Looking for answers from someone who has done a 3800 swap before or is familiar in the 3800/4t65e-hd in general.

1.) What is this hole in the engine block near the backend (underneath the coolant sensor)? Does anything need to be here? A freeze plug?


2.)What is this hole in the transmission bell housing? Does anything need to be here? I had Triple Edge service my transmission so I'm not familiar.


3.) Am I missing bolts on the differential cover?

First 2 pics, just holes, nothing to be concerned with, purpose, who even knows/ last pic, thats where the transmission to block support bracket goes.

Generally speaking, if there are machines holes on an machined surface w/o threads in them in odd out of the way locations on engines and transmissions, they are normally used with locating pins during the various stages of machining the engine block and transmission cases.

The last picture once you install the transmission to engine block bracket, holes 5 & 6 must have bolts in them to properly seal the end cap. If they don't go through the transmission to engine bracket, they need to be installed before installing the bracket. Most if not all of the holes 1-4 will have bolts in them to the bracket.

Here is what the LS4 transmission to engine bracket looks like. Other engines use similar but different brackets.

[This message has been edited by fieroguru (edited 03-26-2023).]

Thank you both for the reply. I think my transmission to engine bracket ended up with the core I gave to Dave, and I didn't receive one back. So that explains it a little bit.