Another Transmission service question

mdjordan2004 · February 1, 2012

Another transmission service question! I know that this subject has been beat to death but I am going to stick it out there again. I have a 2005 GMC Sierra crew cab 4wd Z71 with towing package. I bought the truck with 78k on it and don’t know if the trans had ever been serviced. It now has 125k and all is well with transmission but I am going to change the filter at a minimum with 5 qts of Dextron III or equivalent and install a corvette servo.

I would like to do a complete transmission fluid change using the method of tapping into the output side of the radiator or trans cooler. This procedure is explained very well at http://www.gmfullsize.com/forum/showthread.php?t=179148. Doing the fluid change the way this person did he used the output on the radiator (I am guessing he does not have a trans cooler.

First question is this, if you have a trans cooler would it not be best to tap into the output side of the trans cooler so it would get flushed also? My cooler is in front of the radiator, witch line is the output, drivers side or passenger side?

Second question, what is the percentage risk in doing a complete fluid change at 125k with all new fluid, would it brake trash loose and damage the trans?

Third question, has anyone ever used Redline D4 ATF in a 4i60e transmission? According to Redlines web site this fluid can be used in this transmission safely as a replacement to Dextron III fluid. I have used Redline in my BMW street cars and race cars in the past and all of the products worked grate.

So there it is, if anyone has any experience on these subjects I would love to hear about it.

Thanks

Stevens03 · February 1, 2012

I've had GREAT success using Royal Purple Max ATF full synthetic in the 4L60e. I instantly saw a sold 1-2mpg better, smoother and quicker shifts and dramatically lower temps while towing. If you doing a full swap, I'd certainly consider a full synthetic ATF.

Dropping the pan will get you about 5-6 quarts, but a full swap is 11 quarts. Keep that in mind.

mdjordan2004 · February 2, 2012

Stevens11, Thanks for responding.

I am going to do the full fluid change using Redline D4 ATF full synthetic and run it out of the trans cooler. I bought the fitting and tubing today, total cost of $10. I do think tapping into the trans cooler instead of the radiator itself would insure all the fluid would be purged. The only problem I could think of would be when I undo the line running to the trans cooler the fluid in the cooler would run out when I get ready to reconnect and some air could get trapped causing an air bubble. I would think there would be a way for the air to escape, maybe through fill tube. Any thoughts on that would help.

gmtech4 · February 2, 2012

the lower cooler line fitting on the transmission goes to the COOLER fitting on the rad ,then to the external cooler if equiped then back to the transmission,

dont ask me which side on the external cooler ,get on your back with a light and look at the lines ,its just not difficult ok?,

blowing up a transmission from changing all the oil IS a total pile of crap and all you guys are getting sucked into the myth,

my opinion of course,,

good luck bud

ps,dropping the pan and replacing the filter and the oil is what is recommended and the rumour mill and aftermarket oil change garages have caused the panic about full oil changes ,,,

idk,maybe i dont get it

mdjordan2004 · February 2, 2012

govtech4, Thanks for your input. I did have a chance yesterday to get under my truck and figured out that the output line one the factory cooler is on the driver’s side.

As for changing the fluid I could understand the myth of changing out the fluid on a transmission that was operating properly could be bad, it just never made scene to me. How could it be a bad thing to replace the old fluid? Over time any type of fluid can and will brake down. The fluid will get dirty having very tiny particles of metal in it from the metal to metal contact (that is a given). Also the filter would capture most of that crap and over time could not circulate the fluid as well making the pump work harder. But it is nice to hear others say the same thing.

Now I do believe that a so called back flush would cause a serious problem. Just think if a type of flushing machine pumped the fluid in the wrong direction, which in turn would basically push the fluid backwards through the filter breaking loose all the trash that is in the filter and pan and undo what the filter had been doing for years. I could see a big problem with that and would go as fare to say that has happened and that is where the horror stories have come from.

By using the pump in the transmission there is only one way the fluid can flow. As long as you have hooked up to the correct fitting on the radiator or external cooler itself and if the fluid comes out from where you hooked up to then you should be good. If anyone thinks I am wrong on this please let me know.

Thanks

gmtech4 · February 4, 2012

not wrong at all but im not convinced its nessesary ,if its dark then maybe ,,have fun

mdjordan2004 · February 4, 2012

Did the fluid change Saturday with the help of a grate friend (could not have do it w/o him). The trans fluid was very dirty and the cooler line that runs from the cooler to the trans was starting to leak. Thank God the dealer had one in stock and at a good price. I can't begin to tell y'all what a PITA that was to replace. Did the corvette 1-2 servo also and there is very little room to get that out, another pain. The trans pan was dirty but not as bad as i thought it would have been, no metal either.

Also did the front and rear diffs. As for metal the front diff was another story. The magnet had what seamed to be an inch long of crap attached to it. Rear diff looked pretty good w/o any metal just dirty. Transfer case fluid was dirty but no metal either.

All and all if I can get another 100k out of this truck w/o any major problems I would be very happy. Also would feel that all the work and the high $ fluid would have been worth it. The only fluid that has not been replaced at this point is the power steering, might tackle that in the spring.

demech23 · February 4, 2012

Honestly, I feel that the power steering fluid flush is one maintenance serervice that is most overlooked. Its cheap insureance compared to the cost of steering rack/gear and/or pump replacement. You firgure its one system that has no filters and or magnets to catch any contaminates from the metal to metal wear from all the moving parts.

mdjordan2004 · February 4, 2012

I am going to do that next oild change (2-3 months from now). Does anyone know off the top of there head how much fluid it holds total. If I am going to do it I am going all the way.