Manual transmissions are as popular as ever. Many vintage Pontiacs were originally equipped with Muncie and Borg Warner four-speeds, which remain available new and used. Tremec’s modern five- and six-speed transmissions are durable units that feature overdriven gears to reduce cruising speed and improve fuel economy. A number of companies offer complete kits that allow easy installation into most any Pontiac model.
When dealing with a manual transmission, its input shaft is supported by a bearing or bushing that’s pressed into a machined recess at the rear of the crankshaft. On a Pontiac, the transmission is fixed on the bellhousing using a 4.685-inch clutch-release bearing bore and four large retaining bolts. Two 0.625-inch dowel pins pressed into the rear of the block locate and align the bellhousing to the block, subsequently aligning the crank and input shaft.
If the crankshaft and input shaft centerlines vary significantly, such as when boring a block’s main journals and/or possibly when using an aftermarket bellhousing, it can create a number of operating issues, ranging from poor shifting at any speed to premature bearing wear. Alignment wasn’t quite as critical with older transmissions, but the internal tolerances of modern over- driven transmissions are much tighter, and misalignment greater than 0.005-inch can create operational havoc.
Adjusting the bellhousing’s relation to the block is accomplished by using offset dowel pins, or relocating its holes by over-sizing them and welding in new sleeves. Determining the exact position can be a cumbersome and time-consuming process, typically requiring a dial indicator and magnetic base, and rotating the crankshaft to determine just how far its centerline varies from the bellhousing bore. If the magnetic base moves unexpectedly, it can give a false reading, so repeating the process more than once promotes accuracy.
[1] If your Pontiac is equipped...
[1] If your Pontiac is equipped with a manual transmission, the alignment of its bellhousing can affect transmission operation. Pontiac used a pair of 0.625-inch-diameter dowel pins to locate the bellhousing’s position on the block.
[2] The Bellhousing Alignment...
[2] The Bellhousing Alignment Tool from Browell Bellhousing is an excellent unit that functions as a go/no-go gauge, allowing you to easily and accurately align your Pontiac’s bellhousing. It sells for $135 and is available directly from the manufacturer.
[3] To create its Pontiac...
[3] To create its Pontiac offering, Browell modifies the crankshaft flange of its Chevrolet-specific tool on its CNC mill. It fits snugly over the Pontiac flywheel flange for maximum accuracy.
Browell Bellhousing developed a tool that makes the task much simpler. Its Bellhousing Alignment Tool consists of a fixture that bolts to the crankshaft’s flywheel flange and a separate locating ring that slips over it to easily and accurately align the bellhousing. CNC-machined from billet-aluminum for maximum accuracy, it’s essentially a go/no-go gauge that achieves near-perfect crankshaft-to-input shaft alignment.
The Browell tool is extremely easy to use. With the transmission removed from the vehicle and the bellhousing, clutch and pressure plate assembly, and flywheel removed from the engine, the base simply slides over the flywheel register on the crankshaft and bolts into place. The bellhousing is then fastened to the block using the appropriate hardware and torque specifications, and the ring slides onto the tool. Dowel adjustments can then be made in a much quicker fashion.
Retailing for $135, the Bellhousing Alignment Tool may first seem a lofty expense, but considering how quickly and accurately you can align your Pontiac’s bellhousing, it’s an excellent way to complete the task in a timely manner, and eliminate the guesswork in the process. If it’s still more than you want to spend and you belong to a local Pontiac club, it may be a tool the club can invest in and rent out to members to recoup initial costs and make a few bucks after.
No matter how you perceive it, we say with confidence after using it that Browell’s Bellhousing Alignment Tool is one no manual-trans enthusiast should be without!
[4] Depending upon the model...
[4] Depending upon the model year, the flywheel flange on a Pontiac crank can measure 2.49 or 2.75 inches. Before ordering a Bellhousing Alignment Tool from Browell, we strongly suggest measuring the flywheel flange on your particular crankshaft, since the tool isn’t interchangeable. The pilot bearing that supports the transmission input shaft is seen in the center.
[5] The base of the tool slides...
[5] The base of the tool slides onto the flywheel flange. It’s then bolted into place using your existing flywheel bolts or common 1-inch-long 1⁄2-20 bolts sourced from a local hardware store.
[6] With the bellhousing installed...
[6] With the bellhousing installed and the retaining bolts tightened appropriately, the tool’s locating ring slides over the base unit and into the 4.685-inch clutch-release-bearing bore in the center of the bellhousing. If the ring slides though the opening with little resistance, then the bellhousing is aligned within 0.003 inch of the crankshaft. A maximum spec of 0.005 inch is common with modern aftermarket transmissions.
[7] If the locating ring begins...
[7] If the locating ring begins to bind as it enters the bellhousing, shining a light from behind can help you determine in which direction you’ll need to shift the bellhousing. The gap shown here indicates that this particular bellhousing needs to move toward the 11 o’clock to 12 o’clock position to sufficiently align it.
[8] Insert a feeler gauge...
[8] Insert a feeler gauge between the locating ring and flange at the gap’s widest point to determine just how far the bellhousing is out of alignment. An 0.008-inch feeler gauge barely fits into the gap of this particular bellhousing. It should be relocated until it’s less than 0.005 inch out.
[9] Installing offset dowel...
[9] Installing offset dowel pins is a popular way to modify bellhousing alignment. Those from RobbMC Performance are among the easiest to use and include detailed instructions for proper installation. They’re available in a variety of offsets and sell for less than $30 per pair.