Change Trans Fluid or Not?

[Supercharged111]

I changed my 4L80E fluid at 280,000 and it did fail. On a closer inspection by a shop it was wet wiring causing the fail. That was updated and it’s going fine now.

The harness is a somewhat common failure mode, I had to replace mine when I rebuilt it. Super easy to do while you're changing the filter. I ended up dropping the pan after the rebuild to change it. I potted the back side of the connector with grey RTV.

 

[thegawd]

thanks for that info @df2x4 I'm a need to know guy, a thirst for knowledge. I'll have a read.

thanks man.

Al

 

[Trenton]

Alright @OutlawDrifter, @df2x4, @thegawd, @Christian Steffen, @Supercharged111, @stutaeng, @618 Syndicate, @Pinger, @Erik the Awful, @jjester6000, @PlayingWithTBI,

I've made my decision. I'm going to drain all the fluid, drop the pan, and record how much I drained out. Then, I'll put in a new WIX 58608 Transmission Filter, replace the pan gasket (if it's not reusable), and the fill it with Amsoil OE Dexron VI Automatic Transmission Fluid. And of course, check level with the dipstick when it's warmed up.

I'll probably order 2 gallons and a quart of the ATF since the book "says" 7.7 qts initial fill. Y'all know how that goes. It could be 6 quarts or it could be 8.6 qts.

 

[Supercharged111]

If it has the original gasket from GM, reuse that (assuming it's not hammered) and throw the one they give you with the filter in the trash. The original has a metal frame and is ribbed. This style gasket does not work with aftermarket pans whose rails have a ridge in them to help aftermarket gaskets seal better. Sounds like you have a stock pan.

 

[618 Syndicate]

If it has the original gasket from GM, reuse that (assuming it's not hammered) and throw the one they give you with the filter in the trash. The original has a metal frame and is ribbed. This style gasket does not work with aftermarket pans whose rails have a ridge in them to help aftermarket gaskets seal better. Sounds like you have a stock pan.

Great advice.

 

[Schurkey]

I'm going to drain all the fluid, drop the pan, and record how much I drained out. Then, I'll put in a new WIX 58608 Transmission Filter, replace the pan gasket (if it's not reusable), and the fill it with Amsoil OE Dexron VI Automatic Transmission Fluid. And of course, check level with the dipstick when it's warmed up.

I'll probably order 2 gallons and a quart of the ATF since the book "says" 7.7 qts initial fill. Y'all know how that goes. It could be 6 quarts or it could be 8.6 qts.

I'll go on record as saying this is a bad idea.

Q. What do you get when you have a container full of 12 quarts of sour milk, and you dump out seven quarts of the sour stuff, and replace with seven quarts of fresh milk?

A. You still have 12 quarts of sour milk. (Plus seven more in the drain pan.)

Order 5 gallons of fluid, drop the pan for cleaning. Install the filter and the pan. Dump 5 quarts down the dipstick tube. Pull the cooler tube, direct the fluid into a drain pan. Start engine, dump fluid into dipstick tube as fast as it'll go. When the fluid coming out the cooler tube looks as virgin as the stuff you're dumping in, shut off the engine. Reconnect cooler tube. Start engine, top off fluid as needed. This practically removes all the old fluid.

My Trailblazer took 15 quarts. Yours may need more.

 

[GMTMark]

Hey y'all, I have a 1998 Chevrolet K3500 Silverado CCLB with the 5.7L Vortec and 4L80e trans.

My transmission has no issues and shifts perfectly, but it also has 268k on it and I don't know the maintenance history of it. The fluid is dark red, but doesn't smell burnt. In the almost 4 years and ~28,000 miles I've owned it, I've never changed the fluid.

I've heard horror stories of changing trans fluid and the trans going out at this high of mileage. I just want it to last as long as it can.

I don't tow really heavy right now, maybe 6000 pounds at most. I do go off-roading in the rockies and drive up a lot of mountain grades since I live at 8000 ft elevation. I use Amsoil in the engine, transfer case, both differentials, and I even run their brake fluid, so I'd like to put it in my transmission if it's not a gamble.

So should I change the trans fluid or not?

It should be changed about every 50,000 mi. If yours is only dark red and not brown then you should be ok. What happens is some people don’t do maintenance and when the fluid gets thick from crud it can damage the unit. Then when you change fluid the new thinner fluid causes more problems since the unit is already damaged. I like to do a flush then drop the pan and change the filter. Then top it off. That’s as clean as you will get it.

 

[Nad_Yvalhosert]

My wife had a Camaro when I met her. '90 Rally Sport. The fluid was nearly black at 150k miles. Instead of changing the gasket/filter, I cut the line going the radiator cooler and installed an inline filter assy. It had a screw on oil filter, same as the huge 1 quart Ford. Because of space, I used the shorter 1/2 quard Dodge filter, and changed it every oil change.
That damn 700r4 never missed a shift, never slipped, and by 255k when we junked it, the fluid was a deep red.

Now here's my tie-in. Because tranny fluid is also a detergent, the external filter caught any particles and removed them before they could do any damage to the clutch packs. You wouldn't believe how heavy the first few filters were when I removed them...

If you are at all concerned that replacing the fluid will stir up debris, put in an external filter.

 

[Pinger]

I'll go on record as saying this is a bad idea.

Q. What do you get when you have a container full of 12 quarts of sour milk, and you dump out seven quarts of the sour stuff, and replace with seven quarts of fresh milk?

A. You still have 12 quarts of sour milk. (Plus seven more in the drain pan.)

Order 5 gallons of fluid, drop the pan for cleaning. Install the filter and the pan. Dump 5 quarts down the dipstick tube. Pull the cooler tube, direct the fluid into a drain pan. Start engine, dump fluid into dipstick tube as fast as it'll go. When the fluid coming out the cooler tube looks as virgin as the stuff you're dumping in, shut off the engine. Reconnect cooler tube. Start engine, top off fluid as needed. This practically removes all the old fluid.

My Trailblazer took 15 quarts. Yours may need more.

I can't - after taking you guys to hell and back debating this a few months ago - not endorse the above.
I just don't get half changing something. What does that say? That changing in entirety is bad? Leaving half in is tending towards not changing at all. Is not changing good?

FWIW, I did mine slightly differently to Schurkey but with the same result. Where he ''dump fluid into dipstick tube as fast as it'll go.'' I added 7.3l as initial fill then drained off 6.5l via a cooler hose and then stopped the engine. After that it was just a case of adding to the correct mark on the dipstick. It didn't run dry draining the 6.5l.

The GM manual overstates the pan capacity by 2.3l. It suggests 7.3l (hence my initial fill quantity) but only 5l was in mine (and the stick was showing the level to be correct).

The only reason I didn't employ Shurkey's 'when it's as clean as going in' method was what was coming out was pretty clean (difficult to spot the transition from old to new) and if I'd overshot (it pumps pretty quickly) I could have left myself short as I only had 19l at hand. If there had been someone here to shut the motor down I might have done it that way but between being up front watching the fluid pumping and getting to the ignition key is quite a bit of fluid.

 

[GMTMark]

I almost tried that on my 2012 Impala but I chickened out because I didn’t have someone reliable to shut the engine off in time. Isn’t that pitiful that so many people don’t have common sense to just do that? Getting back to the 4L80, I like changing the filter whenever possible. The combination of filter and flushing seems to work great for me.