Adapting the

Chevrolet & GM Standard Shift Bellhousings

to the

Jeep Borg-Warner T18 Transmission

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 transmission found in 1976-1980 CJ Jeeps.

Product & Features


The 1879 plate style adapter is machined of a 6061T6 billet aluminum alloy, featuring an integrated precision machined bearing retainer.  


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

Applications & Compatibility


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.

GM Bellhousings

GM bellhousings feature either a 4-11/16" rear face bore or a 5-1/8" rear face bore, the latter typically from Chevy / GM trucks from 1968-1991 with the SM465 transmission. Our adapter will work with either. 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 flywheel will need to match the engine. See below for our special LS based engine flywheel as well as several common stock type small block flywheels.

Clutch Assembly 

The clutch and release assembly will need to match the engine with two exceptions:

  • A conversion pilot bushing which is available below to match your application
  • The clutch disc must have a 10 spline 1-1/16” hub and match the pressure plate diameter, also available below

Now is also a good time to consider a hydraulic release system if you don’t already have that type of setup on your vehicle now. Again, parts available below. 


Generally this assembly is used with 76-79 CJ Jeeps as that is the native transmission application. However, any Jeep or vehicle that will accommodate it should be a worthy candidate. 


Any that will accept the standard GM pattern mount. Stock bellhousings abound for Chevrolet, BOP (Buick, Oldsmobile, and Pontiac), GM Gen I, II, III, IV and many others with specialized scattershields using the GM pattern.

Related Products

Bellhousings and adapter rings


The BR4 ring is used to enable use of the SM465 5-1/8” bore bellhousing with 4-11/16” retainers.


If you need a bellhousing, would prefer a new enhanced casting version or would like the LS specific version they can be purchased here:

Chevrolet pattern, Gen I & II small 4 ­11/16” bore

Chevrolet pattern, Gen I & II large 5­ 1/8” bore

Chevrolet pattern, Gen III & IV small 4 ­11/16” bore

Chevrolet pattern, Gen III & IV large 5 ­1/8” bore

Pilot Bushings & Bearings

LS flywheel

This is a beautiful piece and necessary for proper operation on LS based engines. They must have the LS crank offset to work properly. These will accept both the 11” and 12” clutch listed below. The page is here with details.


Bolts necessary for installation


Clutch Kit

As no native GM applications used the 10 spline 1-1/16” hub, pressure plate and disc must be sourced separately. Three sizes are listed below. The 11” listed in the middle is the most common, but all are serviceable depending on your needs. Generally the 10-1/2” is used on the smaller 153 tooth flywheel and is exclusive to that application. The 11” and 12” are usually interchangeable with large bellhousings and standard 168 tooth flywheels. Non-standard applications will need to watch for compatibility.


The disc can be purchased separately for those applications natively using a different spline count



Adjustable Release Bearing

While sometimes not needed in this application, Novak's unique and adjustable throwout bearing assures the right height of bearing, which is the most important factor in any clutch system's successful operation. 


We frequently reach for this adjustable bellhousing arm pivot, which adds additional adjustability and better release arm angles. 


Hydraulic Clutch Actuation

Though not required on all applications, now is an excellent opportunity to upgrade from the likely worn mechanical system. These mechanical systems are usually full of play which is aggravated by years of wear and much more affected by flex in the body/frame relationship, especially when in a twist off-road. You will find that your clutch release point will vary as things twist. With a hydraulic system, that is not the case. All flex is taken up by the braided stainless line which is unaffected by changes in frame to body relationship. If your Jeep has the master cylinder, that part can be reused. More information can be found here.

Parts to do this swap are:





Transmission Tunnel Cover

Because the transmission and transfer case shifters are often in a different location than factory in these Jeeps, this new transmission tunnel cover gives the installer a clean slate. There are no screw holes nor transmission & transfer case shifter holes, allowing the installer to drill and cut them as necessary. An easy way to get a perfect fit is to use the old cover as a template, making cuts as necessary, then overlay on the new aluminum piece for perfect holes.

The finish is natural brushed aluminum, which looks pretty terrific, but it can easily be primed and painted to suit, if desired.

This tunnel cover is compatible only with 1976-1986 CJ Jeeps.


Transfer Case Shifter Kits

The stock shifter may be reused but may opt for a twin stick setup.


Shifter Boots

Necessary for proper sealing this twin-stick style shifter boot is custom molded of high quality rubber and furnished with a stainless-steel bezel ring and stainless steel mounting screws. The stainless ring can be mounted on top or inside of the boot for a cleaner look. This boot works with all of our twin stick kits.



Installation Requirements


Required tools include normal mechanics tools along with a round or rotary file. The adapter is easily and quickly installed onto the T18. Due to design constraints, the transmission's two top ears will require slight elongation with a round or rotary file. This process is simple and will not compromise the strength of the flange. Instructions are included.

Engines & Engine Mounting

mmtj-g3If converting to a V8 in conjunction with this upgrade, aftermarket engine mounts are available to ease its installation. Because of the broad spectrum of engines and vehicle combinations used with this adapter, it would be difficult to list them all here. Whatever your application, Novak likely has the perfect solution. From a 225 Buick V6 in a CJ2A to an LS3 in your JK, we’ve got you covered. 

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

Engine Placement

Engine placement in these applications is an effort in compromise to find the best position overall as a package. Generally the engine will be about 1” or even more towards the left, (driver’s side in the USA) away from the front differential in a CJ application. This gives the best balance of weight and more importantly clearance for the driveshaft going to the front axle. Your tight spots will be steering to exhaust on the left (hold that as tight as you can) and clearance for the front driveshaft on the right. Fore and aft position will vary with the Jeep model and engine. Have a CJ5 and Gen I with a rear distributor? You’ll be better off a little forward for more rear driveshaft length and clearance for that HEI. If you are in a longer Jeep and using an LS engine with no distributor, you’ll have more fan clearance and better balance if you hold it to the rear. Usually for ground clearance tuck things up nicely for height to avoid damage to oil pans and other life giving parts in the Jeep. Common sense and taking a step back to look at things overall goes a long way.


Driveshaft length changes are often required. Most conversions to these transmissions will require that the rear driveshaft be modified to be shorter and front driveshaft longer.

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.

Driveshaft modifications and rebalancing can be affordable when performed by driveline, RV or tractor implement specialists. New driveshafts are an option, but not necessarily a requirement in regards to the actual successful conversion if your existing driveshafts are in good condition.

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. 


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