At the risk of getting flamed

[Big Ugly]

But I swear i did every permutation of a search that I could think of. sooo here's the deal

08 Silverado, 192000 miles. For some time now, If I put the gear shift in d and drive it at highway speeds and then slow down to stop, there is an intense shuddering of the truck... feels like its in the drive train. If I put it in 3rd gear and drive it, the symptom does not appear. I got a feeling this is a pretty common issue but I can't seem to find out anything on it...no codes

5.3 gasoline engine

 

[Black02Silverado]

But I swear i did every permutation of a search that I could think of. sooo here's the deal

08 Silverado, 192000 miles. For some time now, If I put the gear shift in d and drive it at highway speeds and then slow down to stop, there is an intense shuddering of the truck... feels like its in the drive train. If I put it in 3rd gear and drive it, the symptom does not appear. I got a feeling this is a pretty common issue but I can't seem to find out anything on it...no codes

5.3 gasoline engine

What all preventative maintenance have you done to it so far in that 192k miles? When was the last time the fluid and filter were changed?

 

[Big Ugly]

Oil changes regularly, top off when needed replace filters, change plugs and wires, clean throttle body, mas, but me and trannys have a long history...since I did a fluid and filter swap on an old 79 camaro... and the dang thing fell apart on me in a month... I just check tranny fluid for level (hot, in park, level surface) and condition...so far so good... think this may be my downfall? Otherwise, performs flawlessly...even got the oil burning licked.

 

[Black02Silverado]

Oil changes regularly, top off when needed replace filters, change plugs and wires, clean throttle body, mas, but me and trannys have a long history...since I did a fluid and filter swap on an old 79 camaro... and the dang thing fell apart on me in a month... I just check tranny fluid for level (hot, in park, level surface) and condition...so far so good... think this may be my downfall? Otherwise, performs flawlessly...even got the oil burning licked.

Yes, most forget about the transmission when it comes time for service. It is best to keep that fluid fresh just like any other fluid. On new vehicles keep it changed out every 50k miles with a quality synthetic and you will not have any issues for a long time. At least non that are fluid related.

 

[Black02Silverado]

Oil changes regularly, top off when needed replace filters, change plugs and wires, clean throttle body, mas, but me and trannys have a long history...since I did a fluid and filter swap on an old 79 camaro... and the dang thing fell apart on me in a month... I just check tranny fluid for level (hot, in park, level surface) and condition...so far so good... think this may be my downfall? Otherwise, performs flawlessly...even got the oil burning licked.

Yes, most forget about the transmission when it comes time for service. It is best to keep that fluid fresh just like any other fluid. On new vehicles keep it changed out every 50k miles with a quality synthetic and you will not have any issues for a long time. At least non that are fluid related.

 

[Bigredmariner]

Hard to say for sure, but crawl under the truck and shake the driveshaft. Look for looseness in the U-joints, check the yoke at the rear diff and see if you have any play with the pinion bearing. Is there any signs of fluid leakage anywhere under there, especially at the tailshaft of the trans and pinion seal of the rear diff.
If you have a 2 piece driveshaft, check the carrier bearing for wear too.

Doesn't necessarily sound like a transmission issue, more of a driveline/ rear end issue.

Just spit balling here but, when you're in a higher gear then go to coast (let off) the ring and pinion may be binding if the pinion bearings are going bad.
You may not see or feel it as bad when in a lower gear going to coast because the torque is changed quicker on the gear set. You'll have torque going ahead and at coast, kind of takes up the slack, if that makes any sense?

 

[OldCracker29]

Hard to say for sure, but crawl under the truck and shake the driveshaft. Look for looseness in the U-joints, check the yoke at the rear diff and see if you have any play with the pinion bearing. Is there any signs of fluid leakage anywhere under there, especially at the tailshaft of the trans and pinion seal of the rear diff.
If you have a 2 piece driveshaft, check the carrier bearing for wear too.

Doesn't necessarily sound like a transmission issue, more of a driveline/ rear end issue.

Just spit balling here but, when you're in a higher gear then go to coast (let off) the ring and pinion may be binding if the pinion bearings are going bad.
You may not see or feel it as bad when in a lower gear going to coast because the torque is changed quicker on the gear set. You'll have torque going ahead and at coast, kind of takes up the slack, if that makes any sense?

I'm with Jarrod on this one. I'm betting on it being the carrier bearing if you have a 2 piece shaft.

 

[Big Ugly]

I'm with Jarrod on this one. I'm betting on it being the carrier bearing if you have a 2 piece shaft.

Good thought, unfortunately, it's just the one piece shaft... I'll need to add the speeds at which this happens...may help...may not. Thanks for the thoughts so far.

 

[OldCracker29]

Good thought, unfortunately, it's just the one piece shaft... I'll need to add the speeds at which this happens...may help...may not. Thanks for the thoughts so far.

Does this truck have the AFM? If so, disable it and see if the problem goes away...just a thought.

 

[Big Ugly]

Does this truck have the AFM? If so, disable it and see if the problem goes away...just a thought.

Yeah, it has the AFM... I was leaning in that direction myself because putting it in third gear does two things...kills AFM and avoids Overdrive so downshifting isn't a problem (if there is a tranny issue) is there an easy way to turn it off without reprogramming?

so a little more detail...from highway speeds braking to a stop it seems to start shuddering at about 25 mph and the shuddering disappears at 15 mph and plays nice all the way to a stop. A deceleration without braking on a level road renders similar results. No shuddering on leaving a stop. No shuddering on acceleration. smooth operation at highway speeds and no vibrations felt up to 80mph. No shuddering beyond that speed either.