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2004 Chevy Tahoe 2WD 5.3 Flex
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Discussion Starter · #1 ·
Have a 2004 Tahoe with a rebuilt engine. With prior engine and new engine (both engines) the transmission seems to slip or shifts slow from 2nd to 3rd. It does not occur all the time. There is no noise or grinding or jerking It’s perfectly smooth and feels as though it is a slow drug out shift. I changed the transmission filter and fluid a year ago. I also torqued down all valve body bolts per specs with pan off. ATF fluid is Valvoline Max Life Synthetic and levels are good.

I have decided to try Lucas Stops Slip additive. First anyone see and reason not to try it? Second the bottle I have is 24 oz and directions indicate to add entire bottle. Do I need to pump out any existing fluid before adding the bottle?
 

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If your levels are good, you'll need to remove 24 ozs
 

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2004 Chevy Tahoe 2WD 5.3 Flex
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Discussion Starter · #3 ·
Thanks. Added today and drove about 150 miles normal driving. Next weekend going to take it out on interstate to see if there are any improvements.
 

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Lucas works when a transmission is just starting to go out, it does help with slipping. But if the transmission is too far gone don't expect any real results from it.

Lucas claims it can be added without draining the transmission however I would still drain some out personally.

Did it do this before or after you changed your transmission fluid and filter?
 

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You need to be aware of the conditions that make it slip shifting from 2nd to 3rd.
1. During normal acceleration?
2. During medium acceleration?
3. During hard acceleration?

If it slips during medium to hard acceleration, you may need to baby it from now on to make it last.
If it slips during normal acceleration, you better save up for a rebuild. Can't drive it like you stole it anymore, haha.

If it slips, apply piston has a blow-by, 3-4 clutches are getting thin, or line pressure is not enough for clamping friction clutches.
 

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2004 Chevy Tahoe 2WD 5.3 Flex
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Discussion Starter · #6 ·
Lucas works when a transmission is just starting to go out, it does help with slipping. But if the transmission is too far gone don't expect any real results from it.

Lucas claims it can be added without draining the transmission however I would still drain some out personally.

Did it do this before or after you changed your transmission fluid and filter?
thanks. I did remove 24 oz of fluid before adding it. Then is was so thick I poured about 3 oz of fluid in behind it to clean the funnel and dip stick sleeve.
It has slipped like this both before and after the fluid and filter change. My engine blew a lifter in summer of 2019 and the camshaft lobe was chewed up. My rear main seal was leaking also I was already $1500 in so I just had a rebuilt motor installed and kept the old motor for a project. (I have never rebuilt a motor and want to try it). After the engine swap I changed the fluid and filter on trans.
 
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