Vibration at 70MPH

[elwesso]

This is kind of odd... Id like some input...

First of all, i thikn the diff is a little whiney once i get up to about 60.... It still work good, both wheels spin equally when its slick out... I did the test (floor it at a stop in the rain) and that tested ok...

But once i get to about 60-65 i feel like im in a massage chair... Its not the exhaust I odnt think because if I were to maintain speed and downshift to like 3rd or 2nd, it would vibrate the same.....

However, once I get to about 80+ it seems to go away and be fairly smooth... I konw the rotors are warped somewhat, i have the shimmy so ill correct that...

Would what I described be the driveshaft?? Id assume not replace that if I could

[qship96]

rotors,wheel imbalance,non-michelin tires,links,kingpins,driveshaft,trans & motor mounts,could be any one or combination of,start with the cheapest and work your way through till it is gone.

[elwesso]

Let me clarify a few things

The car idles fine.

Lots of suspension stuff new.. Links, tension rods, and so forht... Car handles like new...

I suppose it oculd be brakes but theyre not that warped, just enough for me to BARELY feel it.

Motor mounts are new..... transmission mount should be OK? New transmission with about 30k on it......

[Q45tech]

Vibration in the 60-70 mph range that reduces at 80 mph] in 4th gear is almost always tires, wheels, and brake rotors.

Check all tires/wheels on Hunter 9700 for below 5-7 pounds of radial force imbalance...........probably none will meet this spec. Then find out which wheels are out of spec and repair or replace............Michelin tires will save you lots of grief! Then you know its mostly the wheels at least to start.

Make sure no tire wheel needs more than 15 grams in total to balance as a first step to find the culprit.

A brake rotor that is beyond 0.003" runout wil be feelable. Measure the mounted runout. Have the wheel bearing been CORRECTLY replaced and measured for play. What is condition of rack preload tension.

Change tires first as they are cheaper than each wheel.

Couple of thousand ought to fix the problem..........why I stick with 15".

Always check newish wheels without tires for a go no go determinnation.

[elwesso]

Thank you Dennis...

This is not with my 17/18 in wheels.. right now I have a set of newer 15in turbine wheels off of a 95 Q.... They look to be in very newish condition, mileage is unknown... Tires have about 12k on them, and are firestones... I need to stick with these tires because they are my winter tires, and do very well in the snow... 500 treadwear, could be a lot to do with it as well.....

THe thing is, the vibration is the same with my other set of wheels and tires (maybe a little different, i cant really recall) so that leads me to the rotors a bit more.....

Also, when I said it smooths out, it doesnt get completely smooth, but it does get SMOOTHER... Man I miss my 47k chrome piepans, those had to have been nearly perfect......

I will get them rebalanced, but since I know the rotors are warped, i think ill go that route first... Will probably upgrade to skyline brakes after winter so I dont have to go through with this every 3-5k

The main thing is Im glad its not the driveshaft.. Or at least I dont think it is, ive driven ones with bad shafts and its like a massage chair that slowly gets worse...

[jamesmost]

wesi just had the same thing, a good balancing and alignment set it straightas u knowthe rest ofmu susp is better than newj

[gniknave]

Wes I was going to post this same exact thread until I saw you already did it. I suspected it was tire/alignment related because for me it happens between 55-65mph then goes away above or below that. I need a rear alignment after I get some new struts so I figured that may be the cause, beside the fact I have 17" wheels & tires- I'm sure my heavy chrome doesn't help the situation. Since you're using your 15" winter tires then it HAS to be balancing/alignment related.

[96Qowner]

Wes, this is very similar to a vibration I had before replacing a transmission mount. I'm sure you're aware of the engine harmonic at 2250 RPM. If this corresponds to your vibration peak, you should think in terms of some kind of transferred vibration through the drive train.

Mine would shake from about 72 MPH to 78 MPH with standard gearing on a 96. Was a biatch at 75 MPH cruise speeds.

[JT_MONEY_2004]

Likewise, i'm having a similar shake at around the same cruise speeds. I attributed it to old tires and possible alignment issues. I didn't know a worn transmission mount and warped rotors would produce this type of problem. I know my transmission mount is worn a bit.

[Q45tech]

Almost all rubber isolation components need replacinging every 4 years 60k, that why they are not covered in warranty beyond 4 years ! unlike the drive train parts for 6 years.

[elwesso]

Well I definitely do think its tire or something on the wheels..

Whenever I take a harder corner, the vibration is enhanced on that side... theres also quite a bit of road noise, but that could be since im missing some cladding.....

EDIT: Thought I would add that the car has new engine and transmission mounts... All have about 30k on them

[JT_MONEY_2004]

Can you guys help me and others compile/reference a list of the "rubber isolation components" that are scheduled 60k maintenance Q45tech referenced above.

I'd like to add those components to my running list of "Things 2 do to the Q".

[elwesso]

I think i need to change this...

Its worse about 70 mph but still there at 80+

Maybe driveshaft after all, since it feels like something that is under the car...

[JT_MONEY_2004]

What type of maintenance does the drive shaft need-- beside gear oil?

[AZhitman]

Wes - Given my brief exp with that car, I'd also consider looking at the exhaust... check all hangars. Your "cornering" change leads me to believe it might be related somehow.

Also, dropit into N at 90 and let it coast down thru the vibration range - if it goes away, you may have a DS issue.

[Q45tech]

At 70 mph a 26" 12.6" load radius tire or the attached wheel or brake rotor rotates how many time a second...................the frequency of the vibration.

One out of plane/round spot will create the fundemental frequency, 2 spots will create 2 frequencies .............a tire ,a wheel, and a rotor will create 3 frequencies separated by time.............since the tire, the wheel and the rotor are locked together.......these frequencies only chnge when a component changes [temperature] or the rotational speed cchanges.

Study harmonic relationships. With 4 tires, 4 wheels, and 4 rotors, you get 4x4x4.........64 simple vibrations plus 256 complex ones.

All these constantly add and subtract component values and change with temperature.

Perfect rotors, perfect wheels and $110 [in 15"] tires >$250 in larger sizes are far from perfect but mostly more stable at least for 15,000 miles.

Obviously getting and keeping wheels perfectly round and true is the most expensive part!

True, index and shim rotors, balance and repair/replace wheels often along with ultra premium tires Hunter radial force balanced and you will have low feelble vibrations........from these components.

[elwesso]

Wes - Given my brief exp with that car, I'd also consider looking at the exhaust... check all hangars. Your "cornering" change leads me to believe it might be related somehow.

Also, dropit into N at 90 and let it coast down thru the vibration range - if it goes away, you may have a DS issue.

\

The thing that makes me think its not the exhaust is that when I downshift into like 2nd (manually) and the car is going the same speed, the vibration doesnt change... I think when i let off the accelerator it lets up a little...

Ill try the neutral thing today and take notes... Maybe the center bearing from the driveshaft got messed up after 3 engine swaps or something.. Just trying to troubleshoot... But i do know that it doesnt really get better...

Ill see about getting my tires balanced and rotors checked... the only thing that makes mea little iffy is my old Q wich had VERY warped rotors (thing visible steering wheel shake) and ****ty tires (about teh same age as these) on original rims didnt vibrate like this...

Maybe what Ill do sometime is jack up the rear end of the car and set the speedo to 80 MPH.. If it vibrates, it should be the driveshaft and not the tires......

[911/Q45]

Neutral would just take the engine out of the equation. Jacking up the back would take the front tires out of contention, but the rear tires would still be in play.

[elwesso]

Ok well i did some testing.....

When you hit 75 it is almost like flipping on the switch to the massage feature... Its really bad from 75-80, and then from 80 and on its still there, but not nearly as bad... If you let up from the accel and then hit it again, it gets marginally better/worse, respectively...

From 80 on it stays about the same... Theres a howling that my old Q didnt have, might be noise from the tires and such.... I took it up to 100+ and it wasnt that bad.....

I do know my rotors are warped... So I think ill start with that, as maintenance, and have my rear brake pads replaced..... Then if that doesnt fix it, ill have the tires balanced... IF those things dont fix it, then I know its something driveshaft related... Im hesitant to use anything driveshaft related from my old Q since I know how I removed the engine... Maybe something from the U joint back, as I could see some flexing at the very front part (where the bolts are) as I was lowering the engine.. Probably not supposed to do that, as it states to remove the driveshaft...

However, I may just live it out until spring when I can do skyline brakes You can get kits on eGay for about $300, and Id love to have 4 piston calipers and the ability to use the thicker rotors, which means I wont have to true the rotors all the time...

Edit: I called scottsdale, and the center bearing thing is like $110...

EDIT2: ALso, ill add this little tidbit... I can hear a droning start at about 40, and then it doesnt start vibrating until about 75 like said...

[Q45tech]

When you Hunter 9700 balance the tires wheels [correctly with hot tires and wheels] then you know its the rotors/bearings.........when you index the rotors then you know its's somethings else.

Why for 10 years I have trued my rotors every ~~6-7,000 miles like clock work they warp [ever so slightly].........usually the right front [passenger side] roughest road edge.

If I had been smart I would have changed them to massive brembos long ago..........but 17-18" wheels tires would have just created other problems.$600 per year for stock brakes maintenance or more for 17" wheels and tires and then still some brake maintenance. Coin flip?

[elwesso]

When you Hunter 9700 balance the tires wheels [correctly with hot tires and wheels] then you know its the rotors/bearings.........when you index the rotors then you know its's somethings else.

Why for 10 years I have trued my rotors every ~~6-7,000 miles like clock work they warp [ever so slightly].........usually the right front [passenger side] roughest road edge.

If I had been smart I would have changed them to massive brembos long ago..........but 17-18" wheels tires would have just created other problems.$600 per year for stock brakes maintenance or more for 17" wheels and tires and then still some brake maintenance. Coin flip?

Alright Dennis.. Thank you..

I am pretty sure the skyline brakes (with 32mm rotors) and 4 piston calipers will fit on 16in wheels... Since I already have 16,17,18 in rims available, having to true the rotors every 15k instead of 6k (worse case) would be golden...

Ill get the tires balanced ASAP, but like I said ill wait on the brakes in case I upgrade... Id really pray that its the wheels and tires but I kinda doubt it is, but it cant hurt.....

[DougQ45]

After replacing the transmisssion mount over the weekend, my 75mph vibration is now gone in my 94Q with 58,000 miles!! Also, the car would vibrate when in neutral, that too is gone. The old transmission mount was collapsed maybe an inch or so. Huge difference for only 1 hours work. Wes, you may want to try this.

[elwesso]

Its an idea and ill exhaust my other options.. but the transmission mount was replaced during the engine swap, which was about 1.5 years ago, if memory serves.....

Has maybe 30k on it.....

[Q45tech]

And how long do you think they last [the transmission mount] if there is some defect in positioning [sag] in driveshaft or motor mounts.............if the forces are not perfectly distrubuted [no angles].

Sometimes you have to chage the center bearing shim thickness.

Diff mounts, center mount , transmission mount, motor mounts all work together.

Study the look of the transmission output rubber seal bushing to see any deformity.

Hard to make a worn old car behave like new even for 60,000 miles too much wears and changes.

A never ending story of replace this and that ...........before you get thru replacing what rubber needs replacing it's time to start over.

[elwesso]

OK.. I got the wheels and tires balanced... On a hunter 9700 (i think)...

He said they werent too bad, but he got them to "zero out".....

Vibration is still present

I can feel it at 60mph, its not bad, but its there, and progressively gets worse all the way to 100, but its worse at 75.. its still bad at 80+ but not as bad.....

Seems like its driveshaft, as rotors wouldnt cause this much vibration... The steering wheel doesnt shimmy, like it did in my odl Q with very warped rotors.. Dennis if you ever drove my old Q you might die, original rotors Im pretty sure ...

I wonder if doing the orientation thing as described in the TSBs would help?? I can tell this is coming from below and not from the wheels/suspension, as i would be able to feel it in the wheel, its completely calm there.....

[Jesda]

Did you feel the tires with your hand? You can tell if theyre out of round (at least I could on mine).