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Author Topic: Matra murena 1.6 Differential  (Read 859 times)
Ols
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« on: January 11, 2017, 08:01:50 pm »

Hello Greetings from Serbia, i have murena 1.6, i was driving the car this summer for about 2500 kilmeters after more than 20 years in garage. I am pretty satisfied by the drive so far, i made the engine refubrishment, gearbox sync rings replacement, and i still have problem and noise with first gear while transfering from 2nd to 1st while car is still moving even with in small velocity. Now it is pretty cold and snowy in Serbia in this period so i decided to take murena out for a spin. Although i have summer tyres on it i noticed something strange. It seems that right rear wheel is always spining more and faster while on snow, so in driving i have feeling that car is always pulling back side to the oversteer on the right side, i have never noticed this during summer when roads where dry. Can murena differential broke down in such way that it doesnt distribute power as it should be ?

Best regards.
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GP
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« Reply #1 on: January 12, 2017, 08:47:50 am »

Greetings to "sunny" Serbia,

Never driven a Murena in the snow myself, although I would expect an exciting drive in a mid-engined rear wheel drive car with a low polar moment of inertia (spins easily)!

Before you do anything too drastic, the corner weighting of each wheel on Murena is pretty rubbish in standard setup. When you add the driver on the left hand side it becomes even worse. Try putting 2 x 25kg sacks of coal in the boot as near as you can get to the right rear wheel then see what happens?
Fitting some winter tyres would be prudent too.

Cheers,

Graham

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suffolkpete
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« Reply #2 on: January 12, 2017, 11:26:10 am »

Could it be the brake dragging on one side?
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Ols
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« Reply #3 on: January 12, 2017, 01:06:09 pm »

GP, Thanks a lot for your reply, i will try to add some wight to the right side and try to see what will happen or put one more passenger. When car was on the car lift few moths ago, and i put it in gear both wheel where turning evenly without load.

Sffulkpete, i doubt that brake is dragging because brakes are renewed and also while it was on car lift i could easily spin both back wheels, plus after snow drive once i put my hands on the rim it is not hotter than the right one, and i drove it drove 25 for half an hour kilometers on snow.

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roy4matra
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« Reply #4 on: January 12, 2017, 07:34:19 pm »

Hello Greetings from Serbia... Although i have summer tyres on it i noticed something strange. It seems that right rear wheel is always spining more and faster while on snow, so in driving i have feeling that car is always pulling back side to the oversteer on the right side, i have never noticed this during summer when roads where dry. Can murena differential broke down in such way that it doesnt distribute power as it should be ?
Best regards.

I also suspect that the right rear brake caliper is causing a drag on that side slightly more than the left.  Alternatively, the hand brake section on the right is slightly seized and not allowing the caliper lever to return fully, which again will cause a drag that side.

One test is to stop the car and with the hand brake off, go underneath and make sure both caliper levers are fully off against the stops.  Then without touching either the foot brake or hand brake, drive again in a straight line on the slippy surface and check for spinning again.

It is extremely doubtful the drag would be caused by the differential.

Although you say the brakes feel free and it is not getting hot that side, it wouldn't take much of a drag to cause a difference.

There is one other possibility since the surface is very slippy with cold and snow and you have summer tyres on the car.  The tyre on the right may not be gripping as much as the one on the left.  Unless the tyres have a directional tread pattern, you could try swapping the rear wheels from side to side and see how that affects the grip.

Ideally you should fit some winter tyres as these grip much better below 7 degrees.

Roy
« Last Edit: January 12, 2017, 07:36:49 pm by roy4matra » Logged

Ols
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« Reply #5 on: January 12, 2017, 11:43:28 pm »

Thanks Roy for yoir reply, i will chek the brakes once more to see is there any difference between sides, regarding the tires it shouldnt be a problem since both are new of the same brand and type.
I will probably not change the winter tires because tbe car will stay in the garage until april, i just wanted  to make sure that i wont have problems when driving in season because i am afraid that i can cause serious damage to the car if the grip is not the same on dry roads when i cant notice such ting ...
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roy4matra
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« Reply #6 on: January 13, 2017, 04:20:05 pm »

Thanks Roy for yoir reply, i will chek the brakes once more to see is there any difference between sides, regarding the tires it shouldnt be a problem since both are new of the same brand and type...


And the new tyres might be the problem then.

All new tyres have a releasing fluid on them to aid getting them out of the molds, which makes them less grippy at the start.  This eventually wears off during the running-in process you should always give new tyres.  It may be one is still more slippy than the other, so I still say it would be a good check to try them on the opposite sides to see the result.  Also even new tyres from top manufacturers can sometimes be faulty.  During over 40 years in the motor trade I have experienced quite a number of faulty new tyres that once changed for another, cured the problems the drivers had been having.  It's a quick and easy check anyway.

Roy
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