Change Trans Fluid or Not?

[Supercharged111]

That makes it easier and less of a mess but, I'd change the filter too.

Not as much as you'd think! Ask me how I know.

 

[stutaeng]

My opinion is if you are "relying" on the metal particles floating in your fluid for friction, you already screwed and don't know it.

That's the hypothesis that some folks believe as a fact.

Some shops even have you sign a waiver if you have them change your tranny fluid on a high mileage vehicle. That's what Pennzoil had me do on mine, LOL

 

[618 Syndicate]

Change? Yes. Flush? Nope.

 

[Trenton]

I forgot to point out to you Trenton that I live over 6000' where my trucks do their work and do head up higher to go camping. But I cheat cuz my trucks have blowers. In fact the dually has had it's blower for the majority of its life, I snagged it just outside of Grand Junction back in 2016. These trannies are tough.

Hold up, where'd you get the blower?? I was just in Grand Junction about a week ago.

 

[Supercharged111]

Hold up, where'd you get the blower?? I was just in Grand Junction about a week ago.

1st owner sold around 48k miles. I don't think 2nd owner fell too far from the tree? But he was a pipeline guy.

 

[Pinger]

Flush with a machine? No. Purge using the transmission's pump at idle? Absolutely.

I did the above (after a protracted discussion on this forum!) and am glad that I did just for the peace of mind of having just about all (not just half) of the fluid changed.

A word of caution - it seems that the official GM 'fill quantity' in the manual for the 4L 80E is wrong. Adhering to it will result in over-filling. Measure what came out and us that as guidance and finish with the dipstick.

 

[Erik the Awful]

Flush with a machine? No. Purge using the transmission's pump at idle? Absolutely.

Nope. When I was a tech we had a machine that used the transmission's pump to replace all the fluid. If the car had less than 100k, it worked great. If the car had 200k, it was a matter of weeks before the transmission grenaded. Do not do a complete fluid change on a vehicle with more than 100k on the original fluid.

Ever since 50k, my Mustang had the odd delayed shift and other hiccups. At 100k I dropped the pan, replaced the filter, and refilled the transmission. Ever since then it's run flawlessly. I'm of the opinion now that if you're not rebuilding, don't replace all the fluid. I would love for someone to do a complete, honest, data-driven analysis on why fluid changes cause transmissions to take a dump.

I think jjester6000's strategy of replacing a couple quarts at a time until the fluid quality is good is a solid strategy, but honestly, Trenton, it doesn't sound like your fluid is that bad. Replace the transmission filter and go.

 

[thegawd]

I agree. if the fluid looks good then change it without hesitation. I would probably still change the fluid if it was dirty looking just because I have not personally seen a transmission fail after a fluid change.

the owners manual doesn't contain all or the correct info when it comes to transmission fluid or quantity. the quantity can change based on a few different scenarios such as whether or not the tranny cooler is hooked up or not. they did not come from the factory hooked up, like the 7way trailer plug wiring hidden under the brake booster in the plastic wire loom, the hd tow package requires the cooler to be hooked up after the sale.

the fluid listed in the owners manual is incorrect. do not use dex III tranny fluid, its obsolete. use DEX VI instead, it supersedes all other tranny fluid and is for all gm auto trannys except the new 8 and 10 speeds, those trannys were failing early so gm made a different fluid for those.

absolutely trust the dipstick. warm the engine up to operating temp, move the shifter to each gear selection pausing for a few seconds. this flows fluid into each circuit, then stop in Park, (some say Neutral but use wheel chocks or parking brake) check the fluid it should be at the top of the hash mark.

Al

 

[stutaeng]

BTW, the recommended fluid and filter change interval is 50,000 miles, according to my 04 suburban Owners Manual. I thought I had read somewhere it was 30,000 miles. It's the same tranmission, but don't know if that was the same earlier trucks.

I seem to recall my 99 Silverado said to change it at 100,000 miles the first time? I changed mine like at 113,000 miles or so.

As far as ATF type, I thought the Dexron VI didn't start until like 06 or so? I thought you could use III or VI on the earlier models? And obviously only VI on the later models.

I just dumped almost 12 qts. on my 4L80e I'm swapping on my 99. It's the Dex III. Was planning on running it for some time and change it, since I don't know the history. The guy that sold it to me said it was from his 95 C2500 he wrecked with 150,000 miles. Who knows.

The pan was kinda slimmy, but no metallic particles. The magnet had a bit of this paste-looking stuff. I think that's normal.

 

[thegawd]

well theres still dex 3 to sell and so they do. there is an actual GM service bulletin that states DEXVI replaces DEXIII. that is a fact but I'm not guna look it up.....

old atf breaks down into an acid that starts destroying things inside. changing to dexVI prevents this with its friction modifiers. I dont know, I'm not a tech or a mechanic but this is how I understand it. this information was given to me by the mom n pop race shop that rebuilt my transmission. they have been in the business for over 50 years building trannys and race cars. they built my 4L60E a stage 3HD.

I did in fact use dexIII prior. since Iv swapped a couple trannys I had a couple big bottles of it.

I used all my old DexIII in my John Deer 318 since that's what was in it and it had a leak.

Al