Vibration on deceleration between 40-30 mph. 2006 2WD 4.0 Double Cab

So I had the 3-4th gear shudder around 30-40mph when accelerating. So I searched everything I could in this forum and ended up doing a full transmission flush, filter change, trans gasket replaced, turning the SLU solenoid 1/4 turn clockwise to increase pressure, added 12 oz of lubeguard ATF protectant, and 2 oz of instant shudder fix. I no longer have any shuddering when upshifting, but now my truck seems to have developed a vibration/shudder on deceleration. I feel dumb but I cannot 100% remember if it was doing that before all of that, but I've driven it about 2k miles since then now. Any advice? Is this related to increasing the SLU solenoid pressure?

Key note: It does not matter if the torque converter is involved or not, as it does this on deceleration in 4 or D (overdrive). It also happens when coasting, brakes being applied doesn't seem to be the cause. It also is like clockwork that it will happen every time I decelerate once I'm over 30 mph whether I'm braking or coasting down in speed, the severity randomly varies though, it might be worse after driving for longer periods of time? Haven't had a ton of time to test it over and over. Giving it gas during 40-30 seems to help as it fades if I start to accelerate again.

Not sure if this matters, but there was 0 suspect shavings or anything when I dropped the trans pan, cleaned the magnets etc. Just kind of a dusting of smudge on the magnets, very fine powder like residue that I assume is totally normal.

2006 2WD 4.0L Double Cab 130k miles.

 

Have you checked your U-Joints and carrier bearing?

 

@Dm93 I have not, I had read on a lot of posts on here that the only way to properly check all of that was to have it removed and that you can't really check without doing so? I know I looked at all 3 U-Joints as I was planning to grease all 3 of them, but only the last one closest to the rear differential had a Zerk fitting that I greased, which did not seem to change the issue, the other 2 forward U-Joints were sealed with no Zerk. Is there any way to test without taking the whole drivetrain off?

 

Other than looking for obvious rust around them or play in them no, typically a bad U-Joint will cause a constant vibration or a shimmy on acceleration but I was trying to rule them out.

 

with the truck on flat ground and able to move easy, ie no tension on the driveline. get under it and try to wiggle the end of the shafts to see if you can see extra movement in the ujoints. this is the easy way to check. center joint you can just reach up and grab to see.

 

My guess is U joints or carrier bearing. That’s a 17 year old truck. Have they ever been replaced?

 

@paranoid56 I will try that, thank you. @Sharpish I was able to find on the CarFax report (I have only owned since 5/2022) that the U-Joint(s) were replaced 04/13/2017 at 97,795 (currently 130k). I am emailing Midas who performed the service to see if I can get a detailed invoice to find out how old 1 or all of the U-Joints are. I cannot find a record specifying the Carrier bearing was ever replaced. I also found with Toyota that the rear leaf springs were replaced in 4/2017 at 98,181 miles. Hoping to get to the bottom of this!