My truck has 100K miles on it and I am assuming the transmission oil hasn't been changed. I tried to change the fluid and the filter years ago but the drain bolt was seized in place. Is simply draining the oil and refilling it worth while, or should I have a professional do a flush? Can a flush be done at home?

Thanks!

 

You can get by with a filter change and pan drop. The drain bolts always seize so GM stopped putting them on at some point. Just drop the rear of the pan to drain some of the fluid off, then take the rest of the bolts out and drop the pan.

 

Doesn't the pan only hold a small fraction of the fluid in the tranny system? That's why I was thinking that just replacing the fluid in the pan wouldn't really be worth while. Perhaps I'm misinformed.

 

With 100K on it I would let it be. I have 200K on mine and going to rife it out. I asked the same question awhile back and everyone said if I change it i'll have more problems with the new fluid and the tranny will go out faster. Something about the fluid is a detergent and will eat all the worn seals.

 

new fluid won't eat all the seals, it will eat all the crap holding your tranny together...

 

OP, why don't you think the trans has ever been serviced in the past?

 

If at 100k it hasn't been change don't mess with it imo. I would just top off if it needs. All that grime an sludge in your trans is keeping it goin. If you have it flushed all that will be taking out an you will start having slipping issues arise. Learned that after buying used truck that never been changed.

 

So the **** in my transmission is holding it together?

 

From what I was told an my understanding. If it hasn't been ever changed as parts wear an trans oil thickens. The parts are being coated an protected. Once you flush trans or change fluid all the protection is gone an the new slick oil loosens up all parts an starts slipping. Imo if it hasn't been changed an running good don't mess with it

 

I used to not believe that, but I changed a relative's 4L60E fluid at 150k and a week later guess what happened...