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Old 02-12-2003, 05:35 PM   #1
Slick71
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4 speed to auto swap?

I'm thinking about swapping my 4 speed for an automatic, Turbo 350. I know everyone likes these old 4 speeds, but I'm ready for a change. I've currently got an NP 205 transfer case in my 4X4 and am curious how much would need to be changed? Will the 205 bolt directly up to the turbo 350 that I'm looking at? I think I'll need a new cross member, right? ....and of course I'll need the brackets, cables, etc. Will driveshaft lengths need to be changed? Any ideas or help is definitely appreciated!
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Old 02-12-2003, 06:08 PM   #2
breeh
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Unfortunately, your 205 will not bolt to a TH350. You need a different adapter and the spline count on your 205 is a mismatch to the one required for a TH350 adapter.
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Old 02-12-2003, 07:25 PM   #3
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As Breeh said, the 205 t-case for an auto is different than the 205 used behind a manual trans. If you want to keep your 205, you will need to replace the input shaft to fit behind the TH350, then the adapter to mate the two. I think the overall length of the auto is longer than the 4spd so you will have to relocate your crossmember (not sure if you need an auto crossmember) and probably make driveshaft mods.
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Old 02-12-2003, 07:51 PM   #4
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Thanks Breeh and Pont for the thoughts.....Anyone else have any experience with this swith.......These are exactly the kinds of things that I'll need to know!
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Old 02-12-2003, 10:26 PM   #5
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You already have the correct cross member and drive shafts. All '67-'72 np205 4x4s have the same drive shaft lengths (as long as you compare long bed to long bed, short bed to short bed, etc.) All cross members in the np205 4x4s are the same too. GM made up any mounting and length differences with the adapter.

You need a th350, th350 to NP205 adapter, and a NP205 from an originally equiped th350/np205 truck. As Pont and breeh pointed out the 205 behind your 4-speed won't bolt up to a turbo 350.

Your best bet is to find a complete setup from a truck or blazer somebody is parting out.

You'll also need an auto steering column, the th350 shift linkage, and a radiator with the cooling tank in the side.

When I did my swap I installed a transmission temperature gauge and a transmission fluid cooler. For the amount of work and money I spent on this swap I'm not taking any chances on burning my new tranny up.

Been there done that. Don't be afraid to email or PM with any questions.
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Old 02-13-2003, 06:39 PM   #6
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There is some info on the FAQ page to converting to auto
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Old 02-13-2003, 11:24 PM   #7
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Just checked out the FAQ category....thanks guys!
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Old 02-13-2003, 11:29 PM   #8
Jackal2k9
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hey slick ill trade you autrans hook up stuff, pedal assembly, converter and all for you manual stuff if its in good shape. i have a TCI turbo 350 with a shif kit that has about 5k miles on it and a lokar flor shifter.

oh yah radiator w/ cooler and xternal trans cooler too.
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Old 02-14-2003, 01:55 PM   #9
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Jackal, Is yours a 2wd or 4X4.
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Old 02-14-2003, 08:53 PM   #10
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its 2 wheel drive you would still need to find the transfer case. but manual's with transfer cases were more rare right? trade should be cake.
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