Hello, So my car is acting strange it will start vibrating at certain speeds, for example when passing 75 it starts to shake like a bitch but after it gets to 80 or 85 it isnt as bad, but the trans starts an awkward humming noise that happens in weird intervals. its a t5 trans with 5000 miles on it. only happens at high speeds not high rpm. and onlyl at 75. could it be drive shaft, or maybe tires need to be changed. The drive shaft seems to be in ok condition, just rusted, and i could use some new tires. Any advice helps. thank you!
Vibration at certain speeds
- Thread starter cammed89lx
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bigvino
Member
i have the same problem...but mine start vibrating around 40mph.. my friends told me it might be the engine/tranny mounts.... ill be watching this thread closely!! 
striker911
Member
Could be a number of things in the drive train. The dealer where I bought my 86 thought it was tires so he bought me some brand new cooper cobra tires. Turned out to be the drive shaft. I bought a ford racing aluminum one. I have also seen this problem in u joints and rear ends. But it could still be mounts, cross member, bad tires, or balance on tires. Could still be other things even. Like bent wheel, bearings, trans, bal joint, or tie rod.
A lot of places balance tires at around 35mph. If u want the best balance they need to be able to turn the wheel and tire to 70mph. I took my drive shaft off and took it to a drive shaft shop. They spun it up and it went sort of like a wheel balance. Put weights on it. Only the guy wanted to charge me more to fix my stock one then to buy the aluminum one. Mine now has a vibration under hard launches so thats trans. You still cant rule yours out though. U need to just start eliminating problems.
Let me know what diagnosing you would need help with and ill try to help.
A lot of places balance tires at around 35mph. If u want the best balance they need to be able to turn the wheel and tire to 70mph. I took my drive shaft off and took it to a drive shaft shop. They spun it up and it went sort of like a wheel balance. Put weights on it. Only the guy wanted to charge me more to fix my stock one then to buy the aluminum one. Mine now has a vibration under hard launches so thats trans. You still cant rule yours out though. U need to just start eliminating problems.
Let me know what diagnosing you would need help with and ill try to help.
Three50won
10 Year Member
- Jul 11, 2010
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cammed89lx...where are you feeling the vibrations? Through the seat? The floor? The steering wheel? Are you sure the humming noise is coming from the trans and not the front end (wheel bearings maybe?). I'd say approach it from the cheapest and easiest fix first. Go get those wheels balanced and see what happens.
True.. I feel the vibration come from the middle of the car..(kinda feels like the whole transmission is shaking) but the center console will start shaking back and forth. the car drives as straight as an arrow, and ive noticed its bad at 75, and sometimes at really high rpm's like if i hit 2nd gear and romp on it, then let off it will shake like a bitch. ill get the tires balance/get new ones. theyre beat to crap right now. haha. thanks guys
I have the same problem in my 91 gt, I changed motor and tranny to t5 and now I have this horrible vibration around 50 in 3,4&5th gear, sounds like the tranny but I have noise coming from the rear end (changed from 273 to 373) also. Changed 2 driveshafts, opened case on rear end, checked motor mounts bout to change tranny and hope it fixes
bigvino
Member
Your problem is probably a unblanced driveshaft. There are weights welded on the driveshaft and occasionaly they come off. There is a dab of yellow paint on the driveshat near the rear U joints. It is supposed to line up with the yellow paint on the rear axle flange where it bolts to the U joints. It is doesn't remove the bolts and line up the paint marks. Check the U joints for slack while yiu are under the car.
Check the U joints: They are a known problem with driveline vibrations. With the car on 4 jackstands, crawl under and see if you can shake the driveshaft or twist it by hand with the trans in gear or Park. Next try rotating one of the rear wheels and note any slack in the U joints while turning the wheel forward and backward. You may need a helper to turn the wheel while you watch the U joints for slack or movement. It may be necessary to block the wheel that you aren’t turning to keep it from rotating. Slack or movement of the U joints means you need new U joints, which are about $10-$12 each. Do the front and rear U joints at the same time.
U joint replacement:
]1.) Remove the drive shaft, the rear bolts are 12 MM. You will need a high quality 12 point wrench for this: do not skimp or you risk rounding off the bolt heads. A helper to step on the brake to keep the drive shaft from turning will be helpful. Use your foot to apply pressure to the wrench to loosen the bolts. Note the yellow markings in the drive shaft and write down their alignment.
2.) Put a catch pan under the rear of the transmission to catch the fluid when you slide the yoke out of the transmission.
3.) Remove the snap rings from the bearing caps and it's now big hammer and socket time. Use a suitable big socket as a punch and another bigger one on the opposite side to act as a receiver. Pound away with the big hammer to drive the old U joint bearing cups out. The installation process is the reverse of the removal, except use a block of wood to hammer on rather than a socket. An air hammer is a great tool to have about this time, and it beats (excuse the pun) doing it by hand.
4.) Reinstall the drive shaft, slide the yoke in place. Align the rear yellow markings and install the bolts. A helper to step on the brake to keep the drive shaft from turning will be helpful. Use your foot to apply pressure to the wrench to tighten the bolts.
5.) Check the fluid level in the trans while you have the car up on jackstands. There is a pair of pipe plug filler ports on the side of the transmission. Remove the top plug and stick your little finger inside the trans: if has oil all over it, the trans is full of oil. If not, add Dextron/Mercon ATF (T5) or GM Synchromesh Black ( Tremec 3550, TKO, TKO 500 & 600) until it flows out the top filler port. Put a catch pan under the transmission to catch the fluid when you fill it to catch the overflow. A 4 ft length of ½” garden hose and a funnel is the tool for filling the trans with oil. Insert one end of the hose in the trans filler port and the funnel on the other end. Raise the funnel end up to level with the top of the front fender and pour away until you see some overflow. Put the pipe plug back in and tighten securely.
Get car down off the jackstands and go for a test drive. If the U joints were the problem, your vibration & noise will be gone. If not, it wasn't an expensive fix and you learned something in the process.
Check the U joints: They are a known problem with driveline vibrations. With the car on 4 jackstands, crawl under and see if you can shake the driveshaft or twist it by hand with the trans in gear or Park. Next try rotating one of the rear wheels and note any slack in the U joints while turning the wheel forward and backward. You may need a helper to turn the wheel while you watch the U joints for slack or movement. It may be necessary to block the wheel that you aren’t turning to keep it from rotating. Slack or movement of the U joints means you need new U joints, which are about $10-$12 each. Do the front and rear U joints at the same time.
U joint replacement:
]1.) Remove the drive shaft, the rear bolts are 12 MM. You will need a high quality 12 point wrench for this: do not skimp or you risk rounding off the bolt heads. A helper to step on the brake to keep the drive shaft from turning will be helpful. Use your foot to apply pressure to the wrench to loosen the bolts. Note the yellow markings in the drive shaft and write down their alignment.
2.) Put a catch pan under the rear of the transmission to catch the fluid when you slide the yoke out of the transmission.
3.) Remove the snap rings from the bearing caps and it's now big hammer and socket time. Use a suitable big socket as a punch and another bigger one on the opposite side to act as a receiver. Pound away with the big hammer to drive the old U joint bearing cups out. The installation process is the reverse of the removal, except use a block of wood to hammer on rather than a socket. An air hammer is a great tool to have about this time, and it beats (excuse the pun) doing it by hand.
4.) Reinstall the drive shaft, slide the yoke in place. Align the rear yellow markings and install the bolts. A helper to step on the brake to keep the drive shaft from turning will be helpful. Use your foot to apply pressure to the wrench to tighten the bolts.
5.) Check the fluid level in the trans while you have the car up on jackstands. There is a pair of pipe plug filler ports on the side of the transmission. Remove the top plug and stick your little finger inside the trans: if has oil all over it, the trans is full of oil. If not, add Dextron/Mercon ATF (T5) or GM Synchromesh Black ( Tremec 3550, TKO, TKO 500 & 600) until it flows out the top filler port. Put a catch pan under the transmission to catch the fluid when you fill it to catch the overflow. A 4 ft length of ½” garden hose and a funnel is the tool for filling the trans with oil. Insert one end of the hose in the trans filler port and the funnel on the other end. Raise the funnel end up to level with the top of the front fender and pour away until you see some overflow. Put the pipe plug back in and tighten securely.
Get car down off the jackstands and go for a test drive. If the U joints were the problem, your vibration & noise will be gone. If not, it wasn't an expensive fix and you learned something in the process.
Vibrations due to speed not RPM are almost always one of the following (in no particular order):
- Tire/wheel imbalance
- tire tread defect
- bad Wheel bearing
- " axle bearing
- driveshaft imbalance
- U-joint
- transmission mount (or improper angles b/w tranny and rear)
- bad CV joint (in FWD or IRS cars)
- your imagination
- Tire/wheel imbalance
- tire tread defect
- bad Wheel bearing
- " axle bearing
- driveshaft imbalance
- U-joint
- transmission mount (or improper angles b/w tranny and rear)
- bad CV joint (in FWD or IRS cars)
- your imagination
bigvino
Member
Im here to report my findings! i found out that a driveshaft bolt was missing and another was loose 
this is what was causing my vibration issues.... im going to use thread locker and torque the bolts to specs
this is what was causing my vibration issues.... im going to use thread locker and torque the bolts to specs
foxbodymike87
Active Member
- Jul 12, 2011
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bigvino
Member
I just bought all new Energy Suspension mounts for my engine and trans that I have yet to insall....but I'm sure the majority of my issue lies with the stock steel driveshaft. I noticed that the heavy steel balancer ring that's normally located at the end nearest the trans stock is missing. It's common for the rubber on these to rot out and tear loose...allowing the ring to free wheel on the shaft. A lot of owners just remove them altogether when this happens, instead of replacing the driveshaft...which can be the cause for a lot of headaches.
I'll be picking up an aluminum unit in the spring.
I'll be picking up an aluminum unit in the spring.
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