4x4 help - The 1947 - Present Chevrolet & GMC Truck Message Board Network

1969stepside · 06-23-2008, 10:58 PM

is a 3speed transfer case the same as a auto transfercase? i am going to change my 3speed 4x4 to a auto and i have heard that a 3speed transfer case is different than a auto transfer case help please!!!!!!!!!!!!!!!!!!!!!!!!!!

hdflstf · 06-23-2008, 11:44 PM

My understanding is that the TC is the same (NP205?). The catch is that there is an adapter that bolts to the trans and to the TC. This part will be different.

72 CustomCamper · 06-23-2008, 11:55 PM

I think most 3spd's came with Dana 20 Tcases, but I've been known to be wrong...

Chuck

1969stepside · 06-23-2008, 11:57 PM

i am not shure what i need to do?

72 CustomCamper · 06-24-2008, 12:14 AM

Can you take a pic of your T-case? Then we can help more...

Chuck

sandking · 06-24-2008, 12:41 AM

If you have a 205 case, the input shaft will be different. Your best bet is to find a th350 and an np205 thats already together. That way, you dont have to worry about adaptors or changing the input shaft.

griesel72 · 06-24-2008, 01:12 AM

what is your shift pattern on your 4X4 shifter, if it is a U pattern, than it is a dana 20, if it is the standard line pattern, than it is the 205, unless you have a 1970 or before, than you could have the rockwell, the shifter will lay on the driver's side of the hump, it is best to figure this out first

good luck
DAvid

**special-K** · 06-24-2008, 06:06 AM

I think only Blazer used the Dana20 case.The input shaft on the 3spd 205 is different.

mrein3 · 06-24-2008, 07:30 AM

If you have a NP205, the input shaft on the t-case is a 10 spline shaft. The input on a NP205 for a th350 is a 28 spline shaft.

There is a part between all transfer cases and transmissions. It is called the "transfer case adapter" however there is no such thing as a th350 28 spline output shaft adapter for a 3-speed manual 10 spline input shaft. That is the bad news.

The good news - if you currently have a NP205 in there, is that if you purchase a used th350, adapter, and NP205, you don't have any other drive line mods to make. GM made all the drive shafts the same length. The difference in transmission lengths is made up in the adapter.

When I did my 3-speed/NP205 to th350/NP205 swap I did nothing with the drive shafts. The ones that were in there with the 3-speed are still there.

You will need a flex plate or ring gear, a starter that bolts up to the bottom of the block, and shorter flex plate bolts for back of the crank as the flex plate is shallower than the fly wheel you have now.

Make sure you grab the steering column, shifter, and linkage from the donor too. The stuff I bought for my 1971 4x4 pickup came out of a 1972 Blazer so truck or Blazer doesn't matter for a donor. This includes the shifter linkage. The linkage in my pickup is from the same donor Blazer.

Other than these pieces weighing a lot, this is probably the easiest, most straight forward change I made on my truck in the 15 years I've owned it.

While you have the adapter on the ground, make sure you change the oil seals in it. They keep the tranny fluid in the tranny. Take a look at the drive sleeve in the adapter. If it is grooved you might want to pick up a new one from GM. They are still available. You don't want to lift all this stuff in there to only have the tranny fluid leak.

Oh and if you don't have a NP205 already, never mind. I've never dealt with the dana 20.

**Yukon Jack** · 06-24-2008, 01:04 PM

Assuming your talking about a 1969 4wd and it has not been modified, more than likely you have a Rockwell T221 transfer case. They were never married to an automatic so unless you go the custom adapter route (or do a divorced setup with a 2wd automatic), you won't find an adapter to mate to an automatic.

Here's what a Rockwell T221 looks like

here are some measurements I took of my Rockwell T221

and here is what the NP205 looks like

And here are some measurements I took of one of my NP205's

I don't have a pic of the Dana 20 transfer case.

1969stepside · 06-24-2008, 02:26 PM

so waht do i need to do should i get a 208 transfercase off a 80model k series? would that work better?

**Yukon Jack** · 06-24-2008, 03:37 PM

I'd be more likely to recommend finding an NP205 equipped automatic truck so you can get the NP205, it's adapter and respective auto transmission. I'd also grab the NP205's crossmember even though I believe you could use your existing crossmember if you space it down 1".

Can't beat the strenght of the NP205.

06-23-2008, 10:58 PM	#1
1969stepside Registered User Join Date: Feb 2008 Location: Johnson City Tennessee Posts: 1,208	4x4 help is a 3speed transfer case the same as a auto transfercase? i am going to change my 3speed 4x4 to a auto and i have heard that a 3speed transfer case is different than a auto transfer case help please!!!!!!!!!!!!!!!!!!!!!!!!!! __________________ Greater love hath no man than to lay down his life for a friend. Members i Have met Earl Slick68 1969 Stepside Build thread http://67-72chevytrucks.com/vboard/s...=1#post4253546 Chevy Trucks the longest lasting most dependable trucks on the road

06-23-2008, 11:44 PM	#2
hdflstf Registered User Join Date: Oct 2007 Location: Desert Southwest Posts: 540	Re: 4x4 help My understanding is that the TC is the same (NP205?). The catch is that there is an adapter that bolts to the trans and to the TC. This part will be different.

06-23-2008, 11:55 PM	#3
72 CustomCamper huh ??? Join Date: Nov 2002 Location: Fredericksburg,Va. Posts: 3,368	Re: 4x4 help I think most 3spd's came with Dana 20 Tcases, but I've been known to be wrong... Chuck __________________ 90 Blazer Silverado 350w/ 700R4 and 32" Kelly's "I am a bomb technician. If you see me running try to keep up!"

06-23-2008, 11:57 PM	#4
1969stepside Registered User Join Date: Feb 2008 Location: Johnson City Tennessee Posts: 1,208	Re: 4x4 help i am not shure what i need to do? __________________ Greater love hath no man than to lay down his life for a friend. Members i Have met Earl Slick68 1969 Stepside Build thread http://67-72chevytrucks.com/vboard/s...=1#post4253546 Chevy Trucks the longest lasting most dependable trucks on the road

06-24-2008, 12:14 AM	#5
72 CustomCamper huh ??? Join Date: Nov 2002 Location: Fredericksburg,Va. Posts: 3,368	Re: 4x4 help Can you take a pic of your T-case? Then we can help more... Chuck __________________ 90 Blazer Silverado 350w/ 700R4 and 32" Kelly's "I am a bomb technician. If you see me running try to keep up!"

06-24-2008, 12:41 AM	#6
sandking .....I am working on it..... Join Date: Jul 2007 Location: Anaheim Hills, Ca Posts: 960	Re: 4x4 help If you have a 205 case, the input shaft will be different. Your best bet is to find a th350 and an np205 thats already together. That way, you dont have to worry about adaptors or changing the input shaft. __________________ . . . . . View my build thread HERE

06-24-2008, 01:12 AM	#7
griesel72 Senior Member Join Date: Apr 2003 Location: Howard, Kansas USA Posts: 1,997	Re: 4x4 help what is your shift pattern on your 4X4 shifter, if it is a U pattern, than it is a dana 20, if it is the standard line pattern, than it is the 205, unless you have a 1970 or before, than you could have the rockwell, the shifter will lay on the driver's side of the hump, it is best to figure this out first good luck DAvid __________________ 1969 K10 Custom 10 1997 Z71 2006 Volkswagen Jetta TDI 2006 King Ranch 1980 Wife

06-24-2008, 06:06 AM	#8
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,851	Re: 4x4 help I think only Blazer used the Dana20 case.The input shaft on the 3spd 205 is different. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

06-24-2008, 07:30 AM	#9
mrein3 Registered User Join Date: Feb 2000 Location: Center City, MN, USA Posts: 3,254	Re: 4x4 help If you have a NP205, the input shaft on the t-case is a 10 spline shaft. The input on a NP205 for a th350 is a 28 spline shaft. There is a part between all transfer cases and transmissions. It is called the "transfer case adapter" however there is no such thing as a th350 28 spline output shaft adapter for a 3-speed manual 10 spline input shaft. That is the bad news. The good news - if you currently have a NP205 in there, is that if you purchase a used th350, adapter, and NP205, you don't have any other drive line mods to make. GM made all the drive shafts the same length. The difference in transmission lengths is made up in the adapter. When I did my 3-speed/NP205 to th350/NP205 swap I did nothing with the drive shafts. The ones that were in there with the 3-speed are still there. You will need a flex plate or ring gear, a starter that bolts up to the bottom of the block, and shorter flex plate bolts for back of the crank as the flex plate is shallower than the fly wheel you have now. Make sure you grab the steering column, shifter, and linkage from the donor too. The stuff I bought for my 1971 4x4 pickup came out of a 1972 Blazer so truck or Blazer doesn't matter for a donor. This includes the shifter linkage. The linkage in my pickup is from the same donor Blazer. Other than these pieces weighing a lot, this is probably the easiest, most straight forward change I made on my truck in the 15 years I've owned it. While you have the adapter on the ground, make sure you change the oil seals in it. They keep the tranny fluid in the tranny. Take a look at the drive sleeve in the adapter. If it is grooved you might want to pick up a new one from GM. They are still available. You don't want to lift all this stuff in there to only have the tranny fluid leak. Oh and if you don't have a NP205 already, never mind. I've never dealt with the dana 20. __________________ '70 cab, '71 chassis, 383, TH350, NP205. '71 Malibu convertible '72 Malibu hard top Center City, MN

06-24-2008, 01:04 PM	#10
Yukon Jack Post Whore Join Date: Feb 2000 Location: Rose Hill, KS, USA Posts: 12,686	Re: 4x4 help Assuming your talking about a 1969 4wd and it has not been modified, more than likely you have a Rockwell T221 transfer case. They were never married to an automatic so unless you go the custom adapter route (or do a divorced setup with a 2wd automatic), you won't find an adapter to mate to an automatic. Here's what a Rockwell T221 looks like here are some measurements I took of my Rockwell T221 and here is what the NP205 looks like And here are some measurements I took of one of my NP205's I don't have a pic of the Dana 20 transfer case. __________________ 1970 Blazer with a 400 sbc and 4" lift 1980 Pontiac Trans Am, 455 Oldsmobile 2012 Kawasaki Concours 14

06-24-2008, 02:26 PM	#11
1969stepside Registered User Join Date: Feb 2008 Location: Johnson City Tennessee Posts: 1,208	Re: 4x4 help so waht do i need to do should i get a 208 transfercase off a 80model k series? would that work better? __________________ Greater love hath no man than to lay down his life for a friend. Members i Have met Earl Slick68 1969 Stepside Build thread http://67-72chevytrucks.com/vboard/s...=1#post4253546 Chevy Trucks the longest lasting most dependable trucks on the road

06-24-2008, 03:37 PM	#12
Yukon Jack Post Whore Join Date: Feb 2000 Location: Rose Hill, KS, USA Posts: 12,686	Re: 4x4 help I'd be more likely to recommend finding an NP205 equipped automatic truck so you can get the NP205, it's adapter and respective auto transmission. I'd also grab the NP205's crossmember even though I believe you could use your existing crossmember if you space it down 1". Can't beat the strenght of the NP205. __________________ 1970 Blazer with a 400 sbc and 4" lift 1980 Pontiac Trans Am, 455 Oldsmobile 2012 Kawasaki Concours 14



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