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The GM 5L40-E Automatic Transmission: Common Problems

GM's 5 speed automatic transmission was used widely between 2000 and 2007.
GM's 5 speed automatic transmission was used widely between 2000 and 2007. | Source

The GM 5L40-E transmission is very common in cars of a certain age and, as those cars continue to age, more and more of them are finding themselves in the shop for transmission faults. Fortunately, because the 5L40-E has been around for some time a lot of the faults you’re likely to find are well known and understood, and in this hub we’re going to look at some of them.

Be warned, however; even armed with the knowledge this hub is going to give you, there is no guarantee you’ll be able to fix the problem yourself… unless, of course, you happen to have all the tools and equipment you’d need.

Please be aware that this hub assumes some (but not a lot of) working knowledge of cars and terminology.

The GM 5L40-E Automatic Transmission — A Brief Overview

Before we get into the faults and foibles, I thought I'd include a little bit of background information on this transmission. I've also included a nice video overview below.

The GM made 5L40-E (sometimes referred to as “A5S360R”) automatic transmission is a five speed transmission that saw common use between 2000 and 2007. There are many vehicles that use the 5L40-E, but some of the more common instances include the BMW 5 Series (E39), L322 Range Rovers, and a range of Cadillacs—check the end of this hub for a more comprehensive list of vehicles. It features five forward gears and one reverse, with 4th gear being a 1:1 ratio and 5th gear being “overdrive”. The 5L40-E can come in both two and four wheel drive flavours, though many of the components used are the same or very similar.

GM 5L40-E Common Faults Covered Below
Slipping/Power Loss When Cold
Juddering and/or Leaking Fluid from Pump
Slipping/Power Loss When Warm
Output Shaft Wear
Harsh Gear Changes
Complete Loss of Drive

Slipping/Power Loss When Cold

Symptoms

  • "Flaring" into gear
  • Loss of power
  • "Trans Failsafe" mode
  • ONLY when cold

This is up at the top because it’s usually the simplest to fix. If your transmission seems to slip first thing in the morning, or when its been sat unused for a while, it’s probably a bit low on transmission fluid. As the transmission warms up the oil thins out and expands which, in turn, raises the fluid level, but when it’s cold the fluid level is lower. If the level is low enough, the transmission might struggle to get enough fluid to apply the clutches, hence the slipping.

If this is your problem, you can perform a temporary fix by topping up the oil level, however I must stress the “temporary” part. If your 5L40-E is low on transmission fluid, that fluid must have escaped somewhere, and if you don’t plug that leak, you’ll be topping up your transmission fluid indefinitely... and that's assuming you never run it too low and burn out the box.

Common places for leaks to occur are around the sump (metal pan underneath the gearbox), from the rear seal around the output shaft, or from the pump seal. Unfortunately a leaking pump seal would require the removal of the transmission to remedy. This does tie in nicely with the next fault, however.

Hint: When topping up the oil on any automatic transmission, ensure the engine is running, otherwise the transmission will appear to be overfull when it could be anything but.

Juddering and/or Leaking Fluid from Pump

Symptoms

  • Juddering when driving
  • Fluid leak at the front of the transmission

Though it’s possible for a pump seal to wear down on its own, in 5L40-Es they tend to leak because of a more severe problem. Behind the pump seal is a bush which is responsible for keeping the torque converter steady and central as it spins. In this particular transmission they seem to wear down relatively quickly, allowing the torque converter to “wobble” slightly. In addition to certain driving issues such as a juddering sensation, this “wobble” squashes the seal out to the point that it begins letting transmission fluid through.

The best case scenario here is that you catch the problem early and “only” need to remove the transmission from the vehicle, remove the front end of the transmission, dismantle the pump assembly, and replace the bush and seal. However in some cases this issue can cause damage to the torque converter neck and even the pump itself, and replacing those parts is sure to run you up into a four figure bill!

Hint: There are other things that could cause your transmission to leak from the bell-housing, however none of them can be repaired without removing the transmission. If it's leaking from the front, it has to come out.

Slipping/Power Loss When Warm

Symptoms

  • "Flaring" into gear
  • Loss of power
  • "Trans Failsafe" mode
  • ONLY when warm

It may seem counter intuitive, but transmission slippage when warm is an entirely different issue to slippage when cold. Where a low oil level is exacerbated by cold temperatures, warm/hot oil is not, so slipping when warm is indicative of another problem (crucially this only applies if the transmission is fine when cold).

As mentioned above, the transmission fluid expands when it heats up. This not only causes the oil level to rise, it also causes it to become thinner. Automatic transmissions employ a lot of pressurised components that maintain their pressure through a variety of seals and valves. When those seals start to wear, transmission fluid can escape, lowering the pressure. In cases where a transmission is worn but not completely gone, it may drive fine when the oil is cold and viscous. When that oil heats up and thins out, it can start finding its way out of these worn seals and valves, causing a lack of pressure when applying a clutch.

Unfortunately when this happens, there’s not much to be done below a complete rebuild that can cure the problem. Below is a video on replacing the clutch pistons in a 5L40-E. Due GM's use of "moulded pistons" rather than regular seals, re-sealing is not as simple a task as it would be in other transmissions.

Hint: 5L40-E moulded pistons cannot simply be seated in place without the proper tools. Attempting to do so will almost certainly damage the pistons.

Output Shaft Wear

Symptoms

  • Partial or complete loss of drive
  • Loud metallic noise when attempting to drive

Typically limited to larger four wheel drive vehicles such as Range Rovers, the output has been known to wear down to the point of no longer functioning. Worse still, the entire drive of the vehicle passes through this shaft, so when it wears down, the vehicle no longer drives at all, and tends to make a horrendous racket when it tries.

The shaft is connected to a drum inside the transmission, and as the drum is at the back of the gearbox, not only do you need to remove the transmission to replace it but you also need to take all of the guts out of the gearbox to get to it! The one silver lining here is that the wear of this shaft is external to the transmission, and will not cause any damage to the rest of the box.

Hint: When output shaft wear occurs, check the teeth on the transfer box. Replacing the output shaft and sliding into a half worn transfer box will not end well.

Harsh Gear Changes

Symptoms

  • Harsh gear shifting
  • "Trans Failsafe" mode

When an automatic transmission like the GM 5L40-E changes gear, oil is fed into a sealed chamber, forcing a piston to push against a stack of clutch plates. If the oil were just shot into that chamber all at once, the clutch pack would apply with a harsh thud and make for a very unpleasant driving experience. The 5L40-E gets around this problem with the use of a number of accumulators which allow the oil to be fed in gradually until the pressure is sufficiently high.

The accumulators work by sitting a small sealed piston on top of a spring so that when the oil is fed into the chamber, it pushes the piston against the spring. These springs, however, have a nasty tendency to break. Fortunately repairing this problem is (relatively) easy. You don’t need to remove the transmission, just the valve body which can be found inside the sump at the bottom of the transmission.

Hint: Be extra careful when removing the accumulator housings so as not to rip the gasket. If the gasket rips, the valve body has to be completely stripped down to replace it.

This picture shows the four accumulators removed from their housing. The accumulator spring on the far right has broken in two.
This picture shows the four accumulators removed from their housing. The accumulator spring on the far right has broken in two. | Source

Complete Loss of Drive

Symptoms

  • Partial or complete loss of drive
  • "Flaring" into gear
  • Loss of power
  • "Trans Failsafe" mode

This is the big one. The most common reason for a vehicle running a GM 5L40-E transmission to end up in a transmission repair shop is torque converter failure. For a variety of reasons (torque converter solenoid, worn valves, worn converter) the converter fails and begins contaminating the oil with debris. The debris circulates throughout the transmission and, eventually, begins blocking the filter. Once the filter is clogged up, the clutch packs are starved of oil and begin to slip. The slipping clutches begin to burn up, further contaminating the oil with debris and, well, you get the picture.

If you were very attentive and caught this problem very early, you might get away with an oil flush and a new converter/filter (though I'd be sceptical over how long you'd get away with it for). For most motorists, however, nothing less than a full rebuild and replacement converter will remedy the problem. The easiest way to check for this problem is to remove the sump and check for debris. If the converter has failed in this fashion, the sump will be full of metallic debris.

Hint: Be sure to thoroughly flush out the transmission cooler after a rebuild to avoid old debris getting back into the rebuilt transmission. Many transmission builders just replace the cooler to be on the safe side.

A failed torque converter will leave metallic debris in the sump of the transmission.
A failed torque converter will leave metallic debris in the sump of the transmission. | Source

Please remember that this hub is only detailing the most common problems with the GM 5L40-E transmission, and the most common causes of those problems. There are other faults and there are other causes of these faults, they’re just far less common.

Vehicles Using the GM 5L40-E Automatic Transmission

Though I'd never be so bold as to claim this to be an exhaustive or complete list of vehicles, it is a fairly comprehensive one. Please be aware, however, that there are always exceptions, such as cross-over years where a manufacturer moved from one transmission to another, and even modified cars where a previous owner has fit a different transmission.

The L322 version of the Range Rover is one of the more popular vehicles to utilise the GM 5L40-E automatic transmission.
The L322 version of the Range Rover is one of the more popular vehicles to utilise the GM 5L40-E automatic transmission. | Source
Vehicles Using the GM 5L40-E
2004-2006 Cadillac CTS (RWD)
2005-2006 Cadillac STS (RWD)
2004-2006 Cadillac SRX (RWD)
2006 Pontiac Solstice
2007 Saturn Sky
2004-2006 Holden WL Statesman/Caprice (RWD)
2005–2009 Chevrolet Omega (RWD)
2006–2009 Holden VE Commodore (RWD)
2008–2009 Pontiac G8 (RWD)
2004–2006 Cadillac CTS (AWD)
2004–2006 Cadillac STS (AWD)
2004–2006 Cadillac SRX (AWD)
2002–2005 Range Rover (L322)
BMW 3 Series (E46)
BMW 5 Series (E39)
BMW Z3

© 2016 John Bullock

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    John Bullock (beagrie)10 Followers
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    Fervent writer, avid gamer, guitar lover. In between writing content for HubPages, John earns his sandwiches fixing automatic transmissions.



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