Weird noise coming from the rear.

[PalmerWMD]

1994Q45t, 89k miles, recent engine replacement. redone diff in 4.08.Recent alignment (the day before I noticed it first)

On strong acceleration I hear a weird noise kinda like running a card over bicycle spokes, except somewhat muted.

Appears only when at WOT and then only at very low speeds, usually for just a moment.

In turns, especially low speed tight ones, its a lot easier to provoke and takes les throttle application to make happen.

Noise is accompanied by a noticable vibration thru the seat.

Fred..

[Tweaky_Tom]

I would suggest some GAS-X. That took care of my strange rear end noises.

[PalmerWMD]

i <Knew> someone would say something like this.

Any more constructive comments from anyone?

Fred..

[Tweaky_Tom]

Hehe, i couldn't resist. Im a 240 driver so i can't really help you out. My friend drives a Q so i'll ask him and get back atcha.

[AZhitman]

Fred - Does it speed up with RPM's, or is it related to vehicle speed?

Can you make it happen in Neutral?

Prop the assend up on some sands and run it in Drive so you can listen to the rear diff. That's what mine (in the 'Burb) sounded like before it grenaded (violently).

[PalmerWMD]

my hicas light is on at times if that helps.

Fred...

[forecast]

I think it's your rear diff ... or maybe a half-shaft CV joint.

The shaking in the seat tells me it's almost certainly not something rubbing like a loose cable.

That it only happens under heavy load or cornering causes me to think it's not HICAS related. You also don't report any unusual steering problems.

That it happens more easily on corners (when the diff is doing it's thing) makes me think it's the differential and not the transmission or prop shaft.

However, I would not be suprised if it turned out to be a bad CV joint on one of the half-shafts.

Fortunately you have a back up differntial and set of half-shafts you can install!

Look under the car for torn boots on the half-shafts.

[AZhitman]

His back up diff isn't a 4.08, though!

Fred, was the rear in the 94 a swap or were the gears R&R'ed?

If it was a swap, it's unusual for it to go bad.

But if the ring and pinion were changed, I'm not surprised. I've never seen anyone that wasn't a factory guy be able to build a rear end that would last. Foolish move, IMO, when a 300ZX rear can be found so cheaply.

[forecast]

oh yeah, i missed that the diff was 4.08. That's it redone enforces my thinking that's it the rear differntial.

[AZhitman]

IF it was opened up.

If it wasn't cracked open and it's just a Z swap, then it shouldn't be bad, and perhaps it's just a shaft problem.

I'd still put it on a lift and run it in gear.

[PalmerWMD]

The diff is a re-done diff.new 4.08 gears I am unsure about how many miles are on them but probably 40k or less.

I rreally really hope its the half shafts or CV joints (one otehr guy I know is thinking joints).

I always thought diff started to howl when they go bad?:(

No howling here...

And yes my back-up dif is not a 4.08.BUT since my car is non TCS, non Active the Z rear ends wont work..

Fred..

[AZhitman]

Swapping gears in a rearend is a losing proposition. VERY few people know how to set them up perfectly. Then, subjecting a mis-aligned ring/pinion to 500hp blasts makes short work of it.

Fred, the Z rearend is a direct swap to your car. Non-TCS/non-active is not relevant in this matter from what I've gathered.

The only 2 diffs that I've had go bad did NOT howl. They clicked.

Then they exploded. One violently, with shrapnel everywhere, and one not quite so spectacularly. Both resulted in the driveshaft falling out and being damaged.

[PalmerWMD]

Hmm, do u still have one of those diff available?

[AZhitman]

I have access to more than one, I'll get you some numbers and prices.

[PalmerWMD]

Here's an update:

forecast and I change the rear diff fluid ( he did the work I "supervised";)..)

and it looked pretty good, not at all like a the fluid of a diff thats going.

Also we noticed some wear were the exhaust was baging a hicas rod.since my exhaust vibrates under load that may be the cause.

We put a shop towel there andf the noise I ahd before was no longer reproducible (it was often hard to produce anyway)

So...It seems like my diff <might> be good.

Fred...

[911/Q45]

When I was a kid I tried to convince myself that a bad rear end was an exhaust pipe rattle, looks like you had the pleasure of doing the reverse! Congrats Fred.

[squeefoo]

Does any know offhand how easy (or difficult) it is to zero the speedo back after installing a 4.08? A drive gear change from the donor 300 w/auto trans. perhaps? OOPs I should look in my FSM for starters. -Squeefoo

[PalmerWMD]

There is a gear on the rear housing of the transmission that you switch out.Drivers side.

Kinda easy and kinda cheap as well.

Fred..

[sijoko]

Replace the speedo gear on the Vehicle Speed Sensor with a 19 tooth gear. The color is white for the new gear.

[eQlipse]

Fred, the Z rearend is a direct swap to your car. Non-TCS/non-active is not relevant in this matter from what I've gathered.

The only(

Is this true? I was also under the impression that your car was required to have TCS for the direct swap. If so, I wonder if this swap would apply to '97-01 also?

[PalmerWMD]

I dont think this is accurate.Cars should have the TCS or Active for a straight swap.

Fred..