I'd like to try to change our own automatic transmission fluid in our '95 and '97 Blazer. It looks like a messy endeavor from reading my Haynes manual but I want to try. I have heard that automatic transmission fluid is not very forgiving and that I should consider nothing but Dexron for our Blazers.

I've switched over to pure synthetic engine oil and am wondering if I should switch over other parts of the vehicle too. Amsoil has an automatic transmission fluid which they claim has an extended drain interval of three times what the manufacturer says. Here is their link:
http://www.amsoil.com/products/atf.html

Has anyone had good or bad experiences with synthetic automatic transmission fluid?

Thanks,
-- recurve

Mr. Haynes is probably a great mechanic. His repair manual covers a lot of topics but there are many places where he simply dropped the ball. Changing the ATF (automatic transmission fluid) is one of them. I've come to learn that the technique described in the Haynes manual only flushes HALF of the fluid in your Blazer.

The following is a great link about how to flush and refill the ATF in a Chrysler mini-van. Not everything is applicable but the technique is probably similar in most vehicles. The first suggestion on this web page (from MacFarlane) is similar to what the Haynes manual suggests. The second suggestion (from Bottger) explains how to empty the entire ATF. Here is the link:
http://www.allpar.com/eek/atf.html

Here is a decent link on the S-10 forum. Discusses the same stuff but specific to S-10 pickup (a direct cousin to the Blazer) and also discusses changing the transfer case fluid and differential lubes. Here is the link:
http://www.s10forum.com/forum/showthread.php?t=16537&highlight=atf+flush

Here is an additional link on the S-10 forum. Not quite as good as above but one of the posters describes noticeable improvement with synthetic ATF and he also adds an EXTERNAL ATF filter to attempt to really keep it all nice and clean. Here is the link:
http://www.s10forum.com/forum/showthread.php?t=125076&highlight=atf+flush

Cheers,
-- recurve

Man, you go man! I see you are doing your research. :) Arguably, changing any petroleum based product for synthetic will yeild better results. Especially in cold weather. I have seen gear and tranny fluids stay at the bottom of pans especially in cold winters. Synthetics "creep" on metal parts to keep a film of lube where it belongs. And because sheering strengths of these synthetic films are much better over a wider temperature range than petroleum - indeed, parts wear longer, run cooler, and have critical lubrication at start-up time.

Personally, I have used nothing but synthetics in gearboxes, tranny and engine with *no* trouble. Usually something else totally fatal happens to my vehicles before the engine or driveline dies. If you drive like a "normal" person, switching to synthetics and sticking to your scheduled fluid change intervals will go a long way to keeping everything going.

Thanks. I'm trying hard to learn about good ways to extend the life of our trucks. I think I'm learning, in large part to this forum. I'm good at finding information on the Web, even wrote a book called "The Old Fart's Guide to Internet Searches." Here is its link on Amazon:
http://www.amazon.com/exec/obidos/tg/detail/-/0974218839/

Personally I started using AMSOIL engine oil with 25,000 mile drain intervals. I've also purchased, and am eagerly waiting, for synthetic gear lube and ATF fluid from AMSOIL. I'm pretty convinced that AMSOIL has some of the best engine oil from what I've read and comparing specs - I'm not so sure about the other fluids and lubricants… but I figure it's better than what our trucks currently have.

So, wolfox, what brand of synthetics do you use?

As always, thanks a bunch man,
-- recurve

Plain and simple - Mobil 1 in the crankcase. In a pinch, when Mobil's not available - Castrol Synthetic Blend for High Mileage engines. 10w-30 in winter (just changed today in fact!) 30w in summer.

Valvoline GL-5 certified Synthetic 80w-95 in the diffys.

Redline ATF Synthetic in the tranny and transfer box. (Worth the cash!) Look for the jugs labeled D4 ATF. The C+ ATF is for Dodge/Chrysler automatics. This stuff provides the same type of lubrication as GL-4 spec. rated gear oil, with the viscosities needed in an DextronII/III and *possible IV* application. It's much more stable at high temps and will not degrade as fast as organic fluid bases. Sheering strength of the film is absolutely exceptional. (Sheering strength is the oil's ability to retain a film over moving parts that are under extreme pressure. Like the gear teeth between planetary packs, sprags, etc. in the guts of your tranny.) It is truly a superior product compared the the original Dextron fill. Do a quick google up on the product I mentioned - the stuff is truly a wonder.

Go with Mobil 1 5w30 or Amsoil for engine oil and a good non fram oil filter. K&N, WIX, AC Delco oil filters are the way to go.

Any 80w90 synthetic gear oil will have you going really well.

Watch the transfer case though, I think it take tranny fluid so be sure before you change it.

Correct, the x-fer case rests in an ocean of Dextron. Redline works well here because it is a synthetic formulation that is intended to replace and totally exceed Dextron application.

Excellent, yes, synthetic is the way to go for better fuel economy.

Thanks everyone for their replies. It really is helpful to hear other people with real world experiences and not just looking at a manufacturer's specs and posted testimonials.

I've done a bit more snooping on the Web and found a Dodge Dakota list where people posted a lot of experiences with synthetics in all parts of their vehicles. I'll post the link but the broad message I got from their postings was this:
1) Synthetics drastically extend the life of your vehicle
2) Mobil1 is pretty good and is readily available. It costs less than many other brands but is not in the same league.
3) Amsoil and Redline are both exceptional. These brands are more expensive and a bit harder to find. Amsoil is the toughest to find in a store but is easy to order by mail. Personally, I've read specs for NEO and they seem good too but I haven't been able to find many testimonials.
4) More specifically to this thread, Amsoil ATF and Redline ATF make a noticeable difference in the tranny.

The most interesting post is worth quoting here (related to engine oil). The author talked about Amsoil but probably Redline would provide the same benefit:
"I'll put it to you this way, a friend of mine races mini sprints that constantly turn 11,000-13,000rpms while racing. He ran Mobil 1 for years and had to have the motor rebuilt ever couple races. At the begining of the season about two years ago, someone told him to try AMSOIL. After 3 races, he took the motor to the shop, it was torn down and put back together. Motor builder got in a fight with him telling him that the motor was never run. This went back and forth for almost 20 races. At the end of the season, he took the motor back and it had just started to show very little signs of wear. The motor builder wanted him to run it for another season but he wanted to rebuild it anyway. Moral of the story is that now we run Amsoil in everything and I mean everything, Trucks, cars, boats, Sea-Doo's, Ski-Doo's, motorcycles."

Here is the link to that Dodge Dakota thread:
http://www.dodgedakotas.com/boards/gen/9245.html

Cheers,
-- recurve

Amsoil and Mobil 1 are full PAO synthetic made from chemicals.

Redline I believe is Group III synthetic which is hydrocracked conventional oil stock. By law it is "synthetic" but only Mobil 1 and Amsoil are the true PAO synthetic.

Great forum with all the information on oil you will ever need:

http://theoildrop.server101.com/ubb/ultimatebb.php

Hi BlazerLT, you sure about Redline engine oil?

Here's my limited understanding from what I've been reading. There are four types of "synethetic" oils:
1) Polyalphaolefins (PAO's)
2) Diesters
3) Polyolesters
4) Hydrocracked (Pseudo-Synthetic)

The first three types are truly man-made. The fourth one on the list is crude oil which has gone through an extremely thorough refinement that it is not comparable to regular petroleum oils, it is similar to man-made.

PAO basestocks are the cheapest of the three true synthetics. They have a natural tendency to "shrink" seals.

Diesters and Polyoesters are very similar. You could say that Polyoesters are better Diesters. They provide better pour points than PAO oils and tend to "expand" seals.

To stop the shrinking or expanding of engine seals that synthetic basestocks can cause, they have additive chemicals to counteract this. Sometimes, PAO basestocks are mixed with Polyoester basestocks.

To my understanding, Mobil 1 and AMSOIL are primarily PAO basestocks.

Likewise, Redline is primarily a Polyoester basestock. It is not a hydrocracked oil (fake synthetic). Redline claims that it has superior high temperature performance for racing compared to other true synthetics.

Take care,
-- recurve

Oh, maybe I was mistaken but I thought I saw that they were only hydrocracked but you know what, I think I mixed you up with Royal Purple Synthetic.

Damn colors.

BTW, looks like you have been reading the oil bible and I commend and respect you educating yourself so thoroughly.

Thanks BlazerLT!

Yes I recently read the "Motor Oil Bible" which is a free PDF download from:
http://www.trustmymechanic.com/motor-oil-bible.pdf

This is a big multi-page document with lots of info. I talked more about it in another thread here on automotiveforums:
http://www.automotiveforums.com/vbulletin/showthread.php?t=299005

Take care,
-- recurve

O no! I went to a mobil station and had my front dif and transfer case fluid changed. I don't think those boneheads put autotransmission fluid in there. I checked out my 4wd today and it had trouble engaging and disengaging.

My transfer case fluid should be red like the tranny fluid, right?

Yes, but the front diff should be 80w90 gear oil.

do any gears need anti-slip fluids? I've heard the AWD safari vans need clutch additives for something. Would positraction require this too?

The owner's manual would be a good place to look for that information.

Is positraction the same as a "limited slip" differential? The short answer is "yes" some systems need friction modifiers. But it really depends on the lubricants you use. In AMSOIL's documentation they say their lubes should work on most limited slip differentials but they do make a friction modifier that could be added if needed. Other manufacturers of lubricant probably say similar things.

Cheers,
-- recurve

hahaha,
I wish I could read about positraction in the owners manual :)

I just have the normal GU6 rear end.

By the way, (I would never do this) If you changed the size of your rear differential, would you have to change the size of your 4x4's front too?

Yes, never chage the differentials on a 4x4.

Changing final drive ratios on a 4x4 involves *BOTH* differentials. Don't just rebuild the rear when you slap on larger than spec tires - or if you want rock crawling capacity. If you engaged the 4x4 mode with different gears in the front and rear - well, kiss your x-fer case and propellor shafts goodbye...