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So I need to change my fluid soon. I was told its a bad idea to flush the transmission, so I should just drain it and then replace the filter and add new fluid. Then drain it again after a few thousand miles and put new fluid and filter in. What would you guys recommend? And what is the best type of trans oil I can get?

I have never personally did a flush I have also hear bad things about it but if your looking to get all the old fluid out then you can do it the way I did drop the pan and leave it over night wake up pop the new filter in and oil and you should be set

I got mine changed as soon as I got my bonneville, definitely noticed a difference in smoothness of shifting going to do it again with my next oil change

At 100k btw

I wouldn't flush if you have over 100k miles personally. I think you'll be fine with just one simple drain and refill. Then wait like 25k miles and do it again. Make that your interval.

A flush will not cause any damage that didn't already exist. It may however cause it to show up more quickly. Under most cases, a flush is not necessary. A pan drop and filter change should be sufficient. I use Valvoline, but any good quality fluid should be fine. I also never go over 25k between changes.

How do you guys feel about Penzoil? Seems like that's the only thing I can find that isn't someone's generic brand.

What fluid type should be used?

I'm in the same boat at 159k. I don't know if it has ever been done and I don't feel comfortable with a flush at this stage.

Penzoil is fine. Dex/Merc for the fluid, or you could go with the Dexron VI, but it is likely to be more expensive.

Rather than doing a "flush" with a specialized machine, you can do a fluid change by disconnecting the fluid "out" line from the trans where it enters the radiator- slip rubber tubing over the end long enough to reach a 5gal. bucket on floor. Have a helper ! Start engine and fluid flowing - pour new fluid in as the old, brown fluid exits to bucket. Stop when flow appears to be new fluid-reconnect line- check for proper level-recycle old fluid- drink beers. It take a bunch of quarts of fluid to do this but, it's still cheaper and safer than a pressure flush at a "facility". A pan drop/filter change afterwards is a how I do mine.

Run Dex VI in mine. works great. but you can also run many other premium synth brands for smooth shifts and the synt will stay cooler. DONT flush the system, drain/Filter and refill. Dex III or Dex VI will work, GM recommends Dex VI for all Dex III cars, Except Manual trans cars that call for Dex III. I do't like Pensoil or store brands, you dont need to run Dex VI, Dex III is cheaper and works just fine.

Non Synth Dex III:
Valvoline Maxlife Dex III ATF (synth BLEND iirc)
Valvoline Dex III (Standard)

GM Dex VI (GM Dealer)
Valvoline Dex VI (checker auto parts stocks)
AMSOIL ATF (DEX III Compatible)
Royal Purple ATF (DEX III Compatible)
Mobile 1 ATF (DEX III Compatible)

Yeah, I heard flushing can cause stuff to get clogged in the trans and then eventually break the trans. So I think I will just drop the pan, add new oil and filter, and then do the same process when I get to 110,000 miles. Then from there I will change at 25k marks. I'm not worried about the price, if Dex VI is the best, and its synthetic I will definitely buy that. Thanks for the info guys. One other thing though, what brand gasket should I pick up?

What kind of urban myth is this?

I work at a dealership and we do fluid exchanges w/ filter at 100K, with a "specialized machine".
You realize that only draining the pan and replacing the filter is only removing less than half of the total capacity of the transmission?

Why not get ALL the old fluid out?

Leon

1tinindian wrote:What kind of urban myth is this?

I work at a dealership and we do fluid exchanges w/ filter at 100K, with a "specialized machine".
You realize that only draining the pan and replacing the filter is only removing less than half of the total capacity of the transmission?

Why not get ALL the old fluid out?

Leon

Well from what I have heard is that flushing it can/could cause any fragments to get pushed into places they shouldn't be in. And then after some time it wrecks your trans from the restricted oil flow. This is why I am saying to do a pan drop, replace filter and add new oil and then after a few thousand miles do the same process over again to get the rest of the older oil out. I guess the way I see it, is if people have had bad experiences with the flushing machine, I'd rather stray away from it myself. Cause I really don't need to be buying a new trans anytime soon.

terrancew3 wrote:

1tinindian wrote:What kind of urban myth is this?

I work at a dealership and we do fluid exchanges w/ filter at 100K, with a "specialized machine".
You realize that only draining the pan and replacing the filter is only removing less than half of the total capacity of the transmission?

Why not get ALL the old fluid out?

Leon

Well from what I have heard is that flushing it can/could cause any fragments to get pushed into places they shouldn't be in. And then after some time it wrecks your trans from the restricted oil flow. This is why I am saying to do a pan drop, replace filter and add new oil and then after a few thousand miles do the same process over again to get the rest of the older oil out. I guess the way I see it, is if people have had bad experiences with the flushing machine, I'd rather stray away from it myself. Cause I really don't need to be buying a new trans anytime soon.

What I'm saying, is I'd like to see the documented proof that this has been the root cause of transmission failures.
Heresy= urban myth.

The "specialized machine" is a fluid exchanger that uses your transmissions own pump to draw the new fluid in and pushes the old fluid out.
The "machine" does not pressurize your transmission, nor pushes any "fragments" around that weren't already there, being moved around by the very pump that runs every time you start your engine.

Leon

1tinindian wrote:What I'm saying, is I'd like to see the documented proof that this has been the root cause of transmission failures.
Heresy= urban myth.

The "specialized machine" is a fluid exchanger that uses your transmissions own pump to draw the new fluid in and pushes the old fluid out.
The "machine" does not pressurize your transmission, nor pushes and "fragments" around that weren't already there, being moved around by the very pump that runs every time you start your engine.

Leon

Yeah, but what good is doing that with the original filter in there? The filter should or could be full or fragments that could potentially come loose and circulate in the trans. Not saying it would, but I guess I'd rather take somebody's word for it rather than find out for myself (well now it's not somebody's word but rather more people's words for it). It would cost me 100 bucks to flush the system, and less than 50 to drop the pan and change the fluid myself. I guess I will save my money and potentially save myself from any possible damages the flush could cause.

In many cases, the "flushing machine" is just two large containers. One holds the fresh fluid, and the other collects the old. The pump in the transmission does all the work of pumping the new fluid out of the fresh container, and depositing it into the old container. It isn't any more likely to get particles in place that they shouldn't be than just driving the car. A big minus IMO is that the filter is not changed during the process. Even a flush will not get all of the old fluid out. In most cases, dropping the pan does just fine at refreshing the fluid and is all that is needed...similar to just draining the radiator instead of doing an entire cooling system flush.

Part of the process is to drop the pan, replace the filter, THEN do the fluid exchange.

I'm still not convinced that this process causes transmission failures.
We do several of these a week and have never had a transmission failure due to a flush and filter change.

Besides. if your transmission has that big of fragments in it already, the size that could cause damage, I'd say the tranny is on it's way out anyway.

Leon

you can do either but a drans filter and refill is really all you need.. if your really anal about getting more fluid out you can do it twice after driving a little bit to get it circulated.

I dont think you can mix reg tran fluid with synthetic

you can, you just loose some of the effectiveness of the synth, basically deluding it.