Hummer Transfer case 218 swapping with 242 Model

Hummer Transfer case 218 model can swap with 242 model,what are the spare parts required for swapping.

NSN: 2520-01-163-4999 (21
NSN: 2520-01-409-2512 (242)

Depends on the 242 you may have.
Early one has a 3 bolt tail shaft housing, later has 4 bolt housing.
Parts needed are rear drive shaft, mid drive shaft....from transfer case fwd., small wire harness and light [ T/C lock ].

Thanks For the reply

86humv, got a problem with my 218 transfer case. This 998 will not go into HL or L sitting still with the engine running in Neutral. You move the stick and just touch the gears and it will grind. I have not forced this issue, just touched the tip of the gear teeth. Seems the tranny output shaft wont slow down enough to engage. I can turn of the engine, make the shift in the T/C , then re-start the engine, but that's the only way. Have not tried to shift into HL rolling. Your thoughts?

gsp45 said:

86humv, got a problem with my 218 transfer case. This 998 will not go into HL or L sitting still with the engine running in Neutral. You move the stick and just touch the gears and it will grind. I have not forced this issue, just touched the tip of the gear teeth. Seems the tranny output shaft wont slow down enough to engage. I can turn of the engine, make the shift in the T/C , then re-start the engine, but that's the only way. Have not tried to shift into HL rolling. Your thoughts?

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Take a look at the Operators Manual.

Per page 2-108 of the Operators Manual (section 2-11):

"Vehicle must be stopped, engine off and transmission shift lever placed in "N" (neutral) before transfer case can be shifted. Failure to do this will result in damage to drivetrain."

Lawdog734, Saw that after I posted. Does this also apply to the 242 transfer cases? Thanks

gsp45 said:

Lawdog734, Saw that after I posted. Does this also apply to the 242 transfer cases? Thanks

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yes....and let me add, this applies to any vehicle tcase, but I have seen some go into gear just fine while in neutral....but 99% require engine off, at least on hummer and HMMWV's

Retiredwarhorses, Not entirely correct sir. The CUCV series can be shifted into 4H and 4L with the engine running. They can also shift to 4H and back to 2W while moving. The way I'm understanding this 218 tcase with the 998 is because of the 3L80 tranny has no Park position to allow the tail shaft to slow enough to engage. FWTW

gsp45 said:

Retiredwarhorses, Not entirely correct sir. The CUCV series can be shifted into 4H and 4L with the engine running. They can also shift to 4H and back to 2W while moving. The way I'm understanding this 218 tcase with the 998 is because of the 3L80 tranny has no Park position to allow the tail shaft to slow enough to engage. FWTW

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Not entirely correct either...I have had no less then 4 M1008 and M1009's, they have at times required I shift to neutral and engine off on the tcase. My Hummer H1 has park' and it requires being in neutral to shift tcase...and engine off.
its simple for me....on all HMMWV's I go neutral, turn off engine and shift...been doing it for 20yrs.
just used the HMMWV the other day pulling my forklift out of the mud.
i have have had other hummer H1's that didn't need engine turned off...but in neutral and they shifted fine.
so there was no rhyme or reason....my current 98 with 242 will grind if engine not turned off.

What is the proper way to wire up the TC Lock light when doing the swap? Where do the leads connect and anything special required?

It‘s an LED so it‘s polarized. you can use a very low voltage source like a AA cell and see which side is positive, then run wires accordingly, with or without packard connectors.

I’m pretty sure most t cases in other vehicles do not require shutting off engine to shift. In fact most allow shifting between 2hi and 4hi at speeds up to freeway fast. So this procedure is puzzling to me for sure. Shifting geared mechanisms at rest is usually harder than while stuff I’d moving because of mesh issues. So, this must be a GM thing.