Automatic Transmission rear end "clunk"

[n/a]

Hi, I just bought a 1970 280sl with a automatic transmission. The kickdown function works, but I still have an irritating clunk when I coast up to a stop, any ideas?  It appears that the solenoid on the trans is working (as I have kick down, or am I wrong to assume this?) What else could it be? I cleaned the throttle body today, boy, was it gunked up!  By the way, how hard is the transmission solenoid to remove, and what is the best procedure, thanks!

[Ben]

Maybe the flex disc is poor ?

Regards,
Ben in Ireland.
'64 230SL 4sp.
'03 CLK Kompressor

[Malc]

Is the "clunk" coming from the transmission area??

Check all prop / driveshaft joints and mounts, make sure that the engine/gearbox mounts have not gone all mushy.

One way to check the mounts is to open the bonnet and rev the engine if it moves around alot then the engine/box mounts are getting tired
HTH
Malc

[ja17]

Hello James,
This problem is usually caused by an improperly adjusted venturi switch. Check this string;

http://sl113.org/forums/index.php?topic=243,switch

Keep us up to date.


Joe Alexander
Blacklick, Ohio

[hands_aus]

Hey James,
You can test the 3 position solenoid by putting the gear lever into PARK OR DRIVE (this will stop the engine from starting by mistake) then turning the ignition to ON. Maximum of 20-30  seconds at a time.
If you listen you will be able to hear the solenoid click to the Rear position.
Touch the accelerator pedal slightly and you should hear the solenoid move to the centre position.
Kick it down all the way and you should hear it click to the Kickdown position.
You can free it up and lubricate the couplings through an inspection cover on the right hand side of the transmission tunnel (under the carpet of course) just directly below the dash board edge.

If the idle switch on the venturi unit is adjusted correctly, the constant speed solenoid on top of the inlet manifold should work too. (You should be able to see the linkage move when you have the engine running and you put it into gear.)

Of course it is always worth checking the rubber bushes mounting the rear axle. There is a huge one that supports the axle to the body. It is almost always worn out.
Open the boot and when you look inside you see a shelf. In the centre should be a plastic cover under which will be the worn out rubber mount.
It is relatively inexpensive and easy to replace.

These problems have all been encountered by others. I suggest that you do a search for each topic, grab a glass of something to drink and have a good read.

Bob (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[n/a]

Hello guys,
 I just lookedat this post, and I've got no kick down and rough idle
and missing on one cylinder could it all be connected to miss adjusted
kickn down? also I have to push my shift lever nearly into third to
get it to engauge into drive and move it back into pos 4Th but it kicks up o.k. HELP?
Pagoda Red

red kelly

[rwmastel]

James,
Any luck with your clunk?

Red,
I don't think your idle & cylinder miss problem could be associated to a kickdown switch or 3-position solenoid.  If your automatic shift lever needs pushed to 3rd in order to engage 4th (drive), then it's most likely the plastic shifter bushings.  Search this forum for "shift bushing" and read to your heart's content.  Finally, if you don't have any kickdown function in your automatic transmission, that would be related to the kickdown switch under the gas pedal and/or the 3-position solenoid on the transmission.  Again, search this forum for these key words and read how others have done troubleshooting and repairs on these items.

Thanks,

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[n/a]

Thanks Rodd, yes, I have discovered after setting the linkage/throttle plate correctly that my idle switch is faulty due to a cracked housing so I have ordered a new one. I accessed solenoid at trans, it moves freely, so I will be curious to see what happens when new switch is installed.  I also noted that rear diff mount had never been replaced so I ordered a new mount and will replace that at the same time.  I will report on Thursday when the parts come in what kind of results I get.  thanks for your interest!

[n/a]

Clunk is gone.  New mantra . . . listen to Joe.  My idle switch was defective (venturi switch) New switch, adjusted, no more clunk, a miracle.  I was very happy to have readjusted the throttle plate and linkages prior to this repair, made a huge difference in running/shifting. Also removed throttle body for cleaning, what a mess!  dirtiest throttle body I have cleaned to date! So nice to coast up to a stop and not hear"clunk" on the final downshift.  Thanks to Joe and all, I love this site!

[ja17]

Good job James!

Joe Alexander
Blacklick, Ohio