4spd to automatic - The 1947 - Present Chevrolet & GMC Truck Message Board Network

duceducenine · 03-12-2011, 01:48 AM

i have a 72 gmc 4spd 4x4
i want to switch to AT
will a 79 AT w/ T.CASE WORK?

duallyjams · 03-12-2011, 09:55 AM

Anything will work if you want it to.
measure the over all length of each set up this will let you know about drive shafts and then there is the auto shifter ( column or floor ) is the auto a np205 ect ect

duceducenine · 03-12-2011, 10:05 AM

dont know for sure i havent seen it yet
they want $300 for the combo

duceducenine · 03-12-2011, 10:07 AM

i also have to extend the drive shaft anyways
im lengthening the chassis 22"

LANDC · 03-12-2011, 12:55 PM

Find out what they are first. A chain drive t case isn't worth the hassle IMO. Now if you are getting a 400/205, that is definetly worth the hassle.

duceducenine · 03-13-2011, 12:22 PM

what model is the chain drive t case?

Redcap · 03-13-2011, 12:24 PM

Quote:

Originally Posted by duceducenine

what model is the chain drive t case?

There are a few. You need to find out what model the trans/transfer case combo is in order to determine if it is a good deal or not. $300 for a TH400/205 isn't a bad deal...same price for a TH350/NP203 is a horrible deal.

LANDC · 03-14-2011, 10:41 AM

If I am not mistaken, a 208 is chaindrive and the 203 is a full time 4x4 case. A 205 is gear drive and tough as hell. My 205 turns my 44's behind my BB happily. There is a good chance you have a 205 in your truck right now.

duceducenine · 03-14-2011, 01:08 PM

my t.c. is c-99404 looks to be s 205
so can i drop the 4 spd and put in the A.T.
or do i need one set up for A.T.?

LANDC · 03-14-2011, 03:36 PM

A 205/TH400 setup was used in K30's for a few years 80-83 roughly I think. I don't know of other applications. I think there may be aftermarket adapters available. From what I have heard the 205/400 adapters are somewhat scarce.

csb#356 · 03-14-2011, 04:19 PM

It doesn't really matter what automatic transmission you decide to go with, the 205 that you already have will not work the way it is. It would be easiest to get it to bolt up to a th350, because it would not require any modification to the transfer case but you would need to have about $200 worth of adapters. (unless you can find them used of course). To mount it behind a th400 you will have to fully dissasemble the transfer case and put in a new input shaft as well as have the bearing hole bored out, and then you will also need the 205/400 adapter which is nearly impossible to find used unless you search for a long time. Hope you're not getting confused by all these adapter/ input shaft combos but if I had to make a choice honestly I would go with a th350 and the np205, its a fairly strong transmission, and if you're not doing any towing or really extreme wheeling it will work out very good. Actually to be completely honest I would keep your 4 speed, haha, but I guess you're already set on not shifting.

duceducenine · 03-15-2011, 12:59 PM

i dont mind the 4 spd but nobody else will
be able to drive it.....

LANDC · 03-15-2011, 03:37 PM

Whats the problem then?

coops714x4 · 03-15-2011, 07:32 PM

is this gonna be a daily driver ? if so I would think about a 700R4 they have a lower 1st gear and the overdrive will save wear and tear on your motor AND get better mileage on the highway go look at monster transmissions.com they have the trannys for any application and you can get the adapter from advance adapter I am doing a 71 C/20 4x4 going from the granny 4 to a 700R4 the kit from monster is 2k

duceducenine · 03-16-2011, 12:55 AM

its gonna be the work truck so
the go-fer will need to be able
to drive it too.

Dooley · 03-16-2011, 08:27 AM

Quote:

Originally Posted by LANDC

A 205/TH400 setup was used in K30's for a few years 80-83 roughly I think. I don't know of other applications. I think there may be aftermarket adapters available. From what I have heard the 205/400 adapters are somewhat scarce.

My stock factory built 1988 V30 2 door regular cab has the T400 and 205 transfercase.

As far as the 203 units, part way through the 78 model year they changed the width and tooth pitch of the gears and chain making it harder for the chain to slip after it's worn,(narrowered from 2.5" to 2" and increased the pitch). The 1979 203 would be a good unit. I have had a couple and they were never a problem.

Rede · 03-19-2011, 02:05 PM

Quote:

Originally Posted by Redcap

There are a few. You need to find out what model the trans/transfer case combo is in order to determine if it is a good deal or not. $300 for a TH400/205 isn't a bad deal...

300 for that combo is a steal here...
That same combo 5-6 hours away from me is 800 bucks.

Guess is all depends on the area you live in an how available the parts are.

03-12-2011, 01:48 AM	#1
duceducenine Registered User Join Date: Nov 2006 Location: el sobrante CA 94803 Posts: 284	4spd to automatic i have a 72 gmc 4spd 4x4 i want to switch to AT will a 79 AT w/ T.CASE WORK?

03-12-2011, 09:55 AM	#2
duallyjams Registered User Join Date: May 2007 Location: Deale Md Posts: 4,663	Re: 4spd to automatic Anything will work if you want it to. measure the over all length of each set up this will let you know about drive shafts and then there is the auto shifter ( column or floor ) is the auto a np205 ect ect __________________ James 63 GMC V6 4speed carryall 65 chevy swb bbw V8 auto 68 K20 327/4 speed, buddy buckets 2002 GMC CC Dually Duramax 64 GMC lwb 3/4 V6 4speed SOLD 66 GMC swb bbw buddy buckets SOLD IG duallyjams The only thing that stays the same is constant change!

03-12-2011, 10:07 AM	#4
duceducenine Registered User Join Date: Nov 2006 Location: el sobrante CA 94803 Posts: 284	Re: 4spd to automatic i also have to extend the drive shaft anyways im lengthening the chassis 22"

03-12-2011, 12:55 PM	#5
LANDC Registered User Join Date: Oct 2008 Location: Kelowna, BC, Canada Posts: 93	Re: 4spd to automatic Find out what they are first. A chain drive t case isn't worth the hassle IMO. Now if you are getting a 400/205, that is definetly worth the hassle. __________________ Custom Vehicle, Custom Problems.

03-13-2011, 12:22 PM	#6
duceducenine Registered User Join Date: Nov 2006 Location: el sobrante CA 94803 Posts: 284	Re: 4spd to automatic what model is the chain drive t case?

03-12-2011, 10:05 AM	#3
duceducenine Registered User Join Date: Nov 2006 Location: el sobrante CA 94803 Posts: 284	Re: 4spd to automatic dont know for sure i havent seen it yet they want $300 for the combo

03-14-2011, 10:41 AM	#8
LANDC Registered User Join Date: Oct 2008 Location: Kelowna, BC, Canada Posts: 93	Re: 4spd to automatic If I am not mistaken, a 208 is chaindrive and the 203 is a full time 4x4 case. A 205 is gear drive and tough as hell. My 205 turns my 44's behind my BB happily. There is a good chance you have a 205 in your truck right now. __________________ Custom Vehicle, Custom Problems. Last edited by LANDC; 03-14-2011 at 10:42 AM.

03-14-2011, 01:08 PM	#9
duceducenine Registered User Join Date: Nov 2006 Location: el sobrante CA 94803 Posts: 284	Re: 4spd to automatic my t.c. is c-99404 looks to be s 205 so can i drop the 4 spd and put in the A.T. or do i need one set up for A.T.?

03-14-2011, 03:36 PM	#10
LANDC Registered User Join Date: Oct 2008 Location: Kelowna, BC, Canada Posts: 93	Re: 4spd to automatic A 205/TH400 setup was used in K30's for a few years 80-83 roughly I think. I don't know of other applications. I think there may be aftermarket adapters available. From what I have heard the 205/400 adapters are somewhat scarce. __________________ Custom Vehicle, Custom Problems.

03-14-2011, 04:19 PM	#11
csb#356 Registered User Join Date: May 2009 Location: Pinehurst, Idaho Posts: 311	Re: 4spd to automatic It doesn't really matter what automatic transmission you decide to go with, the 205 that you already have will not work the way it is. It would be easiest to get it to bolt up to a th350, because it would not require any modification to the transfer case but you would need to have about $200 worth of adapters. (unless you can find them used of course). To mount it behind a th400 you will have to fully dissasemble the transfer case and put in a new input shaft as well as have the bearing hole bored out, and then you will also need the 205/400 adapter which is nearly impossible to find used unless you search for a long time. Hope you're not getting confused by all these adapter/ input shaft combos but if I had to make a choice honestly I would go with a th350 and the np205, its a fairly strong transmission, and if you're not doing any towing or really extreme wheeling it will work out very good. Actually to be completely honest I would keep your 4 speed, haha, but I guess you're already set on not shifting.

03-15-2011, 12:59 PM	#12
duceducenine Registered User Join Date: Nov 2006 Location: el sobrante CA 94803 Posts: 284	Re: 4spd to automatic i dont mind the 4 spd but nobody else will be able to drive it.....

03-15-2011, 03:37 PM	#13
LANDC Registered User Join Date: Oct 2008 Location: Kelowna, BC, Canada Posts: 93	Re: 4spd to automatic Whats the problem then? __________________ Custom Vehicle, Custom Problems.

03-15-2011, 07:32 PM	#14
coops714x4 Registered User Join Date: Mar 2011 Location: Cement Oklahoma Posts: 916	Re: 4spd to automatic is this gonna be a daily driver ? if so I would think about a 700R4 they have a lower 1st gear and the overdrive will save wear and tear on your motor AND get better mileage on the highway go look at monster transmissions.com they have the trannys for any application and you can get the adapter from advance adapter I am doing a 71 C/20 4x4 going from the granny 4 to a 700R4 the kit from monster is 2k

03-16-2011, 12:55 AM	#15
duceducenine Registered User Join Date: Nov 2006 Location: el sobrante CA 94803 Posts: 284	Re: 4spd to automatic its gonna be the work truck so the go-fer will need to be able to drive it too.



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