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Novak Conversions

Transmission Knowledge Gateway

The transmission is central to any conversion, both physically and in terms of planning. Making the better choices in a transmission can determine the success, ease and affordability of the rest of the project. Here is our guide:

The transmissions we are most often asked about by our customers include:

Jeep Transfer Cases

Automatic Shift Transmissions

The 6L80 and similar 6L90 are GM's newest and most revolutionary transmissions. Though not yet ready for full acceptance in conversions like the famous 4L60E, they are steadily rising

  • Six forward speeds
  • Compatibility with Gen IV GM engines
  • An electronically operated transmission that is controlled by the networking of a GM Gen IV ECM and integrated TCM
  • Aluminum alloy case with non-integral bellhousing
  • Highly durable, geared very well and smooth operating in both street and off-road environments
  • Adaptable to most Jeep transfer cases, 1980-present
  • Found in some 2007-present GM vehicles

The 4L60E (and similar 4L65 & 4L70) presents the culminated engineering greatness of five decades of GM automatic power transmission design and is the dominant conversion transmission of this era

  • Compatibility with modern GM engines
  • An electronically operated transmission that is controlled by the integrated Powertrain Management Computer
  • Aluminum alloy case with non-integral bellhousing
  • Very durable, geared well and smooth operating in both street and off-road environments
  • Adaptable to essentially all of the Jeep transfer cases
  • Found in some 1997-present GM vehicles

The 4L80E (and similar 4L85) descended directly from the TH400, and improved on it with overdrive and a lockup torque converter

  • Compatibility with modern GM engines
  • An electronically operated transmission that is controlled by the integrated Powertrain Management Computer
  • Aluminum alloy case with non-integral bellhousing
  • Impressively durable, geared well and smooth operating in both street and off-road environments
  • Adaptable to most of the Jeep transfer cases from 1980-present
  • Found in some 1991-present GM vehicles

The 700R4 is the great result of what happens when a company like GM doggedly sticks with it. It was released with its share of bugs, but it didn't stay that was for long. It's a top choice in some of the best Jeep upgrades out there

  • Compatibile with classic and modern GM engines
  • Either hydraulically (700R4 / 4L60) or electronically operated (4L60E) transmission
  • Aluminum alloy case with integral bellhousing
  • Very durable, geared well and smooth operating in both street and off-road environments
  • Adaptable to essentially all of the Jeep transfer cases
  • Found in some 1982-1996 GM vehicles

The TH350 is tough, compact and consistently a very popular choice for a Jeep upgrade transmission

  • Compatibile with classic and modern GM engines
  • Self-shifting hydraulic control
  • Aluminum alloy case with integral bellhousing
  • Strong and smooth operating in both street and off-road environments
  • Adaptable to essentially all of the Jeep transfer cases
  • Found in some 1969-1984 GM vehicles

The TH400 is the Big Daddy of the GM automatics. Brutally tough, relatively efficient and totally buildable

  • Compatibile with classic and modern GM engines, as well as AMC I6 & V8 engines
  • Self-shifting hydraulic control
  • Aluminum alloy case with integral bellhousing
  • Strong and smooth operating in both street and off-road environments
  • Adaptable to essentially all of the Jeep transfer cases
  • Found in some 1964-1995+ GM vehicles

The AW4 transmission was a step into the modern era for Jeep, with its overdrive and electronic control

  • Compatibile with AMC I6 engines
  • Electronic control, via its own computer (when interfaced with an ECM) or an integrated PCM
  • Aluminum alloy case with non-integral bellhousing
  • Moderate strength
  • Found in the 1987-2001 Jeep XJ

Manual Shift Transmissions

- Four Speeds -

The GM SM465 is said to be one of the greatest four-speeds ever built.

  • Compatibility with GM and AMC style engines
  • Iron case and top cover. Deep first gear with direct-drive in fourth
  • Brutally strong, but refined for road and trail manners
  • Adaptable to essentially all of the Jeep transfer cases
  • 1968 - 1991+ GM trucks

The Borg-Warner T18 & T19 transmissions are famous in the truck and off-road world, and this reputation is well earned.

  • Compatibility with GM, Ford and AMC style engines (Ford & Jeep versions)
  • Iron case and top cover. Deep first gear with direct-drive in fourth
  • Extremely strong, but with good road and trail operaion
  • Adaptable to essentially all of the Jeep transfer cases
  • 1966 - 1991+ Fords & Jeeps, primarily

The New Process 435 is a supremely good four-speed with an excellent history

  • Compatibility with GM, Ford, Dodge and AMC style engines
  • Iron case and aluminum top cover. Deep first gear with direct-drive in fourth
  • Tough as nails, but shifts nicely on the street and trail
  • Adaptable to essentially all of the Jeep transfer cases
  • 1966 - 1991+ Dodge & Ford trucks, primarily

The SM420 is the great predecessor of the four-speeds and remains a great choice for several Jeep applications.

  • Compatibility with GM and AMC style engines
  • Iron case and top cover. Deep first gear with direct-drive in fourth
  • Extremely strong, but quite roadworthy
  • Adaptable to essentially all of the Jeep transfer cases
  • 1947 - 1967 GM trucks

The T98 transmission is the predecessor to the T18 and similar in appearance and design

  • The Jeep version is adaptable with GM engines
  • Iron case and top cover. Deep first gear with a direct-drive in fourth gear
  • Plenty strong for any Jeep
  • Retained with the native Jeep transfer case
  • 1955 - 1971 (in Jeeps)

The T176 (and T177 / T178) is native to 1980 - 1986 Jeeps as the medium duty upgrade

  • Compatibility with AMC I4 & I6 engines, and adaptability to GM and Ford engines
  • Aluminum case and top cover. Close-ratio first gear with direct-drive in fourth gear
  • Stronger than the base-option transmissions during this era
  • Compatible with the Dana 300
  • 1980-1986 Jeeps

The SR4 is a car transmission that was installed in CJ Jeeps for two years

  • Compatible with AMC I4 & I6 engines
  • Aluminum case and top cover. Close-ratio first-gear and direct-drive in fourth
  • Neither strong, nor suited to conversions or serious off-road use
  • 1980-1982 CJ Jeeps

The T4 was the standard four-speed in the 1982-1986 CJ

  • Compatible with AMC I4 & I6 engines
  • Aluminum case and top cover. Close-ratio first-gear and direct-drive in fourth
  • Neither strong, nor suited to conversions or serious off-road use
  • 1982-1986 CJ Jeeps

- Five Speeds -

The AX15 is a surprisingly strong transmission, and was a serious improvement over many of its lighter-duty predecessors

  • Compatibility with AMC I6 and other engines, and adaptability to GM and Ford engines
  • Aluminum case. Decently low first gear with overdrive in fifth-gear
  • Surprisingly tough
  • Compatible with the NP231 and adaptable to the Dana 300, Dana 20 and Dana 18
  • 1988-1999 Jeeps

The NV3550 was New Venture's answer to the AX15, and in the same strength, operational and size category

  • Compatibility with AMC I6 engines, and adaptability to GM and Ford engines
  • Aluminum case. Decently low first gear with overdrive in fifth-gear
  • Surprisingly tough
  • Compatible with the NP231 and adaptable to the Dana 300, Dana 20 and Dana 18
  • 2000-2004 Jeeps

The NV4500 is a heavier-duty five-speed as found in full size GM and Dodge trucks

  • Compatibility with GM & Dodge engines with adaptability to AMC engines
  • Iron case with aluminum top cover . Fairly low first gear with overdrive in fifth-gear
  • Quite strong
  • Adaptable to the Jeep Dana 300 and NP231
  • 1993-present GM and Dodge trucks

 

The T5 was the standard five-speed in the 1982-1986 CJ

  • Compatible with AMC I6 engines
  • Aluminum case and top cover. Close-ratio first-gear and overdrive in fifth gear
  • Neither strong, nor suited to conversions or serious off-road use
  • 1982-1986 CJ Jeeps

The AX5 was the light-duty, five-speed transmission in the 1984-2003 XJ, YJ & TJ Jeeps

  • Compatible with AMC I4 engines
  • Aluminum case and top cover. Close-ratio first-gear and overdrive in fifth gear
  • Neither strong, nor suited to conversions or serious off-road use
  • 1984-2003 XJ, YJ & TJ Jeeps

The Peugeot BA10/5 had a gratefully short run in Jeeps

  • Compatible with AMC I6 engines
  • Aluminum case and top cover. Close-ratio first-gear and overdrive in fifth gear
  • Neither strong, nor suited to conversions or serious off-road use
  • 1987-1988 XJ, YJ & MJ Jeeps

- Three Speeds -

The T90 is the most famous of the Jeep three-speed transmissions

  • Compatible with Willys I4 & I6 engines and adaptable to GM engines
  • Iron case and top cover. Close-ratio first gear with direct-drive in third-gear
  • Fairly strong and extremely compact
  • Compatible with the Dana 18 and easily adaptable to the Dana 20
  • 1946-1971 Jeeps

The T150 was strong, and the last of the Jeep three-speeds

  • Compatible with AMC engines and adaptable to GM and Ford engines
  • Iron case and top cover. Close-ratio first gear with direct-drive in third-gear
  • Fairly strong and extremely compact
  • Compatible with the Dana 20
  • 1976-1979 Jeeps

The T15 was the strongest of all the three-speeds

  • Compatible with AMC engines and adaptable to GM engines
  • Iron case and top cover. Close-ratio first gear with direct-drive in third-gear
  • Very strong and quite compact
  • Compatible with the Dana 20
  • 1972-1975 Jeeps

The T14 is the T15's little brother. Not too tough but a pretty good gearbox

  • Native to Buick then AMC engines and adaptable to GM engines
  • Iron case and top cover. Close-ratio first gear with direct-drive in third-gear
  • Moderate strength and fairly compact
  • Compatible with the Dana 18 & 20
  • 1968-1975 Jeeps

The T86 is kind of a T90 knock-off. It was the transmission first offered with the Buick V6 engine

  • Compatible with the Buick V6 engine
  • Iron case and top cover. Close-ratio first gear with direct-drive in third-gear
  • Moderately strong and compact
  • Compatible with the Dana 18 readily Dana 20
  • 1946-1971 Jeeps

- Six Speed -

The NSG370 has the Benz air about it. Lots of gears and a unique, but durable design

  • The NSG370 replaced the NV3550 and was offered behind both the 4.0L Engine as well as a version behind the Mopar 2.4L I4. It is generously rated for torque handling
  • Aluminum case with integrated bellhousing
  • Compatible with the Jeep NP / NVG transfer cases.
  • 2005-present Jeeps