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Adapting the

Chevrolet & GM Standard Shift Bellhousings

to the

Jeep Borg-Warner T18 Transmission

Jeep T18 Adapter kit to GM Bellhousings

Kit 1879, adapting GM bellhousings to 1976–1979 Jeep CJ T18 transmissions

This adapter assembly makes for a strong and convenient adaptation of classic standard shift GM bellhousings to the T18 four-speed transmission, as it was the optional, premium transmission found in 1976-1980 CJ Jeeps.

Novak's 1879 adapter is precision machined from aluminum alloy, and is designed to join GM bellhousings to the 1976-1979 Jeep CJ version T18. It is 3/4" thick, featuring an integrated bearing retainer. Included are the GM bellhousing locator / throwout sleeve, seal and hardware. The total adapted length of the T18 with this adapter is 12-1/2".

The adapter installs onto these transmissions with no change of input gear or other transmission internals. Cutting the transmission input shaft is not required as the adapter spaces the transmission properly for the GM crank and clutch assembly. A new pilot bushing is required for this assembly. See Related Products below for the one matching your particular GM engine.

Kit Contents

The kit includes the adapter plate, throwout sleeve, seal, hardware, and instructions.

Applications & Compatibility

Compatible Transmissions

Only the T18 from the 1976 - 1979 Jeep CJ's with an input shaft stickout length of ~7" (measured from pilot tip of shaft to front face of transmission case) is compatible with this conversion. The similar T18 transmissions from other Jeeps of this era feature longer input shafts and different gearing, and are not candidates for this kind of conversion.

If you are adapting to an earlier Jeep CJ T18 or FSJ T18, jump here.

Compatible Engines

Nearly all GM Generation I-III engines are compatible with this conversion, including Chevrolet Small Blocks, Gen III+ V8's, Chevrolet V6's and Chevrolet I6 engines. Also, Buick, Olds, Pontiac, and other GM engines are compatible with this adapter assembly if you have a standard shift classic GM bellhousing and flywheel for your engine. Even some of the front wheel drive and unique engines could be made to work with this adapter using certain factory or aftermarket bellhousings sharing this common bellhousing / transmission bolt pattern.

GM Bellhousings

Chevrolet Muncie Saginaw Bellhousings

The classic Chevrolet bellhousing, with the four-bolt rear pattern. Buick, Olds, Pontiac and other bellhousings with the same rear face are equally compatible.

your GM bellhousings will typically feature either a 4-11/16" rear face bore or a 5-1/8" rear face bore, the latter typically only from Chevy / GM trucks from 1968-1991. Our adapter will works natively with the smaller bore bellhousing and with the larger bore bellhousing if you choose the 5-1/8" press-on spacer ring. If you are unsure of your bellhousing bore, buy the ring and return it after your build if it turns out you don't require it. See Related Products, below.

Clutch Assembly

Because of the 1-1/16" x 10 spline configuration of these transmissions, there is not a typical off-the-shelf clutch kit available for this swap. However, the installer can use a Jeep or Ford disc with the available pressure plate below.

Be aware of the following clutch configurations - see Related Products below for more information:

  • 153 tooth classic flywheels typically use a 10-1/2" clutch assembly
  • 168 tooth classic flywheels typically use a 11" or 12" clutch assembly
  • Gen III+ engines should use a taller aftermarket flywheel that normalizes the clutch kit to a classic 168 tooth style

The pilot bushing included with most clutch kits will not be compatible with the pilot tip diameter of these transmissions. See Related Products below to select your proper pilot bushing.

Clutch Release

The factory style bellcrank linkage system can be retained if the installer uses a GM release arm, #RAGM. This release arm is the best choice of release arm for either a GM engine swap in 1972-1986 CJ models, and some FSJ Jeeps - with the factory mechanical release system (not hydraulic). It's proper length gives the correct release action for GM clutches and is compatible with later rod & bellcrank linkage systems found in these Jeeps. See Related Items, below.

Some installers use this as a time to upgrade the factory's direct bellcrank style linkage with hydraulic release. Master cylinders from later CJ's and YJ Wranglers (the 1987-1990 version being most popular) can be installed on earlier CJ firewalls, and your GM bellhousing will accept one of Novak's popular #HCR Series slave cylinder kits, which include the release arm. For these and the appropriate hydraulic clutch line, see Related Products, below.

Clutch release bearings need to be a GM compatible unit. Because of the various heights of pressure plate fingers, consider Novak's adjustable throwout bearing assembly, available in Related Products, below.

For more theory and in-depth discussion about clutch systems, see Novak's Guide to Clutches, Linkages and Bellhousings.

Related Products


LS Vortec Gen 3 crank pilot bushing to Ford

Bushing, pilot, GM Gen. III cranks to Ford T18, NP435 & Jeep T150, T18 (1976-1979) transmissions, #PB-6071176

This pilot bushing is for Ford transmissions to most Gen III+ crank flanges, with the exception of some earlier truck 6.0L & 4.8L versions, as discussed here.

GM crank to Ford pilot bushing

Bushing, pilot, GM Gen. I-III (1955-2000) cranks to Ford T18 & NP435 transmissions, #PB-3901176

This pilot bushing is for classic Chevy, Buick and other GM cranks to many Ford input shafts. This includes early GM Gen III cranks that have the extended depth crank flange. Click here for more details on these pilot bushings.

Ring, sizing, precision, 4-11/16” GM bearing retainers to 5-1/8" bore bellhousings, #BR-4

Press this ring onto the retainer of the Novak adapter if you have the 5-1/8" truck bellhousing as found on so many GM engines from 1968-1991. If you are unsure of the bore diameter of your Chevy bellhousing, you can buy this ring and return it if unused.

Jeep to GM Clutch Release Arm

Arm, clutch release, GM engine to post-1971 Jeeps, #RAGM

As discussed above, this is the release arm needed to release a GM clutch disc when retaining the factory 1972-1986 bellcrank linkage system in CJ and some other models of Jeeps.

Adjustable clutch release throwout bearing

Bearing, clutch release, throwout, Novak adjustable, GM version, #TB1

This release bearing assembly uses a telescoping and locking design which spans the range of shortest to longest GM throwout beareings that were ever available. It is helpful if the installer wants a one-and-done solution that avoids trips to the parts store, and sometimes for bearing heights that just aren't made anymore by GM or the aftermarket.

Hydraulic clutch retrofit kit for GM bellhousings, #HCR

Novak's popular HCR series clutch release slave kits will bolt onto your existing GM (Chevy or Buick) bellhousing and provide you with the foundation for a strong, smooth, adjustable, servicable and durable clutch release system. See the details and options here.

Hydraulic release master kit for Jeeps

Assembly, clutch line and flex hose, stainless and poly wrapped, 7/16-24 inverted flare, DOT fittings, 46-1/4 in overall length, #HCR8

This durable hose will join your master cylinder to the Novak hydraulic slave kit.

Hydraulic release master kit for Jeeps

Cylinder, hydraulic clutch release, master, Jeep YJ, 1987-1990

This YJ master cylinder is great for upgrades from CJ bellcrank mechanical linkages to hydraulic, used in conjunction with Novak's #HCR slave cylinder assembly, adjacent. The CJ usally has markings on the firewall for its installation, and our instructions will show you how to set up the pivot points, pedals, etc.

Adjustable clutch arm pivot

Pivot, ball stud, clutch release arm, adjustable, GM bellhousings, #3855G

This handy clutch release pivot stud is what we reach for when setting up a clutch system. Unlike factory GM pivots, it can adjust for better clutch arm geometry and clearance with the bellhousing window.

GM LS Vortec Bellhousing

Bellhousing kit, GM LS / Vortec engines, #GM621-LS-K

Kit, bellhousing, GM Gen III+ engines to Muncie / Saginaw transmissions, 4-1/16” bore, compatible with 168 tooth flywheel & 12” clutch. Includes the pivot stud, release fork boot and flywheel cover.

GM Chevy Bellhousing

Bellhousing kit, classic Chevy Small & Big Block engines, #3899621-K

Kit, bellhousing, Chevy 90 degree engines to GM transmissions, 4-11/16 bore, 12” clutch, 168 tooth flywheel, enhanced casting. Includes the pivot stud, release fork boot and flywheel cover.

Extended depth flywheel for GM engines

Flywheel, GM Gen III/IV V8 engines, 168 tooth, offset version, billet, SFI, 35 lb, for standardized 12” clutches, #LS400-35X

This flywheel standardizes LS engines so they can use standard off-the-shelf clutch kits like earlier Chevrolet engines. Their extended height makes up for the shorter cranks in most LS / Vortec / Gen III+ engines. Bolts and clutch kit available, adjacent.

Bolts for GM engine flywheel to crank

Bolts, 11mm x 1.5mm, LS engine crank, extended length, 4.8, 5.3, 5.7, 6.0L, LS1, LS6, #330-2802

These bolts will fasten your flywheel to your GM Gen III+ crank. They are high-strength alloy and feature the unique GM thread pitch.

Clutch disc

Disc, clutch, 11” x 1-1/16” x 10 splines, Ford style, #CD1226

Use this disc in a 11" or 12" GM pressure plate

Pressure plate for GM conversion

Pressure plate for 11 inch clutch, GM, diaphram, low hat, 1958-1979 GM applications, #361784

This diaphragm pressure plate will work on a classic GM flywheel with a 1-1/16" x 10 spline clutch disc.

T18 Parts

Parts for the T18 Transmission

Gaskets, rebuild kits, etc. are available for the T18 transission. See them here.

1976-1986 Jeep floor tunnel cover

1976-1995 Jeep CJ & YJ Floor Tunnel Cover

Start with a clean slate tunnel cover for your 1976-1995 Jeep CJ / YJ floor. Cut your shifter holes and install boots onto it as required. Material is aluminum. Can be painted. More info here.


Installation Considerations

Engines & Engine Mounting

GM Engine Mounts for JeepsNovak engine mounts are available to ease the installation of your GM V6 or V8 engine. Novak has engines mounts for most Chevy, Buick and GM Gen III+ V8's.

Novak's engine mounts, feature vibration dampening, superior strength and useful adjustability - adjustable even after the engine is installed. The design, strength, and affordability of our mounts are second to none.

Engine placement in these Jeeps should consider the following points:

  • Left-right offset location is similar to factory at ~1-1/4" to the driver's side
  • Avoid installing the engine too low (axle clearance and other issues)
  • Avoid installing the engine too high (transmission tunnel interference, etc.)
  • Set your engine to 4-7 degrees of tilt rearwards, like the factory engine & powertrain
  • It is usually best that Chevy and Gen III+ V8 engines install approximately 3" further forward, using the back of the engine block face as the datum
  • When mocking up your engine installation location, pay special attention to radiator and fan clearance.
  • Firewall modifications are not expected.

Since Jeeps featuring the T18 transmission are "high-hood", clearance for classic Small Block and high Vortec (truck style) intakes and accessories are not a problem.

Driveshafts

Driveshaft length changes may be required. Chevy engines (with their rear distributors) can install around 3" further forward than AMC engines. It is also recommended that LS family engines be installed 3" further forward than the factory block (using the back face of the block as the datum point) for exhaust clearance, firewall access, etc.

Because of the engine placement and transfer case SYE kits are frequently installed with many of these conversions, you may end up with a longer rear driveshaft (very desirable for lifted Jeeps) and a shorter front driveshaft.

Some installers, concerned about the expense of new or modified driveshafts, attempt to let the existing driveshafts dictate engine, transmission and transfer case location, often to the detriment of the project. Our recommendation is to prioritize the correct position of drivetrain components over saving a few dollars which is usually regretted in the long run with compromised positioning.

Jeeps that require extensive travel or specialty-built driveshafts have this option available through several fabricators across the nation. These are normally specified after placement of the new transmission and measured at vehicle ride height. As the rear driveline gets shorter, it is often advantageous to us a Double Cardan or “CV style” rear shaft with the correct geometry at the axle to minimize vibrations and possible binding.

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.

Engines & Engine Mounting

GM Engine Mounts for Jeeps Novak engine mounts are available to ease the installation of your GM V6 or V8 engine. Novak has engines mounts for most Chevy, Buick and GM Gen III+ V8's.

Novak's engine mounts, feature vibration dampening, superior strength and useful adjustability - adjustable even after the engine is installed. The design, strength, and affordability of our mounts are second to none.

Engine placement in these Jeeps should consider the following points:

  • Left-right offset location is similar to factory at ~1-1/4" to the driver's side
  • Avoid installing the engine too low (axle clearance and other issues)
  • Avoid installing the engine too high (transmission tunnel interference, etc.)
  • Set your engine to 4-7 degrees of tilt rearwards, like the factory engine & powertrain
  • It is usually best that Chevy and Gen III+ V8 engines install approximately 3" further forward, using the back of the engine block face as the datum
  • When mocking up your engine installation location, pay special attention to radiator and fan clearance.
  • Firewall modifications are not expected.

Since Jeeps featuring the T18 transmission are "high-hood", clearance for classic Small Block and high Vortec (truck style) intakes and accessories is not a problem.

Novak Gen III+ engine mounts for 1976-1986 Jeep CJ models will remove any guesswork from the engine installation location as they are predetermined for the best location and engine clearance margins.

Driveshafts

Driveshaft length changes may be required. Chevy engines (with their rear distributors) can install around 3" further forward than AMC engines. It is also recommended that LS family engines be installed 3" further forward than the factory block (using the back face of the block as the datum point) for exhaust clearance, firewall access, etc.

Because of the engine placement and transfer case SYE kits are frequently installed with many of these conversions, you may end up with a longer rear driveshaft (very desirable for lifted Jeeps) and a shorter front driveshaft.

Some installers, concerned about the expense of new or modified driveshafts, attempt to let the existing driveshafts dictate engine, transmission and transfer case location, often to the detriment of the project. Our recommendation is to prioritize the correct position of drivetrain components over saving a few dollars which is usually regretted in the long run with compromised positioning.

Jeeps that require extensive travel or specialty-built driveshafts have this option available through several fabricators across the nation. These are normally specified after placement of the new transmission and measured at vehicle ride height. As the rear driveline gets shorter, it is often advantageous to us a Double Cardan or “CV style” rear shaft with the correct geometry at the axle to minimize vibrations and possible binding.

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.

Also See