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6L90E swap to 6.2L diesel

4.7K views 5 replies 2 participants last post by  Mogman  
#1 ·
Hello all, I am a newbie here and am looking for some information and am having a hard time finding a forum that matches my issue.
I have a couple HMMWV (Humvees) and I have done a Duramax/Allison1000 conversion on one, I am looking to get rid of the lossy and under geared TH400 in #2, the low 1:1 gear ratio and non lockup is really a problem with running high RPM trying to keep up with #1 (DuraVee)
So I just picked up a 6L90E with transfer case (would have preferred a 6L80E) and am wondering if anyone can enlighten me as to what it will take to mate it to the 6.2L, as far as I have read the bell housing should bolt up so I am mainly concerned about the torque converter, not concerned about the electronics or other issue at this time just the engine/transmission connection. I do have the correct flex plate for a 700R4 (was in the works before I stumbled onto the 6L) and of coarse the originalTH400 which is different.
 
#2 ·
It should be very doable. Chevy ran the same bell housing bolt pattern from way back to the present. The only thing that changed is they moved the upper left bolt to the center/top. But that can be drilled out or left out. The only other thing they really messed with was crank offset from the mounting surface of the block and there’s only 2 options to my knowledge. Old style (sbc, bbc, 6.2, 6.5, early ls) and new stile that the crank flange is closer to the front of the engine. So my thinking is with just a cheap little adapter (basically the same thing as a wheel spacer) you should be able to bolt it right up with probably a flex plate for the vehicle the tranny came from since it probably has 6 bolts for the converter instead of 3.


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#6 ·
Thanks, it looks like the 6L T/C pilot is about 0.4" longer, (because the LS crankshaft is 0.4" shorter) so the answer might be the 0.4" bellhousing adapter plate from Lakewood, elonging the holes in the gen 1 flex plate to allow the LS 11.1" bolt pattern instead of the gen 1 11.5" and installing 0.4" spacers and longer converter bolts.