Driveline vibration.

[MagicRat]

Hello folks, I have a problem here and I would like your opinion.

1984 Toyota Supra, 280,000 km, 5 speed, 2.8 liter DOHC straight six (5mge engine) all stock.

This car has a driveline vibration noticable in 4th and 5th gear at any speed over 40 mph. it is quite mild except between 50 to 60 mph. At 50-60 it gets worse, (a moderate vibration) and smooths out somewhat over 60, but is still noticable.

It is noticably worse in 5th gear than 4th. It's pretty uniform whether I am on the gas or coasting. Also, it shakes even when I shift to neutral at that speed.

This car has independent rear suspension, where the differential is boltd to the chassis.
The driveshaft is a 2 piece design ahd was just rebuilt with all-new u-joints and one new driveshaft tube. It is straight and properly balanced.
It did vibrate worse before the driveshaft was fixed.

The hanger bearing is older, but still good.

So......... any thoughts on the cause and remedy?
I suspect the engine and/or transmission mounts, but I cannot figure out why the vibration is worse in 5th than 4th.

[TheSilentChamber]

If your going 60 and drop it down to third does it stay the same or does it go back down like it would be when in the normal 3rd gear range(noise wise)? I usually try to start with the simplest things, such as the tires.

[2.2 Straight six]

are all the wheels properly balanced?

i'm not suggesting anything, it's just often the simple stuff is to blame.

[MT-2500]

Originally Posted by MagicRat

Hello folks, I have a problem here and I would like your opinion.

1984 Toyota Supra, 280,000 km, 5 speed, 2.8 liter DOHC straight six (5mge engine) all stock.

This car has a driveline vibration noticable in 4th and 5th gear at any speed over 40 mph. it is quite mild except between 50 to 60 mph. At 50-60 it gets worse, (a moderate vibration) and smooths out somewhat over 60, but is still noticable.

It is noticably worse in 5th gear than 4th. It's pretty uniform whether I am on the gas or coasting. Also, it shakes even when I shift to neutral at that speed.

This car has independent rear suspension, where the differential is boltd to the chassis.
The driveshaft is a 2 piece design ahd was just rebuilt with all-new u-joints and one new driveshaft tube. It is straight and properly balanced.
It did vibrate worse before the driveshaft was fixed.

The hanger bearing is older, but still good.

So......... any thoughts on the cause and remedy?
I suspect the engine and/or transmission mounts, but I cannot figure out why the vibration is worse in 5th than 4th.

On a two piece drive shaft the U joints need to be timed.
This link may help.
http://members.troublecodes.net/crun...re%20shaft.jpg

And as said a vibration at 50-60 points to tire balance.
If all else fails here is a link to the best tire balancer going Hunter gsp9700.
They will almost balance a square tire.
http://www.gsp9700.com/pub/search/FindGSP9700.cfm
Good luck MT

[curtis73]

Is it a fast vibe like a gear noise, or is it slow like as if you had a tire out of balance?

I always look to the driveshaft first if its a 2-piece. The carrier bearing is always suspect so unless you're sure its good, replace it.

Does that car have a guibo... a rubber shock joint between two pieces of the shaft? If so, even if it looks good it could be the problem.

How are the rear CV joints? How about the rear diff lube level?

Sorry for the vague guesses, but this is a chassis I'm not familiar with. I know you're more technically savvy than I am but I'm just trying to chip in..

.... and what's this "km" you refer to... are you a foreigner? I'm not sure we can help you Are you vibrations metric or english?

[mazdatech177]

sounds like it could be tires, or a bent wheel. i doubt that an 84 supra has all four wheels perfectly true. its been my experience that a vibration that builds to a peak then tapers off is a tire balance/wheel issue

[GreyGoose006]

if it is different in 4th than 5th at a constant speed, then it could be the driveshaft is out of balance.
you said it was balanced, but have you checked to make sure the weights havent flown off?
if you are sure the wheels are still perfectly balanced, make sure all the lug nuts are securely tightened to 150lb/ft or whatever it specifies.

[534BC]

A lot might be told by haveing one drive it at the "worst" speed and have a passenger set or climb around in various spots on the car (is it more than a 2 seater?) anyways the increase load may change things if 2-4 people are in it.

Also a chase vehicle can spot a tire out of balance a lot of times if you can drive together on hi-way.

Another test can be to block car up and spin wheels at the worst speed and then jack it up so that suspension is unloaded and spin wheel at worst speed. It may help you pinpoint at least which axle and/or which wheel or shaft is wobbling by watching it.

[MagicRat]

Thanks for the info, guys.

Its defintely a high frequency vibe. A tire vibe is often lower frequency than what I get. Also, all the tires are new and the rims are true, as far as I can see; already checked them. The problem existed with the old tires, too.

Driving around recently, I noticed the vibe is worse when I let off the gas at speed and is best when just enough power is applied to maintain a constant highway speed. It gets worse again as more power is applied.

Possibly the engine torque is twisting the engine/trans combo enough to cause a driveline angularity problem. I am sure the mounts are original and pretty loose.

The pinion bearings and half- shafts have lots of miles and are still tight but pretty suspect. I'll check them out, too, alog with the wheel bearings.

Thanks again.

[curtis73]

Now that you put it that way...

Ring and pinion. Mine whine like an Italian whore. Years of use and wear increase the tolerances, and they whine the same way as if you had installed them with too much backlash.

What really tipped me off was the "let off the gas" thing.

[MagicRat]

Originally Posted by curtis73

Ring and pinion. Mine whine like an Italian whore.

Uh, I though that was 'Spanish whore'

http://www.automotiveforums.com/vbul...d.php?t=630856

Excellent point. The diff sings a merry song above 65 mph, and has considerable backlash.

Just today, I was considering if the vibe was diff related because the shifter is directly mounted on the trans and it does not vibrate more when the car shakes, so the vibe may not be related to a trans shake.
Still, I wonder why it shakes more in 5th gear than 4th, at the same speed.

Well, the car comes off the road for our 4 months of winter, so I can pull it apart at my leisure.

[curtis73]

Originally Posted by MagicRat

Uh, I though that was 'Spanish whore'
.

Dude.... I was talking about a GM in the other post GMs whine like spanish whores and Toyotas whine like Italian whores. You haven't had much experience with whores, have you

Still, I wonder why it shakes more in 5th gear than 4th, at the same speed

Possibly since the margin between positive acceleration, neutral acceleration, and negative acceleration is a much finer line in 5th than it is in 4th. Tomorrow I'm taking a trip down to Long Beach. I'll try mine in OD and D and see if my Italian.. no wait.. spanish whore whines more in one gear over the other.

[Moppie]

We have an old Toymota truck at work that only whines in 5th. '
My guess is theres less load on the diff, which lets the worn surfaces start to move against each other in ways they not supposed to.

[MagicRat]

Originally Posted by curtis73

You haven't had much experience with whores, have you

If my wife is around, that's my story and I'm sticking to it.

The situation is getting a bit worse. I have noticed a rear wheel bearing rumble now.
It may be time to pull the rear end apart, with new bearings, rebuild the diff and possibly CV joints.

BTW the previous owner, a friend of mine liked to take this car to the local road course (Shannonville Motorsport Park) and chase the Porsches, so the driveline has been worked hard.

[534BC]

How about a contershaft bearing in the output of transmission (if it's set up that way)