Trans.Fluid Changing??...

[Arnold]

I feel like doing it myself..changing to synthetic..as part of changing
the dif's.,t.case,engine.. to synthetic.. major maintenance.
 01 3/4 ton Burb .4L80. 150K Trans. works perfect, fluid looks,smells perfect. Has been done before.
  I have done a fair bit of homework..seems to be about half and half.
Do it/don't do it. I am surprised by the #of shops that WON'T do it!

  Any thoughts on this?
  Thanks..

[1800guy]

I'll let somebody else weigh in on full synthetic vs partial - I'd like to know that myself, esp. for towing.

As far as shops not wanting to do changes, they probably feel the perceived risk is higher than the reward.  You know your tranny is working good and has been taken care of - they don't know that.  Believe it or not, there are people out there who are not completely honest.  "My trans was okay until you messed with it", etc.

[BFS57]

Hello;
I'll weigh in on this but it wasn't synthetic that was changed.
Our 02 Trailblazer developed a "bucking bronco" thing while shifting (I think it's 4L 60E) so I took it to the dealer and had them do a $180.00 flush/replace fluid in it and that eliminated that problem and presently, we have logged over 150K of happy (no major problems) motoring!
I would use the trans fluid that is recommended unless someone gives you a warranty of some sort for changing to synthetic!

Bruce

[Crosley.In.AZ]

I doubt any shop would provide a warranty on trans operation after a fluid change  with a high mileage transmission.

At that mileage, change the fluid with what ever you like. I doubt the results will differ between syn or dino oils or a mixture of both.

Unfortunately many of the modern auto trans now use a PWM shift system (PWM = pulse width modulated) and the syn fluids are used for longer oil service life, smoother shifts.

[Arnold]

Thanks very much guys!

  I am going to do this the careful way..Mercon VI is reccommended
which from what I have dug up is pretty much synthetic anyway.
  I will siphon out 1 litre..add a litre of Mercon VI..drive it for a few thousand..do 2 litres ditto..then 4..then drop the pan,change the filter.
I am not going to flush it.

  GM reccommends synthetic for the rear diff..(14 bolt)..and not the front?
  And I have one of those part time transfer cases with an "auto" 4wd feauture that calls for "Auto Trac" fluid.

  The engine gets 10/30 synthetic. and a longer oil filter..IF I can find one?