Rear end or transmission?
Rear end or transmission?
Wondering if anyone knows what might be going on with my Q when I am on the highway cruising at 60mph and up and I press the pedal for full throttle it feels like I've been hit in the rear end when it downshifts to it lowest gear. The car takes off like a bat out of hell and it's always shocking the acceleration.. but all the other times downshifts are smooth and graceful.. this is new behavior, the "boom". Is it the torque converter, or a rear end issue? The shifts are all normal other times. I still have the rough rumble feel in the rear if the car getting on the highway that Infiniti said they couldn't feel or detect... But anyways, this slam boom hit of power can not be a good thing and I've never felt any vehicle downshift with such a violent thud. It truly feels like the car is a baseball and it's being hit with a bat and leaps forward. Once it reaches its top rpm shift point after the "boom" it shifts normal.. if I keep doing it trying to diagnose what I'm feeling, it gets more pronounced and aggressive, so I stop. Ideas? (Besides stop flooring it..) Merging onto I-26 on the mountain sometimes gives no other option...
Re: Rear end or transmission?
Strange one. Most recent time I've felt this was in a Jag with the ZF 6 speed transmission. Took that to the dealer and they reflashed something according to a TSB.
Otherwise, when my Qx4 was misfiring on one cylinder, it did feel like small thumps coming from the rear axle. You would have a light for such a terrible misfire though.
Otherwise, when my Qx4 was misfiring on one cylinder, it did feel like small thumps coming from the rear axle. You would have a light for such a terrible misfire though.
Re: Rear end or transmission?
It is strange, I don't have any lights on.. it doesn't do it on downshifts that I lightly press the pedal for a little speed increase, but when I floor it, it thuds so hard into gear and as soon as it "hits" it's pulling hard all the way up to shift. Almost like dropping it into drive while revving it up sitting at a red light, that same boom..of engagement
Re: Rear end or transmission?
Have your rear differential and rear sub frame mounts inspected-they are rubber and eventually fail by cracking or dry rotting.I had this exact same issue on my old 300zxturbo,sounded like someone was hitting the under side of the car with a rubber mallet when quickly going from steady state cruise to full throttle condition.
Re: Rear end or transmission?
Yes that's exactly how it feels.. hard for me to describe such a incident or behavior. Thank you for the input. I'll surely have it checked. It's so odd to me that the car always passes perfectly and has yet to need anything of moderate age/time/milage based wear items repaired or replaced. I should be thankful they don't have a list a mile long but I'm beginning to believe that they are looking the other way due to parts availability and or the lack of knowledge on the part of the younger stock of mechanics that don't want to get into or fool with such a unique beast. It's like a senior citizen monster lol.. I noticed on the lot at Infiniti that you'll be hard pressed to find a new model with as much or more than the 3rd gens horsepower.. you have to step up to high line sports models.. still a good deal my 05 was..