High speed vibration, need help
07-04-2017, 11:10 AM
#1
High speed vibration, need help Hello,
I am getting a speed related vibration. Does it in 4,5 and 6th gears. It's vibrating the floor/seat and is very high frequency vibration. Seems like it's coming from the rear. Gets worse as I go faster.
A little background.
LS1/T56 swapped into an RX7 which uses a "fixed" diff so angles shouldn't really change when under load.
New trans and motor mounts.
New Driveshaft shop driveshaft, which was rebalanced once since this issue started, that didn't help at all. And new U-joints
Different tires, rotated wheels front to back, no changes
Played with angles, I have an accurate digital angle finder on the way to double check them though. Currently looks like 1.5 at both trans and pinion with a 4 degree drive shaft angle. So should be good.
In addition to the angle part, I have moved the tail shaft up and down about an inch or so and it makes no impact to this issue.
Very slight leak at tailshaft but I get no play in the yoke/tailshaft connection, at least none that I can feel.
No play at pinion.
Have ran it on a lift, still get the vibration, if I remove the driveshaft there is no vibration.
The biggest catch is the vibration goes away if I push the clutch in. But the vibration doesn't occur in 3rd gear at 6800 rpms and will in any higher gear.
Plus it's not the 5/6th gear issues since it does it in 4th.
Speeds are 100+ for this to occur, I track the car and expect close to 160mph which I can't even attempt at this point. I figure the higher speeds are just showing an issue that might not be as bad yet as one to appear at a lower speed but not sure. This happens right around 100mph regardless of being in 4,5, or 6th.
It will do it as long as I am in gear, so in accel, decel, or maintaining speed, clutch in makes it disappear immediately.
Any ideas?
I am getting a speed related vibration. Does it in 4,5 and 6th gears. It's vibrating the floor/seat and is very high frequency vibration. Seems like it's coming from the rear. Gets worse as I go faster.
A little background.
LS1/T56 swapped into an RX7 which uses a "fixed" diff so angles shouldn't really change when under load.
New trans and motor mounts.
New Driveshaft shop driveshaft, which was rebalanced once since this issue started, that didn't help at all. And new U-joints
Different tires, rotated wheels front to back, no changes
Played with angles, I have an accurate digital angle finder on the way to double check them though. Currently looks like 1.5 at both trans and pinion with a 4 degree drive shaft angle. So should be good.
In addition to the angle part, I have moved the tail shaft up and down about an inch or so and it makes no impact to this issue.
Very slight leak at tailshaft but I get no play in the yoke/tailshaft connection, at least none that I can feel.
No play at pinion.
Have ran it on a lift, still get the vibration, if I remove the driveshaft there is no vibration.
The biggest catch is the vibration goes away if I push the clutch in. But the vibration doesn't occur in 3rd gear at 6800 rpms and will in any higher gear.
Plus it's not the 5/6th gear issues since it does it in 4th.
Speeds are 100+ for this to occur, I track the car and expect close to 160mph which I can't even attempt at this point. I figure the higher speeds are just showing an issue that might not be as bad yet as one to appear at a lower speed but not sure. This happens right around 100mph regardless of being in 4,5, or 6th.
It will do it as long as I am in gear, so in accel, decel, or maintaining speed, clutch in makes it disappear immediately.
Any ideas?
07-04-2017, 08:15 PM
#2
I chased a high speed vibration just like this last year up until this spring. I thought I was getting a vibration in 4th still so bought another custom driveshaft first. Ended up being the loose 5/6 gear. As easy as it is to pull the t56 tail housing off and check for this, I would advise doing so.