Forged chromoly 1350-series slip yoke, 30-spline, for the Chrysler A727 TorqueFlite, A833 manual and 30-spline T56, part 3-3-3931X.
A big-block Mopar that leaks fluid out of the tailshaft no matter how many seals you install, a drag car that has twisted or cracked its factory yoke on the launch, or a TorqueFlite build that needs a stronger driveline than the factory parts: that is who buys a chromoly slip yoke. Part 3-3-3931X is a forged chromoly, fully machined slip yoke with a 30-tooth spline for the Chrysler A727 TorqueFlite automatic, the A833 four-speed manual, and Tremec T56 gearboxes built with the 30-spline output shaft. It cross-references to the Sonnax T3-3-3931HP pattern and is machined for a 1350-series U-joint.
The slip yoke is the front end of the driveshaft. Its internal splines ride on the 30-spline output shaft, and its outside diameter rides in the extension housing bushing and the tailshaft seal. As the rear axle moves up and down on the springs, the driveshaft gets longer and shorter, and the yoke slides in and out on the splines to make up the difference. Every pound of torque from the converter and planetary gearset passes through those splines and into the U-joint ears, so the yoke has two jobs at once: carry the load, and give the seal a smooth, round surface to seal against.
On a 727 the yoke barrel is also the only thing holding the rear of the output shaft centered in the extension housing bushing. A worn barrel lets the shaft wobble, which wears the bushing, which then eats the seal. That is why a leaking 727 tailshaft is so often a yoke problem rather than a seal problem.
Pull the driveshaft and look at the barrel under a light. If you can catch a fingernail in the seal track, a new seal will not hold. Slide the old yoke back onto the output shaft and rock it: noticeable play points to a worn extension housing bushing as well, and that bushing should be replaced at the same time. Rule out the transmission itself before you buy driveline parts. A clunk can also be band or clutch slop inside the unit, and a 727 that leaks from the pan or front pump is a different repair. If you are chasing an electrical shift problem, read our 727 guide on why the TorqueFlite has no shift solenoids; its shifting is governor and throttle-valve controlled.
This yoke fits the A727 TorqueFlite, the A833 four-speed and 30-spline T56 transmissions. Sonnax notes the pattern also suits the 30-spline T56 found in Viper and Aston Martin applications. Count your output shaft splines before ordering, because many T56 units use a different spline count, and four-wheel-drive 727s that bolt to a transfer case do not take a slip yoke at the transmission. Sonnax lists the T3-3-3931HP at 30 splines, 1.680 inch journal diameter, 4.760 inch barrel length and 6.630 inch centerline-to-end length, with a full spline and no counterbore. Measure your old yoke the same way and compare before installing, since a yoke that is too long can bottom out against the output shaft when the suspension compresses. If you are unsure, send us your year, VIN and transmission and we will check it. Browse the rest of our 727 TorqueFlite parts while you are at it.
Moving to this yoke means a 1350-series U-joint, so the driveshaft must have a matching 1350 weld yoke or a 1350-to-stock conversion joint. Before installing, clean the barrel and check it for shipping nicks; even a small burr will cut a new seal. Lube the splines and the barrel with clean transmission fluid, install a new tailshaft seal, and slide the yoke in straight so the seal lip does not roll. With the vehicle at ride height, check that the yoke has travel in both directions. Top off the transmission with the correct fluid for your unit; most owners run ATF+4 or Dexron in a 727. A U-joint puller makes the joint swap at the driveshaft end far easier than a hammer and socket. If the transmission is coming apart anyway, our A727 master rebuild kit covers the seals and frictions inside.
One last check on built cars: confirm the driveshaft is long enough that the yoke still has full spline engagement at full droop, and that there is room at full bump. Shortening or lengthening the shaft is a driveline shop job.
| Part number | 3-3-3931X (Sonnax T3-3-3931HP) |
| Material | Forged chromoly, CNC machined |
| U-joint series | 1350 |
| Spline count | 30 |
| Journal diameter | 1.680 in |
| Centerline to end | 6.30 in |
| Fits | Chrysler A727, A833, Tremec T56 (30-spline) |
| Weight | 3.0 lb |
It is built for the A727 with a 30-spline output shaft, the A833 four-speed and 30-spline T56 units. Count the splines on your output shaft and measure the old yoke's centerline-to-end length before ordering. If you are not sure, send us the year, VIN and transmission and we will confirm it.
It is machined for a 1350-series U-joint. Your driveshaft needs a 1350 weld yoke or a conversion joint that matches 1350 on the transmission end.
If the yoke barrel has a groove or pitting where the seal rides, a new seal will leak again. Replace the yoke, the seal, and the extension housing bushing if the old yoke has side play on the output shaft.
Top it off to the full mark with the fluid your unit calls for. Most 727 owners run ATF+4 or Dexron. Check the level hot, in Park, with the engine running.
No. It is a full-spline yoke with no counterbore, the same as the Sonnax T3-3-3931HP pattern it cross-references.
