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is it bad to change tranny fluid

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is it bad to change tranny fluid

Postby 1985 chevy 2500 [OP] » Jul 23 2011, 5:40am

alright so iv looked around and every site is telling me its bad to change tranny fluid after a certain time or whatever if anyone has some answers and know if it is or isnt itd be nice and also if it is bad plz write why it is to so i know and thanx.oh btw its a 85 gmc 2500 crewcab 2wd automatic tranny 350 v8
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Re: is it bad to change tranny fluid

Postby SilverSurfer » Jul 23 2011, 6:21am

The short answer is no, it is not a bad thing UNLESS your tranny is slipping already. The general thought is that if your tranny is slipping the crap floating around is the only thing causing enough friction to keep you moving. But that won't last forever. If it's slipping it's time for a replacement/rebuild.

If it's not, change often.
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Re: is it bad to change tranny fluid

Postby Z15 » Jul 23 2011, 1:34pm

I would not listen to anyone telling you not to service the transmission as they have no idea what condition it may be in. I seen 10, 20 year old trans that were like new on the inside. The miles and who was driving it are the major factors.

Time has nothing to do with it. How many miles on the vehicle? If its still running the original ATF then its 26 years old fluid and time and heat will have an affect on it. Heck most lube manuf. only give the shelf live of new fluids about 5 yrs.

The only way to know the condition of your trans is to drop the pan and observe. A professional can tell a lot by just looking at what is or is not in the bottom of the trans. If there is nothing settled in the pan than the trans have seen little if any wear. Any sediment in pan is not good.

I had a customer here come in last fall with a 2000 Furd SD F350 Dulley. He had never had the transmission fluid changed and he had 100,000 miles on the truck. He had just bought a new and bigger (huge) 5th wheel and was planning in heading to Fla for the winter. He took is to the local trans pro, they dropped the pan and found is like new. He called me up and said, bring my 5 gallons of ATF. They changed it all out, he went to FL and is back and the truck never skipped a beat. PS-He also towed a 14ft trailer behind his 5th wheel with 2 M/C in it.
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Re: is it bad to change tranny fluid

Postby jking002 » Jul 27 2011, 2:44am

I agree with silversurfer and z15. It depends on what kind of condition the tranny is in. Pull the dip stick out and look at the fluid on it. smell it also. If it looks black or smells burnt then I wouldnt change it, but if its pretty clean or looks good then go ahead and change it.
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Re: is it bad to change tranny fluid

Postby JimboInNO » Jul 28 2011, 4:13am

Something I read on another board and saved . Its unnerving to do it the first time but after I got started it worked like a charm and was easy . Just a bit time consuming . This is not a trans flush which is probably what you've heard to avoid . This is using the pump in the trans to push out all of the old fluid . I found a brass hose barb fitting that went into where the top trans line goes into radiator . Hope you find it useful - I did ! By the way , get the fitting and don't hold it in by hand as mentioned as an option .
As posted by Butch on denalitrucks.com:

I'll pass along a great trick I learned from my drag racing days to change all the tranny fluid in the transmissiom, converter and cooler. I used to change the fluid in my race tranny every 20 runs, and this is a great time saver.

1) If you have over 10000 miles since the filter was last changed, drop the pan, clean it
completly, change the filter and bolt back up with a new gasket. (If you jump ahead and get the fitting in and pump out the first 3-4 qts before you drop the pan it will be empty and much cleaner to do the filter change) If you have less
than 10000 you can skip ahead to #3, although its always safer to change the filter
and clean and check the pan for particles or clutch pieces (not a good sign!)
2) Add 3 or 4 qts new fluid to bring it to the full mark on dipstick.
(DON'T START IT)
3) Remove the upper transmission line from the radiator, only very little fluid will drip,
if any at all, because its higher than the transmission.
4) Screw a short fitting into the radiator that you can attach a piece of tubing to. It is and odball fitting size on our newer trucks, and some just stick the tubing in the hole and hold it, a little messier but it works. You will need about 2 or 3 feet of 3/8 clear plastic
tubing. Clear gas line works great, but you can use almost any plastic or vinyl
tubing.
5) Clamp the tubing onto the fitting you put in the radiator and run the tubing over the
radiator support and out the front of the truck and into a gallon or larger jug.
I tape a big nut as a weight on the end of the tube to keep it in the jug, if you have a
helper they can just hold it in.
6) Start the truck. Fluid will start pumping out the tube into the jug. Watch the tube
untill you see bubbles or hear a bubbling sound and immediatly shut the truck off. It
will take about 30 seconds and will pump out 3-4 quarts of fluid.
7) Add 3-4 quarts of new fluid, to the full line on the dipstick, empty the jug (don't
forget that) and start it up again as before and watch for bubbles, and shut it off
again.
8) Repeat again, adding 3-4 quarts, empty the jug, start, watch for bubbles and shut
off.. If you really want to be assured that you have 100% change, add just 2 more
quarts and repeat. If the fluid was dirty, or the new fluid is a different color, you will
see the color change in the clear tube, this is when you know you have changed all
the fluid. I usually watch for the fluid color change rather than the exact number of
quarts.
9) Remove hose, replace fitting with transmissiom line, fill transmission to full line,
start the truck and warm up, when hot check and fill to line on dipstick.

You've just changed and flushed every drop of old fluid from the transmission, converter and cooler system. If your changing to synthetic, you will be 100% synthetic, none of the oil will intermix with this flushing procedure because the fluid follows one path from the filter to the pump, through all the transmission passages, through the converter and then out the cooler line and back to the pan. As my Denali only has 7000 miles on it I haven't changed it yet, but in my last truck, a 2000 Sierra 5.3, it took 14 quarts as i remember to flush it. Be safe and get 15 quarts. This is not a back-flush and will not dislodge any particles in the tranny. It is completly safe and easy to do. It may sound difficult but once you get the fitting made, you can do a complete flush in less than an hour for only the cost of the fluid.

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Re: is it bad to change tranny fluid

Postby Z15 » Jul 28 2011, 12:49pm

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Re: is it bad to change tranny fluid

Postby koolz71 » Jul 28 2011, 12:50pm

Good question and great responses..Ive never had a good answer to this
Crap, my hampster fell off the wheel and it broke its leg.

Check out my blog



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