There is relatively little information (surprise, surprise...) and much conjecture about this LT4 oil pump issue. Here's what we do know for certain:
- oil pump failures on 2017 and 2018 model year cars polled significantly higher at this site in the ZL1 subforum, see screenshot below
- the failure mode is exactly the same in almost every case, the part cracks at the same exact location in each affected vehicle
- GM had at least four revisions of this oil pump
- Katech tested all GM pump revisions and found that they all failed load testing, but the newest revision(s) were able to withstand higher loads before failure
However, what we are only guessing at is when these stronger GM oil pumps began to make it into ZL1s, and how durable they actually are, given the discrepancy between the poll and Katech's results, of which I would put more trust in the latter (especially since some people polled with a 2016 car when the first model year of the ZL1 was 2017).
Katech are also manufacturing and selling a high quality
replacement oil pump that has a stronger design and zero failures to date, at least none documented in this forum.
If I were in the market for a ZL1, I would buy a 2018 and consider the cost of immediate oil pump replacement with the Katech pump as part of my purchase price. GM's service history may or may not show any oil pump replacement, but a conscious seller who already installed a new (hopefully Katech) oil pump will be able to present the invoice.
I have not personally replaced the pump on my LT1, but yes, the engine has to be partially disassembled for this job.