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2007 GMC Sierra 1500 four-wheel-drive. I was driving to work the other morning and I blew the upper transmission line off the transmission lost all fluid and of course my vehicle slipped and slipped until I finally couldn’t move anymore, Spent several hours repairing the line, getting a new one putting it on, added fluid, drove home fine, it drove 25 miles to work the next morning fine, Halfway home from work it started slipping again. I pulled off the road, started driving it again, it went in first fine, shift it into second fine, and does not shift out of second it tries to but then it slips and revs high and I can drive it in second gear but I’m afraid I’m gonna hurt it. Then I noticed I didn’t use dexron 4 for transmission fluid, I drained it immediately, and changed filter but it still slips rather than going into 3 gear or higher, Any thoughts before I pull the tranny

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  • Welcome to Motor Vehicle Maintenance & Repair! You said you didn't use DEXRON 4. What is it you put into the transmission? Commented Oct 18, 2022 at 10:02

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If I understand your question, you lost all the fluid in your automatic transmission but continued to drive it until it "slipped and slipped".

Then you repaired the leak but put the wrong fluid in and drove 25 miles or more.

I think it's very likely that you have caused internal damage to the "clutches" and other components inside the transmission. I think it was the initial empty running and not the wrong fluid that did the damage although the wrong fluid may have contributed after a while. Hard to say.

At this point, however, you're either in need of a transmission rebuild or a replacement.

Sorry to be the bearer of bad news but the fluid in a transmissions serves multiples purposes but one of those is proper lubrication and cooling. By running it "dry" you deprived it of both of those and "smoked" it internally. I have no doubt that on teardown there will be severely damaged components evident.

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  • The fluid I used was Gastrol Dex/Merc blend
    – KOBA5150
    Commented Oct 18, 2022 at 20:03
  • In my opinion the fact that you ran the thing dry is much more significant than using the wrong fluid. But, as noted, the wrong fluid may have added to the already significant damage.
    – jwh20
    Commented Oct 18, 2022 at 21:42
  • I was unaware that a line blew off the transmission, so when slippage started, I was trying to figure out what was happening and I probably continued operating the truck for 3/4 of a mile. Wouldn’t think that would do to much damage but again, I don’t know. Then I repaired and filled it with the wrong fluid. Ran fine for about 30 to 35 miles
    – KOBA5150
    Commented Oct 19, 2022 at 1:15
  • By the time the slipping started, the damage had been done.
    – jwh20
    Commented Oct 19, 2022 at 10:19

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