Where a low oil level is exacerbated by cold temperatures, warmhot oil is not, so slipping when warm is indicative of another problem (crucially this only applies if the transmission is fine when cold).Former automatic-transmission repairer, welder and hobbyist game developer.BA Transmissions 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 youre likely to find are well known and understood, and in this article were going to look at some of them. Be warned, however; even armed with the knowledge this article is going to give you, there is no guarantee youll be able to fix the problem yourself unless, of course, you happen to have all the tools and equipment youd need. Please be aware that this article 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 Id include a little bit of background information on this transmission. 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 Cadillacscheck the end of this article 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 SlippingPower Loss When Cold Juddering andor Leaking Fluid from Pump SlippingPower Loss When Warm Output Shaft Wear Harsh Gear Changes Complete Loss of Drive SlippingPower Loss When Cold Symptoms: Flaring into gear. If your transmission seems to slip first thing in the morning, or when its been sat unused for a while, its 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 its 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 dont plug that leak, youll be topping up your transmission fluid indefinitely. 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. Behind the pump seal is a bush that 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.
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