How to Identify Your Transmission Yoke
Tape measure or ruler
Measuring calipers (digital calipers, dial calipers, or even Vernier calipers for you math people out there)-We've used digital calipers in the article to make it easier to see the measurements as we take them
Something to write with and a piece of paper
What we're going to be determining:
- Spline count
- Spline size
- Ground hub diameter
- Centerline of u-joint hole to end of yoke measurement
- Which type of u-joint (either outside lock up or inside lock up)
- Bearing cap diameter (needed for both inside lock up or outside lock up u-joints)
- Measurement across yoke ears (for outside lock up type u-joints)
- Measurement between yoke ears (for inside lock up type u-joints)
At this point, it's a good idea to make a bullet list of the counts and measurements above so we can fill in the information as we take our measurements.
Now that we've got our yoke and measuring tools all gathered up, let's go to step one!
Step 1: Count the number of splines inside the yoke
If your yoke is like the one in the picture, it has what is called a "blind spline." This is a fancy name for a wide spot in the splines that is the same size as two splines. We count the blind spline as if it were two complete splines in our spline count.
(If your transmission/transfer case yoke doesn't have the blind spline, it's a good idea to mark one of the splines with a marker to help keep you from losing count.)
We can see in this image that our transmission yoke has 26 splines that we can count, plus the blind spline. This means that our yoke is a 26 based on 27 spline yoke (usually written as 26/27). Now, let's go ahead and write our spline count down.
Step 2: Measure the spline size (also known as the major spline diameter)
This is the overall measurement of the transmission yoke splines. To measure, we pick two spline cutouts that are directly across from each other. Then, we use the portion of our calipers that spreads out to measure between these two points.
Note: We're not measuring from one actual spline point to another. Rather, we measure the cutout, triangular space next to the spline point where the spline on the transmission/transfer case spline will fit into.
In the photo, we can see that the transmission/transfer case yoke overall spline measurement (major spline diameter) is around 1.182". Go ahead and write this measurement down.
Step 3: Measure the ground hub diameter
The ground hub diameter is just a fancy term for the size of the round barrel of our transmission yoke that will slide into the transmission. This is the surface that your transmission output seal will seal against when your yoke is installed. To measure, we use the main part of our caliper and close it in on the round surface.
In the photo, we can see that the ground hub diameter measures 1.503", or just over an inch and a half. Now, we write this measurement down.
Step 3: Determining the centerline (of u-joint) to end of yoke measurement.
This is a really easy step. To measure, we simply stand the yoke up on a flat surface and measure from the centerline of the u-joint hole to the end of the round part of the yoke.
We can see from the photo that our centerline to end of yoke measurement is about 5 and a half inches. Write this measurement down.
Step 4: Determining universal joint type
The first thing to consider when we're trying to find out which type of u-joint our transmission/transfer case uses is the "lock up" type. For most u-joints, the type of lock up falls into one of two categories:
- Outside lock up
- Inside lock up
Outisde lock up u-joints use a circular type of snap ring that fits into a machined groove on the transmission yoke as seen in the photo below:
Inside lock up u-joints use a c-shaped snap ring or clip that fits on to the u-joint cap itself. The u-joint hole on the yoke would lack the groove as shown in the photo below:
If you determine that your yoke is the outside lock up type, we just need to know the diameter of u-joint bearing cap and the outside width of the yoke to figure out which type of u-joint your yoke uses.
Here, we're using the smaller portion of our calipers that spreads to measure the cap diameter and we can see that the bearing cap diameter is around 1.0625". No matter whether your yoke is inside or outside lock up, write this measurement down.
Here, we're using the large portion of our calipers to measure the outside yoke width and we can see that the measurement is around 3.514". If your yoke is the outside lock up type, write this measurement down.
If your yoke is the inside lock up type, we still need to know the bearing cap diameter (seen in the picture above). However, our yoke measurement is slightly different. Instead of measuring the outside width, we measure the distance between the yoke "ears" to determine the inside lock up measurement:
Here, we're using the smaller portion of our calipers that spread out and we can see that the inside lock up measurement is around 2.5605". If your yoke is the inside lock up type, write this measurement down.
And that's it! Now that we have counted our splines, measured our spline size, measured the centerline to end, and determined our u-joint type and the relevant measurements, we can figure out which type of yoke we have.
As always, if you have any questions, feel free to e-mail us at firstname.lastname@example.org or call 501-626-0570 and we'll be happy to help you!