What could be the problem with my 6L80 transmission?

[Gms1987]

My name is Kyle. I have a 07 Yukon Denali AWD with 230,000 miles on it. Bought at 204,000 and these problems have been around since purchase and have not gotten worse. Don't know if tranny fluid was replaced before I took ownership and I haven't had it changed. Fluid looks used, but still looks like tranny fluid.


1st issue
While driving in the city (no faster than 25 mph) when shifting from 2nd to 1st (windows up or down) I hear a metal clank and the truck feels like someone stabbed the brakes for a split second. Keep in mind, doesn't matter what time of year, day, night, warmed up or cold start... this happens.

2nd issue
While driving in the city, if I make a left hand turn off a one-way to a one-way (no stop signs or lights) or a right turn at a stop light, while it's green, when I go to give it gas it revs for a second then I'm moving again. This also happens while going straight and coming to red light that turns green just as I'm within 0-10 feet of coming to a complete stop.

Any suggestions would be greatly appreciated.

 

[Foggy]

IMO time for a quality rebuild. The 1-2 and 2-1 shift is a known issue even in
an otherwise healthy trans... Maybe yours was rebuilt before you purchased it.
I personally would drop the pan and change the filter and inspect the pan and magnet
for debris.. This is the only way you can really see the health of the trans. This is your
first step. Or have a reputable trans shop do that work

 

[Geotrash]

My name is Kyle. I have a 07 Yukon Denali AWD with 230,000 miles on it. Bought at 204,000 and these problems have been around since purchase and have not gotten worse. Don't know if tranny fluid was replaced before I took ownership and I haven't had it changed. Fluid looks used, but still looks like tranny fluid.


1st issue
While driving in the city (no faster than 25 mph) when shifting from 2nd to 1st (windows up or down) I hear a metal clank and the truck feels like someone stabbed the brakes for a split second. Keep in mind, doesn't matter what time of year, day, night, warmed up or cold start... this happens.

2nd issue
While driving in the city, if I make a left hand turn off a one-way to a one-way (no stop signs or lights) or a right turn at a stop light, while it's green, when I go to give it gas it revs for a second then I'm moving again. This also happens while going straight and coming to red light that turns green just as I'm within 0-10 feet of coming to a complete stop.

Any suggestions would be greatly appreciated.

It’s also possible that in the clank you’re hearing is coming from your front differential mounts. I replaced both of mine in my 2007 in the driveway. Took me about 45 minutes.

 

[89Suburban]

Could also be the driveline slack going in and out with that type of mileage on it. Mine always clunks into 3rd gear if I am too light on the gas pedal.