4 speed to auto swap? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Slick71 · 02-12-2003, 05:35 PM

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!

breeh · 02-12-2003, 06:08 PM

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.

Pont · 02-12-2003, 07:25 PM

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.

Slick71 · 02-12-2003, 07:51 PM

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!

mrein3 · 02-12-2003, 10:26 PM

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.

smokekiki · 02-13-2003, 06:39 PM

There is some info on the FAQ page to converting to auto

Slick71 · 02-13-2003, 11:24 PM

Just checked out the FAQ category....thanks guys!

Jackal2k9 · 02-13-2003, 11:29 PM

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.

Slick71 · 02-14-2003, 01:55 PM

Jackal, Is yours a 2wd or 4X4.

Jackal2k9 · 02-14-2003, 08:53 PM

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.

02-12-2003, 05:35 PM	#1
Slick71 Registered User Join Date: Feb 2001 Location: Savannah, MO. Posts: 513	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! __________________ 1972 Chevy Blazer 4X4 Savannah, MO. www.thefarmatadair.com

02-12-2003, 06:08 PM	#2
breeh Recovering 67-72 Addict Join Date: Oct 2000 Location: North Bend, WA Posts: 1,788	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. __________________ 68 Short Fleet 4x4; 427; BTO Level 3 700R4; NP205; Dana 60 front and rear; 4" lift with 35's; Disc brakes; AGR variable ratio steering; factory bucket seats; factory tach and tilt. "Friends call me cruzer cuz I like fast cars and fast women"

02-12-2003, 07:25 PM	#3
Pont I need another Barley Pop Join Date: Feb 2001 Location: Grants Pass, OR Posts: 1,629	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. __________________ 67 Short Fleet 4x4 04 Honda CRF450R 89 Toyota 4-Runner 34 Ford 2 door sedan - Long term project ---------------------------------------------- There is a very fine line between "hobby" and "mental illness"

02-12-2003, 07:51 PM	#4
Slick71 Registered User Join Date: Feb 2001 Location: Savannah, MO. Posts: 513	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! __________________ 1972 Chevy Blazer 4X4 Savannah, MO. www.thefarmatadair.com

02-12-2003, 10:26 PM	#5
mrein3 Registered User Join Date: Feb 2000 Location: Center City, MN, USA Posts: 3,254	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. __________________ '70 cab, '71 chassis, 383, TH350, NP205. '71 Malibu convertible '72 Malibu hard top Center City, MN

02-13-2003, 06:39 PM	#6
smokekiki Mike Join Date: Jan 2003 Location: west chester pa Posts: 2,473	There is some info on the FAQ page to converting to auto __________________ 70'c/10, 71 suburban4x4 402bb, 72suburban 4/6 drop, 72k/5 4x4 blazer 4" lift 35 tires

02-13-2003, 11:24 PM	#7
Slick71 Registered User Join Date: Feb 2001 Location: Savannah, MO. Posts: 513	Just checked out the FAQ category....thanks guys! __________________ 1972 Chevy Blazer 4X4 Savannah, MO. www.thefarmatadair.com

02-13-2003, 11:29 PM	#8
Jackal2k9 Registered User Join Date: Apr 2002 Location: Katy, Texas Posts: 171	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.

02-14-2003, 01:55 PM	#9
Slick71 Registered User Join Date: Feb 2001 Location: Savannah, MO. Posts: 513	Jackal, Is yours a 2wd or 4X4. __________________ 1972 Chevy Blazer 4X4 Savannah, MO. www.thefarmatadair.com

02-14-2003, 08:53 PM	#10
Jackal2k9 Registered User Join Date: Apr 2002 Location: Katy, Texas Posts: 171	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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