Adapting the

Chevrolet & GM Standard Shift Bellhousings

to the

Jeep T98 Transmission

as found in

Utility Wagons, Trucks & Gladiator Trucks

Jeep Adapter kit to GM Bellhousings

Kit C5, adapting the Jeep T18 & T98 with factory 7/8” plate and ~8” stickout input shaft

This kit is for Jeep Wagons & Trucks that were factory equipped with the I6 engines and the Borg-Warner T98.

The adapter is 1-1/2" long, machined from high-grade aluminum alloy, featuring thick flanges, a heavy cross-section. This kit is used in conjunction with the 1" iron factory adapter plate found in these trucks. See descriptions below for bellhousing options.

The adapter is easily installed onto the T98 using normal mechanics tools. Transmission disassembly is not required for the scope of this project. Instructions are included.

Kit Contents

Included is the adapter housing, GM bellhousing locator / throwout sleeve, seal, and hardware.

Applications & Compatibility

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 1-1/8" x 10 spline configuration of these transmissions, use an off-the-shelf GM clutch kit (pressure plate & disc) with this conversion.

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.

Transmissions

This kit is for Jeep Wagons & Trucks that were factory equipped with the I6 engines and the Borg-Warner T98. Jeep T98's can vary, and some versions require special adapter components.

For M715 trucks, see our #C715 kit.

Related Products


GM crank to Ford pilot bushing
Jeep T14 to GM pilot bushing
Jeep to GM Clutch Release Arm
Adjustable clutch release throwout bearing
Hydraulic release master kit for Jeeps
Hydraulic release master kit for Jeeps
Adjustable clutch arm pivot
GM LS Vortec Bellhousing
GM Chevy Bellhousing
Extended depth flywheel for GM engines
Bolts for GM engine flywheel to crank
GM clutch kit
GM clutch kit
T18 Parts

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.

Also See