Vibration over 60mph.

[alcyon]

So most of you guys know my story last year, about my diff and steering centering. Well I finally settled my steering rack centering and got a full alignment and tire balancing and the car is going straight now. However, since I thought the car is ok now, I opened up the throttle and went up to 70mph, and found that the car vibrates at anything over 60mph. The vibration seems to be coming from underneath and the rear, and I can feel it through the doors too.
My first suspicion is the propeller shaft. It was rebuilt by some idiot who calls himself a pro. Why do I suspect the prop shaft? Well because he rebuilt it with new U joints with grease zerks, yet I do not see any additional weights welded to the tubings, which mkes me suspect that the centering might be slightly off and balancing was not done.
Has anyone encountered a similar issue like mine ?
There is a week long holiday next week, I found some else nearby who says he can center and balance the prop shaft, but he will only open shop end of next week. Gonna send the prop shaft to him to check it out.

 

[Asterix]

The easiest thing to check first is the alignment of the u-joints. If they're not pointing in the right direction, it will vibrate. Just changing u joints should not affect the balance.

Next, check the runout at the joints. It should be 0.002" (0.05mm) or less.

Weber State University has an excellent series of Youtube videos about driveshafts. They will make you appreciate how critical it is to get it right. It's not hard, but it requires care when assembling the new joints.

 

[alcyon]

The easiest thing to check first is the alignment of the u-joints. If they're not pointing in the right direction, it will vibrate. Just changing u joints should not affect the balance.

Next, check the runout at the joints. It should be 0.002" (0.05mm) or less.

Weber State University has an excellent series of Youtube videos about driveshafts. They will make you appreciate how critical it is to get it right. It's not hard, but it requires care when assembling the new joints.

Unfortunately, the u joints were not swapped as per TSRM. you see, this so called pro removed the old U joint and replaced them with a compatible unit, without circlip cuts. So instead of securing with circlip, he put thick washers in the outside holes to "cap" the bearings, then welded the washers in to prevent the U joint from moving around. As usual, these 3rd world bozos never checked with me if this method is acceptable to me or not.
So the centering is certainly suspect. Plus, since the new joints have zerks, why are there no new weights welded in ? By logic it should have weights to counterbalance the zerks, at the very least.

 

[Asterix]

Wow. Just wow. Sorry you get to deal with the mess.

 

[alcyon]

Here are pics of how he secured the u joints.

 

[figgie]

oh boy! wrecked that u-joint up and all 4 corners. damn.
Was that an OEM driveshaft?

You might have to put a grinder to those washers and remove them and see if there is any damage to the joint cups themselves.

A "pro"... yeah right!

 

[Asterix]

They also used a hammer on it - you can see the dents in the first picture.

That said, this driveshaft is tricky to get apart with a press and pullers because of the yoke shapes. I swapped u-joints on a Jeep driveshaft once and it was cake because the yokes had large flat areas for the press and puller.

 

[alcyon]

My mechanic suggested I go for a 1pc steel shaft. So he got one made.



The new shaft feels like its half the weight of the OEM one with the bearing.
The OE shaft front half OD is 60mm, and rear section OD is 82mm.
The 1 pc is 75.15mm, in between both diameters.
Here is the drawing I made.

I tried using the critical speed calculator in @Piratetip 's signature link but its not working, could some one calculate the critical speed for this shaft assuming wall thickness is 2mm.
And oh yes, should i grease the slip yoke splines ?

 

[Piratetip]

I can run some calculations on it for you later.
What is the tube length between the welds?

 

[Piratetip]

I am assuming 40inches between tube welds.
Though the necked down sections before the weld will affect the calculation some.
Need your full tire size also.

Your gear ratio is 4.56 yes?

I can give you some numbers once you send that info over.

 

[alcyon]

I can run some calculations on it for you later.
What is the tube length between the welds?

between welds is 41.5", yes ratio is 4.56, tire diameter 25.5" tube OD 3", thickness should be 0.083".
Do I need to grease the slip yoke splines ?

Update, installed the prop shaft


Overall, since the wall is thin, there is a bit of resonance when the car is starting up on high idle. I tested the car up to 60kmh on short trips and the car has more get up and go since the new shaft is half the weight. The little increase in noise is hardly noticable. Still worried about the critical speed though, hopefully i can do 180kmh (112mph) , that is the max speed limited by the ECU.

 

[Piratetip]

With those inputs I see these RPM's
Critical speed - 11295
1/2 critical speed - 5648

You could hit the 1/2 critical speed at around 92MPH with your tire size and rear end ratio.
Critical speed would be around 188MPH

These values may be slightly lower by a couple MPH or so, due to the necked down sections being smaller diameter.

That's what I see with my calculations

 

[alcyon]

With those inputs I see these RPM's
Critical speed - 11295
1/2 critical speed - 5648

You could hit the 1/2 critical speed at around 92MPH with your tire size and rear end ratio.
Critical speed would be around 188MPH

These values may be slightly lower by a couple MPH or so, due to the necked down sections being smaller diameter.

That's what I see with my calculations

Amen to that, i saw on some websites listing a 44" U joint center to center, the critical speed was anywhere from 5700rpm ,7800rpm, or 9200rpm.
With you saying its 11295rpm is very reassuring. That means even up to de limited top speed of 215kmh it should be ok.
.
From my calculation ,11295 shaft rpm in OD is 11295x0.705 = engine RPM is 7962, way over the revs I would ever go up to.
And you are certainly right, 188mph, sure I wont reach that speed lol.

 

[Piratetip]

Yep.
Just remember that 1/2 critical speed can also potentially induce vibrations as well.

 

[alcyon]

I took it from 60mph to 75mph for a few seconds today. No vibrations.

 

[alcyon]

Guys, I was going through the SUpra Heritage Parts program, and there is a propeller shaft, they listed two types of joints.


Mine came with the V joint (Staked). Any idea why there are 2 different designs? I would think the M type is easier to service.

 

[figgie]

Yep.
Just remember that 1/2 critical speed can also potentially induce vibrations as well.

curse resonance!

 

[Piratetip]

Chaos! Looks real cool in slow motion right before failure.

 

[3p141592654]

V joint is a later design that is cheaper. Toyota was on a cost cutting mission for the 89+ update. I replaced my M center bearing with a V center bearing and have no issues. V bearing was quite a bit cheaper.

 

[alcyon]

V joint is a later design that is cheaper. Toyota was on a cost cutting mission for the 89+ update. I replaced my M center bearing with a V center bearing and have no issues. V bearing was quite a bit cheaper.

is it ok to use a M type front half with V type rear half ?