Should I do a flush?

[trail2005]

Hi everyone first port here. Three weeks ago I purchased an '05 Trailblazer ext 4.2
I took it to a nearby shop where they focus on transmissions so they could do a flush. They said that there seems to be minor issue when the tranny changed to 2nd to third but other than that the car works fine. They recommended me not to change the fluid. It has 106k and I am not sure if I trust these guys. I looked underneath and noticed all the bolts on the pan where loose and one was missing. Do you guys think I should do a flush? Or just leave the fluid in there like they said? Thanks!

 

[Matt]

Any idea on the maintenance history? If not, I'd do a flush (myself, not a shop) and fill. Get another bolt too while you're at it.

 

[RedEnvoyDenali]

I am with Matt but i have a terminology problem. I don't like the term "FLUSH".

I will never do a flush but i will do a "CHANGE". A flush to me is using a machine to push the OLD fluid back or pulling it out. With a change you can do a 1/2 change or a full change. 1/2 change is drop the pan, change the filter and refill with about 5 or 6 L of fluid. A full change means using the Gerotor pump (there is video on how to do this) to pump out through the feed line to the cooler in the rad and then change the filter and add about 13 or so liters of new fluid.

You will notice that the filter gets changed with either change, these are cheap and better safe than sorry.

Sounds like the shop doesn't want to drop the pan, change the filter and clean the pan. Very Lazy

This is just my opinion but never lost a transmission in 50 years of driving and have several tranny's over 150K kilometers and one 1976 GMC Van (now dead vehicle) but had over 350K miles before the body died. In addition i fully subscribe to the idea of a Tranny Cooler, towing or not.

 

[Matt]

RED explained it better than me...I wanted change but had a brain fart.

 

[trail2005]

No idea on the maintenance on it. So far I 've changed oil, differential fluid, and transfer case fluid which btw came out very dark. When I check the tranny fluid it still looks red so that might be good? I will go ahead and do a full change then and see how it goes.

 

[Sparky]

Forward "flush" isn't bad as that is just a total fluid change. What is bad is when they do a "reverse flush" as that knocks all the stuff off the filter etc and shoves it backwards into the tranny. Horrible, horrible idea.

 

[Mounce]

I wouldn't flush it with a machine with that many miles on it. Pan drop or diy "flush" would be fine and a great idea though.

Just an FYI, shops around here make you sign a waiver if you're over 75k to do a machine flush so that they're not held responsible if your transmission goes out due to it. That's why I wouldn't recommend it, even places that do the flushes know it's a bad idea.

Here is info about the diy flush shown by our very own, MAY03LT. also a few threads floating around here about it.

 

[trail2005]

Thanks again everyone for your help! I'll be doing the DIY change in a couple of days.

 

[smt 59]

Make sure you purchase a good quality change kit, filter, gasket etc. And most importantly use a high quality synthetic transmission fluid, I recommend Amsoil, it costs more now but saves in the long run.

 

[trail2005]

Make sure you purchase a good quality change kit, filter, gasket etc. And most importantly use a high quality synthetic transmission fluid, I recommend Amsoil, it costs more now but saves in the long run.

Any recommendation on the kit, gasket and filter? i was already planning on using amsoil.

 

[DAlastDON]

Any recommendation on the kit, gasket and filter? i was already planning on using amsoil.

The filter comes with a new pan gasket and filter gasket. You will have two options on the transmission filter. Shallow or deep pan. The shallow pan is flat from front to back. The deep steps down lower from front to back. Look underneath to see which on you have.

To remove the filter just grab it and pull straight down with some force. The filter gasket is a bastard to remove. Most, including myself, reused the old one. To keep the pan gasket aligned when reinstalling the pan dab some vaseline or RTV at each bolt hole to hold it in place. Tighten the pan bolts in a criss cross pattern like you would lug nuts on a wheel.

 

[Sparky]

I also reuse the filter seal. If it holds the filter up then it is fine.

I prefer the filter kits that give you a rubber gasket than a cork one. Just my preference.

I use Valvoline Dex/Merc ATF (red jug).

 

[Mooseman]

Dexron VI is the recommended fluid now. It's synthetic so you get all the goodness with it. Just get a good brand filter with the rubber gasket.

A little trick for holding the gasket in place on the pan. Use a few of the bolts through the pan and into the the gasket holes. The holes are just a bit smaller just for this purpose.

 

[smt 59]

Any recommendation on the kit, gasket and filter? i was already planning on using amsoil.

I always use OEM from the dealer, I don't like to play around with transmissions, to costly if they screw up from sub standard parts.