Diff and axle problem

[Ren]

Hi all, I recently rebuilt my rear brakes but while doing it I thought I would fit a set of large O rings that I was told not to fit to the axle bearings. I wont tell you who told me not to put them on as he is a well respected member of the 356 community and it would be unfair. Anyway while in there doing the O ring the bloody axle full inward toward the diff. I quickly pulled the axle back into place and continued to fit the brakes and complete the car. i tested the brakes and they are fantastic. I did a great job. I have not noticed any leaks so great thats sorted. But and its a big but. I think one of the fulcrum plates has come loss in my diff. Im not driving the car because I dont want to bugger my freshly rebuilt by PR Services 356 C gearbox. When I tested the car I was getting a slight nocking noise from the right side (the troublesum axle side) but only when I hit a bump. Also had a bit of a nock noise when I tried reverse going up hill.

One other thing, for some reason the shift pattern had mover slightly.

Im going to have to remove the brakes, axle tubes and pull the diff out to replace the fulcrum plate (I think). How difficult is it andd has anyone got any reliable advise before I do this nasty job. Right now I hate myself, my tub and the person who shall remain nameless.

Arrrrrrrgggggtgtgt.

Dave (RHD t-5)

[Rustbucket]

depends what you define as a knocking sound.
Could be a slightly skew brake pad/shoe?
Also try retightening the axle nuts- if they are old then its poss you were able to 'tighten' them as before but now its all bedded in they have loosened up a bit. This all happened to me on my old Type3 squareback anyhow... so double check the castle nuts and ensure the split pin is doing its job- and try the wheel has no freeplay before a restrip.
Also confused about this O-ring business.....what reasons were given to not refit them ?
Not sure about the change of shift pattern.....I'd ask PR services first just to check !!

[Ren]

I used a torque wrench I borrowed from a truck place to tighten the castle nuts down to 400lbs so they are real tight. I have a very small amount of movent in the hub. The brakes went together fine. All pins and springs back the way the should be and all coppper greased up. Breaks are good. The nock noise is like if I hit a bump that the axle has hit its bump stop hard but very quickly. I was told not to fit as they will cause a leak. Caused a leak without them. PR Services supplied the box I have emailed them but no reply yet. Come on Mike get on that PC and get back to me. I realy dont wont to have to strip the diff.

[Graham]

The fulcrum plate can fall behind the axle,you might be able to jack that side of the car up and put it in gear and see if you have a bit of movement,this might be hard because you might get a bit on the diff,gears etc etc.
I have in the past been able to wiggle them back into place,but Ive never done this with a box in the car.
Thinking about it,if the axle went inward,there should'nt be a problem,Ive found its when the axle is moved outward then the plate can fall behind.
Could it be the axle shimming on the large plate that bolts to the gearbox?
too many paper shims and the axle will knock against the diff cover.
you could check this by removing the axle from the torsion arm,removing the shock absorber,and then moving the axle in and out to see if you have any play.
Also re-check all the mounting nuts and bolts just in case.

I dont think its the diff,have a look and tell us what you can see.
I will see if I can help anymore!

[Ren]

all bolts are tight I double checked last night. There are no paper gaskets on the case where the axle plates attach and no paper gasket on the trailing arm. Bearing case bolts are upto 30lbs as per the workshop book, castle axle nut is 400lbs. Brakes work fine. Slight bearing movemnt when the car is jacked up but nothing that would fail an MOT. I tested the car again last night with a gental small drive round the bloke and no noise untill I hit a bump then the axle made its worrying nocking noise. Its not the bump stop or the big hoop. Wheel is on tight. Torsion bar housing is fine. I cant think of anything else. Mike Smith from Pr has contacted me a said its not the box. Any ideas welcome. I cant use the car like that.

[nickT]

Hey Ren,
have you checked the front gear box mounts ??
What sort of knock is it ? a big thud or a metalic 'ting'
Cheers Nick.

[Graham]

How easy does the car bounce on the rear,try bouncing it and see if you get the noise,I cant belive there are no paper gaskets on the axle mounting plate,Ive done dozens of 356 gearboxs and they've all needed the shimming gaskets,not enough and the axle will be tight and wont move up and down freely and it will "Creak/Knock" too loose and it could knock.

[Ren]

I have bounced the rear end and no noise. All mounts are as old as the box (1 year) and tight. I dismanteled the rear brakes and bearings and found no problems but after another refit and test - the nock is still there. Its not a small metal ting sound but more of a tunk sort of sound. It happens when I hit a bump. Im also concerned that the axle fell inwards towards the diff so much that it looked like it was sticking up at an angle. Thats got to be wrong. It did this when I first got the box and first fitted it but was told thats not a problem.

Ive been in touch with Mike Smith at PR he said check its all tight which ive done so im open to any suggestions.

[Rustbucket]

prob left a spanner in the engine bay

[Graham]

Its nothing silly like the exhaust box hitting the engine shelf or the tail pipes knocking against somthing??

or could it be a dry rear torsion bar bushing creaking?

[Ren]

All torsion bushings are well greased and only 1 year old. I have chated with Paul Smith (Mikes son) and im going to take engine out and check the bolts that hold the hoop in place. They are 45 years old and one could have sheared through. Apart from that its all thats left to check. Spanner ?

[Ren]

Hi all, thanks for the replies but im still not sure what the problem is. I was told its not a box or diff problem but the other day I took my othre half for a day trip to Halfords to get new wiper blades. She noticed the box an diff sounded like helicopter rotor blades. She also noticed that the nock noise happend when I turned right. i checked fluids and all ok. Nothing left to check except the box and diff and they are ment to be fine. Any suggestions Please. I dont want to blow up an almost fresh box.

[sprintstar67]

did you replace the rear bearing? Having had failures on both bugs and 356s it can sound like rotor blades.
A purely visal inspection won't necessarily show the wear causing the noise.
Bearing noise also increases under load ie turning right or left. Does it increase with engine speed? that indicates the box, or road speed? that indicates something in the driveshafts, brakes or bearings.
One last one, I do know a guy who experienced a similar thing after hitting a kerb during some extreme sideways action, turned out ot be a slightly bent drum rubbing on the back plate.

[Ren]

I had no sideways action just fitted large O rings. Every thing was fine until then. Im getting all kinds of replies from 356 Registry. Im now worried about clutch alignment and the clutch thrust bearing after reading the registry im sick book. Gears select ok and pedal hight looks good. Its just these noises of which the helicopter sound is getting worse. Starting to sound dry. It cant be the box I recently topped up the level at the weekend after a last ditch attempt to find the problem. Bugger I wanted to use car to go to a wedding and Silverstone.

[nickT]

Hi Ren, any luck with finding the problem yet ?
Nick.