Vibration at 4k RPM

Talk and Tech about turbocharged 924/944/968 cars
Post Reply
User avatar
Spencan
Posts: 141
Joined: Tue Jan 25, 2022 11:05 am
Location: Gilroy, Ca
Has thanked: 118 times
Been thanked: 27 times
This past month, I have all of a sudden started to have a vibration that I can really feel at 4k rpm. It seems to peak at that point. I can go past that point and it seems to lessen. The car feels normal all the way up to 3600 or so and then progressively vibrates more the closer I get to 4k.

Balance shafts or something else?

TIA
'89 Turbo S-Glacier Metallic Mods: Evergreen Turbo-"Raptor" stage II, Bell custom intercooler, FTech 9 DME & OBD+, Tial 38 Wastegate, GFB EBC, A-Tune, 3" Turbo Back Exhaust, Cross-Drilled rotors, refreshed suspension

#1

Top
User avatar
Tom
Site Admin
Posts: 8548
Joined: Fri Jun 25, 2021 2:04 pm
Location: Silicon Valley, CA
Has thanked: 888 times
Been thanked: 3826 times
Contact:
Contact Tom
Spencan wrote: Thu Feb 19, 2026 8:24 pm This past month, I have all of a sudden started to have a vibration that I can really feel at 4k rpm. It seems to peak at that point. I can go past that point and it seems to lessen. The car feels normal all the way up to 3600 or so and then progressively vibrates more the closer I get to 4k.

Balance shafts or something else?

TIA
Where is the vibration -- steering wheel, engine, chassis?

#2

Top
User avatar
Spencan
Posts: 141
Joined: Tue Jan 25, 2022 11:05 am
Location: Gilroy, Ca
Has thanked: 118 times
Been thanked: 27 times
Engine/shift knob/steering wheel
'89 Turbo S-Glacier Metallic Mods: Evergreen Turbo-"Raptor" stage II, Bell custom intercooler, FTech 9 DME & OBD+, Tial 38 Wastegate, GFB EBC, A-Tune, 3" Turbo Back Exhaust, Cross-Drilled rotors, refreshed suspension

#3

Top
barnwerks
Posts: 89
Joined: Sun Mar 10, 2024 7:21 am
Has thanked: 1 time
Been thanked: 34 times
That is the rpm range where balance shaft timing issues typically show up. Also, look for differences in mode with the clutch engaged and dis-engaged.

#4

Top
User avatar
Spencan
Posts: 141
Joined: Tue Jan 25, 2022 11:05 am
Location: Gilroy, Ca
Has thanked: 118 times
Been thanked: 27 times
No vibration when the clutch is not engaged. It only happens while driving in-gear.
Last edited by Spencan on Fri Feb 20, 2026 7:03 pm, edited 2 times in total.
'89 Turbo S-Glacier Metallic Mods: Evergreen Turbo-"Raptor" stage II, Bell custom intercooler, FTech 9 DME & OBD+, Tial 38 Wastegate, GFB EBC, A-Tune, 3" Turbo Back Exhaust, Cross-Drilled rotors, refreshed suspension

#5

Top
AudiSport
Posts: 177
Joined: Sun Jul 11, 2021 12:03 pm
Has thanked: 5 times
Been thanked: 59 times
So no vibration sitting still? Only when rolling?

#6

Top
User avatar
Spencan
Posts: 141
Joined: Tue Jan 25, 2022 11:05 am
Location: Gilroy, Ca
Has thanked: 118 times
Been thanked: 27 times
Sorry for the confusion. I edited my post: vibrating only when in gear.
'89 Turbo S-Glacier Metallic Mods: Evergreen Turbo-"Raptor" stage II, Bell custom intercooler, FTech 9 DME & OBD+, Tial 38 Wastegate, GFB EBC, A-Tune, 3" Turbo Back Exhaust, Cross-Drilled rotors, refreshed suspension

#7

Top
User avatar
johnb
Posts: 313
Joined: Thu Jul 08, 2021 5:57 am
Has thanked: 108 times
Been thanked: 74 times
If it only happens in gear, and it depends on the rpm and not road speed, then it has to be something in the torque tube, right? If it was the engine it would happen in neutral. If it was something in the wheels or tires it would depend on road speed. Still it's odd that you'd feel it through the steering wheel. That should be pretty well isolated from everything else.

Maybe it's the engine but it only happens under load. Can you tell if it's affected by load? If you accelerate past 4k and then lift and let it coast in gear, does it happen again on the way down?

#8

Top
User avatar
Tom
Site Admin
Posts: 8548
Joined: Fri Jun 25, 2021 2:04 pm
Location: Silicon Valley, CA
Has thanked: 888 times
Been thanked: 3826 times
Contact:
Contact Tom
Spencan wrote: Fri Feb 20, 2026 7:04 pm Sorry for the confusion. I edited my post: vibrating only when in gear.
So you can rev it to 4k in the driveway and it does not vibrate? How about in neutral, at 4k, but without touching the clutch pedal? If it vibrates doing that, does it stop when you push the clutch pedal down?

#9

Top
User avatar
Spencan
Posts: 141
Joined: Tue Jan 25, 2022 11:05 am
Location: Gilroy, Ca
Has thanked: 118 times
Been thanked: 27 times
I was wrong. It’s vibrating when in neutral too, just not as much/bad as when driving
'89 Turbo S-Glacier Metallic Mods: Evergreen Turbo-"Raptor" stage II, Bell custom intercooler, FTech 9 DME & OBD+, Tial 38 Wastegate, GFB EBC, A-Tune, 3" Turbo Back Exhaust, Cross-Drilled rotors, refreshed suspension

#10

Top
Post Reply