Hey guys a have a 1997 Gt with a Automatic trans. I’m having a issue with a bad vibration at high rpms and It goes away as it shifts and feels like it’s coming from the rear and I also get a bad vibration at higher speeds anything over 55 really then after 80 it goes away. Any ideas would be great thanks a lot
Vibration at high rpms from rear of car and high speed
- Thread starter Justasn95
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08GT500
5 Year Member
Hi, Sorry to hear about your issue.
This is both RPM dependent and also occurs at 55-80MPH, changes when shifting upwards? Does it occur if left in L2 driving at Variable RPM’s, speeds? Any Change when Car is turning left or right, or any shudder when shifting? The car running a tune to change shift points, firmness?
Any Check engine lights? Try pulling codes anyway. May still be DTC’s present without a CEL.
May/may not be Transmission related...i’ll Try the most common issues, leaving the Trans out for now..
Did this occur/worsen with time, or begin one day- suddenly? Any recent mod? Lowered?. Starting simple........
A) In neutral or park, at different RPM’s, can you feel a vibration through the steering wheel, at different RPM’s.. then-
B) If driving and you’re at the RPM where vibration occurs, shift to Neutral & see if vibration persists.
1) Tire(s) balanced, alignment done. Inspect the tires for bubbles, any cracking, belt breakage, missing weights, rim(s) dented, etc.
2) The driveshaft is balanced, weight plates welded on, verify presence (should be visible).Line marking correct position on the rear end flange should exist. Moving the assembly 90 degrees & rebolting May help imbalance.
3) Poly Trans, Motor/other aftermarket bushings may cause vibrations versus stock rubber types. Verify no Trans mount or motor mounts are broken, rubber separates, insert
Crowbar & pry slightly.
4) Worn front or rust infiltrated driveshaft universals will vibrate.Inspect. Axle on jack, rotate back/fro while looking/listening for excessive/audible play.(in Neutral).Chock Frt.Tires for safety. Pull Calipers if any movement exists & check for axle play in/out; runout. Safety issue.
5) Pinion angle needs to be about 1/2”, or around 2.5-3” across ‘Stang’s driveshaft length, front to rear. Car lowered, Suspension modified?
6) E-Brake cable a bit tight, hanging up slightly, tight Caliper(s), Check
rotor(s) for end play, function. Bleed if needed.
7) Any Trans Oil leaks, Trans/output driveshaft seal, Trans fluid /filter serviced recently?
8)Minor Flexplate crack, when the vibration occurs, is it under load, or driving at sustained speed, RPM?
- Any Mods made to the Car recently, or around the time you may have done before/when you first noticed the issue?
Good luck checking it out, if it’s a Trans issue, it likely won’t be one of the above. These Trannys can take a pretty good beating & survive. If it needs to be rebuilt, or just has a simple issue, I’ve known of a few that had bent mainshafts with the described symptoms, but don’t worry that deep at the moment, the few questions answered will help.
- John
This is both RPM dependent and also occurs at 55-80MPH, changes when shifting upwards? Does it occur if left in L2 driving at Variable RPM’s, speeds? Any Change when Car is turning left or right, or any shudder when shifting? The car running a tune to change shift points, firmness?
Any Check engine lights? Try pulling codes anyway. May still be DTC’s present without a CEL.
May/may not be Transmission related...i’ll Try the most common issues, leaving the Trans out for now..
Did this occur/worsen with time, or begin one day- suddenly? Any recent mod? Lowered?. Starting simple........
A) In neutral or park, at different RPM’s, can you feel a vibration through the steering wheel, at different RPM’s.. then-
B) If driving and you’re at the RPM where vibration occurs, shift to Neutral & see if vibration persists.
1) Tire(s) balanced, alignment done. Inspect the tires for bubbles, any cracking, belt breakage, missing weights, rim(s) dented, etc.
2) The driveshaft is balanced, weight plates welded on, verify presence (should be visible).Line marking correct position on the rear end flange should exist. Moving the assembly 90 degrees & rebolting May help imbalance.
3) Poly Trans, Motor/other aftermarket bushings may cause vibrations versus stock rubber types. Verify no Trans mount or motor mounts are broken, rubber separates, insert
Crowbar & pry slightly.
4) Worn front or rust infiltrated driveshaft universals will vibrate.Inspect. Axle on jack, rotate back/fro while looking/listening for excessive/audible play.(in Neutral).Chock Frt.Tires for safety. Pull Calipers if any movement exists & check for axle play in/out; runout. Safety issue.
5) Pinion angle needs to be about 1/2”, or around 2.5-3” across ‘Stang’s driveshaft length, front to rear. Car lowered, Suspension modified?
6) E-Brake cable a bit tight, hanging up slightly, tight Caliper(s), Check
rotor(s) for end play, function. Bleed if needed.
7) Any Trans Oil leaks, Trans/output driveshaft seal, Trans fluid /filter serviced recently?
8)Minor Flexplate crack, when the vibration occurs, is it under load, or driving at sustained speed, RPM?
- Any Mods made to the Car recently, or around the time you may have done before/when you first noticed the issue?
Good luck checking it out, if it’s a Trans issue, it likely won’t be one of the above. These Trannys can take a pretty good beating & survive. If it needs to be rebuilt, or just has a simple issue, I’ve known of a few that had bent mainshafts with the described symptoms, but don’t worry that deep at the moment, the few questions answered will help.
- John
08GT500
5 Year Member
Hi, question w/many possibile answers, no history, simple approach helps isolate or nails it, nonetheless, helps one get to know their car, while seeking an answer. It’s “win-win”.
A & B listed should help isolate the area, any questions, just ask.
Friendly FYI, a little history, how the issue started (one day, or started slow & became worse with time, like I’d asked, makes it easier to figure out on this end. Answer to you is less vague. No worries!
Best of luck!
-John
A & B listed should help isolate the area, any questions, just ask.
Friendly FYI, a little history, how the issue started (one day, or started slow & became worse with time, like I’d asked, makes it easier to figure out on this end. Answer to you is less vague. No worries!
Best of luck!
-John
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