How To Set Transmission Angle

| How-To - Chassis and Suspension

How to Get the Right Pinion Angle

The simple set up to correct rear axle pinion angle, eliminate driveshaft vibration, and improve performance.

Building a hot rod ways working all the angles, and at that place are plenty of angles to work. Ane of the more of import angles is the angle between your transmission output shaft (which is the same as the crankshaft angle) and the rear axle pinion angle. Connecting these two angled pieces is the driveshaft. If you want a happy, vibration-gratis driveshaft, the crankshaft line and the pinion angle line must exist parallel.

The transmission output shaft is typically above the centerline of the pinion. As the rear suspension and beam travel up and downwardly, the distance betwixt the manual output shaft and the pinion is constantly changing. The splined yoke on the transmission input shaft allows the driveshaft to movement in and out as the rear axle housing moves up and downwards, finer irresolute the length of the driveshaft. Universal joints on both ends of the driveshaft allow the angle to change without binding. The driveshaft is doing all that while passing a few hundred horsepower back to the differential—pretty impressive.

Every bit impressive as the work of a driveshaft is, information technology has limitations. Ideally the driveshaft angle should be 3 degrees or less. Since we accept already established that the transmission output shaft and the pinion input shaft must be parallel, that means 3 degrees at each stop. The angles are actually equal just opposite; three degrees downward at the transmission, three degrees upwards at the pinion.

This story was originally published online December xiv, 2022, and has been edited and reformatted by Tim Bernsau.

Irresolute Pinion Angle on a 1960 Corvette

Nosotros learned virtually mismatched pinion angles while building the chassis for our 1960 Corvette. The 348 big-block W-motor and 700R4 combination was mounted on a 3-caste angle. Our Currie rear axle assembly had a 5-degree bending. We needed to change the pinion angle to three degrees so the lines through the crankshaft and pinion would exist parallel.

This geometry should exist built into your engine mounts and transmission mounts and as well the mounting of your rear axle. If you are using a iv-link rear suspension, the pinion angle is easily adapted by changing the lengths of the bars that locate the rear axle. If your rear axle is mounted on parallel leaf springs, similar information technology is on our Corvette, things are a flake more complicated. Here'south how we solved the problem.

Understanding Pinion Angle

This simplified drawing serves to illustrate that the angle of the pinion should exist equal, simply opposite that of the transmission output shaft (same as the engine crankshaft angle). In our instance the manual was 3 degrees down, while the pinion was corrected to 3 degrees up, resulting in parallel drivelines.

Getting iii Degrees

We could accept added spacers to the manual crossmember to change the bending to 5 degrees, matching the pinion angle. However, the ideal driveshaft angle is 3 degrees or less, then increasing the transmission to 5 degrees would take been a poor pick, leading to premature universal joint wearable.

Irresolute Pinion Angle Is Uncomplicated

On a solid rear axle mounted to parallel leaf springs, pinion angle is determined by spring pads welded to the axle housing. Changing the angle is equally simple as adding wedged shims between the rear beam housing and the springs to slightly rotate the housing upwards or downward. Putting the thick cease of the wedge to the rear lowers the pinion; putting the thick border to the front end raises the pinion. Shims are available in different corrective angles. We ordered a set of 2-caste shims from Summit Racing in order to reduce the v-caste pinion angle to three degrees.

Installing Shims

Installing the shims is as simple as unbolting the U-bolts on ane side of the rear axle housing, inserting the shim, then snugging the U-bolts. However, on our awarding, we had one trouble.

We Encountered a Problem

The rear axle housing on our Corvette is located on the leaf spring, using the center bolt in the jump pack equally the locator. When we put a shim between the spring and the housing, the pin was barely protruding through the new shim. We wanted full appointment of the head of the spring pin into the spring pad on the rear axle, and were not comfortable with the information technology not passing completely through the locating hole in the spring pad. We ready about removing the spring pin, adding a spacer, and reassembling the leap pack. The first step to removing the pin was firmly clamping the spring. with two large C-clamps, removing the heart spring pin, and adding the fabricated spacer before reassembly.

Pulling the Jump Pin

With the spring leaves firmly clamped together, a socket removes the nut while vise grip pliers hold back on the head of the pin.

Calculation a Spacer

We used a 3/viii-inch nut as a spacer. The threads were drilled out of the nut using a three/8-inch drill. This enabled the spacer to slide over the spring pivot.

Filing the Nut

A few minutes with a file knocked the corners off the nut, making it the aforementioned diameter equally the head on the jump pin bolt.

Success!

Here you can encounter the spacer slipped over the bound pivot, finer extending the head of the bound pivot. Our shim pack came with 2 long spring pads, and then adding a spacer was no problem. This gave united states of america total date of the pin into the spring pad hole on the housing. Unbolt one side at a time to forbid the housing from rotating.

Reinstalling the Leap Pin

The spring pivot and spacer are now reinstalled in the spring, belongings all the leaves of the spring together in the process. The C-clamps tin now exist removed.

Mission Accomplished

With the ii-degree shim in place the head of the spring pivot protrudes plenty to fully engage the pigsty in the spring pad that is welded to our Currie rear beam housing.

Rear Housing Retightened

The rear axle housing was bolted in place—and while ii degrees may not audio similar much, the change in pinion angle fabricated a noticeable change for the better.

Checking Angles

After inserting the ii-degree shims on both sides and re-tightening the U-bolts, nosotros checked the angle using a simple bending finder on the face of the universal U-commodities surface. The angle was now at the correct 3 degrees.

At the Transmission Stop

A check of the engine crankshaft bending also showed 3 degrees, and so we were spot-on. If the crankshaft bending had required modest tweaking, we could have accomplished that shimming the transmission mount, but there's a limit to the size of the shims since you lot do not want to stress the engine mounts. If your transmission crossmember is a bolt-in unit you lot tin sometimes shim the entire crossmember. Our motor/trans combination required no shimming and we were pleased to see we had aplenty clearance above the X-member of the frame.

Right Angle

The Inland Empire Driveline aluminum driveshaft has a good, moderate bending with no take a chance of whatever universal articulation binding.

Double Checking

Practice not overtighten the U-bolts property the universal caps in place on the rear axle. Overtightening to the yoke can cause vibration. Proper torque is 17 lb-ft. When the car is finished, be sure to recheck the pinion angle. If the torso weight has changed the pinion bending, this process can be repeated with different sized shims.

On the Road

At present it was fourth dimension for a test drive. A driveshaft bending vibration is high frequency, every bit it is rotating twice engine rpm when in straight drive. This vibration may testify upwards on acceleration or deceleration. Adjust the pinion downward to correct acceleration-related vibrations and upwards to correct deceleration vibrations. Plus or minus 1 degree is generally enough to cure the problem. Before adjusting any angles check the U-bolts holding the driveshaft to the pinion.

We are pleased to announce our car drives perfectly shine, with no driveline vibrations at all. Having a brand-new aluminum driveshaft set on the proper angle ensures many trouble-free miles and long universal joint life.

Source: https://www.motortrend.com/how-to/pinion-angle-change/