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Adapting the

Chevrolet & GM Standard Shift Bellhousings

to the

Jeep T98 Transmission

as found in

Kaiser M715 & M72x Military Trucks

Jeep Adapter kit to GM Bellhousings

Kit C715, adapting GM small & big block bellhousings to the M7xx T98 transmission

These terrific M715 & M725 "5/4-ton" trucks are great conversion candidates, and make even more excellent vehicles when converted to Small Block or even Big Block Chevy power.

These plate style adapters are machined from high-grade aluminum alloy, featuring thick flanges and a heavy cross-section.

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.

Contents

Included are the two adapter plates, GM bellhousing locator / throwout sleeve, and hardware.

Installation Requirements

The adapter is easily installed onto the T98 using normal mechanics tools. Instructions are included. Disassembly of the transmission is not required for the typical scope of this conversion.

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 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.

Compatible Transmissions

This kit is specifically for the M715 Borg-Warner T98.

Related Products


GM crank to Ford pilot bushing

Bushing, pilot, GM Gen. I-III (1955-2000) cranks to Jeep T90, T86 & T98 (M715) transmissions, #PB-3901136

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.

Jeep T14 to GM pilot bushing

Bushing, pilot, GM Gen. III (2001- ) cranks to Jeep T90, T86 & T98 (M715) transmissions, #PB-6071136

This pilot bushing fits in GM Gen III+ Vortec / LS cranks and matches the pilot tip of the T90, T86 & T98 as found in these Jeeps.

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.

GM clutch kit

Kit, clutch, GM & Chev. V8, 12”, 10 spline x 1-1/8”, includes pressure plate, disc, alignment tool, #04-064

This kit is compatible with the Novak LS flywheel (adjacent) and classic factory Small & Big Block 168 tooth flywheels for most Chevy engines. It features a pressure plate with great holding power but civilized release pressure.

GM clutch kit

Kit, clutch, GM & Chevy 10-1/2”, 10 spline x 1-1/8”spline, incl pressure plate, disc, alignment tool, #04-021

This kit is compatible with classic factory Small Block 153 tooth flywheels for many Chevy engines. It features a pressure plate with good holding power but civilized release pressure.

GM clutch kit

Kit, clutch, GM & Chev. V8, 11”, 10 spline x 1-1/8”, includes pressure plate, disc, alignment tool, #04-049

This kit is compatible with classic factory Small Block 168 tooth flywheels for many Chevy engines. It features a pressure plate with good holding power but civilized release pressure.

T18 Parts

Parts for the T98 Transmission

Gaskets, rebuild kits, etc. are available for the T98 transission. See them here.

Stick, transmission shifter cane, T18, 3-1/8 in. finger x 29-1/4 in. tall, #T18SS-3125-29250

Shifter stick for T18 & T98 transmissions,


Engine Placement

Classic Chevy Small block installation into the M7x5 will require minor firewall modifications to clear their rear distributors, if leaving the transmission in the factory location, which we generally recommend.

However, GM Gen III+ engines (distributorless) do not require this and are recommended over the classic Chevy engines for this and other reasons.

Since engine fore-aft and left-right offset location is dictated by the transmission location, the installer should be careful to install the engine at the same height and crank centerline at about the same location as the outgoing factory engine.

Driveshafts

Driveshaft and jackshaft length changes are not required nor recommended for this conversion.

Axles

Use of the uncommonly strong factory axles in these M7x5 trucks is completely acceptable with this conversion. Axle upgrades are not necessary, but they may be chosen for reasons external to this transmission upgrade. However, gearing changes for better road gearing may be considered.

Also See