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TRANSMISSION NOISE DIAGNOSIS


mickeyw
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Hi All,

Your help is required please with transmission noise diagnosis, but first a little history...

My truck is a V8 90 with 4 speed ZF auto, 1.41:1 LT230, and standard rover axles/diffs.

I recently fitted a another LT230 (for a ratio change). I fitted a new cross drilled transfer gear and bearings in this. Bearing preloads were checked during assembly. Intermediate shaft was removed to facilitate the preload check, then refitted and checked again.

The ZF had a new output shaft fitted with the longer splines to suit the cross drilled input gear. The bolt securing this was Loctited and torqued up as per the book.

I also had the rear diff and shafts out to reseal the leaking diff to axle joint.

After fitting I drove the Ninety for a week with no undue noises or anything odd. Then all of a sudden I have this noise occur, that as far as I can tell is road speed, not engine speed related.

The noise is not easy to describe - something along the lines of a high pitch whirring is about the best I can come up with. It becomes evident after about 15 MPH, does not increase in volume but does increase in pitch. It is not the kind of noise that I'm inclined to ignore but is easily drowned out with some music :o

First thoughts were 'have I forgotten to fill something with oil?' All oils have since been checked, including stuff that had not been touched (front diff & swivels & auto box), nothing was missing but the front diff oil looked a bit goopy so I changed that.

Also checked there is nothing rubbing on the tyres, props or engine pulleys. All UJs have been recently serviced.

I am at quite a loss as to what else to check really. My first suspicion was the new trf box, but everything looked healthy enough inside and rotated as it should.

Sorry this has got a bit long, but has anybody got any ideas please??????

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Hi All,

Your help is required please with transmission noise diagnosis, but first a little history...

My truck is a V8 90 with 4 speed ZF auto, 1.41:1 LT230, and standard rover axles/diffs.

I recently fitted a another LT230 (for a ratio change). I fitted a new cross drilled transfer gear and bearings in this. Bearing preloads were checked during assembly. Intermediate shaft was removed to facilitate the preload check, then refitted and checked again.

The ZF had a new output shaft fitted with the longer splines to suit the cross drilled input gear. The bolt securing this was Loctited and torqued up as per the book.

I also had the rear diff and shafts out to reseal the leaking diff to axle joint.

After fitting I drove the Ninety for a week with no undue noises or anything odd. Then all of a sudden I have this noise occur, that as far as I can tell is road speed, not engine speed related.

The noise is not easy to describe - something along the lines of a high pitch whirring is about the best I can come up with. It becomes evident after about 15 MPH, does not increase in volume but does increase in pitch. It is not the kind of noise that I'm inclined to ignore but is easily drowned out with some music :o

First thoughts were 'have I forgotten to fill something with oil?' All oils have since been checked, including stuff that had not been touched (front diff & swivels & auto box), nothing was missing but the front diff oil looked a bit goopy so I changed that.

Also checked there is nothing rubbing on the tyres, props or engine pulleys. All UJs have been recently serviced.

I am at quite a loss as to what else to check really. My first suspicion was the new trf box, but everything looked healthy enough inside and rotated as it should.

Sorry this has got a bit long, but has anybody got any ideas please??????

hi,i had this a month ago seemed to be coming from front end, so i checked uj's on front props,and changed them still the same, took prop off drove with difflock noise went, so i thought it was the front diff so i changed that, noise came back after a few days, got under car again, and there seemed to be alot of play in out put shaft of t/box, so now looking to change roller bearing, but saying that there's oil coming out of front diff again so it might even be pinion bearings, hoping it's only oil seal, also had a little vibration around gear stick area, never rains but pour's :(:) defender dinky

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A bit more info following more experiments tonight.

When driving I really can't decide whether the noise comes from forward or aft.

I've not tried it with diff lock in, but diff lock definitely does disengage.

Noise is somewhat increased when in low range? Does this indicate it stems from primary box?

Forgot to mention earlier that all wheel bearings have been checked and spin freely.

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