Another loud clunk thread

2020 Tundra. Really specific situation. Makes a loud clunk/bang sound and jolts the truck a bit only when I am approaching a stop going up hill without pressing anything (brake or gas) while I am leading up to the stop. So basically I’ll accelerate, coast up the hill a bit not pressing anything, start to press the brake and BANG. Had a load in the other day and it was pretty significant. Unloaded lower scale sound. Obviously I am trying not to do this going forward but any idea what this could be? It’s coming from behind me for sure. I read that it could be the slip yolk, but I don’t really know how any of that works to be honest and I know there are no zerks to grease it on the 2020. Just wondering if anyone else has experienced this.

 

Side note: I did drain and fill my tranny a few months back but it runs and shifts just fine so i cant see it being that right?

 

Maybe a long shot but possibly check your carrier bearing? There might be a a little play in there when the driveshaft in unloaded. I agree that it's likely not the transmission, that doesn't make sense to have a hard shift when there's no power being applied.

 

Thanks. I’ll take a look and see.

 

I retorqued the carrier bearing, wasn’t loose. Gave it a little wiggle too and all good.

 

Did you ever figure out your issue?

 

Negative. Just avoiding triggering it for now.

 

im getting the same symptoms as you, do you get the clunk noise when reversing and then shifting to drive?

Ive read online that the issue could be the tire size? what size tires are you on? I'm on 35/12.5R17

 

No. Only when coasting uphill to a stop. It’s fine going reverse to drive. Just normal shifting sound. I do have larger tires on it but 275/70/18 which is a little less than 34, so nothing that big. I’ve been researching as well, most say it’s just a normal thing that happens in my situation. Not sure about yours specifically.

 

Sounds as if it might be the transmission downshifting since it is triggered by your applying brakes while decellerating. Also, re-check the transmission fluid level to be sure it is correct.

 

I did just the other day just to make sure. Added an about a quart I had left over and drained off about 3/4 of that quart. I also put the check plug back in when the stream started to waiver a bit as opposed to a trickle. Can’t image 1/4 of a quart would cause that but ynever know.

 

I think you are likely correct about the addition of 1/4 of a quart not being the issue.

I've observed in my truck that if I drive for long periods in stop and go traffic after the engine and transmission have been fully warmed up for a long period, that downshifts to first at slow speeds when coming to a stop can be abrupt and not always smooth. In asking the dealer about this, I was given the usual "that is normal for this transmission" answer that service reps like to say, but I think they are correct since my transmission has been totally reliable in the many miles since I first observed this. I don't know how abrupt your downshift is, so naturally you will have to make the assessment about whether your situation is 'normal' or something more serious.

 

Yeah agreed. It’s always been a bit of a clunky transmission at slow speeds, but the loud bang and truck jumping forward was definitely not normal. I feel like it’s happened before too a few years back and I just made sure to not repeat the circumstances that caused it. I’m not too worried about it really, just wanted to see if anyone else has experienced something similar.