When I was installing my trans cooler yesterday I noticed that my trans fluid is in very bad shape. If I drop the pan I will not be getting as much as I could, however if I take the return line off and let the engine idle in park it should push most of it out, then drop the pan and change the filter. Would it be worth doing this? Also I know dexron III is recommended but I also heard GM switched to dexron IV. True or false?

Thanks for the help!

 

Never flush a auto trans. I would get out as much of the old fluid as you can. Then use dex 3. I've heard you can use dex 6, but costs alot more then dex3.

 

Flushing an auto trans fine. Most transmission shops have equipment for this.

Whatever you do, DO NOT flush it by making it empty itself, as you described. That's really bad because it deprives the trans of lubrication in key areas.

The fluid coming back from the trans cooler doesn't usually just go into the pan. Instead, it goes to lubricate the transmission. When you take that hose off and put it in a bucket, the parts that are usually lubricated from the return flow of trans fluid from the cooler are running dry, which is bad.

 

Just drop the pan, change the filter, and gasket and refill. Its not necesary to flush it, and if the flush is done wrong, it can hurt something.

You can use dex 6, and it is synthetic, but like was said its a good amount more expensive. When I ordered my FLT Level 3 and Yank, I used Valvoline Dex/Merc after I confirmed with Andy@FLT.

 

how long has it been since it was changed? if its been awhile changing it might be too late.

 

You could always change the fluid in the pan multiple times, with a few hundred miles in between each change. It's not ideal but it would probably be better than nothing.

Also, Dex VI is better than Dex III, and can be added to a Dex III system with no problem. There's a great tech article floating around somewhere on this forum that compares Dex III and Dex XI... a search might turn it up. And yea, Dex VI is way more expensive!

 

I'm probably going to continue to run dex 3.
I looked at the fluid again today and it isn't AS bad as I thought it was. It still has a decent red tint to it, just somewhat dark. But no burnt smell or chunks floating around in it.

A trans shop wants 75 bucks to drop the pan, change the filter, and flush it with their machine. However I can drop it myself and change the filter, then refill around 5-6 quarts instead of them getting around 12 correct?

I'd say it's been 4-5 years and 25-35,000 miles...

 

Drop the pan, change the filter, do your self a favor and leave the old pick up tube seal in there unless you have made skills, run to walmart and buy some wallyworld super tech dex 6, its synthetic and api approved to be just as good as name brands @ under $4 a qt. As mentioned on B.I.T.O.G. forum, 5qt fill for pan and filter. I run it in mine and I am freaky picky about my lubes.

 

I'll probably do this.. It's ok to mix synth dex 6 with dex 3 correct? I'll probably do it once now and once in a thousand miles to get more of the old fluid out. It's probably better for the trans than having it flushed all at once correct?

 

Ive never been a fan of the flushing process. I feel its just best to do as described above. Just drop the pan, change the filter, refill and run it for 1500 miles or so and repeat. Twice should be sufficient.

 

I was told by GM tech that dex 3 is now dex 6. So I put about 9 qrts dex 6 in the trans when I did my TC swap. You can still get dex 3 in auto stores though so whatever you wanna use.
Iv was talked out of doing a full flush by a trans shop because he said he has seen more than enough evidence that they are very risky. Many trans failures so he says. If I was you I would drop pan and change the filter. Then do it again a few hundred miles or so later.

 

My pan actually only took about 4qts but yours could be different.
Drop the pan yourself and clean it out good. Clean off the magnet good.
Dex 3 is fine but I would put a decent brand in there.

 

I would thinkk its fine to mix it. I have done it before.
I have heard to much new fluid isnt good and may shock the trans but idk if I believe that. When I did my yank 3600 I stood up the trans on its tail to get everything I could out. Then I put about 9 qts of new dex 6 in. Trans has been perfect and it has 96k on it.

 

Pan and filter.....old school.

 

I am not sure but I think the dex 6 is synthetic if so most makers of stall converts state that synthetic fluid is a "no-no",if you are stalled you may like to check with your maker
just my .02'
Johnny

 

Its a synthetic blend (so iv been told). On the yank card that came with the ss3600 it says dex 6 is fine.

 

Yeah I just read a ton of threads on this.. Temping to stay with dex III..

 

Oil change shops should have the required equipment too.

I've used a couple of these machines in the past. They would hook in-line to your trans -> radiator lines. The car is started up, then out with the old and in with the new.

 

That GM tech article also says that Dex III systems should be topped off with Dex VI from now on.

 

Damn, now I'm torn on what to do. I do have a 3800 tq convertor.. but I'm worried to stray away from what has been working.