here.

Article No.: TCTIP-04-08
Author: Ed Lee
Total Pages: 2

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