Rough 1-2 shift when accelerating hard

[Danneman]

Hey y’all. 99 Yukon, 4WD, 5.7L, transmission code M30. Butter-smooth shifts up and down all gears under all conditions except 1-to-2 when “accelerating in spirited fashion,” is otherwise perfectly fine when driving grandfatherly (good luck doing so in Chicago area without getting shot). What I experience is a very slight delay (very - probably half a second, if that) and then an unpleasant “jerk” as the shift is made.

Recently changed fluid and new filter, fluid was pretty dirty I’m told. Likely suspects? Sticky solenoid?

Many thanks for any thoughts! -DW

 

[Livewire]

Made an account to chime in that I also have the same issue with my 95 Yukon 4WD 5.7L. Unless I'm accelerating like a turtle, it'll do the same thing as said above from 1 to 2. Also jerks from Park to Reverse most of the time, some times it's not as rough but when it is, there's a clunk sound. Has no problem with Park to Drive and the other gears while driving

 

[Gordo1728]

On occasion a trans fluid/filter service can do more harm than good. Double check fluid levels. If the condition continues or worsens you could attempt a trans flush, but it's a 50/50 chance of either improvement or getting worse. Any codes in the transmission control module?

And as for Livewire, as far as the clunk/jerk when shifting into reverse, check your u-joints. When my u joints failed it would clunk shifting into reverse, and again when going into drive.

 

[Danneman]

On occasion a trans fluid/filter service can do more harm than good. Double check fluid levels. If the condition continues or worsens you could attempt a trans flush, but it's a 50/50 chance of either improvement or getting worse. Any codes in the transmission control module?

And as for Livewire, as far as the clunk/jerk when shifting into reverse, check your u-joints. When my u joints failed it would clunk shifting into reverse, and again when going into drive.

Interesting, I wouldn't have thought that. But the problem was present before and after the fluid/filter change, with no detectible difference...fluid levels are fine, and no codes.

X2 on the u-joints.

 

[willxfs]

Could be the TCC regulator valve. Sonnax makes an upgraded part for this. Not sure how difficult the job is. My transmission started doing the harsh 1-2 upshift after 220K miles (only when the fluid got real hot, after towing anything for 20 miles or long highway travel). I ended up getting a rebuilt transmission about 4 years ago but wish I knew about the tcc valve by sonnax at the time and tried that first. There's alot of info out there if you google harsh 1-2 upshift and 4L60E. Good luck.

 

[ccapehartusarmyINF.(ret)]

l

On occasion a trans fluid/filter service can do more harm than good. Double check fluid levels. If the condition continues or worsens you could attempt a trans flush, but it's a 50/50 chance of either improvement or getting worse. Any codes in the transmission control module?

And as for Livewire, as far as the clunk/jerk when shifting into reverse, check your u-joints. When my u joints failed it would clunk shifting into reverse, and again when going into drive.

i did a tranny flush on my 2002 tahoe and mine went from a slight problem to catastrophic
my 3-4 clutch packs were pretty warn i guess and the flush just tipped them right over the edge
i lost 4th the same day and shortly after no more 3rd gear

 

[Gordo1728]

l


i did a tranny flush on my 2002 tahoe and mine went from a slight problem to catastrophic
my 3-4 clutch packs were pretty warn i guess and the flush just tipped them right over the edge
i lost 4th the same day and shortly after no more 3rd gear

As I said, a flush can make it better or worse. Had a P1811 (last 2 digits of code may not be right) on a Pontiac Aztec, delayed/hard shift between 1-2 shifts. Flushed around 25 quarts through over a year ago and customer is still driving with no issues. However we attempted on another GM application, grand Prix I believe, same code same condition, trans failed on the test drive.

It's more of a last resort before coming to the conclusion that there is an internal issue and replacing or rebuilding the unit.

As for solenoids, it's almost the same deal, it could help, but it might not. The issue could be worn out clutches.