hello,
I have an Infiniti M35 RWD with an automatic 5-speed transmission that I enjoy driving in manual mode. I notice that sometimes when I am accelerating hard, like going onto the highway, I can get a hard knock from the rear of the vehicle when shifting from 2nd and 3rd, when especially hard, dynamics may indicate a skid has occurred (though I don’t feel it). I have never noticed this one way or another without dynamics since it’s always on unless I get stuck in the snow or something.
I am pretty sure this is something I’m doing to cause this, and not a fault of the transmission, and it happens less now than when I was first driving it in manual, I feel that I’m doing something to prevent it, but I am not sure what exactly.
Why does this happen, and what do I need to be aware of to deliberately prevent this from happening? I can’t really imagine it’s good for the car.
I don’t think manual shifting caused
the problem. I too often accelerate hard, in automatic mode, on on ramps since, where I live, the ‘slow lane’ is about 80 MPH.
You might have either a universal joint beginning to fail or a problem with the pinion/ring gear backlash. Though I would think this would be noticeable when going from drive to reverse. Not just on a 2-3 up shift.
But I will defer to other respondents.
How could you possibly be doing this? It is an automatic transmission that allows you a manual shift. The car was built to withstand full throttle upshifts. There is software controlling the transmission that won’t allow you to do dumb things like down shift when the engine would over-rev. There is really nothing you can or are doing to change how it shifts.
Doesn’t mean something is not wrong… but that is up to you to find! It isn’t clear from your post… is it gone now? Or just less? I’d get the rear of the ground - on safe jackstands - and check for excessive play in the half-shafts, backlash in the differential, looseness in the driveshaft, things like that. You don’t say how many miles on the car or even the year so it is tough to pinpoint anything special to check.
f your vehicle has a hard time shifting gears, jerks when shifting, or otherwise shifts in ways you don’t expect it could indicate something is either wearing out or starting to fail. In today’s computer controlled transmissions, an erratic shift could be due to a bad sensor or shift solenoid. These types of problems can often be checked using a transmission or factory scan tool that can check pressures and solenoid operation when it’s plugged into your car. Shifting can also be affected by line pressures that are affected by low fluid level, dirty fluid, a clog or the transmission pump going bad. Lastly, erratic shifting can be caused simply by worn parts usually causing over revving or loose shifting.
+1
However, it would help all of us to come up with good guesses if we knew the model year and odometer mileage of this vehicle, as well as the maintenance record for its transmission and its differential.