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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / May 2007Definition of changing tranny fluid
Both my cars (Lexus LS400, Land Rover Disco) have auto trannies, and the manuals say to change the fluid every 30K miles. In general, does this mean a full flush, or drain what you can (30-40%) and replace? >Both my cars (Lexus LS400, Land Rover Disco) have auto trannies, and >the manuals say to change the fluid every 30K miles. In general, does >this mean a full flush, or drain what you can (30-40%) and replace? The general expectation is a drain and replace. A full flush is probably a better idea, though, on a transmission that has been well-maintained. If you're up to 100,000 miles and doing the first change, however, the flush is probably a bad plan. --scott  Signature"C'est un Nagra. C'est suisse, et tres, tres precis." Drain the torque converter if it has a drain plug. Most transmission pans don't have a plug so you must remove the pan to empty it. > Both my cars (Lexus LS400, Land Rover Disco) have auto trannies, and > the manuals say to change the fluid every 30K miles. In general, does > this mean a full flush, or drain what you can (30-40%) and replace? SignatureMike Walsh West Palm Beach, Florida, U.S.A. > Drain the torque converter if it has a drain plug. Most transmission pans don't have a plug so you must remove the pan to empty it. > [quoted text clipped - 5 lines] > Mike Walsh > West Palm Beach, Florida, U.S.A. Drainage-wise, removing the pan (on both models here) does nothing that just removing the drain plug would do, doesn't it? I've had both pans off before. > > Drain the torque converter if it has a drain plug. Most transmission pans don't have a plug so you must remove the pan to empty it. > [quoted text clipped - 9 lines] > that just removing the drain plug would do, doesn't it? I've had both > pans off before. Depends on whether or not there's a filter or screen up in there. If there is, you should clean or replace it while you have the pan off. I'd stick a strong magnet inside the pan, too, to catch metal debris... can't hurt, although it will only catch steel, not aluminum. nate > > > Drain the torque converter if it has a drain plug. Most transmission pans don't have a plug so you must remove the pan to empty it. > [quoted text clipped - 20 lines] > > - Show quoted text - Yep, both have SS mesh screens if I remember correctly. What I did once when I got water in the rover tranny was just change it several times (around 13 times I remember) until it was clear again. Aamco could not do the flush. Anyway, my understanding from the above responses is that a 'regular' oil change is one single drain and refil, which in my case is around 40% of the fluid. Cheers all, Dean "Dean" <deanbrown3d@yahoo.com> wrote in message > Yep, both have SS mesh screens if I remember correctly. What I did > once when I got water in the rover tranny was just change it several [quoted text clipped - 8 lines] > > Dean You are right that a normal change replenishes only a percentage of the fluid. IMHO, the pan should be dropped, examined and cleaned. This allows you to see if there are metal filings in the pan, or if there is a sludge of clutch lining material. As previously posted, some transmission have a magnet permanently installed, and I have never cleaned out a pan that did not have some debris stuck to the magnet. You definitely dont want sludge or solids circulating around in a tranny. Valve body clearances are too refined to tolerate a bunch of crap in a tranny. You dont want varnish either... So regular maintenance, from the time the car is young, is a practice I have always followed and believed in. I have only had one tranny failure, at 100,000 miles, and it was one of those damnable Metric 440T4's (many of which failed much earlier). Technically, there is no such thing as "changing" fluid. If you avoid the word "change", it'll be clearer to all parties involved. You either "drain" it, like an oil change, or you "flush" it like a transmission flush. So, you should never flush a transmission without first draining it and changing the filter. If you flush a transmission, and it then fails, it was most likely ready to fail anyhow. Avoiding a flush to try and protect the transmission really isn't in your best interest. If you manually turn the torque converter (a big screwdriver pried against the gear teeth will turn it) you might find a drain plug, which will allow you to remove more fluid than is in the pan. > > Drain the torque converter if it has a drain plug. Most transmission pans don't have a plug so you must remove the pan to empty it. > > [quoted text clipped - 9 lines] > that just removing the drain plug would do, doesn't it? I've had both > pans off before. SignatureMike Walsh West Palm Beach, Florida, U.S.A. > If you manually turn the torque converter (a big screwdriver pried against the gear teeth will turn it) you might find a drain plug, which will allow you to remove more fluid than is in the pan. I havent done much transmission work in years. A long time ago, many converters had drain plugs. Then there seemed to be a period where very few of them did. I dont know what is the state of the art just now. |
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