I'm about to turn 72,000 miles on my 02 Blazer 4dr 4wd and am looking at changing the transmission, differential & transfer case fluid all at once. I never used the 4wd on it yet, but would prefer to change it anyways.

Has anybody used Royal Purple ATF Fluid or their gear oil made for the 2 cases?My last car had a tranny problem so I want to try and extend the life of this one as much as possible with regular fluid changes. Any input would be great, or other brand recommendations, looking to change the fluids this weekend or next. Thanks.

 

I've never used any of the expensive brands of trans fluid. I do run Mobil 1 75w90 gear lube in my diffs though...

As far as the transmission goes, I have installed a drain plug in my trans and drain the trans about every 15-20k. I have done this on many vehicles. The main enemy of transmission fluid is heat. The transmission is a closed system so there will be no outside debris added like the engine with combustion by products, etc. As such, the trans filter really doesn't need to be changed anywhere near as often. But to install a drain plug in the pan, you will need to drop the pan and I would recommend that you change the filter at that time.

I would recommend that you add an aux transmission cooler while you are at it. That will dramatically extend the life of the transmission fluid.

For the transfer case, the type of fluid used really depends on the case. If you have the Auto feature, then you need to use Autotrak II fluid from the dealership. It really isn't that much more expensive and it has all of the appropriate friction modifiers for the clutches in the t-case. If you have the regular t-case, then ATF is perfectly fine to use.

On the rear diff, if you have RPO code G80, then you have to make sure that your gear lube has the proper friction modifiers for the locking/limited-slip diff. I believe that the gear oil must be GL-5 compliant for use with limited slip diffs.

 

HI, I'm new to this site but not to cars/suvs/etc..I am a retired ASE mechanic forced into retirement by a job accident, anyways I have always hear of true gear heads using royal purple for their tricked out motors pumping out 5-800 ponies so there has to be something about this stuff or there wouldnt be such a percentage of gear heads using it, secondly when they do a trans. service, you have to be careful as to which one youre getting, if youre getting charged for no more than5-7 quarts of ATF youre getting "El Cheapo" trans service,I.E: they just drop the pan,change the filter and add fluid that is lost through the pan which is roughly 5-7 quarts, in reality your trans holds over 12 quats of ATF most of it is in the torque convertor (automatics only!) and that fluid does not run out and get changed simply by dropping the pan, you need to suck it out with a specially designed machine that hooks to one of the trans lines that go the radiator where inside resides a trans fluid radiator seperate from the radiator, it just cools down trans fluid in a closed loop, anywaysin a real trans service which should be over 120$ at least they unscrew on of the lines and hook it to the trans mission who in turn sucks every last drop from your transmission, then they replace it with 10-14 quarts of new ATF and a filter, if you are getting charged for all this you are getting the real deal, if youre only paying for the filter 4-5 quarts of ATF and 20-30$ for labor youre getting a incomplete fluid change. So make sure to mention that you want the whole trans flused and if they cant do it, theu dont have the machine so go elsewhere that garauntees upfront that you are getting a FULL trans flus, go for it it will prolong the life of a tranny and like the other gentlman posted heat is you worst enemy I would install another trans coller from a common well known source, like Jegg's or JC Whitney which over as long as they well knwn