404 diff wobble

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Dan404

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Tadpole
Tadpole
Joined
Feb 9, 2023
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Sydney
Hi guys,

I have a 404 which runs well but the diff is a bit wobbly. By that I mean when travelling at certain speeds the car has jerky motion. I was told by the previous owner that it was due to a worn pinion.

At some stage I’d like to get that diff sorted. I’ve heard the pinion can be flipped to the less worn side but I’ve never worked on these cars before so have no idea what I’m doing.

Im thinking I should probably get a new pinion anyway, what are your thoughts on that?

Also, not sure if I feel confident enough to the job myself, I’ve changed plenty of banjos in old Holdens but this looks slightly more complicated.

Any advice on where to buy the pinion or who would be best to do the job would be greatly appreciated.

Cheers,
Dan
 

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Surge was a problem with some Peugeots at steady speed. I'm scratchy remembering the details given it was the 1970's but I remember it being discussed. Others will know more. Don't be too quick jumping in to do the diff before you confirm it's the problem.
I vaguely remember they could surge if the ignition timing/ carby settings were wrong.
 
Russell Hall said:
Surge was a problem with some Peugeots at steady speed. I'm scratchy remembering the details given it was the 1970's but I remember it being discussed. Others will know more. Don't be too quick jumping in to do the diff before you confirm it's the problem.
I vaguely remember they could surge if the ignition timing/ carby settings were wrong.
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That’s interesting, thanks for the tip. Maybe I’ll start with a good tune up first.
 
A worn distributor can do this. If you have access to a low mileage 403/404/504 dizzie try doing a swap to see if it makes a difference. Of course adjust the dwell angle and ignition timing correctly. I bought a brand new dizzie for my 403 many years ago and have never had a problem with surge.
 
Yes as above advice I would check engine tune first,spark plugs,spark plug insulators for tracking,plug leads,distributor cap for cracks/tracking,carbon brush in dist,cap for condition,rotor button for play on shaft and wear at tip,distributor base plate/points,condenser,shaft for wear.carby throttle shaft for wear (leaking air past shaft) on carburettor.if engine tune is all set ok and hunting still happening check rear tyres/wheels for ovality/out of round.if still happening I would look at universal joint at rear of gearbox,then diff,(final drive)crown wheel and pinion…jim
 
This is all great advice thank you. The car does tend to pop a little when going down hill if I am not accelerating. By pop I mean not as loud as a backfire but the exhaust makes a popping sound - I assumed it’s timing but maybe it’s something else.

I’ll start with a good tune up - plugs, leads, dizzy bits and timing and then see what what happens.

By the way, I have tubs and tubs of 404 parts which came with the car. If anyone is looking for a part they can’t find, give me a shout and I’ll see if I have it. There are late model instrument clusters, chrome headlight rings, starters, carbies, rubber floor mats, switches and all sorts of bits and pieces.
 
Popping whilst going downhill can be wear in the distributor shaft. Very easy to check....Pop off the rotor and grab the centre shaft and see if it moves sideways at all. It should be solid as a rock.
 
only yesterday i saw this listing
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* noting 17 weeks old * from a a Banyo, Qld vendor on fb marketplace - of interest to someone reading this thread, maybe.
 
I had this surge under drive in my first 404 Coupé - the bronze crown wheel was unevenly worn around its circumference and a bit Swiss cheesy due to the wrong oil having been used by previous owners. Solution was to remove it and reverse it along with the bearing races +spacers inside the diff. With the unworn side now contacting the worm under drive, the surge was completely gone and none was noticeable on the over-run either.
 
Mike Tippett said:
I had this surge under drive in my first 404 Coupé - the bronze crown wheel was unevenly worn around its circumference and a bit Swiss cheesy due to the wrong oil having been used by previous owners. Solution was to remove it and reverse it along with the bearing races +spacers inside the diff. With the unworn side now contacting the worm under drive, the surge was completely gone and none was noticeable on the over-run either.
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I have a NOS new worm and wheel in my 1966 404. No surge or noise of any kind in 6 years. Using R40 oil changed every couple of years.
 
Mike Tippett said:
I had this surge under drive in my first 404 Coupé - the bronze crown wheel was unevenly worn around its circumference and a bit Swiss cheesy due to the wrong oil having been used by previous owners. Solution was to remove it and reverse it along with the bearing races +spacers inside the diff. With the unworn side now contacting the worm under drive, the surge was completely gone and none was noticeable on the over-run either.
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Out of interest, where did you get the work done or did you do it yourself?

Just gathering information in case the surge in mine is the diff.
 
GRAHAM WALLIS said:
I have a NOS new worm and wheel in my 1966 404. No surge or noise of any kind in 6 years. Using R40 oil changed every couple of years.
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I have such a set in NOS as well but there's no need to use it at this moment because the one in my present car appears to be more or less perfect. Peugeot Classic makes new ones now. I do have the factory rear axle tool kit in case it's needed by me or the subsequent inheritor(s) of my car.
 
Beano said:
Popping whilst going downhill can be wear in the distributor shaft. Very easy to check....Pop off the rotor and grab the centre shaft and see if it moves sideways at all. It should be solid as a rock.
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Thanks for the tip - mine is a bit sloppy. I’ll try a replacement dizzy first and then go from there.
 
Interesting that everyone always blamed the worm drive differential............ until 504's started exhibiting the same symptoms. Usually the dizzy is the culprit MTBW
 
Would almost guarantee surge is due to diff wear. I own three 404’s and they all did this to varying degrees. I reversed the crown wheel assembly in the worst offender and this totally transformed the car to drive. It was quite a simple operation so don’t be put off.
 
So, I suppose, try the easy things first. Check the distributor shaft first, and then consider the diff.
 
Johno404 said:
Would almost guarantee surge is due to diff wear. I own three 404’s and they all did this to varying degrees. I reversed the crown wheel assembly in the worst offender and this totally transformed the car to drive. It was quite a simple operation so don’t be put off.
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It starts with the distributor then the diff wears due to that. I had surge in my 1800 504 with hypoid. Cured surge in my 403 by changing to a Bosch dissy.
 
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