Help!! Clunking noise from diff when reversing

[mille]

Hi,

We just discovered that when reversing and accelerating (in a straight line), a strange rather loud clonking noise comes from the rear axle/differential. The sound continues and follows the speed -clunk-clunk-clunk.  When reversing and de-clutching there is no clunking sounds. When driving forward there are no clonking sounds, but there is a 'cooking' noise which comes from the diff. This 'cooking' noise dissapears when coasting in neutral.

Some time ago I checked the oil level in the diff and found that nearly 3/4 liter was missing as a consequence of a leaking seal! Is this clonking a result of the low oil level- did we run the diff almost dry and ruined it? Together with fresh gear oil we added a Bardahl additive which has now cured the leaking seal.

The clonking does not sound right, and I am worried that something is really wrong!

Any views and advise is most appreciated! Thank you for your help!

Cheers

/Finn  

1964 MB 230 SL Euro 4-speed silver metallic with black interior

[JimVillers]

Finn .... Closely inspect the driveshaft before getting into something more difficult.  A flex disk, U-joint and center bearing support can cause the type of clunking you describ.

Jim Villers
190SL, 230SL 5-Speed, 190E 2.3-16 Kompressor, MGB 5-Speed

[65auto230sl]

hi finn,
i agree with jim, check the entire drive line and closely inspect the two bolts that mount the center support bearing to the underside of the car. it sounds to me like you have some sort of a driveline issue, not necessarily a differential going out. if the driveline looks good ie. center support bearing, flex disc, u- joints, bolts etc. i would then drain the diff. and inspect for metal in the gear oil. also check the supporting tube slip joint mount. if you search rear axle differential mount replacement you will see it as part #151 in the illustration. mine went out some time ago and it was the cause of a clunk noise in the rear of my car. my "clunk" noise was only when i put it in drive or reverse, it wasn't continuous like yours but i assume if it was completely shot it could be. keep us updated, good luck.
bo
65 230 sl

[waqas]

Just to be sure, how does one go about checking the soundness of the tube slip mount? (since so little of it is visible)  Raise the car from the differential and see how far down the left axle-half hangs?

WAQAS in Austin, Texas

[waqas]

Finn,
While you're checking the driveshaft and flex coupling, see if there is any oddness with the driveshaft rotation while it spins clockwise AND anti-clockwise. If the clunking is driveshaft-related, the problem may manifest itself only when rotating in one direction (hence affecting only the reverse-gear).

WAQAS in Austin, Texas

[65auto230sl]

waqas,
i'm sure there is a more "correct" way to check the slip tube mount but the way i found this to be my problem was i had a friend get in the car, start it (with the brake being depressed)and put it into gear as i was looking under the car at the diff. i was able to see the movement of the entire differential shift up or down as the shifter was placed from park to d or park to r. it was very easy for me to see where the "cluck" noise was coming from.

[mille]

Thank you guys. Bo mention "supporting tube slip joint mount". I am not entirely sure I know what this is and where it's located. Could you shed some light on that?

Thanks

/Finn

[mille]

Tried to reproduce the clonk sounds today, but could not! We tried over and over again. When we experienced the clonks we had just mounted new KYB gas shocks front and rear and the reversing was on an not-so-even dirt road. Maybe the new shocks had to 'settle-in'? We will keep a sharp ear on the transmission in the future.

By the way, I can really recommend new shocks. Yes, the damping of the KYB's are rather firm, but we like it as it transforms the car and the drive is now really sharp and responsive.

Cheers

/Finn  

1964 MB 230 SL Euro 4-speed silver metallic with black interior
[/quote]

[JimVillers]

Finn ... You didn't mention inspecting the differential support in the trunk.  If the top plate is resting on the frame, that might be your clunk problem.  There should be a quarter of an inch or so for the transmission to move around a little.  You can also inspect the mount while you jack up the differential.

Jim Villers
190SL, 230SL 5-Speed, 190E 2.3-16 Kompressor, MGB 5-Speed

[mille]

Thank you Joe, you might have a point here. I will be away most of the week, but will check upon my return and shall post my findings.

Thanks again for all your help.

Cheers

/Finn

[seattle_Jerry]

I had a 220D and was getting an occassional kluncking sound took the differential cover off and several of the bolts that hold the gears had worked themselves loose over the years. They were sitting in a mound at the bottom of the differential. No previous work had been done on the diff.

Looking back I shouldnt have sold that car. My dad bought it one year old in 71 and I sold it in 98. Great car.

1967 230SL Havana Brown Auto with A/C