4L80E Direct Drum Problem

direct drum-both

The drums pictured above is a 4L80E direct drum (also called high/reverse). The Reman\Converted drum is pictured on the left & the stock-used left is on the right. The problem is a shortage of good used 4L80E drums, so someone came up with a way to convert the GM 400 Roller Clutch style drums (they are easy to find because nobody wants them because they aren't as strong as the sprag style). The sprag style is very popular in GM 400 High Performance & HD units as well as the 4L80E..

Below picture, using a pocket screwdriver, points to a small ledge that gives the outer sprag race proper clearance so that you can install the triple wrap snap ring that holds it on.  

Good-Drum

Drum below does not have the proper ledge, this causes problems when trying to install the triple wrap snap ring. If you finally get the snap ring in, you'll find the sprag is locked down in both directions because w\o the proper ledge for clearance, the outer race is locked against the drum (locked in both directions spells Disaster).

I hope this information helps others because it wasted a lot of time in my shop.

Bad-converted drum

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