Adapting the
GM Muncie SM465
to the
Jeep Models 207, 231, 242, 249, 241J & 241OR Transfer Cases
* Note that we recommend you also purchase the transmission mainshaft bushings required when changing a 465 mainshaft, as discussed in Transmission Mainshaft Replacement, below. |
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Our SM465 to the Jeep New Process (or New Venture) transfer cases conversion makes for an impressively strong and capable assembly both on-road and off-road, and it remains one of our most popular manual transmission to transfer case combinations.
The adapter kit is designed for compatibility with the Jeep NP207, NP231, NP242, NP249 & NP241OR "RockTrac" transfer cases.
The Adapter
The Novak SM465 to Jeep NP / NVG transfer cases adapter is very compact at only 3.2" long for a combined transmission and adapter length of 15.2". The adapter itself is cast and machined of a high-grade aluminum alloy, featuring thick flanges, a heavy cross-section and strength-adding gussets.
Muncie 465 Versions
All versions (2wd or 4wd) and any year of the SM465 can be adapted to these transfer cases.
Applicable Jeeps
Many of these conversions are for the YJ Jeeps, in which the SM465 is a terrific match. Even earlier Jeeps that are being retrofitted with the NP231 or similar later transfer cases accept the SM465 well. However, TJ and XJ Jeeps with their significant dash consoles may pose an inteference problem with the SM465's shifter and top tower. The SM465 is a shorter and taller transmission than factory options in these later Jeeps. Individuals should be aware of this caveat.
A later but rare version of the SM465 features an aluminum top shifter cover with a rearward shifter offset that mitigates this problem. Installers with access to such a transmission might consider it.
Transmission Mainshaft Replacement
This SM465 conversion kit comes with a new output shaft to be installed in your Muncie transmission that was originally a 2wd or 4wd version - either works equally well. The Novak mainshaft is of a premium alloy steel, precision splined and specially hardened for strength and against wear, providing a superior interchange. This shaft connects the transmission output directly into the existing 21 or 23 spline NP / NVG input gear for the strongest connection. Transfer case disassembly is not typically required. However, please note our 21 vs. 23 spline discussion below and its warranty caveat.
Mainshaft replacement is largely straightforward. Good work is within easy reach of the careful home mechanic and instructions are included. We also recommend our basic gasket & seal kit, or our all-inclusive master rebuild kit, depending on your assessment of your transmission's condition. See our SM465 parts page for information on these items.
Transfer Case Input Gears
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New Process input gears come in varying spline counts and lengths. Whichever you have, we've got you covered. A seal spacer sleeve (image, below) is included and pre-installed in your Novak adapter in the event your transfer case has a short input gear. |
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 21 vs. 23 splinesWe're often asked about whether the 21 spline style connection is strong enough, vis a vis the 23 spline version. In most situtations, 21 splines will be adequate.  This is due to the fact that we don't use friction welding on our shafts, and that much of the punishing torque multiplication takes place within the transfer case low range, which occurs after the input portion of the transfer case. However, we have seen limited instances where 21 spline shafts have failed where 23 would not have. As such, our parts warranty extends only to our 23 spline version shaft. If you are certain that you must have maximum strength, then you may purchase from us a 23 spline input gear for your NP2xx in conjunction with the 23 spline version of our kit. However, this may not be money best spent in some situations. |
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Transmission Rear Mount
This transfer case adapter's design is based on Novak's Universal Series adapters that feature a modular mounting and support system. Included with the adapter kit is a steel base that is a highly configurable mounting foot, and is ready to accept our industry standard urethane isolator mount, available for purchase (below). This is our preferred rear mount unit. Our kit is designed for it, and its usage is essential to protect powertrain components from the flex and jar typical of any automobile, but especially Jeeps.
Whether you are assembling onto a stock cross member / skidpan or if you are setting up a high-clearance skid plate, you will find it to be a clean and simple process.
Transfer Case Strength and Condition
The New Process / New Venture (NP / NVG) transfer cases are very well matched to the SM465. They are uncommonly strong, feature good gearing and are compact and servicable. They are capable of power ranging up through V6s, V8s and even the Chevy Big Blocks.
It is not requisite that you rebuild your transfer case to successfully complete the conversion, but it may be a good time to do so if your transfer case leaks or has many miles of service. We've made our 231 service kits and our all-inclusive master rebuild kits available for this purpose.
Engine Compatabilities & Engine Mounting
AMC Jeep engines are compatible with the GM SM465 transmission. See Adapting GM Transmissions to AMC Bellhousings.
AMC (258, 4.0, etc.) engines may be left in the factory location in virtually all SM420 installations.
An SM465 installation is often done in conjunction with an engine conversion into the Jeep. These engines include the Chevrolet Small Block V6 & V8, from 1955-2006 or the Gen. III+ V8 and some other GM motors. Carbureted, TBI and TPI engines are all compatible with this transmission.
Engine Crank to Transmission Pilot Bushing
This transmission can be married to stock (i.e., AMC I6) as well as conversion (i.e., GM V6 / V8) engines, and a custom pilot bushing will be required in many instances. Some common choices with the SM465 transmission are listed below:
>Bushing, pilot, AMC cranks to the SM465
>Bushing, pilot, GM Gen. I-III (1955-2000) cranks to SM465
>Bushing, pilot, AMC cranks to the SM465
For pilot bushings not listed, see our full collection. |
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Transfer Case Clocking
Our adapter is clocked optimally for slightly better ground clearance than factory locations, which is actually quite good. The Jeep transfer case belly will sit a fair amount higher than the transmission itself.
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| Many of our customers upgrade their NP / NVG shifter while doing the conversion. Our #SK2X makes the conversion easier than it's ever been. |
Transfer Case Shifter
This transmission conversion will allow for the retention of the factory shifters, or allow you to upgrade to the Novak #SK2X shifter assembly for a simpler conversion and a clean shifting, direct linkage system.
Transmission Shifter
Use of the OEM style transmission shifter for the SM465 is usually easily done. The installer may opt to bend the stick to fit the particular Jeep application.
We can supply a new, straight stick that replaces the factory unit. This stick can be custom bent to the driver's preference and will sometimes restore a more solid feeling to the shifting of a 465.
Driveshafts
Driveshaft length changes are sometimes required, as this geartrain combination is typically shorter than most factory Jeep combinations. Some potential conversion engine installations sit further ahead than OEM engines in the Jeep's bay and will allow for better driveshaft angles, especially when done with this very short combination.
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| Novak's MM Series engine mounts, featuring excellent vibration dampening, superior strength and impressive adjustability - adjustable even after the engine is installed. |
Some of our customers, fearful at the perceived expense of new or modified driveshafts, attempt to let the existing driveshafts dictate engine, transmission and transfer case location, sometimes to the detriment of the project. Driveshaft modifications are usually inexpensive when performed by driveline, RV or tractor implement specialists. New driveshafts are an option but seldom a requirement in regards to the actual successful conversion. Jeeps that require extensive travel or specialty-built driveshafts have this option available through several fabricators across the nation.
Engines & Engine Mounting
A 465 installation is sometimes done in conjunction with an engine conversion into the Jeep. These engines include the Chevrolet Small Block V6 & V8, from Generations I, II, & III, 1955-2006. Carbureted, TBI and TPI engines are all compatible with this transmission. Ford and various AMC engines are also compatible.
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| A turn-key 465, professionally built, adapted and delivered to your door - ready for a variety of engines and Jeep transfer cases. Read more... |
AMC (258, 4.0L, etc) engines may be left in the factory location in virtually all 465 installations.
Axles
Use of factory axles is completely acceptable with this conversion. Axle upgrades are not necessary, but they may be chosen for reasons external to this transmission upgrade.