Transfer case information.

[onlydriveagm]

This may sound like one of the dumbest questions asked here but I cant find the drain plug on my transfer case sorry I don’t know which transfer case is but its a massive case. The truck is a 77 Chevy blazer drive train and offered in 77 was the New Process 203, New Process 205 and I think the Dana 20. It has a 350engine and th350 Trans any help would be appreciated

[mudtrux]

Pull out the lowest bolt, on the rear cover, for the front output shaft.

[Chapes]

dana 20's are very small and have a Dana or Spicer Stamp on them. 203's are aluminum full time 4wd, and 205's are cast part time 4wd. so that should help identify your case. once you find out what it is look at an exploded diagram

[HELLRAISER]

203's are aluminum full time 4wd

203's are also cast 208's are aluminum.

[Chapes]

whoops my fault

[mudtrux]

I'm assuming it's a 203. 203's usualy have a chrome Hurst type shifter and commonly found behind automatic 1/2 ton chassis.

[onlydriveagm]

Pull out the lowest bolt, on the rear cover, for the front output shaft.

i think its got the 203 in it the truck is in a friends grage so i will look tomarrow if it is the 203 is this how you drain it

[mudtrux]

Yes

[Diggerz]

i would think it is a 205, but i guess you'll find out

[riverbasher]

Most of the blazers of that vintage came with 203's, unless a 205 was swapped in at some point.

[Diggerz]

i know my step dads balzer has a 205. its a 75 though. i dont know much about chev's.

[onlydriveagm]

I got it drained thanks for the help I never would have found that bolt or thought it would be a drain

[mudtrux]

So are we going to get taxi rides arround mudfest?:D

[onlydriveagm]

ya it will be there

[cityrednecks]

hey dan, Ill call up brian to try and get a taxi sign before the weekend

[bogger333333]

Nice Tech page

[bogger333333]

Bulletproof t-case.

[bogger333333]

Someone may need to put a chain in one of these.

[bogger333333]

Jeep guys will like this.

[bogger333333]

Lot better lowrange than a 205.

[bogger333333]

What can I say its a Borg-warner.

[bogger333333]

Ok for a full time case

[toofast4you_yamaha]

what trucks are common to have this T case

[mudtrux]

Yea, thats about what mine looked like when it exploded:eek:
I still run 'em, there cheap
Thanks for all the diagrams.

Can you put up the o2 cheat for the rear? thanks again Twisted:D

[toofast4you_yamaha]

where those common on 75 ford f 250s . and is it easy to switch it to a 205 . and another thing on my f 250 there isnt a bottom brace for it . is there one to buy or what or how should i go about maken a crossmember for it

[bocephus]

to find out what kind of transfer case u have go under the truck and look at the tag on the t-case and for a crossmember jsut use ur own head and fab something up its jsut a junk of metal

[toofast4you_yamaha]

ok . sounds good didnt know if u should make it more of a skid plate or actually try to bolt it too it

[redchevy383]

what changes with differnt gm trannys/transfer cases? ie th400/203 as apposed to a 400/208

[mudtrux]

I think the overall length (the 208 is longer), and the 208 rear shaft is a slip/plunge style

[redchevy383]

I was thinkinking of going from the 203 to the 208 just for the lighter and lower ratio aspect of things

[redchevy383]

so a 208 will on the back of my tranny if i change the mounting plate. i got a 400/203 the spline counts are the same it didnt say nothing about length so i assume they are the same

[redchevy383]

ok thanks for the help i was told a while ago that the tranny output shafts changed from t-case to t-case dude didnt know what he was talking about or he wanted to sell me something. i got a 208 and adapter plate laying around i think

[redchevy383]

Any chance you have a th400 to 205 hourglass adapter laying around or know someone that does?

not off the top of my head all the 205s i know of are behind a 4 speed but ill do some lookin around for ya.

[redchevy383]

wow I take it they are pretty rare there is one on ebay for 250.

[Gutter Runner]

Heres some info I stumbled upon while surfing one day. This may be helpfull to some.

Chevy 203
Input Spline: We have run into three different input spline configurations on these cases.
10 spline: Used behind SM465 transmissions
27 spline: The units supplied with a T350 automatic have a 27 spline female input shaft.
32 spline: This is the preferred shaft, as it is the strongest. These came behind Turbo 400 trannies.
Bolt Pattern: Is an asymmetrical pattern unique to the 203. It is possible to disassemble this case and re-drill it for the 6 bolt circular pattern. An adapter is also available to mate this case to Jeep, Dodge or Ford 6 bolt circular applications: adapter PN AA50-0202
Ford NP203 Transfer Case
The Ford NP203 has a 31 spline female input. The bolt pattern is the Ford rotation of the 6 bolt circular bolt pattern.
Use with a Klune-V Extreme underdrive:
Use the Klune with the 31 spline output. These units will bolt up directly.
Dodge NP203 Transfer Case
The Dodge 203 has a 23 spline female input. Later model Dodge transfer cases use the 6 bolt circular bolt pattern. Early Dodge 203s use the same front bolt pattern as the early Chevy unit. It is an asymmetrical pattern unique to the 203. It is possible to disassemble this case and re-drill it for the 6 bolt circular pattern. An adapter is also available to mate this case to Jeep, Dodge or Ford 6 bolt circular applications: adapter PN AA50-0202

NP205 Transfer Case

http://www.txwheelers.com/tcase/clip_image001.jpg

Note 8 bolt "racetrack" bolt pattern on early Chevy. Late Chevy will have the six bolt circular pattern, similar to the Ford, except the Chevy unit will have the front output yoke on the passenger side, like the early Chevy.
Input Spline: We have run into three different input spline configurations on these cases.
10 spline: The most common were units supplied with a 4 speed which typically had a 10 spline male input shaft. Crawler output shafts are available to mate to the 10 spline cases.
27 spline: The units supplied with a T350 automatic have a 27 spline male input shaft. In order to couple the 27 spline units to a Klune-V Extreme Underdrive, it is necessary to disassemble the case and replace the input gear with a 10 spline male or 32 spline female. (Either gear is available through Klune-V.)
Notes:
· The 10 spline input is a direct replacement in this case.
· The 32 spline is stronger than the 10 spline input.
· To use the 32 spline gear in this case requires machining a larger opening in the case to accommodate the larger bearing used with the 32 spline input.
32 spline: The units supplied with a T400 Automatic have a 32 spline female input. We have seen both a short (about 1.5 to 2.0" stickout) versions of this gear. This gear is directly compatible with the Klune-V Extreme Underdrive, which can be supplied with a 32 spline output shaft. Longer spacers are required with the long input.
http://www.txwheelers.com/tcase/clip_image002.jpg
The Ford NP205 transfer case uses the 6 bolt circular bolt pattern . It has a left hand drop (driver's side). It is supplied with a 31 spline female input.

[ox_man]

also to mention the dodge 205 married version has like 3-4 bolt that are internal for bolting up the the adapter.

I have a Complete rebuild manual on the 205 if anyone wants pm me for details

[onlydriveagm]

Which transfer case is better for mud I got a 77 Chevy blazer 205 on a th350 and a 76 Chevy K2500 with a 203 on a th350

[ox_man]

205 for sure, gear to gear lighter than the 203, it is stronger. or even better yet a 203/205 combo use the front half of the 203 in front of the 205 then you have trhe options of 2:1 or 4:1

[shakes_nig_rig]

when you put the full time kit in depending on which style you get make sure to index the pinion cross becouse it is reused and if u put it in one way it looses the freeplay on the berings. i found that out at school when i put a full time kit in a 83 ish chev. took that thing apart 4 times before i figured out what the it was.

[onlydriveagm]

I came across a posting twisted wrench had posted on another forum a couple years ago and found it interesting and figured I’d put it on here hope you don’t mind twisted wrench
I took it from hotrodders.com/forum


Twistedwrench
No officer I won’t do it again Join Date: Mar 2005
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re: Transfer case - NP 203 - 205

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I’m over tired and didn’t feel like pulling out just the stuff you need so I dumped it all here. Some of this info should help.

Bolt Pattern:
All GM NP205 cases 1971-1985 had a 8 bolt "racetrack" bolt pattern
All GM NP205 Cases 1986-up had a 6 bolt circular bolt pattern

Input Spline: GM Used four different input shaft configurations on these cases.
10 spline: (1971-85) The most common were units supplied with a 4 speed which typically had a 10 spline male input shaft.

27 spline: (1971-79) The units supplied with a T350 automatic have a 27 spline male input shaft.

32 spline (Short); 32 spl (Long): The units supplied with a T400 Automatic (also SM465 86-up) have a 32 spline female input. We have seen both a short (about 1.5 to 2.0" stickout) and long (more like 3-3.5" stickout) versions of this gear. This gear is directly compatible with the Klune-V Extreme Underdrive, which can be supplied with a 32 spline output shaft. Longer spacers are required with the long input.

Also see data on swapping input gears lower on this page.
1979 to 1985 GM NP205: 8 bolt "racetrack" bolt pattern:
During these years, the GM NP205 showed up behind Turbo 400 and SM465 Transmissions in 1 Ton trucks only.. 1/2 and 3/4 T trucks began to be supplied with the NP208 instead. SM465 units will still typically use the 10 spline input. Turbo 400 units have the stout 32 spline female input (in most cases the short 32 spl input, about 1.5-2.0" stickout) however still uses the 8 bolt "racetrack" bolt pattern.

Chevy, Dodge and Ford all used variations of this transfer case. All were chain drive to the front output. Some were full-time 4WD while others were part time. While the whole case is very large heavy and clunky, they have attained popularity through the use of the front "range box" section which is then adapted and mated to the front of another transfer case, a dual transfer case setup commonly known as a "Doubler".
Transfer Case Specifications:
Low Range reduction ratio: 1.96:1
High Range: Direct (1:1)


Chevy 203

Input Spline: GM used three different input spline configurations on these cases.

10 spline: (1971-79) Used behind SM465 transmissions

27 spline: (1971-79) The units supplied with a T350 automatic have a 27 spline female input shaft.

32 spline: (1973-77) This is the preferred shaft, as it is the strongest. These came behind Turbo 400 trannies.

Bolt Pattern:
Is an asymmetrical pattern unique to the 203. It is possible to disassemble this case and re-drill it for the 6 bolt circular pattern. An adapter is also available to mate this case to Jeep, Dodge or Ford 6 bolt circular applications: adapter PN AA50-0202

Ford NP203 Transfer Case
The Ford NP203 has a 31 spline female input. The bolt pattern is the Ford rotation of the 6 bolt circular bolt pattern.
Use with a Klune-V Extreme underdrive:
Use the Klune with the 31 spline output. These units will bolt up directly.
Dodge NP203 Transfer Case
The Dodge 203 has a 23 spline female input. Later model Dodge transfer cases use the 6 bolt circular bolt pattern. Early Dodge 203s use the same front bolt pattern as the early Chevy unit. It is an asymmetrical pattern unique to the 203. It is possible to disassemble this case and re-drill it for the 6 bolt circular pattern. An adapter is also available to mate this case to Jeep, Dodge or Ford 6 bolt circular applications: adapter PN AA50-0202

Transfer Case Specifications:
Low Range reduction ratio: 2.6 to 1
High Range: Direct 1:1
Chevy, Dodge and Ford all used variations of this transfer case. All were chain drive to the front output, with a light weight aluminum case. Most used a slip-yoke rear output. We are not aware of a Fixed yoke conversion for this case. While these units will hold up under moderately heavy off road use, they are not considered the preferred swap due to the chain drive and thin aluminum case.
Bolt Pattern:
6 bolt circular pattern. Note: This pattern is almost symmetrical, however it is not and will only bolt up one way. Chevy, Dodge and Ford all used the same bolt pattern, However with a different ROTATION of the pattern. Dodge and ford are close, and swaps might result in a useable Tcase droop angle, however Chevy units are about 90 degrees different and cannot be interchanged. Ford units have a driver side drop, While GM units are passenger side drop.

Chevy 208

Passenger side drop (front driveshaft). This Tcase has the GM rotation of the 6 bolt circular bolt pattern.

Input Spline: We have run into two different input spline configurations on these cases.

27 spline: The units supplied with a T350 or 700R4 automatic have a 27 spline female input shaft.

32 spline: This is the preferred shaft, as it is the strongest. These came behind Turbo 400 or SM465 transmissions.


Ford NP208 Transfer Case
The Ford NP208 has a 31 spline female input. The bolt pattern is the Ford rotation of the 6 bolt circular bolt pattern.
Use with a Klune-V Extreme underdrive:
Use the Klune with the 31 spline output. These units will bolt up directly.
Dodge NP208 Transfer Case
The Dodge 203 has a 23 spline female input. It uses the same front bolt pattern as the Chevy unit. The Klune is available with a 23 spline output shaft to match up to this application.

Transfer Case Specifications:
Low Range reduction ratio: 2.6 to 1
High Range: Direct 1:1
Chevy, Dodge and Ford all used variations of this transfer case. All were chain drive to the front output, with a light weight aluminum case. Most used a slip-yoke rear output. We are not aware of a Fixed yoke conversion for this case. While these units will hold up under moderately heavy off road use, they are not considered the preferred swap due to the chain drive and thin aluminum case.
Bolt Pattern:
6 bolt circular pattern. Note: This pattern is almost symmetrical, however it is not and will only bolt up one way. Chevy, Dodge and Ford all used the same bolt pattern, However with a different ROTATION of the pattern. Dodge and ford are close, and swaps might result in a useable Tcase droop angle, however Chevy units are about 90 degrees different and cannot be interchanged. Ford units have a driver side drop, While GM units are passenger side drop.

Chevy 208

Passenger side drop (front driveshaft). This Tcase has the GM rotation of the 6 bolt circular bolt pattern.

Input Spline: We have run into two different input spline configurations on these cases.

27 spline: The units supplied with a T350 or 700R4 automatic have a 27 spline female input shaft.

32 spline: This is the preferred shaft, as it is the strongest. These came behind Turbo 400 or SM465 transmissions.


Ford NP208 Transfer Case
The Ford NP208 has a 31 spline female input. The bolt pattern is the Ford rotation of the 6 bolt circular bolt pattern.
Use with a Klune-V Extreme underdrive:
Use the Klune with the 31 spline output. These units will bolt up directly.
Dodge NP208 Transfer Case
The Dodge 203 has a 23 spline female input. It uses the same front bolt pattern as the Chevy unit. The Klune is available with a 23 spline output shaft to match up to this application.

Hope this info helps. Are you going to spend more time on road then off? If the truck isn’t going to see major pounding and crawling. I would suggest moving to the 208. It is lighter and so much quieter and smoother on the road. My friends and I use the 205 for crawlers and the 208 for road babies. The 208 is reasonable, easy to find and a breeze to go through internally. Just my opinion. And what has worked well for me. oh yea, here is a link to some more info. http://chevy.off-road.com/chevy/art...l.jsp?id=200867