I have a question about my transmission in my Bonneville. The car has 251,800 miles, the last time the transmission fluid was changed was at 187,000 miles. Would it be wise to change it again. Its not low, actually a little over full and dirty. BUT the car has ALOT of highway miles. I really don't want to risk changing it without advice. It doesn't give me hell and runs really good.

Drop the pan, only do the filter and top it off change. A full fluid flush is not recommended at that mileage and congrats on having that much on it.

I would recommend that you drain all of the fluid you can by dropping the pan, cleaning the pan, and changing the filter. The procedure is in techinfo. You will only replace about half of the fluid this way, but your chances of damaging the tranny are essentially zero. This is NOT the case with having your trans flushed. It can be beneficial when done right, by competent personnel using equipment that is maintained and working properly, but there is room for error and cutting corners with flushing procedures, and when done poorly, can destroy your trans.

With a drain and fill you can simply repeat the procedure when it is convenient, and you will have replaced 75% of the fluid. One more time gives you 88%, etc. Inexpensive and safe way to service your own transmission. Can be messy, though. I use a really big blitz drain pan and try to avoid windy days .

[edit: geez Boost, I gotta type faster!]

I'm gonna be doing this same job on my Bonnie in the near future. I have never touched my tranny. Figure with 131K it'* time to at least change the filter!

How much fluid should we plan on adding after dropping the pan?

You start with about 4 quarts and then check the level adding until it'* the right level.

Thanks yall. I have all the equipment, and access to a lift to service my transmission. The filter kit is going to cost me $14. I was also wondering if it was possible to put the new Dexron IV transmission fluid in my transmission. I've heard that it is really good fluid that they put in the new 2005-up GM transmissions. If not I'll just pick up some Dexron III.

Stick with the original fluid designed for it.

Question about flushing the Trans on a fluid change....
Is it safe for the trans to drop the pan/fluid, clean, put a new filter on, put the pan back on and then pour 4 quarts of new fluid in .... this is the part I am wondering if it will hurt the trans...

take the top radiator trans line off, connect hose to it and put the open end into a backet. Now start the car and let the trans pump out about a quart to a quart and half. Turn the car off, put two more new quarts of fluid in the fill tube. Then start the car again and let it run until you pump out a quart to a quart and half. Turn the car off and fill with two more quarts of new fluid. Repeat this until trans fluid runs red and new. Then reconnect top trans line to radiator and top off trans fluid to correct level.

Will this type of trans flush hurt the trans?

Thanks,

Luke

I have never done it that way but....If the top hose is indeed the one that is from the trans pump to the cooler, (you will know as soon as you start the engine if the fluid begins to flow from it) I don't see any problem with doing it that way. Especially if you just do a little bit at a time as you describe. But, before you do that, make sure you drop the pan and clean it along with the magnet. And remove the old filter and install a new one before you do the home flush method. That way, you avoid circulating dirt and crud.

This might take a lot more fluid than you imagine, though.

[edit: I am not sure what part of the trans is going to be starved for fluid returning from the cooler if you try this. You need to hear from someone more knowlegeable on the 4t6xe'* to be sure, like mkaake, or willwren]

I would still recommend just doing the pan drop and refill, again after a few miles if you like, as the safest possible method.

A quart will come out much quicker than you can imagine. Have a helper and don't let it run longer than a few seconds. If you do...you will drain much more than a quart.