131mirafiori forum

I have an occasional clunk coming from the rear axle, possibly the n/s. It doesnt do it all the time but sometimes after braking then accelerating slowly or reversing out of the garage after its been sat overnight. I cant make it do it to command....It isnt the rear brakes & i have replaced brake compensator & all arms, springs, bushes etc. Only the brake backplate is original.  Has anyone else suffered this??  I have a spare axle from what i beleive is from a mk2 1600tc.  Are they identical??

I have had this and it was a broken tooth on the pinion and this is always the first thing to break on these axles. Drain the oil out and remove the backplate and take a look.
your other axle from a mk2 supermirafiori will be the same axle and ratio 10/39 unless it was from an automatic 1600 T/C in which case it would be a 12/43 which will fit but your 131 wouldn't do more than 102mph (even with a 2000 t/c) as the gearing bottoms out, I know this because I once bought a sport that someone had fitted an automatic 12/43 axle to.

Don't forget, if its a ting rather than a clonk, the propshaft splines need greasing. 

    Roger......

Thankyou David and Toad.  It sounds like the noise a suspension spring might make if it moved out of position then returned instantly although it definetly is not this. I wonder why the sound comes from one side.... If i take the rear cover off as David suggests, where can i get another gasket (rear cover joint shown in haynes manual)??  Secondly, should the diff be broken, is it possible to replace without taking the axle off the car?? 

I would say unlikely as it needs careful setting, you have to get a new crown wheel and oinion set, and then set up the pinion mesh and back lash.   Change axle for uprated on, I banged one of these behind a 1400 OHV lump
 
   Roger...........

I have a 2 litre axle for sale if you do indeed need one. I also have an Argenta axle which is supposed to be stronger but it's a 4.1:1 ratio.

You can remove the differential unit in situ, unbolt the halfshafts and pull them out to clear and then undo the two bolts on the caps on either side of the diff unit and you can pull the whole unit out but undo the pinion nut first, having said that you really need the tool for measuring the backlash but I have just thrown them in and guessed the clearance with the shims I had available but this can be a bit hit and miss and if you get it wrong they will whine and won't last that long.
I have a new backplate gasket but its in two halves, if you like I can put in together and draw round it to give you a template to make one yourself.
Also beware as there are differences between mk2 and mk3 axle internals as I recall the bolts that retain the crownwheel to the case are bigger on mk3 and I think the pinion may be slightly different where it fits through bearing ? (from memory), also but this shouldn't affect you the inner halfshaft splines are bigger diameter on mk3 axles.
Mk3 131 axles are slightly wider than ones from mk2 and the halfshafts won't interfit as mk3 ones are slightly longer and as mentioned spline diameter slightly larger anyway but you can fit complete mk3 axle into mk2 (inc sport) and use sport wheels but very close to arches but ok on standard 185/60 x14 tyres (mk2 sport rims come out more than mk3 super rims) .   David

Wait there, are we barking up the wrong tree here ? as you said its seems to be on one side.
Check the cone on the axle where the spring sits and the damper is bolted as I had a 131 that this rotted right through and rattled around but this would result in no damping on that side and be very bouncy, worth a look though before you start taking things apart.
Check the top (short) trailing arms aswell as these can crack and open up (axle end) but this is more of a clicking sound and makes car feel a bit soft on the side that is affected.