LS swap in a 1978 K25 with a 4L80E

[THI]

I am currently in the process of getting the body off the frame so it can be cleaned up and painted. I have two LQ4's, one complete with 160K and the other is fully machined and ready for re-assembly with flat-top pistons. I am leaning towards the fresh rebuild similar to an LQ9 with a Truck Cam. As is set things up, I know the engine can be placed in the "normal" position which is 1" ahead of where the stock SBC or BBC would be placed, or it can be set back that 1" so the back of the LS engine is where the TH400 that was in the truck would be placed. I also realize that the 4L80E is 1-1/2" longer than the TH400 and uses the same adapter for the NP241C (pass drop) t-case that I have for this project. I am using the 1985 and later "W" crossmember and short adapter.

For those of you who have put an LS in a Square Body with 4L80E, where did you end up placing the engine and what accommodations did you need to make for the transfer case? Thank you.

Tom

[toddoky]

Originally Posted by THI

I am currently in the process of getting the body off the frame so it can be cleaned up and painted. I have two LQ4's, one complete with 160K and the other is fully machined and ready for re-assembly with flat-top pistons. I am leaning towards the fresh rebuild similar to an LQ9 with a Truck Cam. As is set things up, I know the engine can be placed in the "normal" position which is 1" ahead of where the stock SBC or BBC would be placed, or it can be set back that 1" so the back of the LS engine is where the TH400 that was in the truck would be placed. I also realize that the 4L80E is 1-1/2" longer than the TH400 and uses the same adapter for the NP241C (pass drop) t-case that I have for this project. I am using the 1985 and later "W" crossmember and short adapter.

For those of you who have put an LS in a Square Body with 4L80E, where did you end up placing the engine and what accommodations did you need to make for the transfer case? Thank you.

Tom

The 85-up TH400 transfer case adapter you have is not going to work directly with the 4L80 transmission. The O.D. of the index ring on the adapter will need to be turned down to fit the smaller diameter of the 4L80 case. Once that is done, you will discover that the mounting feet bosses on the adapter are going to experience interference with the 4L80 pan.
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[THI]

Originally Posted by toddoky

The 85-up TH400 transfer case adapter you have is not going to work directly with the 4L80 transmission. The O.D. of the index ring on the adapter will need to be turned down to fit the smaller diameter of the 4L80 case. Once that is done, you will discover that the mounting feet bosses on the adapter are going to experience interference with the 4L80 pan.
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Thank you for reminding me, I looked through my parts laying around and I did find an adapter with the correct part number (casting 15654927) for the 4L80E to NP241 so that by itself is not an issue.

Would still like to know from those that did this swap where they ended up with engine placement and other mods they had to do to the driveline.