tech2

is the vibration gone if you decel in neutral

yukonxl78666

So, 3 things. 1) unbeknownst to me the front struts were lifted by over 1/2 inch causing a drive shaft angle issue. i removed spacers. 2) turns out that 1 ujoint was worn + 3) motor mounts needed replacing. Fixed all 3 and my sub 20mph vibration is gone. I think the motor mount replacement made the biggest difference. Hope this helps.

Suburban2007

my 07 suburban Z71 does the same thing around 25-20mph. I've had the transmission and rear end rebuilt in the past year but this only started happening in the past few months. the thing I've noticed is when the vibration occurs, the eco mode is in v4 mode but whenever I use tow/haul mode it will still switch the v4 but just before it hits 25-20 mph it switches to v8 and no vibration. it also doesn't do it when I manually down shifts.

07 T-Ho

Upon deceleration, the engine goes from 8 cylinder mode down to 4 cylinder mode. If you have a broken motor mount that's most likely what's causing the vibration. If your motor mounts are fresh then there's something else out of alignment or more so out of balance. Harmonic balancer, flexplate, torque converter. I bought a gadget on Amazon, it costs about $200. It allows the engine to operate on all 8 cylinders all the time. MPG suffers a bit but, no vibration when I decelerate.

Oldirongut

Transmission Shudder

firemedic0822

I am having the same issue. About 10k miles ago I replaced the motor because my lifters went. I had the same shudder before the engine swap. 25-20 decelerating. Recently my transmission started slipping really bad on the highway in 4th gear. I got a new transmission and put it in today. On the way home from my friends shop it was fine but the trans temp got up to 210. Prior to the new motor I’d never see temps like that, even pulling my 5000lb boat at 85mph the highest temps I’d see was 203. I got the truck home and went to the grocery store and the shudder came back. So now the shudder is still there and the trans temp got to 210 degrees. I’m beyond frustrated. The truck is a stock Z71 2 wheel drive. Any suggestions.

Lynnb

I joined the forum just for this situation. My son's 2007 Suburban (2WD - 1500, with 5.3 and 250k miles) is having this same issue.
I drove it last night. Shudder from the transmission when decelerating. Normally happens between 25 and 20 mph. I slowed down going up a hill WITHOUT applying the brakes. Still did it. That eliminates any brake issue.

I then put it in neutral while slowing down, again, going up a hill. No shudder. That tells me it IS a transmission issue.

My first guess was the lock up clutch in the torque converter wasn't disengaging smoothly. Digging a bit further, I took it for a drive at highway speeds. The TC is NOT locking up as it should. This could be as simple as a transmission service and replacing the solenoid. Although I did not experience it, my son says it also downshifts VERY HARD sometimes when he is passing at highway speeds. So... I believe i will replace BOTH the TC lock up solenoid and the downshift solenoid when we service the transmission.

Will report back. BTW, his trans temp never got over 160, so I don't believe it is temp related.

mountainmanjoe

that doesn't necessarily indicate a transmission issue. It just means there was no torque on the driveline.
You need to look at all the possibilities mentioned in this thread.

hanky

I have to agree with mountainmanjoe, because a few critical items can get overlooked and we come to a faulty conclusion.

If we just looked at a driveshaft coasting under no load ,(torque) , it can look good and as soon as we apply some load to it, it can start whipping around and that s what is happening when we move to neutral we remove the load..

Lynnb

This is such a specific speed (25-20) and only under decelaration (with and without brakes), experienced by multiple folks.
First post indicates that it doesn't shudder when manually downshifted. That means the driveshaft will still be slightly "loaded", but the shudder goes away. "The vehicle does not do this when accelerating nor does it do it if I manually drop it into any other gear other than Drive, and also does not do this if I have the Tow/Haul option engaged."

Also, two posters have indicated that putting in "tow" mode makes it go away. Just sent my son a text telling him to put it in tow mode next time he drives, and see if it goes away.

Don't get me wrong; I will still look at motor mounts and check the u-joints for wear, as I don't want to leave any stone unturned.
I find it odd that this is a somewhat recurring problem (maybe not on a huge scale) and that this thread has been around since 2019 with no definitive solution.