5L50E Planetary

A 5L50E that suddenly loses a range, buzzes or grinds under load, or drops steel chips in the pan may have sheared the splines on its sun gear shaft. This listing is a used GM planetary sun gear shaft, GM part number 96025500, removed from a 2004 Cadillac XLR that was running and driveable when it was dismantled. It suits owners of the 4.6L Northstar Cadillacs that used the 5L50E who need one hard part rather than a whole transmission.

What the sun gear shaft does in a 5L50E

The 5L50E is the heavier-duty version of GM's Strasbourg-built 5L40E, rated at 311 lb-ft, and it is built around a Ravigneaux planetary gearset: a compound set with two sun gears sharing one carrier and one ring gear. The input sun gear shaft drives one of those sun gears, so the ratios that run through it stop working the moment its splines or teeth fail. Gear ratios are 3.42, 2.21, 1.60, 1.00 and 0.75, with 3.03 reverse. GM's later catalog lists the 2004-2006 input sun gear shaft for these Cadillacs as an assembly that includes the forward clutch roller inner race, which is why the shaft and its hub travel together.

The photo shows the splined shaft with its clutch hub and plate stack still assembled, as it came out of the XLR. Look over the photos before you order so you know exactly which pieces you are receiving.

Symptoms of sun gear shaft or gearset trouble

• Sudden loss of drive in forward ranges while reverse may still work
• A grinding or buzzing noise that follows road speed
• Bright steel particles on the pan magnet, not just friction debris
• Gear ratio codes such as P0731 through P0735 that come back after the fluid is changed and adapts are reset
• A worn or chewed spline that you can feel as rotational slack between the shaft and the gear it drives

How to confirm before you buy

Start with a fluid check and a scan for ratio codes. A slipping forward clutch, a worn valve body bore and a failed shaft can all look the same from the driver's seat, so check line pressure before you condemn hard parts; our line pressure testing guide covers how. If ratio codes are stored, our P0730 gear ratio code guide explains how to tell which gear is slipping. Once the unit is out, inspect the shaft splines, the sun gear teeth and the bushing journals under good light, and check the forward clutch roller race for pitting.

Fitment

This shaft was pulled from a 2004 Cadillac XLR, which used the 5L50E behind the 4.6L Northstar. Cadillac also used the 5L50E in the 4.6L 2005-2006 STS and 2004-2006 SRX, while the lighter 5L40E went into V6 Cadillacs, the Solstice and Sky and several BMWs. Those units look alike, and GM revised sun gear shaft part numbers over the run, so match GM 96025500 against the number for your vehicle, check the identification tag on the left rear of the case above the pan rail, or send us your year and VIN and we will check it before you order. See every part we carry for this unit on the 5L50E parts page.

Install notes

• Lay out every thrust washer, bearing and selective spacer in order during teardown, and check bushing journals on the shaft for scoring.
• Lubricate the shaft and bushings with transmission fluid or assembly lube on reassembly and confirm the shaft turns smoothly in its bushings.
• Verify the forward clutch one-way roller freewheels in one direction and locks in the other before final assembly.
• Replace the seals, gaskets and frictions while the unit is open; the 5L50E overhaul kit covers the soft parts, and the 5L50E input drum is the next hard part to inspect when a shaft has failed.
• Flush or replace the cooler, fill with Dexron III-specification fluid as listed in the GM specifications for the XLR, about 9 quarts dry for a complete overhaul, and perform a relearn after the repair.

Which vehicle did this shaft come from?

It was removed from a running, driveable 2004 Cadillac XLR with the 5L50E transmission.

Will it fit a 5L40E?

The 5L40E and 5L50E share a design, but GM used different part numbers across the two units and over the years. Match GM 96025500 to the number for your vehicle or send us your year and VIN to check.

Is this new or used?

Used. It is an original GM part pulled from a working transmission. Check the photos for the exact condition and included pieces.

What fluid does the 5L50E use?

GM specifications for the XLR list Dexron III, with about 9.0 quarts for a dry complete overhaul. Use the current GM-approved Dexron fluid for your vehicle.

What else should I replace when the sun gear shaft fails?

Inspect thrust washers, bushings, the forward clutch roller race and the input drum, replace seals and frictions with an overhaul kit, and clean the cooler so debris does not return to the new parts.

• Checking Transmission Line Pressure
• Gear Ratio Codes P0730 Diagnosis
• Transmission Slipping Diagnosis Guide
• Transmission Rebuild vs Replacement Cost