Punto differential - Help urgently please!

Are they sure? The last Fiat gearbox I worked on had an interesting design feature in that the inner CV boot housing bolts onto the gearbox, in so doing it holds the taper roller bearing that supports the crown wheel, so with the drive shaft out the crown wheel flops about.!! That sounds rather similar to your description. It catches you out the first one you see !!

Mrcheerful

The act covers up to 6 years so they cannot use the excuse that you are out of your 3 year warranty. Given the low milage you should have a good case. Also the fact that the garage is also comming down indicates they know they have some liability.

In practice they may admit some liability and pay part of the costs. It is probably down to how hard you argue your corner. A solicitors letter may work wonders.

I would think it is worth spending a few quid on a solicitor to find your exact position.

This is only my personal view though.

Good luck and let us all know the outcome.

"Paul Edwards"

Thanks. I am aware of the legal point. I am more concerned at this stage with understanding what I should be looking for tomorrow.

The crown wheel is attached to the diff cage. The pinion is the gear wot drives it - ie on the output of the gearbox. In other words, they are a gear set.

Thanks for the input guys. I have now been to see the gearbox in bits, and it is clear what happened.

The crown wheel is manufactured in two parts, the diff cage looks like a hub, and it has the planetary gears inside. The crown wheel gear teeth are made separately as a ring and then pressed onto the outside of the hub, probably with the teeth part being heated up so that it contracts onto the hub and grips it well. The gear teeth part came loose from the hub, so that I lost drive, which is the same symptoms as a slipping clutch.

The question is what caused that to happen? One explanation would be tolerances, ie the gear teeth were a bit too big, and the hub was a bit too small, so when they were pressed together the bond was not strong enough. (That's my view.) The alternative is that the car has been misused in some way. (That's Fiat's view.)

As far as I know, the car has been driven reasonably sensibly. It is only a

1.2 litre 8v engine, so there is not a huge amount of power going through the gearbox. The car is 4 years old and it's only done 20k miles, although this particular join in the assembly is not an item that would be expected to wear out. The gearbox engineer said that he has seen this sort of failure before, nearly always where the car has been modified with wider wheels than it was designed for. My car has not been modified.

Any ideas? I can't see any obvious way of telling why the item failed after

20k miles.

Ask fiat for goodwill, if not forthcomimh then go to watchdog, local papers etc., however badly treated it was 2ok is inadequate!

I got the brush-off I expected, so I'm issuing proceedings.

It should not fail in that manner, even with abuse. If you were to drop in an engine of vastly greater power I might expect it. And I dont see how wheel width has any effect whatsoever on such a diff failure? Wide wheels can only stress the suspension components (and it will) - the diff has no clue what width wheels it is driving. Even larger diameter wheels cannot put more torque through the diff than the engine can produce - and since you might use the engines max torque to overtake someone in 5th 10 times a day...

The only abuse you might find that could overload the join is snap-loading the transmission - 5000rpm, step off the clutch sorta thing. Dynamic loading would be massive, but I'd expect the clutch to be shredded first unless there was an inherent weakness....but then you ARE having a clutch replaced at 20K miles...which isnt very normal for an underpowered tin box unless its had its nads thrashed off ...

Ahh sorry, slight adjustment, i re-read your post - i see the clutch is OK and the gearbox was the cause of the slipping, in that case (and looking at your clutch and flywheel should prove whether it was driven hard - i.e. if it looks like mine did after i drove it hard

it is unacceptable for a gearbox to fail in that time. J

My thoughts exactly. However, where do I go for an independent statement of that? I am having to issue proceedings, so it would be helpful to get some sort of independent report. However, in the small claims track of the court system I could not reclaim the costs of a report, and my claim is going to be 800 Pounds. So, spending say 500 Pounds on a report is just not feasible.