Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.
The 6 bolt round pattern started in 1985, not 1986.Np205
NP205
The NP205 gear driven transfer case is considered by many to be the king of bulletproof. It was supplied in many GM, Ford, International and Dodge full-size trucks.
GM NP205
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.
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 (from SM465 Applications): (1971-85) The most common were units supplied with a 4 speed which typically had a 10 spline male input shaft.
27 spline (from Turbo 350 applications): (1971-79) The units supplied with a T350 automatic have a 27 spline male input shaft.
32 spline SHORT (appx 2" stickout)
32 spl LONG a(appx 3-5/8" stickout)
These are both from (Turbo 400 applications) (also some SM465 86-up may have used a 32 spl input.) We have seen both a short (about 2.0" stickout) and long (3-5/8"" stickout) versions of this gear. The adapter casting in both cases is 4-3/8" long. With the short input, the trans will have an output shaft that sticks out of the main case of the trans appx 4" With the Long input, the trans will have a shorter mainshaft: Sticks out of the main case about 2.5"
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.
1986 and Later GM NP205: 6 Bolt circular bolt pattern:
At this point GM updated the unit to use the same 6 bolt circular bolt pattern used on the NP208, and all subsequent GM full size 4x4 truck applications. All of them are the 32 spline female input, although those we have seen are the long (about 3.5" stickout) 32 spl input.
Front Output
GM used two front output shaft configurations, one had a spline count of 10, the other was a 30 spline. 10 splines came before 1977 (roughly) 30 spline shafts came after 1977 (again, roughly). One quick way to tell them apart is by the fact that 10 splines came with a 1310 series yoke output, capable of accepting a CV or yoke driveshaft. 30 spline shafts came with the flat flange on the output, capable of accepting the GM 3R series CV joint.
The 10 spline output will accept the stock 1310; Or a separately purchased 1330 or 1350 Spicer u-joint yoke, and the 1310 CV yoke. The 30 spline flange will accept the 1330 or 1350 CV joints.
Rear Output
The most popular version Is a 32 spline shaft / fixed yoke and will accept a 1310, 1330, or 1350 u-joint yoke, and the 1310 CV yoke.
Some were slip yoke, with a longer tailhousing.
NP205 Pics
Round Pattern 32 Spline w/ Long Female Input:
You must be registered for see images attach
Racetrack Pattern 32 Spline w/ Short Input Female Input:
Racetrack Pattern 27 Spline w/ Male Input (Used for Th350 and can be adapted to 700r4 also)
You must be registered for see images attach
You must be registered for see images attach
