Strange Decelerating Noise

[Rick]

W55 Gearbox, 1 piece drive shaft, Hilux diff.

The noise is in the drive train it has nothing to do with the engine, unbalanced tires, sticking brakes, pads, suspension etc…. As the noise only happens when in gear.

It sounds like a type of grinding noise its a hard one to describe.

The noise seems to only happen between 3500rpm – 2500rpm while decelerating only.

Noticeable the most in 4th gear, then 3rd, and then 2nd, you can hear it in 5th but it is the quietest of the gears.

The noise seemed to have developed since I replaced the clutch but it could have appeared before then but I wouldn’t have heard it because I was racing at the time.

I thought the sound was coming from the rear, so I checked the drive shaft universal joints and they are fine, next I pulled the diff head out and that also appears to be fine. The diff was rebuilt not long ago with new bearings, but with it out I did notice the axles were touching the LSD center so 4mm from each axle was machined off and when reinstalled the noise is still there, I would have thought 4mm from each side was enough to clear? Maybe it’s still the cause of the problem?

Last resort I will have to remove the gearbox and see if it’s the clutch or it maybe the gearbox.

Any one had a similar problem or knows what the cause is?

[matt dunn]

what is the clutch centre,

is it a solid centre or sprung centre?

[Rick]

Its a sprung centre clutch.

[stolic]

does the noise disappear when you put pressure on the clutch pedal?

possibly something screwy with the release bearing, or your input shaft.

[Crucible]

IMO,

I would think if it where youre clutch it would have the same noise on acceleration also, not just deacceleration

and as for the diff, the crownwheel and axles would be turning at the same speed in a "straight line' so I wouldnt think the axles touching the lsd would be the problem, maybe if it where there on corners.

gearbox bearings tend to whine, dont generally grind as youre describing.

Hmm thats a tricky one!

The box doesnt have a seal shroud on the tail end of the box?, you havent knocked it when pulling it out and its now knicking the driveshaft? The driveshaft hasnt got any new dents etc?

[matt dunn]

The reason i asked about the clutch is I had it in my Evo Lancer.


When an engine is decellerating, it is not at a constant speed,

so the gears in the gearbox are loaded in reverse direction,
i.e. the car is driving the engine,
and as each cylinder fires, it loads back the other way for a second as the engine drives the car, then back again.


Sounds like an exhaust rattle, and only happens in the lower RPM range
as above that the decleration force it too great.


To test it


Drive the car in gear up to the rpm above it happens,
and lift off and coast still in gear and it ill make the noise,

do it again, but turn off the ign to sto; the engine firing,
but leave it in gear etc all the same.

If it goes away that is the problem, but only seen it with solid centre clutches.

[CelicaGT8]

spigot bearing?
Wheel bearings?

[stolic]

come to think of it, my flatmate had a similar issue in his silvia after we did his rb25det swap. he had his drive shaft made too long. it still fit but had no play to allow for diff movement forward and back. at certain loads and rpm it would grind, and it would grind in reverse also.

easy to check without removing anything

[sergei]

The noise you are describing is normal gear backlash noise.
Very common on with non-standard clutch.
It is loud rattling noise from gearbox.
How to check if it is backlash - pulling on the gear stick while in gear (but not enough to disengage it) should calm it down; as well as applying throttle.

I've heard this on almost every single modified car with stiffer centre springs/without centre springs clutches. Even TRD clutches do that.

It sounds like "brararahahrararhararharahrahr" and goes away once you apply throttle.

I say check oil, and if it is ok, ignore it.

[Rick]

Small Update.

I swapped out my diff head for a spare one I had, took it for a test drive and the noise was still there so that eliminates the diff.

The noise is just too loud to just ignore, sounds like a concrete mixer.

[matt dunn]

Try this and report back

Drive the car in gear up to the rpm above it happens,
and lift off and coast still in gear and it ill make the noise,

do it again, but turn off the ign to stop the engine firing,
but leave it in gear etc all the same.

[Rick]

Drive the car in gear up to the rpm above it happens,
and lift off and coast still in gear and it ill make the noise,

do it again, but turn off the ign to stop the engine firing,
but leave it in gear etc all the same.

It still makes the noise when in gear with the engine off.

[QikStarlie]

you have the rubber boot over the gear shifter/tunnel hole? my gearbox makes similar noise as you describe (w55 behind 4age) but is 10x louder with boot removed.