1983 500SL Drive Train Backlash

[low farm]

Is backlash in the drive train more likely to be the autobox or back axel?

 

[Myros]

i'd say axle

i thnk you could check by raising one rear wheel, and measuring the lash with it in D ( or all the gears) and then the same again in P. That might show the amount of lash . Or I might just be off my trolley again. (engine off of course)

 

[low farm]

Thanks Myros.

Are there any technical figures as a guide to how much free play there should be at the road wheel?

 

[Myros]

I have a data book in the glove box.

give me a while and I'll have a shufti. I'm thinking if P locks the box, then any lash should be down to the axle. You'd have to keep the direction of (attempted) rotation the same though. Theoretically, if the lash is in the boz, it woud be greater in D 321 than in P, and vice versa. Maybe I'm just too off the wall with this idea. Someone put me out of my misery.

 

[low farm]

I am getting keen now Myros.

Will get the jack out tonight and see what happens.

Sounds like a good plan to me.

I just wonder if backlash in the axel is down to worn gear teeth?

 

[television]

I have never known backlash to be a gearbox problem, it is a combination of half shafts, prop shaft U/J's to Diff bearings.

just by jacking up one side if the car whilst in park, the raised wheel can be turned in both directions and the free play can be seen

 

[Myros]

Thanks Malcolm

So, if low farm locks the various elements of the drive train, he should be able to measure the lash of each portion. I've had a look at the data book, and it doesn't give any free play figures for the drivetrain.

 

[wireman]

Hand turn the prop shaft in neutral, wheels on floor & parking brake on,
any free play in the diff crown wheel and diff will be found.

 

[low farm]

Jacked up the LH rear wheel as soon as I got home tonight.

With brakes off and gearbox in P measured 15mm play at the wheel rim.

Does not work in R N D 2 1 or B as the gearbox turns freely!

It will be a result if the gearbox is ok and only the rear axel needs attention.

Will be contacting Autotechnic shortly.

Might push the boat out and have the subframe bushes replaced at the same time, (if the axel needs to come off).

Many thanks for all your collective advice.

 

[MIW615]

Jacked up the LH rear wheel as soon as I got home tonight.

With brakes off and gearbox in P measured 15mm play at the wheel rim.

Does not work in R N D 2 1 or B as the gearbox turns freely!

It will be a result if the gearbox is ok and only the rear axel needs attention.

Will be contacting Autotechnic shortly.

Might push the boat out and have the subframe bushes replaced at the same time, (if the axel needs to come off).

Many thanks for all your collective advice.

Do as wireman says - what you are "feeling" using the method above is not only the wear between the crownwheel and the pinion but also any other wear between the roadwheel and the differential.

Manufacturers don't give data for this type of test, the only data is for when the differential is on the bench being overhauled.

Having said that if you have measured 15mm at the roadwheel I would expect the measurment at the propshaft to be somewhere around 10mm

 

[wireman]

MY 124 250d has about 10mm of backlash at the rear UJ, it clonks slightly on over run if I am being a wee bit pushy with my driving. That said its done this for thousands of miles and does not seem to be degrading.
I hope it lasts forever.

 

[MIW615]

MY 124 250d has about 10mm of backlash at the rear UJ, it clonks slightly on over run if I am being a wee bit pushy with my driving. That said its done this for thousands of miles and does not seem to be degrading.
I hope it lasts forever.

How many miles has your car done?

Most cars with this type of axle go through "a settling in period" from new - this is because when the crownwheel and pinion is set up from new there is minimum backlash between the crownwheel and the pinion and over the first few thousand miles the crownwheel and pinion settle in (mesh) as do the bearings so the backlash will increase quite a lot from it's original setting. Once it has reached this point the backlash normally will not increase any more, that is not untill after many thousands of miles later, when then the bearings start to fail thus increasing the backlash and subsequently resulting in "clonking" and axle whine.

 

[low farm]

The Car has now done nearly 110,000 miles.

We are only putting on 2,500 per year.

I am going to contact our Friendly Mercedes fitter at the end of the summer and look into the cost of new rear axel bearings.

The clonking wireman refers to is the perfect description!, and yes with careful driving you can control it.

Pleased to hear all the positive feedback and hopefully reasured that it is not a serious problem.