Accel/Decel Feel?
Thread Starter
Pro
Joined: Sep 2016
Posts: 720
Likes: 205
From: Michigan
Accel/Decel Feel?
Hi All,
Now that I'm getting my '69 Coupe running better with its matching #'s 350/300 engine, I'm getting more of a chance to drive it, and push it a bit.
I'm starting to perceive something when I shift through the gears aggressively, either upwards or downwards.
Not sure if this is normal or not, or something specific to Posi-Traction rear ends.
When I shift up hard or down shift aggressively, I'm getting a sideways slight "hip shift" from the rear end. Almost feels like torque steer, but in the rear wheels.
Feels like one side is engaging slightly before the other.
Doesn't happen on "tame" shifts, but more on pushing the car hard up the gears.
Do I have something slipping in the rear diff? Or is this typical for Posi's?
Thanks,
Now that I'm getting my '69 Coupe running better with its matching #'s 350/300 engine, I'm getting more of a chance to drive it, and push it a bit.
I'm starting to perceive something when I shift through the gears aggressively, either upwards or downwards.
Not sure if this is normal or not, or something specific to Posi-Traction rear ends.
When I shift up hard or down shift aggressively, I'm getting a sideways slight "hip shift" from the rear end. Almost feels like torque steer, but in the rear wheels.
Feels like one side is engaging slightly before the other.
Doesn't happen on "tame" shifts, but more on pushing the car hard up the gears.
Do I have something slipping in the rear diff? Or is this typical for Posi's?
Thanks,
Last edited by Bergerboy; Oct 17, 2016 at 10:19 AM.
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
You probably have something moving in the suspension under higher torque loading. A limited slip (positraction) axle will not steer the car. A locker or spool will steer the car from the axle under unequal tire rotational speeds, like one tire has lower air pressure than the other, but a limited slip will "slip" an axle to allow the differential to accommodate differences in axle rotation. Also, a malfunctioning limited slip would exhibit the steering characteristics you describe at all speeds and loads.
Thread Starter
Pro
Joined: Sep 2016
Posts: 720
Likes: 205
From: Michigan
Thanks Gerry,
Yeah - the "slip" is more like a slight sideways hop or twist feel when the clutch gets popped with any aggression at all. Also has occurred in similar downshifts when the reverse torque gets applied to the rear wheels.
Like I said, something akin to FWD torque steer felt from the front end, but now coming from the rear end.
Sometimes accompanied by a knock or a pop sound.
I don't feel it during normal, more tame shifts - just when leaning into it somewhat.
Yeah - the "slip" is more like a slight sideways hop or twist feel when the clutch gets popped with any aggression at all. Also has occurred in similar downshifts when the reverse torque gets applied to the rear wheels.
Like I said, something akin to FWD torque steer felt from the front end, but now coming from the rear end.
Sometimes accompanied by a knock or a pop sound.
I don't feel it during normal, more tame shifts - just when leaning into it somewhat.
Le Mans Master
Joined: Aug 2006
Posts: 7,419
Likes: 1,554
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Take a close look at the front trailing arm bushings, the condition you describe indicates the bushings are worn out.
where I would start as well.
