300E driveline slop
 

Car is a manual 1987 300e with around 165,000 km on clock.

Have a small amount of play in the driveline, which is most evident with the clutch engaged on the overrun coasting to a stop.

I have recently replaced the front flex disc and transmission mount, which improved the problem considerably, howevr there is still sufficient play somewhere in the driveline to be annoying.

I have visually checked the rear differential mounts and they seemed to be ok, although I plan to check them more thoroughly by jacking the chassis up and moving the diff this weekend.

My mechanic suggests it may be play in the differential gears, which I suppose is possible if the PO did not change oil as often as he should have. This is likely. Mechanic also suggests if this is the case, it might be possible to adjust the play with shims. Does anyone have experience of this?

Another suspect is the balance weight mounted behind the front flex disc.

The balance weight is a three point triangular mounting secured to a metal collar with rubber. The rubber damper material has worn and the inner mounting has been tack welded to the outer collar (I know, I keep discovering bodges like this. Wish I'd known more about the car and taken a closer look before I bought it)

Bearing in mind that the balance weight was apparently discontinued on the later 124s (what we know as the Masterpiece edition, the last E320/124s) , I'm asking whether anyone has experience with the function and purpose of this weight and whether it being in sub-standard condition is likely to cause the driveline problems I'm getting?

Plus, of course, any other tips for keeping things smooth in the driveline.

Most people take the balance weight off and leave it off.

If the slop were due to low or no oil in differential, the rear axle would be VERY noisy.

The most likely place for the slop are the flex disks and the differential mounts. The front flex disk fails first because it deals with much more heat. If you replace it, pay close attention to which way you put it in. It is marked in German, so look closely at the one you are taking out and compare to the new one.

Also shake the driveshaft up and down to check the center bearing carrier.

Good luck,

Hi Larry,

thanks for the reply.

I saw your earlier post about putting the front disk on correctly and double checked when it went on. I'm pretty sure I replaced the original item so no doubt the rear is ready for renewal as well. I'll be checking that when I look at the diff mounts.

Thanks for the tip about the balance weight, my mechanic also suggested taking it off so nice to have that confirmed.

No thoughts on wear in the diff gears? Ever heard of this happening?

One thing to check when re-newing the rear flex disc is the centering pin a.k.a. the Driveshaft Support. It centers the rear driveshaft onto the differential, contains a rubber ring that holds grease inside. Likely the rubber ring has worn out as it has on mine.
Replacement requires removal of the driveshaft, a good time to do your center support as I should do mine. (vibration at 35-40mph, no load, from center of car) on mine.

The U-Joints may also need to be replaced. Looks like a driveshaft overhaul is in order.

I believe driveline backlash like this is a combination of wear at several locations. I have the same problem with my 190E-2.3 Sportline 5-speed now showing almost 230,000km. I noticed service documents from the previous owner mentioning the problem. In response, the previous owner had the flex couplings replaced, engine mounts replaced and differential overhauled. Despite all this there is still backlash which I have simply learned to live with. Unless you are rough with it (or have clutch shudder as mine does cold after sitting for several days) there is no obvious problem. Checking components underneath does not reveal any one problem area. Instead, a combination of wear at various points appears to add up to cause the problem. I believe much of it may well be in the various splines, particularly on the rear axles. Remember also that backlash before the differential needs to be around 3 times more than backlash after the diff to have the same effect due to the gear ratio of the diff. My high kilometre 350SLC has noticeable wear in the rear axle splines which gives consderable backlash, masked only by the fact it has auto rather than manual transmission. As for the balance weight at the front flex coupling, I believe this was unique to the manual versions. My manual '90 190E has it whereas my auto '90 300TE (and '73 350SLC) do not.

There is only one u-joint in which the bearings turn an infinitessimal(sp?) amount. When the u-joint goes on these driveshafts it results in a stiff spot and will cause a vibration. Unlike a solid rear axle car where there are two u-joints and they can where to a point of significant slack.

Good luck,

Driving down the mountain today I'm more and more thinking its a worn damper issue instead of something serious. Still planning to check the diff mounts and rear flex disk first and hope that's the problem. Was raining last weekend so spent my time thinking about it in front of the TV instead of getting under the beast to check. Will report back soonest.

While I'm here, anyone like to report on probable life of the rear flex disk? I've seen it suggested that the front should be good for 60,000 miles. My front disk was looking pretty shagged when I swapped it out at 100,000 miles, although the fact that the balance weight had been welded up suggests it may have been changed or at very least looked at sometime in the dim and distant. Center bearing was OK.

Same goes for the diff mounts, how long before they need replacing?

inspection update
 

OK, have had a chance to inspect the driveline bits. Rear flex disk is OK, diff mounts are ok, problem diagnosed as play in the diff by lifting the wheels off the ground and twisting the prop shaft to see where the slack is.

Based on advice from my mechanic and parts shop, parts which will need replacing are the outer seals, plastic shims and the centre pin for the gears. As soon as I can take the car off the road for a day or two, will be atatempting diff refurbishment. Any tips or suggestions welcome.

By chance does your car have a limited slip diff?

My experience with them on Corvettes is that as the clutches wear, axle yoke end play and differential gear backlash increase. This can cause "slop" in the drivetrain. It is especially noticeable when you start from a dead stop with a lot of steering lock and there is relative movement of the differential gears. Open differentials don't have the same problem since there is no clutch pack that wears noticeably with use.

You can qualitatively check for differential gear backlash, by having a helper hold one wheel while you wiggle the other wheel back and forth and "feel" for the play. More than about 1/16 turn play means the differential gear backlash is high. Note that "differential gear" backlash is not the same as ring and pinion backlash - two different gearsets. A lot of guys get them mixed up.

Duke

Now there's a question. Unless they are included as standard in the 300E, I'd say no but to be honest, I have no idea.

Always thought an LSD was a performance item, used in race cars and the like. Not something that would be fitted to a sedate German sedan, fun driving car though it may be

Unfortunately, a LSD was not available for my car, but it really needs one. They were standard equipment on contemporaneous US model 560 SELs and 16Vs.

Don't know what specific market your car was sold in, but I know that certain equipment that was not available either optional or standard on US models was available on models sold in other markets.

A LSD is easy to check. Jack up one rear wheel and DOUBLE CHOCK the opposite front wheel. If you can turn the raised wheel by hand it's an open differential. If it's an LSD it will take a torque wrench on a lug nut to turn and a healthly LSD should require at least 40 lb-ft of breakaway torque.

Duke

OK, diff was rebuilt this weekend and driveline slop is gone, which has at least allowed me to feel what I suspect is worn rubbers somewhere in the rear suspension. oh well.

some points in case anyone is think of doing the same.

1) Find someone who has done this before
2) Don't try to do it on your own, you need 3 people if you don't have any jigs to hold the diff case still while you try to undo the bolts
3) Don't forget to buy a new case gasket when you buy the parts (doh!)
4) You will need a new diff pinion shaft, two plastic washers and probably the two thrust washers. the gears dont wear. Oh, and three new oil seals. May as well change the diff mounts while you're at it.
5) It will take at least one day.
6) Getting the diff and and off the car is best accomplished using a lift.
7) Don't forget to buy new oil when you buy the parts (double doh!)
8) You need a special tool to lock the diff in order to undo the bolts
9) You will need weirdly bent spanners
10) Your torque wrench won't fit
11) Read Point 1 again

Good luck.