5L50E Overhaul Kit 1999, new and ready to install. Fits the 5L50E. Ships fast from the USA.
This is a TransTec overhaul kit, part 2439, cut for the GM 5L40E and 5L50E five-speed automatic from 1999 onward. If your Cadillac STS, SRX or XLR, or an all-wheel-drive BMW 3 Series or X5 with the 5L50E, is leaking at the case, slipping once it warms up, or slow to pick up Drive on a cold morning, and the unit is coming out for a rebuild, this is the soft-parts foundation the rebuild starts from. It is the reseal set only: gaskets, sealing rings, lip seals, O-rings and small parts, with no friction or steel plates.
The 5L50E is the heavier-duty member of the Strasbourg-built 5L40E family, rated for vehicles up to 5,000 lb GVWR and about 311 lb-ft, with the same 3.42, 2.21, 1.60, 1.00 and 0.75 forward ratios. Every clutch in it is applied by a piston sealed with rubber, and fluid reaches the rotating drums through cast iron or Teflon-type sealing rings on the shafts and support. When those rings wear grooves or the piston seals harden with heat and age, apply pressure bleeds off before it reaches the clutch, which is why a high-mileage unit slips even if its frictions still look serviceable. The pan gasket, case and cover gaskets and the external lip seals keep the fluid in. This kit replaces all of them in one go so every circuit seals again after teardown.
Scan for transmission codes and look at commanded versus actual gear and slip data before condemning seals. A pressure gauge on the line tap tells you whether the pump is making pressure and where it is being lost; our line pressure testing guide walks through it, and the slipping diagnosis guide covers what to rule out first. Burnt, black fluid and heavy friction material in the pan mean you need frictions and steels too, not just a reseal.
The kit is listed for 1999-up 5L40E and 5L50E units, which share the case and most sealing locations. Documented 5L50E applications include the 2004-2006 Cadillac XLR and SRX, the 2005-2006 STS, the 2001-2006 BMW 325xi and 330xi, and the 2001-2004 X5 3.0d. Transmission Digest notes the 5L50E appeared in Cadillacs only with the 4.6-liter engine, so a V6 Cadillac is likely a 5L40E. To be sure, read the ID tag on the left rear of the case just above the pan rail; on BMW look for a G or Z on that tag. Send us your year and VIN if you want it checked. Every part we carry for this unit is on the 5L50E parts page.
| Fits | 5L50E 1999 |
| Part type | Overhaul Kit |
| Condition | New |
| Brand | OEM |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. It contains gaskets, sealing rings, seals, O-rings and small parts. If your clutches are worn or burnt, pair it with frictions and steels or choose a master rebuild kit.
Yes. The kit is listed for both the 5L40E and 5L50E from 1999 up, since the two units share their sealing points. Confirm your transmission from the ID tag on the case.
Read the ID tag at the left rear of the case above the pan rail. Transmission Digest notes the 5L50E was used in Cadillacs only with the 4.6-liter V8, and its valve body uses separator plate code 374.
The filter and pan gasket, any worn sealing ring lands on the shafts, and the pump if its gears or bushing are scored. Worn valve body bores are a known 5L50E problem and are worth checking while it is apart.
Plan on clearing adaptive values with a capable scan tool and driving through all gears so the control module relearns shift timing. A rebuilt unit running on old adapts can shift harshly at first.
