Q45 rear end vibration

[vr4_for_fun]

Hi,I just bought a 98 Q45t with 77,000 miles. I've checked all the maintenance records and everything seems in order including a transmission flush at 55k. I seem to be getting a vibration in the rear end of the car starting about 40 mph which doesn't seem to change if I put the car in nuetral. I know it's not the tires cuz I just put new snows on the car and nothing changed. I have it scheduled to have the rear diff fluid replaced tomorrow with Redline Shockproof/Mobil 1 mix (any idea how much the rear diff holds???). I am also planning to have the transmission fluid and filter replaced with Mobil 1 as soon as I can find someone to do the work as I live in New Hampshire and the closest Infinity dealer is over an hour away. Is there anything else I should be checking?? Also, I've already had the coolant flushed and replaced and have a K&N air filter on its way. Anything else I should be planning to do?

Thanks very much for any information/help you can provide!!

By the way, I bought the car in Texas and just drove it the ~1800 miles back to NH! It was a great road trip and the car is terrific!! I even averaged about 22 mpg cruising 80-90! I thought that was great for a v8!!!

Thanks again!Randy98 Q45t (The Lowrider ;-) )2002 WRX (~285 HP):icesangel

[Q45tech]

Have the rear rotor/hubs checked to make sure they are in spec [0.0028" MAX lateral runout]. Emergency brake too tight/frozen?Check wheels for in spec.

Put the car on a lift and accelerate to vibration speed look feel each rotating component.

35-40 mph is where you start to feel a bad drive shaft but usually not a problem until after 120k , unless it was impacted by a rock or something.

[vr4_for_fun]

Thanks for the reply!

rear brakes and rotors were just done at the Infinity dealer in TX at about 70k. I'm glad you mentioned the e-brake cuz it's too 'loose' and doesn't hold the car. Where is the adjustment for it? Any idea on the rear diff fluid quantity? I just want ot make dure I have enough Redline/Mobil 1 when I take it in...

Thanks again!

[DAEDALUS]

I think the rear diff holds about 1.5 qts (1st gen at least); buy 2 qts and that should cover it. E-brake adjustment can probably be done through an access port on the rotor. Look for a hole on the face of the rotor with a rubber plug. Remove the plug, then use a screwdriver to turn the little "spiked wheel" dealie. Go all the way till the pads hit the rotor, and then back it off 5 or 6 clicks. Did you get a factory service manual with the car?

[Q45tech]

Just because the brakes were done by a dealership doesn't mean they checked the rotors for runout or indexed them this is an extra cost option. And quite time consumping on the rear as it takes two technicans..........one to turn the opposite wheel slowly while the runout is observed by the other.

Brand new factory rotors can be mounted on an out of spec hub and thus become out of spec!

7,000 miles is plenty of time to warp a rotor especially if the pin lube drys or caliper is not centering properly!

[vr4_for_fun]

Thanks Guys!

I'll have them run it up while they have on the lift tomorrow and check for vibration. Unfortunately I didn't get the factory service manuals (I do have the owners manuals though). Is there a good source for them? Now that you mention the run out, I think they may have done that too. I'll check the maintenance records when I get home tonight because I remember the previous owner complaining about feeling vibration through the gear shift...

Speaking of the transmission, is there some place online I can order the screen/filter to replace it when i have the pan dropped?

Thanks again!

[PalmerWMD]

...

Speaking of the transmission, is there some place online I can order the screen/filter to replace it when i have the pan dropped?

infinitipartsusa.com

Gives great discounts to us.Be sure to identify yourself to Joe or his assistant as a NICO member.

Fred...

PS: Infiniti of Lisle is also very very good but i dont have their URL memorized