Change Trans Fluid or Not?

[Supercharged111]

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.

If you're purging a hurt trans with nuked fluid that's different than the OP's scenario of healthy trans and oxidized fluid. I've had a 100% success rate with 150k+ mile transmission purges. Also with sub 150k mile trannies. The Envoy and my 1500 are creeping up on their purge intervals again and they'll get this treatment.

 

[Christian Steffen]

I vote pan drop and filter change, but I doubt a full flush will hurt it. Like supercharged said, these are tough transmission.

 

[Trenton]

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

Some transfer cases require Dexron III and NOT Dexron VI. The Borgwarner 4401 t-case in my truck is that way. Thats why Dexron III still sells.

 

[Trenton]

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.

The only way to do a trans flush is record how much comes out and fill it with the same amount, anyway. The initial fill amount is almost never right on any vehicle.

 

[thegawd]

I understand what your saying, the service bulletin I read didnt say anything about tcases or transmissions, it was only for the fluid.

 

[thegawd]

here it is.... I dont see anything about tcase/trannys just the vehicles that use it.

(this is a copy n past from another forum)

Vehicle Level Transmission and Drivetrain Automatic Transmission/Transaxle Fluid - A/T Technical Service Bulletins A/T - DEXRON(R) VI Fluid Availability


A/T - DEXRON(R) VI Fluid Availability
Notes

Bulletin No.: 04-07-30-037B

Date: June 12, 2006

INFORMATION

Subject:
Release of DEXRON(R) VI Automatic Transmission Fluid (ATF)

Models:
2007 and Prior Passenger Cars and Light Duty Trucks
2003-2007 HUMMER H2
2006-2007 HUMMER H3
2005-2007 Saturn Relay
2005 and Prior Saturn L-Series
2005-2007 Saturn ION
2005-2007 Saturn VUE with 4T45-E
2005-2007 Saab 9-7X

Except 2007 and Prior Chevrolet Aveo, Epica, Equinox, Optra
Except 2007 and Prior Pontiac Torrent, Vibe, Wave
Except 2003-2005 Saturn ION with CVT or AF23 Only
Except 1991-2002 Saturn S-Series
Except 2007 and Prior Saturn VUE with CVT, AF33 or 5AT (MJ7/MJ8) Transmission Only

Supercede:

This bulletin is being updated with the 2007 model year. Please discard Corporate Bulletin Number 04-07-30-037A (Section 07 - Transmission/Transaxle).

DEXRON(R)-VI ATF

General Motors Powertrain has recently upgraded to DEXRON(R)-VI ATF with the start of 2006 vehicle production.

Only 2005 and prior models that currently use DEXRON(R)-III may use DEXRON(R)-VI as a replacement.

All 2006 and future models that use DEXRON(R)-VI are to be serviced with DEXRON(R)-VI fluid only.







DEXRON(R)-VI is an improvement over DEXRON(R)-III in the areas shown.

2006-2007 Transmission Fill and Cooler Flushing

Some new applications of the 6L80 six speed transmission will require the use of J 45096 - Flushing and Flow Tester to accomplish transmission fluid fill. It is highly recommended that the clean oil reserve of the machine be purged of DEXRON(R)-III and filled with DEXRON(R)-VI.

 

[df2x4]

here it is.... I dont see anything about tcase/trannys just the vehicles that use it.

(this is a copy n past from another forum)

Vehicle Level Transmission and Drivetrain Automatic Transmission/Transaxle Fluid - A/T Technical Service Bulletins A/T - DEXRON(R) VI Fluid Availability


A/T - DEXRON(R) VI Fluid Availability
Notes

Bulletin No.: 04-07-30-037B

Date: June 12, 2006

INFORMATION

Subject:
Release of DEXRON(R) VI Automatic Transmission Fluid (ATF)

Models:
2007 and Prior Passenger Cars and Light Duty Trucks
2003-2007 HUMMER H2
2006-2007 HUMMER H3
2005-2007 Saturn Relay
2005 and Prior Saturn L-Series
2005-2007 Saturn ION
2005-2007 Saturn VUE with 4T45-E
2005-2007 Saab 9-7X

Except 2007 and Prior Chevrolet Aveo, Epica, Equinox, Optra
Except 2007 and Prior Pontiac Torrent, Vibe, Wave
Except 2003-2005 Saturn ION with CVT or AF23 Only
Except 1991-2002 Saturn S-Series
Except 2007 and Prior Saturn VUE with CVT, AF33 or 5AT (MJ7/MJ8) Transmission Only

Supercede:

This bulletin is being updated with the 2007 model year. Please discard Corporate Bulletin Number 04-07-30-037A (Section 07 - Transmission/Transaxle).

DEXRON(R)-VI ATF

General Motors Powertrain has recently upgraded to DEXRON(R)-VI ATF with the start of 2006 vehicle production.

Only 2005 and prior models that currently use DEXRON(R)-III may use DEXRON(R)-VI as a replacement.

All 2006 and future models that use DEXRON(R)-VI are to be serviced with DEXRON(R)-VI fluid only.







DEXRON(R)-VI is an improvement over DEXRON(R)-III in the areas shown.

2006-2007 Transmission Fill and Cooler Flushing

Some new applications of the 6L80 six speed transmission will require the use of J 45096 - Flushing and Flow Tester to accomplish transmission fluid fill. It is highly recommended that the clean oil reserve of the machine be purged of DEXRON(R)-III and filled with DEXRON(R)-VI.

Discussion about Dexron 3 vs 6 in transfer cases starts in post 134 of this thread, four posts down on this page.

https://www.gmt400.com/threads/transfer-case-stupid-question-thread.995/page-14

Basically it seems to be concerns about viscosity. GM is recommending part number 88861800 "Manual Transmission and Transfer Case Fluid" instead of Dexron 6 in any transfer case that originally called for Dexron 3.

That said, I've been running Dexron 6 in my Suburban's NP243 transfer case for over two years now with zero negative effects.

 

[OutlawDrifter]

Definitely drop the pan, new filter, and a refill. I'd recommend pulling the plug on the next two oil changes and refilling as well. That should give you a close to complete swap with fresh fluid, without the hassle of pumping it out through the lines.

And I've been using the OE Amsoil tranny fluid with good results for a few years in all my GM stuff.

 

[Supercharged111]

Definitely drop the pan, new filter, and a refill. I'd recommend pulling the plug on the next two oil changes and refilling as well. That should give you a close to complete swap with fresh fluid, without the hassle of pumping it out through the lines.

And I've been using the OE Amsoil tranny fluid with good results for a few years in all my GM stuff.

I tried that in my 4L60 and the fluid never got near as clean as when I pumped it all through.

 

[Andrew7]

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.