Trans fluid - can't find type recommended; also rear seal leak stopped on its own?

[centuryhouse]

I searched the forum and read a number of posts here recommending Dextron III, and saying NOT to use Dex/Merc, or Dextron VI as they can cause problems with old seals.

Unfortunately, all I can find at the stores are either ATF, Dex/Merc, or Dextron VI.

Where do you guys get the correct fluid?

Also - what would make my transmission's rear seal leak several quarts after I put my rear drive shaft back on (replaced u-joint & yoke), but then after I moved the car the other day the leak has completely stopped? I drove it again, and still no sign of leak.

[michael bustamante]

dex/merc is dexron III im pretty sure

[FirstOwner69]

I don't think Dexron III is made since GM won't license the name. Dex/Marc is supposed to be the one to use. I would NOT use Dex VI. I put Dex/Merc in mine.

From Wikipedia:
"The fluid specification for Dexron-VI was introduced in 2005, and was first used as the GM factory-fill automatic transmission fluid for model year 2006. All Dexron-III licenses expired permanently at the end of 2006, and GM now supports only Dexron-VI fluids for use in their automatic transmissions, although fluids asserted by their manufacturers to meet Dexron-III standards continue to be sold under names such as Dex/Merc. These fluids are not regulated or endorsed by GM."

[leddzepp]

Do not use dexron VI. Dex/merc is used in place of dexron III.

[cdowns]

Could b the leak stopped cause it all leaked out below the leak

[centuryhouse]

OK, thanks. I thought I had read in one post NOT to use Dex/Merc, but it is possible they were wrong or that I misread it.

[cleszkie]

I always worry when things stop leaking on their own. Usually means they are low or out of fluid.

If you have a 4x4, your auto tranny can push its fluid into the transfer case if the adapter seals/o-ring are bad. I had a TH350 that would push its fluid into my NP205. I would have to periodically add fluid to the tranny and drain fluid out of the t-case.

[Stocker]

Originally Posted by cdowns

Could b the leak stopped cause it all leaked out below the leak

Originally Posted by cleszkie

I always worry when things stop leaking on their own. Usually means they are low or out of fluid.

My thoughts also....

Originally Posted by cleszkie

If you have a 4x4, your auto tranny can push its fluid into the transfer case if the adapter seals/o-ring are bad. I had a TH350 that would push its fluid into my NP205. I would have to periodically add fluid to the tranny and drain fluid out of the t-case.

Yep, mine used to do the same thing.

[centuryhouse]

Mine is just a RWD.

I'll check the fluid tonight and see where it is. I assume you check with engine running, in neutral/park?

[Stocker]

Yes, and fully warmed up (and obviously on flat ground, like a concrete slab). And though I've personally never done it, some say to cycle through Drive and Reverse. I usually don't bother with that because in order to warm it up, it has been driven, so.....

Actually, with some vehicles it makes a difference whether it is in Park or Neutral. Not positive but I don't think it matters on our trucks. I always put it in Park, because, well, it is parked at the time!

[68is4me]

I have used Dexron VI in all of my older vehicles and never had a problem. Why is it recommend not to use it?

Here is the description of dex vi from my gm parts catalog.

[68is4me]

Opps forgot attachment.

[centuryhouse]

I ran the truck around the neighborhood then checked the fluid - it shows perfectly at full. And after driving it 3 times, still not a hint of a leak anymore.

At least a quart had leaked out so it must have been over full since I bought it 2 months ago. I checked the fluid at the time and it was slightly over, but I was mainly checking for smell & color at that time.

Of course, now that the leak is gone I find that my reverse lights, rear running lights, and brake lights have all suddenly gone out :-(
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[cleszkie]

Make sure that the vent on the top of the tranny case is clean and not clogged up with oil/grease/dirt. If this vent is clogged, the tranny can build up internal pressure and force ATF up and out of the filler tube. I actually had this happen to me a while back.

[mike16]

and check your coolant fluid as well sometime tranny fluid will end up mixed with coolant fluid. if thats happening you'll know soon enough when the coolantfluid color changes or your tranny fluid turns nasty brown foam.

Keep an eye on tranny fluid level and clean up the area around the output shaft of your transmission. watch for any leaks. might be a very good idea to shop for a rear seal and a gallon or two of fluid.

[cooperhw]

an automatic trans sitting will cause the weight of the driveshaft snout to sit in one place (gravity) and actually have a low spot or dent on the seal. Driving them can loosen up the seal and cause it to actually seal again. not always,

[centuryhouse]

Good information guys, thanks.

No fluid contamination between coolant / oil / transmission fluid, so that's good.

I've purchased a new seal, but am going to hold on to it for now and keep an eye on any leaking that might occur.

[centuryhouse]

A side question: when I stomp the gas pedal at road speed, it doesn't go into passing gear. What operates that, and how should I troubleshoot / fix?

[bigmac73]

check your kick down cable , probably not adjusted right,

http://www.summitracing.com/parts/tci-950640
this is the tranny fluid I use

[msgross]

Originally Posted by cooperhw

an automatic trans sitting will cause the weight of the driveshaft snout to sit in one place (gravity) and actually have a low spot or dent on the seal. Driving them can loosen up the seal and cause it to actually seal again. not always,

that would explain why my 96 z71 leaked a bit after sitting for a few months... now that I'm driving it more it stopped.

[centuryhouse]

[QUOTE=bigmac73;7323745]check your kick down cable , probably not adjusted right,


Where is it, and how do you check it?

Thanks for the rec on the fluid btw!

[Econman]

You can buy Dexron III on the shelf at Napa.