Novak Conversions Adapter 4L81-BL32 Kit

Adapting 4L80E transmissions to Jeep New Process 231, 242, 249 transfer cases, 32 spline late input gear version.

Adapting the GM 4L80-E Transmission to the Jeep Models 207, 231, 242, 249 & 241OR Transfer Cases

Novak's 4L80E transmission to the Jeep New Process (or New Venture) transfer cases conversion makes for one of the strongest geartrains possible for both on-road and off-road, and has become an increasingly popular transmission to transfer case combination.

Product & Features

The Adapter

The Novak 4L80 to Jeep transfer cases adapter is compact at only 3.0" long for a combined transmission and adapter length of 29-1/4" (equivalent to a ~22-5/8" manual transmission). The adapter itself is machined of a 6061 billet aluminum alloy, featuring thick flanges and a heavy cross-section.

Transfer Case Clocking & Rotation Options 

Our adapter is drilled for multiple clocking locations from near-factory (20 degrees down) to near-flat (3 degrees down). However, pan clearances and front axle width may inhibit the flatter options.

Rear Mount Provision 

This transfer case adapter's design features a modular mounting and support system and mounting base, ready to accept our industry standard urethane isolator mount, available for purchase below.

Contents

Billet adapter housing, transfer case input or transmission output depending on kit selection, seal spacer, seal, transfer case to adapter gasket, transmission to adapter sealing ring, fastening hardware, steel mounting base, and instructions.

Applications & Compatibility

Transmissions

All versions and years of the 4L80E can be adapted to the NP (New Process) transfer cases. Both the 2WD and 4WD versions work equally well with the correct adapter option. 

Output Shaft Speed Sensor

1991 - 1996 4L80E's should feature a speed sensor at the driver's side rear portion of the case (see image, below), whether they are 2wd or 4wd applications. 1997 and later 4wd applications often omit the rear sensor as this data is available from the transfer case output shaft in factory applications. This adaptation requires that this sensor and its internal reluctor ring be installed by a transmission building professional for proper operation.

Option I: Transmission Output Shaft Version

The 4L81-A adapter is compatible with all versions of the 4L80E. If you have a 2wd 4L80E, a 4wd 4L80E that is undergoing a rebuild anyway, are unsure what 4L80E you have (or will have at the time of the conversion), are missing the rear speed sensor, or your transfer case was just rebuilt (doesn’t leak) and you’d rather not open it back up then the 4L81-A kit is your best choice. The new 23 spline 4L80E output shaft is machined from stock material through an extensive process ensuring maximum strength and a precise fit. The new Novak shaft splines directly into the OEM style input shaft of a 23 spline transfer case. The 241OR Rubicon must use the 23 spline output version. This requires disassembly of the transmission, and we recommend the services of a transmission professional.

The basic installation is a 2-2.5 hour bench job and will include at least simple gasket and seal replacements. Be sure that if your transmission is missing the output speed sensor it is added at this time. See below for the correct parts. This is a good time for a more thorough master rebuild and update of the Hydra-Matic. Many consider one of our complete Novak remanufactured and upgraded transmission packages. The advantage of a superior, professionally built transmission, tested and ready to bolt in delivered to you is definitely worthy of consideration. 

The E & L designate early or late as described below. Please choose the correct version if using an output shaft replacement adapter:

Early vs Late 4L80E Oiling

In about 1997, GM changed the way the rear bushing is oiled in the 4L80E transmission. The shafts are not interchangeable and you will need to identify for sure which version you need.

• The first design has two lube holes in the sides of the case bushing journal. Lube flows through these feeding the output shaft and forward to the planets.
• The second design does not have the lube holes instead has a tube feeding oil from the valve body. 

Option II: Transfer Case Input Shaft Version 

One 4wd version of the 4L80E is ready to bolt up to our 4L81B adapter kit. Disassembly of the transmission is unnecessary as the 32 spline 4wd style output shaft (which protrudes about 3" from the rear face of the 4L80E transmission main case) is correct for this kit version. Disassembly of the transfer case is necessary to install a new matching 32 spline NP input gear.

The input gear installation is a 2-3 hour bench job and usually includes either a simple gasket and seal replacement or preferably a full rebuild of a tired transfer case, especially a chain replacement. It is not requisite that you rebuild your transfer case to successfully complete the conversion. However, it is certainly worth consideration especially if your transfer case leaks or has many years of service. You will be going all the way into the front of the transfer case to install in the input gear. Our superior quality New Process master rebuild kits along with a top quality chain are the perfect solution for the job and are available below.

Early vs Late Input Gear Style

The NP/NVG input gears are divided early and late about 1993-1994. However there are no guarantees that things are original or that the change was made as a clean break 93 down and 94 up. If in question, the input bearing width on these models is a good indicator. “E” Early uses a 24mm wide bearing and “L” late is 16mm wide. The photos above show the differences in width of the bearing location and the stepped shoulder between the bearing and the gear. The 241JK transfer case is a special case requiring special gears. It is a late cut with additional machining required.