In this video, I do an autopsy on a 4L60E that I recently built for a customer which lost 3rd gear within only 200 miles! Unfortunately, these things occasionally happen to all builders however the cause of this one mystified me. So after receiving the transmission back from the customer, I elected to film and document the tear down for both transparency's sake as well as to determine what went wrong and why so that learnings can be applied to all my 700R4 and 4L60E rebuilds going forward.

Note: Valve Body will be tested in a separate video featuring the Sonnax test plate for 4L60Es (it was previously tested prior to letting the trans go out the door nothing remarkable was observed in testing).

Viewer's Note: There will be a follow up video on this transmission once I complete my investigation, which is expected to wrap within a week or so of this video's publication date (2.15.24).