TH400 into 72 K20 CHANGES/PROBLEMS - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**w314speed** · 11-20-2007, 07:21 AM

I am planning a swap from TH350 to TH400.... What will I need to expect using the stock NP205.
Thanks

cobinder · 11-20-2007, 08:23 PM

Depends on what 205 you have. If it's the old style (figure 8 bolt pattern)Your gonna need the mounting adapter made for the 400 (ebay $100) and your going to have to replace the input shaft on your 205 with one that has 32 spline female. Advance might make an adapter for the 4 different old style 205 input shafts.

**w314speed** · 11-20-2007, 08:34 PM

I have the old style 205- figure 8 pattern and I have the adapter. I would need the 32 spline conversion done! Will the trans cross member and TC mount need to be relocated??

Thanks for all you input!!!

jeffspower · 11-20-2007, 09:07 PM

Done it on my '72 K20. Crossmember will need to be moved further back, shorten rear shaft, lengthen front. You might have to modify the shifter a bit to come thru the floor properly, as it sits further back too.

11-20-2007, 07:21 AM	#1
w314speed Senior Member Join Date: Jun 2005 Location: atlanta Posts: 2,315	TH400 into 72 K20 CHANGES/PROBLEMS I am planning a swap from TH350 to TH400.... What will I need to expect using the stock NP205. Thanks

11-20-2007, 08:23 PM	#2
cobinder Everything is work in progress Join Date: Apr 2006 Location: Denver Colorado Posts: 326	Re: TH400 into 72 K20 CHANGES/PROBLEMS Depends on what 205 you have. If it's the old style (figure 8 bolt pattern)Your gonna need the mounting adapter made for the 400 (ebay $100) and your going to have to replace the input shaft on your 205 with one that has 32 spline female. Advance might make an adapter for the 4 different old style 205 input shafts. __________________ Good luck with your truck! How much?! It's just an old truck part!! 49 International on a 80 GMC 3/4ton 4x4 chassis 48 International KB-5 2 ton dump bed 04 Honda CRF "500" 09 Honda CRF450 fuel injected rocket 03 Suzuki hayabusa carbonfiber wheeled monster. 02 Ford diesel stretch van (toy hauler) 01 38' Monaco diesel pusher motorhome

11-20-2007, 08:34 PM	#3
w314speed Senior Member Join Date: Jun 2005 Location: atlanta Posts: 2,315	Re: TH400 into 72 K20 CHANGES/PROBLEMS I have the old style 205- figure 8 pattern and I have the adapter. I would need the 32 spline conversion done! Will the trans cross member and TC mount need to be relocated?? Thanks for all you input!!!

11-20-2007, 09:07 PM	#4
jeffspower Well, Whoop-dee-do! Join Date: Mar 2003 Location: Easton, Mo. pop.- me & scarcely a few others Posts: 2,302	Re: TH400 into 72 K20 CHANGES/PROBLEMS Done it on my '72 K20. Crossmember will need to be moved further back, shorten rear shaft, lengthen front. You might have to modify the shifter a bit to come thru the floor properly, as it sits further back too. __________________ '68 GMC shortbox 4x4 350/SM465/T221- bought it in '83 SOLD '72 K20 500 Cad/TH400/NP205 SOLD '92 Chevy 2500 6.5 mech TD 4L80E crusty daily driver '72 Monte Carlo... sweet low mile toy '11 Dodge Challenger IE 392 6spd... midlife car

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