Transmission Service

[papanots]

I have a 2002 LS with 84,000 KM. The service manual says to service the automatic transmission at 83,000KM. Through the years, people have always told me that the transmission should never be touched because doing so would create problems in the future. This to me is just an old wive's tale. Anyone here had this type of servicing done (oil and filter)? If so, was there a difference with any regards to the car's performance - good or bad?

[Stretch58]

I have my transmissions serviced about every 56000 KM(35,000 Miles). Every other time, I also have them flushed. Never have had to have an overhaul(knock on wood). Not regularly servicing transmissions, I would think would be an idea that provides transmission shops with a lot of overhauls.

[MCO_Death]

Originally Posted by Stretch58

I have my transmissions serviced about every 56000 KM(35,000 Miles). Every other time, I also have them flushed. Never have had to have an overhaul(knock on wood). Not regularly servicing transmissions, I would think would be an idea that provides transmission shops with a lot of overhauls.

Flushing it is always a good idea, think of it like changing the oil for your engine.

I had to purchase a new transmission after clocking ~155,000 Miles on it. I don't even know what that is in KM... But for being a police car tranny, 155k is a darn good stretch.

[GM_trannyman]

I usually recommend 30K for a trans service interval for cars used normally, 30K for trucks used lightly, and less than that if they are pulling something.

That said, it is not an "old wives tale" that servicing or flushing a transmission can cause problems. It is quite true, and I have seen it, but this only applies to units that have been neglected.

Transmission fluid has very powerful detergents in it. I work on transmissions quite a lot, and my hands are never cleaner than when I have been working with ATF all day. In fact, I sometimes use it to clean my hands when they get really dirty.

The detergent breaks down over time. In the normal operation of an automatic transmission, a certain amount of sediment is produced from normal wear of the clutches and bands. The detergent keeps all this stuff in suspension, so when you change the fluid regularly, you get rid of it. When the fluid gets old, the detergent breaks down, and the sediment starts to accumulate in the nooks and crannies of the trans. It is very similar to mud or thick grease.

Problems occur when the fluid hasn't been touched in 100,000 miles, and then someone gets it "flushed." No matter what anyone tells you, flushing WILL NOT remove all the accumulated sediment from a neglected trans - but it will do a great job of stirring it up, and that's where problems start. The crap that has been sitting harmlessly in the trans now gets broken up by the fresh detergent in the new fluid, and it gets in the valve body and wreaks havoc, making valves stick, etc., and possibly causing transmission failure.

My advice:

1. Service your transmission regularly and you will have no problems.
2. Flushing is not necessary if you observe the regular service interval. It won't hurt anything, but it is a service that is oversold because it's a money maker for shops.
3. If you have it flushed, have them replace the filter. The pan must be removed to do this, and it typically isn't included with a "flush" service.
4. If the trans has been neglected, flushing can cause problems.
5. If your trans has very high mileage and has not been serviced in a long time, and is working properly, DON"T MESS WITH IT. Run it until you have a problem, then deal with it.

And to answer your question, papanots, go ahead and get your trans serviced. Have them drop the pan, change the filter, and examine the sediment in the pan for abnormal stuff. Go ahead and have it flushed if you want, but the problem I have with flushing is that many places flush the trans and change out all the fluid before inspecting the pan (or don't pull the pan at all.) I can tell a lot about a customer's transmission by looking in the pan.

Good luck!

[MCO_Death]

Originally Posted by GM_trannyman

words

Problems occur when the fluid hasn't been touched in 100,000 miles, and then someone gets it "flushed." No matter what anyone tells you, flushing WILL NOT remove all the accumulated sediment from a neglected trans - but it will do a great job of stirring it up, and that's where problems start. The crap that has been sitting harmlessly in the trans now gets broken up by the fresh detergent in the new fluid, and it gets in the valve body and wreaks havoc, making valves stick, etc., and possibly causing transmission failure.

words

I wonder if this is what led to my transmission failure... Had a full service when I bought my Impala used @ 143k miles, Tranny flush, oil change and whatnot. 10k miles down the road the transmission failed.

[57chevyragtop]

I agree with GM trannyman, Excellent post! I've talked with many Trans tech over the years and 99% say that the flushing can cause problems by stirring up particles that have settled. Changing the filter and the four or five quarts is just fine if done regualarly 50-60K depending on driving habits, more often if you pull heavy loads or live in mountain regions. The High detergent content of the 4-5 qts is sufficient to replace any breakdown in remaining oil composition. I have done this for 40 yrs and never had a tranny problem.

[papanots]

Thanks for all the input folks (what a great site this is!!). I will have my tranny serviced (oil and filter) this coming week. No flushing. I now have 85 000KM (52 000 miles). All comments very much appreciated.