I purchased a 1995 Blazer LS 2D 4x4 with the manual (on the floor) transfer shifter about a month ago. It had only 72,800 miles on it. It now has about 74,000 and I was wanting to flush the transmission and replace all 11 quarts of ATF with Mobil 1 full synthentic ATF (and, of course, the filter). All of the mechanics at all of the shops around here tell me to leave it alone and to NEVER change any of the fluids except the engine oil, saying my truck will probably never run right again if I do. I'm confused! I've always changed all the fluids in every used vehicle I've ever purchased. The truck is in almost pristine condition and drives VERY well. The coolant however, is some shade of grey and I can smell antifreeze through the vents. No leaking, so I don't know what's going on there. I'm definately changing IT anyway! What say y'all on the other fluids - ATF, transfer case, axles, brakes... Change them or leave them alone? Thanks in advance!!!

 

those mechanics are somewhat right...but to NEVER change it? ehhh...


With only 74k miles on it i think you'd be ok with doing a pan fluid/filter change. But i wouldnt do a full 1 quart flush. You'll be alright. Just get a pan change.
(they change the filter and 5 quarts of fluid which fills the pan.)

edit :
if you smell coolant in the vents then your heater core is starting to leak. for the tcase,double check it but i think in 95 the tcase is still just regular atf fluid. 2 quarts i believe. Change it when you do the pan change. For the axles,if you want to change it do it. Mine was never changed until like 160k miles and it still looked "ok".

 

The only questionable fluid change would be performing a 4L60e flush - You will get pros and cons from everyone on that - check the fluid for appearance (color) should be a clean light red , smell (not burnt) and feel -it should feel "right" between your fingers ... all of that can be checked from the dipstick I don't like the flush idea , but I do drop the pan and replace the filter and then refill . Never a problem vs many reported flushing issues .

 

Being a mechanic in a shop where we sell trans, coolant, etc flushes every day I have always questioned the "Do not flush theory" I haven't had any issues after flushing a vehicle in the last 5-8 years, BUT I do hear about all these horror stories of components blowing apart after flushes were done always made me wonder Am I just lucky?

My personal vehicles get what the owners manual suggests

 

That's silly. You definitely change the coolant, sooner the better but if you smell it in duscts might as well wait till you change the heater core. Might only be weeping now but it will open up more.

The ATF.. they have a point. About ten years ago, all the lube shops were pushing transmission flushes and many older vehicles trannys went out right after.
Remember this.. it's not just miles that count but age too and the environment while vehicle is sitting. Which is a lot in your case. The trans breathes as temp goes up and down and is sure to have picked up condensation. Which makes sludge.
But it all depends what you find whne you drop the pan. If the fluid is all nice and clear and barely any sludge in the corners.. Go ahead.
So.. MY OPINION based on projecting from experiece and seeing what happens to other people.. if that pan is not pristine..
Do NOT flush it. DEFINITELY DO NOT put in synthetic. IT will break loose deposited sludge which may not dissolve before it finds a tight place in your trans valve body.

 

My 2 cents - Change the ATF with a pan drain and refill or a power flush as long as the machine uses the tranmission's own pump pressure and not by using a pump built into the flushing machine. A dealer will use Dexron VI which is the latest version and is synthetic, so the question of synth or not is moot.

 

Okay. Now I'm more confused than before. If I drain the fluid and it's still pink, remove the pan, and find it very clean, and there is no offending odor, then go ahead and flush... or change just the filter and the five quarts of ATF? Also, can I mix Mobil 1 ATF with the existing fluid? Their website clamis: "According to ExxonMobil, Mobil 1 Synthetic ATF is of the following quality level: Allison C4 - GM DEXRONŽ IIIH - GM DEXRONŽ IIIG - GM DEXRONŽ IIE - GM DEXRONŽ IID - GM DEXRONŽ II - GM DEXRONŽ - Ford MERCONŽ -Voith H55.6335.3X - MAN 339 V1 - Volvo 97340 - Volvo 97341." "Mobil 1 Synthetic ATF meets or exceeds the requirements of: JASO 1-A - Ford MERCONŽ V." You can see the rest of their sales pitch on the Mobil 1 website. It says to not use it in any transmission requiring DEXRON VI, but mine would require III or VI anyway (don't know why they decided to skip the IV and V). So do I use Mobil 1, Valvoline MaxLife, or go with a conventional DEXRON III equivalent? There are too many variables in this equation!

 

Thanks to all. I think I'm gonna have the GMC dealership that a friend of mine works at do the transmission service. For $225 it includes full flush, new GM filter and all 11 quarts of Dexron VI. It also comes with a 6 month/6000 mile warranty. Is this an okay deal or shoud I just change the stuff in the pan myself or flush the thing myself. It's only $160 for the flush and fill, but I really do want a new filter.

 

If the $160 job also has a warranty, that's the way I would go. Otherwise, you're paying $65 for them to drop the pan and change the filter.

 

my work says the same thing, but 75k isnt that much, its more for the people who have 150k and have never changed it. i guess the rumor is that the dirty trans fluid is kinda gritty and helps with shifting properly if the trans is worn out.