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NM6 fluid change

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Old Jul 2, 2008 | 03:36 PM
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Default NM6 fluid change

Hello gang, I'm planning on changing my 6 speed transmission fluid and would like to find out if using the GM brand is the best choice and what steps should be observed when doing the fluid change. My 98 coupe has 90K miles and it never been changed. I've heard that Amsoil is best for a 6 speed Trans but is their a part number that I should stick to?

Thanks
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Old Jul 2, 2008 | 05:42 PM
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I have been running the Amsoil ATF in mine since new. Shifts good and no issues. You need four quarts.
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Old Jul 2, 2008 | 05:48 PM
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I've been using the RedLine ATF for the last 6 years/15,000 miles. So far, so good....
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Old Jul 2, 2008 | 05:58 PM
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I have been using Mobil 1 ATF for 5 years with no problems.

Bill
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Old Jul 2, 2008 | 06:46 PM
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definatly go with Royal Purple synchromax do a search, just did mine and made a difference
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Old Jul 2, 2008 | 08:36 PM
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1997-2000 C5s use paper blocker rings. Only certain synthetic fluids are okay for these, Amsoil ATF and ATD are okay. Mobil 1 is NOT okay.
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Old Jul 2, 2008 | 09:13 PM
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Originally Posted by enos44
definatly go with Royal Purple synchromax do a search, just did mine and made a difference
Your gonna get different opinions on this, but when I was searching the forum I found that MOST here recommed the Royal Purple. That's what I put in and it worked great.
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Old Jul 2, 2008 | 11:33 PM
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Another vote for Royal Purple Syncro Max!! REALLY smoothed out the shifting in my 2000 FRC!!
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Old Jul 3, 2008 | 01:51 PM
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Royal Purple Synchromax!!!!! Pep Boys stock it!
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Old Jul 3, 2008 | 06:11 PM
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Default Royal Purple Synchromax

thanks for the information. Does anyone have the Service manual on how to change out the manual trans fluid?

Thanks
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Old Jul 3, 2008 | 06:39 PM
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Just open the driver's side fill port, then put your pan under the tranny, then open the passenger side drain.

After draining for 10 or 15 mins, put the drain plug back in. Pump the new oil into the fill port untill it runs out a little. Put the fill plug back in.

Some people like to try and over fill the case with ATF, but IMHO it is not needed.
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Old Jul 7, 2008 | 02:06 PM
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The service manual says 4.1 qt capacity but after draining I can only get 3.25 qt back in. Is that normal?
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Old Jul 7, 2008 | 06:02 PM
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Originally Posted by voda1
The service manual says 4.1 qt capacity but after draining I can only get 3.25 qt back in. Is that normal?
Probably not unusual,,especially if the car was not level or a little nose up.You may want to repeat the process one day in 10k or so just to minimize the effect of the old stuff polluting your fresh fluid!!
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Old Jul 7, 2008 | 11:55 PM
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Originally Posted by vettenuts
I have been running the Amsoil ATF in mine since new. Shifts good and no issues. You need four quarts.
Same here, well not since new but a notible difference from the stock fluid!
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Old Jul 16, 2008 | 11:33 AM
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Originally Posted by Oldvetter
1997-2000 C5s use paper blocker rings. Only certain synthetic fluids are okay for these, Amsoil ATF and ATD are okay. Mobil 1 is NOT okay.

I have a 1998
Can the Royal Purple be used in my manual trans ?
Thanks
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Old Jul 17, 2008 | 01:19 AM
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Originally Posted by Dave1998
I have a 1998
Can the Royal Purple be used in my manual trans ?
Thanks
Yes,, one of the FEW synthetics that is safe for the older style blocker rings!! DO NOT USE MOBILE 1,,or you'll be rebuilding the transmission eventually!!
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