Shudder at 20mph on deceleration.

[Writefast]

So this is my next repair. I have a subtle but distinct shudder on decel. It’s most noticeable at 20 mph, may start being noticeable earlier at around 25 but it really ramps from 23-22 down to 20. It gets increasingly less noticeable down to about 13 mph then it’s imperceptible if it’s there. Happens with brakes and coasting. I don’t feel it in the steering. Don’t feel it in the pedal. I just “feel” it. SOTP maybe? It’s less noticeable when I manual it to 3rd and decel but it’s still there. Haven’t been able to test 2nd or first yet. The way it comes on and dissipates fees like a sympathetic vibration. Motor mounts? Never had a mount fail so no clue what that feels like. Ideas?

 

[Dustin Jackson]

Bad motor mounts would certainly make whatever is happening more noticeable. One way to check motor mounts is to gun the throttle really good from a stop and if you notice a thud or clunk that is probably your motor twisting under the hood because the motor mount has work and the engine is able to move around. Another way you can check is pop the hood and put the Yukon in drive, hold down the brake while you give it a good amount of throttle and you should be able to see the motor jump around if the mount is bad.

Another thing to check is is AFM is engaging or disengaging causing shuttering, you can to this by monitoring the V8 and V4 indicators on the MPG display.

Lastly, if the plugs and wires haven't been done in a while a weak spark would cause similar symptoms but I think the problem would be more pronounced over 45mph when the TC has locked up.

 

[Marky Dissod]

It’s less noticeable when I manual it to 3rd and decel but it’s still there. Haven’t been able to test 2nd or first yet.

V4mode should not be available in 3rd 2nd or 1st - but check anyway.
Next time you are decelerating from 30MpH, move the shifter into neutral.
If the shudder is not there in neutral, change your ATF and ATF filter with Dex6.
@NickTransmissions

 

[NickTransmissions]

So this is my next repair. I have a subtle but distinct shudder on decel. It’s most noticeable at 20 mph, may start being noticeable earlier at around 25 but it really ramps from 23-22 down to 20. It gets increasingly less noticeable down to about 13 mph then it’s imperceptible if it’s there. Happens with brakes and coasting. I don’t feel it in the steering. Don’t feel it in the pedal. I just “feel” it. SOTP maybe? It’s less noticeable when I manual it to 3rd and decel but it’s still there. Haven’t been able to test 2nd or first yet. The way it comes on and dissipates fees like a sympathetic vibration. Motor mounts? Never had a mount fail so no clue what that feels like. Ideas?

Let's start with what year, engine and transmission your Tahoe or Yukon has, how long this has been happening, what (if any) significant service work was done recently (what was done, when) - provide those details and we can respond based on that new info...

 

[mountie]

I had a similar 'shudder' from my 700r4 ( '88 GMC truck)...... It was a bad lock up in the ( torque converter ) Maybe , Nick Transmissions will chime in ??

I don't have any knowledge of the differences of converters from then, and newer.

 

[Dustin Jackson]

His signature says 07 and he said he puts it into “3” so guessing 4l60e

 

[NickTransmissions]

His signature says 07 and he said he puts it into “3” so guessing 4l60e

Thanks, Dustin - sig doesnt show up when holding my phone vertically and wasnt exactly sure how to interpret "manual it into "3", lol...

Id agree, converter is likely going bad...He can confirm with a bi directional scam tool with trans and tc data streams displayed while driving. Any converter slip speed outside of reference ranges would verify a bad TCC...