In today's local paper under the Auto Plus section I found a differing opinion than what I have read before on the BB regarding changing transmission fluid. Someone wrote into Bob Sikorsky's "Drive It Forever" column asking wether it was advisable to change the tranny fluid on a car with over 100k. He replied that assuming the car had never had it done before, changing the tranny fluid would cause all the old seals to leak. This would be because the new fluid would attack the "false seals"(old dirt and grime) and leak past them. He also stated that replacing the seals is a costly endeavor. This caught my eye because I was planning on changing the fluid in my m47 shortly using Redline products with the overfill method. I have read several times on the BB that the m47's usually have to be rebuilt around 150k. Mine is now at 174k so I want to do all the preventitive maintnence I can to keep from having it rebuilt. What should I do? I am a senior in high school so I don't have money to put into seals or a rebuild. Thanks in advance for any suggestions.

Manual trannies just don't get that dirty inside. I've opened up some pretty high milage M46's, just to find everything fairly clean. (Worn to hell, but clean...) Maybe in an auto box, but not in a manual. It doesn't create heat to break down the oil and create sludge...

If you have an M47, do as is advised below; drain, fill with cheap fluid to "rinse", drain again, and then fill with your favorite. Overfill. Raise the drivers side of the car to tilt the whole thing so you can get a little more in there. M47's like being overfilled. (I also heartily recommend Redline, it's like new-tranny in a bottle.)

-Paul Demeo
1990 780T

If you're going to go to Redline from filthy trans fluid, here's what you should do first:

Change the Type F fluid out of the box and put in new Type F fluid. Just the cheapo Wal Mart brand is fine; you'll only have it in there for a little while.

Change it out after a day, a week, a month, whatever. Just not long enough for it to get dirty again. it's washing out the gearbox.

Then drain it and put in the Redline MTL (I'm sure that was the product you were referring to). Buy two quarts and make sure that you have the car jacked up on the left so that the trans can be overfilled to two quarts, if possible. If you think you might spill some (me) then buy three. ANd have a good way figured out to get the stuff into the transmission. The bottles it comes in will not work for that.

Then, IF you have leaks after that, switch back to Castrol Type F (non synthetic). But you shouldn't have many leaks on the M47. They don't usually leak until they're ready to puke.

--
chris herbst, five volvos.

I've heard this before and don't agree with it. If a transmission seal is held together by dirt, then it will leak shortly anyway. Not changing the fluid will guarantee that crud continues to circulate and cause wear. The only reason we have not heard this said of engines is because the obvious is true: by not changing engine oil, the engine would seize.