50-6902 : GM 700R4 to GM NP205 Adapter Kit (replacing TH400) (#50-6902)

50-6902 : GM 700R4 to GM NP205 Adapter Kit (replacing TH400)

Advance Adapter
The GM 700R4 main shaft kit is used when replacing a TH400 in model years 1971-84. Once installed into the 700R4, the output side of the 700R4 looks identical to a 4WD TH400 that is being replaced. The adapter kit includes a new output shaft, plastic washer, adapter plate, TH400 gasket, o-ring, metric fastening hardware, and adapter instructions.
Transfer Case
The adapter assembly fits 1971-84 GM NP205, 1971-79 NP203 transfer cases that were previously used with a TH400.This adapter assembly requires that use of the original GM TH400 4wd adapter.
This kit is designed for exclusive use with the 700R-4 / 4L60 / 4L60E. The overall case length of the transmission is 23.375”, has non-removable bell housing, and a 4 bolt square rear case. Late model 4L60E automatics will have removable bell housing and a 6 bolt hex pattern rear case.
Note: The late model 4L60E automatics will require VSS kit. We manufacture two styles of VSS kit's, 716073 fit model years 1993-96 and 50-0405 fit model years 1997 to current. 




The early GMs 1968-70 used a Dana 20 style transfer case and no adapters are available for these vehicles.

In 1971, New Process introduced a model NP203 (chain-driven), and NP205 (gear-driven) transfer case. Both of these transfer cases used various input splines. As a general rule, all of the transfer cases that couple to a TH350 automatic are normally a 27 spline input; when coupled to a manual transmission a 10 spline input; and when coupled to a TH400 a 32 spline input.

The NP203 was used from 1971 to 1979. This transfer case was mated to the TH350, TH400, and SM465 transmission.

The NP205 was used from 1971 to 1991. The 1971-79 NP205 was only found mated to the TH350 and the SM465 transmission. For 1-ton vehicles between 1979 to 1984/85, GM used a TH400 and the SM465. The TH400 was equipped with a female 32 spline input, while the SM465 retained the male 10 spline input. These model transfer cases had a figure-eight front bolt pattern. In 1985 to 1991 vehicles, GM started using a different version of the NP205. The input spline for both the TH400 and the SM465 transmissions was a female 32 spline, and the front bolt pattern changed to circular bolt pattern. NP205 27 Spline  NP205 10 Spline TC

In 1981, GM introduced the NP208 chain-driven transfer case. The NP208 also has a circular bolt pattern, and had either a 27 or 32 spline input. In 1988, GM next introduced the NP241 chain-driven transfer case. This transfer case, as far as bolt patterns and splines are concerned, is identical to the NP208.

The NP205 is sometimes hard to identify. The data plate for this transfer case is located on the upper front of the case; but many times this information has been worn off, and subsequently a NP205 gets confused with a NP203 transfer case. The easiest way to identify the NP205 is by the rear 3 bolt cover on the idler shaft. NP205 3-bolt cover

Once you know that you have a NP205 transfer case, the next thing is to identify the make (GM, Dodge or Ford).  The casting numbers on these cases are of no help.  The Ford transfer case is the easy one to identify since it is a left hand drop (front driveshaft on the driver’s side).  The Dodge and GM NP205s are a bit more difficult.  The cases are identical, both having the figure-eight bolt pattern.  Counting the front input gears are the easiest way to distinguish between the two.  GM transfer cases use either a male 27 spline (TH350), a male 10 spline (SM465), or a female 32 spline (TH400) input gear.  The Dodge NP205 was either a female 23 or male 29 spline input gear.  The GM female 32 spline shafts were offered in two stick out lengths:  1979 to 1984/85 had a short stick out, while the 1985-91 had a long stick out.  The 32 spline stick out is important to know when adapting to a different transmission.  NP205 10 Spline top  NP205 LINKAGE CLEARANCE ON CASTING

The NP205 input gears, no matter what vintage or model, are always the same internally.  This allows you to swap the input shaft between the various model transfer cases.  One difference that must be taken into consideration is the front input shaft bearing.  The male 10 & 27 spline GM transfer cases used a smaller bearing than the female 32 spline transfer case. The last thing that should be noted is the bolt pattern change that occurred on the case of the GM NP205 transfer case.  In 1985, the case was changed from a figure-eight bolt pattern to a circular-six bolt pattern.  This circular bolt pattern is identical to that of the NP208/241.  The stock adapter housings that GM used are similar; however, the NP205 stock adapter housings have a notch in them for transfer case shifter linkage clearance. 

NP205 originally coupled to a TH350:  This transfer case, used in vehicles between 1971-79, has a male 27 spline input.  The bolt pattern is a figure-eight configuration.  TH350 TO NP205 Stock Cast  TH350 to NP205 Stock Casting 2

NP205 originally coupled to a SM465:  Used in vehicles 1971 to 1984/85, this transfer case has a male 10 spline input.  The bolt pattern is a figure-eight configuration. SM465 to NP205 Casting  SM465 to NP205 Casting2

NP205 originally coupled to a TH400:  Used in 1979 to 1984/85 vehicles, this transfer case has a short stick out of 1.50”, and a female 32 spline input.  The bolt pattern is a figure-eight configuration.  This transfer case uses a larger front bearing than the 10 and 27 spline transfer cases. NP205-TH400 casting 1  NP205-TH400 casting 2

NP205 originally coupled to a SM465 or TH400:  Found in 1985-91 vehicles, this transfer case has a long stick out of approximately 3.50”, and a female 32 spline input.  The bolt pattern is a circular-six configuration.   This transfer case uses a larger front bearing than the 10 and 27 spline transfer cases.  When using this transfer case, caution should be used with regards to the length of spline engagement.  Transfer cases with this long stick out may require a spacer adapter PN51-6910 or modifications to the transmission output shaft for proper spline engagement without pre-loading the transmission or transfer case bearings.  NP205 Input  NP205 32 Spline Input

NP205 Stock Couplers (Power Sleeves):   As the ongoing aging process of GM NP205 transfer cases continues, so does the good availability of replacement part from the dealerships.  The most recent GM components that started to become hard-to-find items are the power sleeves.  We now offer both the stock GM 27 spline and the stock 10 spline.  The 27 spline was offered in two designs:  one that used a bearing support in the adapter housing, and one that floated on the transmission and transfer case splines.  We only offer the later one which is centered by the splines.  Our PN52-9503 fits the 4WD TH350 transmission to the 27 spline NP205 transfer case, and PN52-9504 fits the 10 spline SM465 transmission to the 10 spline NP205 transfer case. NP205 10 Spline coupler 

NP205 Stock Replacement Adapters:   The same goes with the adapter housings as does the power sleeves. We offer a stock TH350 to NP205 adapter PN50-5302. We offer SM465 to NP205 10 spline pattern PN50-4708 and a TH400 to the early pattern NP205 PN51-3202.

NP205 addition notes:  Slip yoke and fixed rear outputs used depending on wheel base of the vehicle.

Front outputs: 71-77 10 spline front output shafts and normally used 1310 or 1310C.V. yokes. 77-91 30 spline front output and normally had a flange front yoke Saginaw U-joints.

All Chevy NP205’s were married units. All Chevy NP205’s 1971-1984 have fig 8 bolt pattern

TH350 71-79 transmission used a male 27 spline input and small input bearing with a coupler sleeve figure 8 bolt patterns. SM465 71-84 used a 10 spline male input and small input bearing with a coupler sleeve figure 8 bolt patterns. TH400 79-84 female 32 spline input large input bearing figure 8 bolt pattern no coupler used and female input sticks out 2” from the front of the case. 1985-1991 Only used in 1 ton dually or 3+3 cab trucks (unless special order) Circle 6 bolt pattern 32 spline female inputs with the large input bearing. This was used behind TH400 and SM465.  In 1991 production vehicles and special built Chevy railroad trucks in 1992 were offered with a NP205/4L80E. These cases have a 40 pulse VSS tail housing and special 4L80E adapter casting.  2 different length inputs used (short input 2” known to be used in 1985 W/TH400 and most were long 3.5” stick out from the front of the transfer case. All Circle 6-bolt SM465 are the long input)


GM 700R4 & 4L60 Transmissions  

The 700R4 Automatic Overdrive Transmission was GM’s answer to the American consumer’s desire for better fuel economy. First introduced in 1982, the 700R4 was met with wide fanfare as the ideal transmission. The transmission featured an impressive 30% overdrive while also offering a low first gear of 3.06. The improved fuel economy added with a low off-road first gear made this transmission an immediately popular choice for conversions. 

The 700R4 was basically designed to replace the retired TH350 transmission. The 700R4 was used in rear wheel drive passenger vehicles, S-series trucks, Blazers, ½ ton pickups and even a few ¾ ton trucks. The transmission was offered with the standard V8 90° bolt pattern which also included the 4.3 V6. A smaller 60° bolt pattern was also available for some smaller V6. Engines like the 2.8. The bolt pattern on the rear of the transmission was the same 4-bolt pattern as the TH350 but used metric bolts. The transmission always used a 27 spline output shaft. The 4wd output shaft protruded out of the transmission with a stick out length of 2.75". This stick out was approximately 2" longer than the TH350.

 Another unique feature to the 700R4 was the lock up torque converter. This feature essentially locked up the torque converter to create a direct mechanical connection similar to a manual clutch transmission. By locking the converter at highway speeds the slip of the converter was eliminated. The results were lower RPMs and significant loss of generated heat. Although the 700R4 is not an "electronically" controlled transmission, this feature was controlled by a PCM. We offer a lock up kit under Part # 23-700R which can be used with carbureted engines or applications outside of the GM engine family. The 700R4 also uses a TV cable (or Throttle Valve) to control the shift points and line pressure. It is critical that special attention be used during the adjustment of the T.V. cable. Although GM should be credited with the introduction of such a revolutionary transmission, the transmission did suffer from a few glitches. GM persevered with the development of the 700R4, and to their credit, the transmission received all of the necessary upgrades by 1987. Something else to consider in researching and selecting a 700R4 is the wide aftermarket support available. Automotive aftermarket manufacturers have had over 25 years to master and perfect this transmission. The availability of better clutch packs, shafts and building techniques has allowed this transmission to reach several strength levels. The 700R4 can now be built around the consumer’s needs, which spread a wide spectrum from conservative highway vehicles to extreme completive racing and rock crawling vehicles. 

In 1990, GM decided to code and rename their transmissions, the 700R4 is best described as a 4 speed, longitude transmission rated for vehicles around 6000 lbs. It was this information that was used to change its name to 4L60; therefore, a 700R4 and 4L60 are the same transmission. Later the transmission would become electronically controlled and the name was changed to 4L60E.

 In 1990, GM decided to code and renamed their transmissions, the 700R4 is best described as a 4 speed, longitude transmission rated for vehicles around 6000 lbs. It was this information that was used to change its name to 4L60; therefore, a 700R4 and 4L60 are the same transmission. Later the transmission would become electronically controlled and the name was changed to 4L60E.

Forward Speeds .... 4 

Dates Produced .... 1982 - 1990

Manufacturer .... General Motors        

Case Length .... 23.375 

Bellhousing Length ... Integral

Over All Length .... 23.375

Case Material ... Aluminum   

Output Shaft Spline .... 27   

1st Gear Ratio .... 3.06 

2nd Gear Ratio .... 1.63

3rd Gear Ratio .... 1.00

4th Gear Ratio .... .690

Reverse Gear Ratio .... 2.29       

Transmission Weight .... 175lbs  

GM 4L60E Transmissions 

GM manufactures this transmission in two versions. Both these transmissions use a reluctor ring connected to the GM engine computer for proper shifting points. The first version is a mirror image of the 700R/4L60, but it requires the reluctor ring. The second version is found in most of the 1997 & newer vehicles. The case and bellhousing are no longer cast together (now a removable bellhousing design). This transmission no longer has the square bolt pattern on the output side, but is equipped with a hex bolt pattern similar to a TH400.  

4L60E 4 bolt tail housing early design 1993-1996  Available in the same two case designs as 700R4 metric (60 degree V6) and 90 degree Chevy V6/V8. This transmission looks the same as a 700R4/4L60 but has a large round electrical plug on the passenger side of transmission and no T.V. cable was used. This transmission shifted by the engine PCM. There are aftermarket stand alone shift controllers available for the 4L60E. The one we recommend is the Compushift controller which we carry under our Part# P4L110.  

This transmission needs 40 pulse per drive shaft revolution (VSS) for proper shifting. GM installed a VSS sensor in the transfer case on 4x4 models and in the tailhousing on 2WDs. A low range switch is used on 4WDs to send a signal to the computer that the VSS must be adjusted for the transfer case low ratio. We design most of our adapters to have a VSS sensor in front of the transfer case. This allows the computer to always see a accurate reading from the VSS and keeps the transmission from having shifting problems. The sensor can be located after the transfer case; however, the computer must be programed to accept the transfer case low ratio. Stock GM transfer cases have a stock ratio of 2.72:1.   

4L60E late removable bellhousing design  

In 1997, GM changed the 4L60E transmission case to a removable bellhousing design. This was so one transmission case could fit all GM engines including LS series of motors. Care must be taken due to different torque converter bolt patterns and length for each of the bellhousings. The stator and input shaft also had some variations. Be careful interchanging bellhousing and converters on these transmissions. The length of the main case is shorter and now has a 6 bolt pattern on the tailhousing. The case length including bellhousing is 21.735" on Gen I and II V8 and 22.366" Gen III / LS V8. In 2001, GM introduced 4L65E (HD version of 4L60E). This included a 5 pinion planetary gear set vs. 4 pinion in the 4L60E. The 4L70E was introduced with even more upgrades which included stronger output shafts and reaction shells for use in GTO, Silverado SS, Trail Blazer SS, and other high performance vehicles. 

Forward Speeds               ....            

Dates Produced                ....           1993 - 2007 

Manufacturer    ....           General Motors                                 

Case Length       ....           23.375 (1st gen) 15.435 (2nd gen)

Bellhousing Length          ...            Integral (1st gen)  6.315" (2nd gen)

Over All Length ....           23.375 (1st gen)  21.750 (2nd gen)

Case Material    ...            Aluminum                            

Output Shaft Spline        ....           27                            

1st Gear Ratio    ....           3.06

2nd Gear Ratio  ....           1.62

3rd Gear Ratio   ....           1.00

4th Gear Ratio   ....           .696  

Transmission Weight      ....           195LBS (1st gen)   163LBS (2nd gen)

Max Engine Torque         ....           360 to 400                             

Fluid Type           ....           Dextron VI

Fluid Capacity    ....           11 Qts

Gross Vehicle Weight Rated        ....           8600

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