I've got this random driveline thud. Labor Day weekend I replaced my rear U-Joint and diff fluid with Synthetic 75W-90 and a Friction Modifier. Anyways, in the last few weeks I've had this weird downshift thud, it's only happened twice, and once when turning the engine over.
Both times it happened when moving, I was slowing for a light, and to make my street. The thud sounded like it was directly under my knees. A little in front of the pedals. I'm wondering if it might be the front driveshaft, or it's U-Joint, which I didn't replace. It's a pretty harsh thud. Another possibly related issue, the truck jerks on downshift deceleration, it almost feels like the downhill jerk in cruise before the last software update. It pushes the truck and I have to apply a bit extra brake pressure. I'm stumped. Everything looks fine, the truck runs the gears just fine, it starts fine in the morning and does my daily commute issue free.
Both times it happened when moving, I was slowing for a light, and to make my street. The thud sounded like it was directly under my knees. A little in front of the pedals. I'm wondering if it might be the front driveshaft, or it's U-Joint, which I didn't replace. It's a pretty harsh thud. Another possibly related issue, the truck jerks on downshift deceleration, it almost feels like the downhill jerk in cruise before the last software update. It pushes the truck and I have to apply a bit extra brake pressure. I'm stumped. Everything looks fine, the truck runs the gears just fine, it starts fine in the morning and does my daily commute issue free.