Adapting the
Chevrolet & GM Standard Shift Bellhousings
to the
Jeep T90 Transmission
This adapter assembly makes for a strong and convenient adaptation of classic standard shift GM bellhousings to the T90 three-speed, as was the popular transmission found in 1946-1971 Jeeps.
|
||||
Option I: T90A Transmissions These conversion kits will work with most Chevrolet V8's & Chevrolet V6's (Gen. I thru Gen. III+), Buick V6's, the Iron Duke I4, some Chevy I6's and other GM engines.
Novak Adapter Versions Available
This adapter is simlar to our #G9N kit, but is 2-5/8" thick instead of 3/4". The #G9N offers an alternative to owners of T90C and T90A transmissions.
The Adapter
This plate style adapter is cast and machined of a high-grade aluminum alloy. featuring a precision machined bearing retainer. Included are the GM bellhousing locator / throwout sleeve, seal and hardware.
Our included retainer is configured for the standard 4-11/16" bore bellhousing. If you have a truck style, 5-1/8" bore bellhousing, add our #BR4 sizing ring to your order.
T90 Versions
If you are not sure of your T90 version, see this guide.
The T90A is found in 1946 to 1962 CJ2A, CJ3A, CJ3B, CJ5, CJ6, M38, M38A1, and also four-cylinder Utility Series Wagons & Trucks.
The T90J is found in 1952 to 1965 four-wheel-drive Utility Wagons & Trucks and Wagoneer & Gladiator Trucks when replacing the I6-226 and 230 "Tornado" engines.
The T90C is found in 1963-1971 Jeeps. Installers should note that a conversion to this version of the T90 would require a new cluster gear. This adds ~$90 to the expense of the conversion and raises the 1st and 2nd gear ratios from 3.44 to 2.98. This may or may not be in the swappers best interest. However, contact us if you do want to go this route. A GM transmission like the SM420 or SM465 may be a better option in this case.
Installation
The adapter is easily and quickly installed onto the T90. Full disassembly of the transmission is not required. Cutting the transmission input shaft is not required as the adapter spaces the transmission properly for the GM crank and clutch assembly.
GM Bellhousings
GM bellhousings 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 work with both. If you are uncertain of your bellhousing bore, choose the 5-1/8" press-on spacer ring that can be used or omitted to cover either situation. The ring is easily returnable for credit if not used in the installer's application.
 |
||
| The classic Chevrolet bellhousing, with the four-bolt rear pattern. Buick, Olds, Pontiac and other bellhousings with the same rear face are equally compatible. | ||
If you're using a GM bellhousing that has a 5-1/8" bore, you will require the following sizing ring:
|
||
Choosing Your Pilot Bushing
Your pilot bushing choice will depend on your particular GM engine. See our Pilot Bushings page to select this critical component for your conversion.
Flywheels
For GM engines prior to the Gen. III+ Series (LS & Vortec, 1997- present), you will use your GM / Chevrolet flywheel as per factory to your engine, which can be either the 153 tooth version or 168 tooth versions.
If you are using a GM Gen. III+ engine, we strongly recommend the use of our extended height LS / Vortec flywheel to normalize the clutch system. It features 168 teeth and is compatible only with 12" clutches.
 |
| This is the right and recommended GM Gen. III+ flywheel to use to standardize the clutch assembly, and acheive proper clutch geometry and release action. |
Clutch Assembly
This conversion uses readily available clutch components based on GM pressure plates and their geometries.
Whether you choose to use the smaller (10-1/2" to 11") or the larger (12") clutch assembly is your preference. Jeep CJ's are typically lighter vehicles and the smaller clutches are generally adequate and offer easy clutch pedal pressure. The larger clutches have more holding power and still have very reasonable pedal pressure when using the diaphram style pressure plate. A more detailed discussion on this topic is available here in Novak's Knowledge Base.
Full Clutch Kit
For a full premium clutch assembly:
 |
||||
Clutch Release System
Both factory mechanical and factory hydraulic clutch release systems can be made fully compatible with this conversion. A more involved discussion of this topic can be read here.
Mechanical Linkage
Installers using mechanical releases should use Novak's #RAV6 release fork, which features the correct leverage ratio for a GM pressure plate in 1945-1971 CJ Jeeps.
|
||
Hydraulic Linkage
Individuals wishing to use their factory hydraulic master cylinder or who wish to upgrade to a hydraulic system can use Novak's #HCR hydraulic clutch retrofit assembly in conjunction with a master cylinder from a 1980-1986 Jeep CJ (7/8") or 1987-1990 Jeep YJ (3/4"). Custom firewall installation and clutch pedal modification may be required. Select your slave cylinder diameter to match.
 |
| Hydraulic clutch retrofits make for smooth, non-binding and easily adjustable clutch release systems. |
Throwout Bearing
The dwindling number of off-the-shelf release bearings and the bearings provided in the many full clutch kits on the market are, counterintuitively, not always the right length bearings for that particular pressure plate and can cause a clutch that will not fully release due to too short of a bearing, or a burned up bearing when they're too long and constantly riding the fingers.Novak's fully adjustable release bearing handily solves this concern, and is recommended for this conversion.
 |
| Novak's adjustable GM release bearing is the ultimate answer to setting up an optimal conversion or factory style clutch system. |
Engines & Engine Mounting
The Novak engine mounting system offers the best designs on the market for strength, ease and flexibility of installation. Whether you are installing a classic Small Block, a V6 or a Generation III powerplant, we've got you covered.
In any scenario, it is critical that the engine be installed (as the Jeep engines usually are) with an offset of 1" to 1-1/2" to the driver's side. Other engine mounts on the market - especially the bolt-in versions - do not take this into account and make other placement decisions for the installer that do not take the full powertrain into account. Novak offers what we have found to be the most intelligent engine mounting system for Jeeps available, allowing the installer to make an easy and satisfying decision as to powertrain placement with the new engine, T90 transmission and Dana 20 transfer case all considered.
 |
| Novak's MM Series engine mounts, featuring excellent vibration dampening, superior strength and impressive adjustability - adjustable even after the engine is installed. The design and strength and affordability of our mounts are second to none. |
Engine Cooling
For your GM engine, we will suggest the use of our RadLock high-performance conversion radiators, which are rugged, easy to install and are extremely efficient in cooling in even the most demanding environments.
 |
| Our RadLock radiators offer a highly efficient and extremely durable cooling solution for your GM conversion engine. |
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 engine upgrade.
 |
| GM V8 engines, Generation I through Generation III+ are popular choices as are the Chevy V6s. The Buick V6 is also a good choice. |