Stiffer clutch springs - PeachParts Mercedes-Benz Forum

Bajaman · #1 05-01-2009, 02:21 PM

Does anyone know if there is a clutch with stiffer springs available? It is very easy to get my 4spd stick wagon into an oscillatory bucking mode. For example, if I abruptly let up on the go peddle and then get back on it, the car will buck violently until I dampen it by letting off the go peddle again. This seems like the stiffness of the springs ( or perhaps I have a broken spring) in the clutch may be one of the culprits. Any other slop in the drive train is also obviously not going to help this situation. All the driveline rubber is new, diff seems tight. Thoughts?

Number_Cruncher · #2 05-01-2009, 02:26 PM

I would be more inclined to fit a damper to the accelerator linkage on the IP, to limit the rate at which the fuelling demand can be reduced.

These were quite a common fitment on 1970's and 1980's diesels fitted with manual gearboxes in Europe.

Although not an MB pump, this one has such a damper fitted;

http://cgi.ebay.co.uk/PEUGEOT-306-XSARA-1-9-TURBO-DIESEL-LUCAS-INJECTOR-PUMP_W0QQitemZ230337976302QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item230337976302&_trksid=p3286.c0.m14&_trkparms=72%3A1689|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A0|293%3A2|294%3A50

Bajaman · #3 05-01-2009, 02:31 PM

I thought this was to help smooth out the shifts (keep engine rpm up). Even without "trying" to get this oscillation, it can happen under light acceleration/lower rpm. It really is a drivetrain vibration problem. Maybe this is another reason the 617 had a heavier flywheel.

Number_Cruncher · #4 05-01-2009, 02:35 PM

Does it matter what gear you are in?

charmalu · #5 05-01-2009, 02:50 PM

Does your shift lever move back and forth when you goose it and let off?

Mine was doing that. I did a 4 spd swap, and was using the transmission mount for the automatic. changed it to one used in the 300D`s thru 81. also used in the SL`s until 89. it has the small oval hole it it. there is a metal piece that attaches to it, with a bolt going through the oval hole.

this solved the problem. there was too much give in the rubber mount.

I have seen those linkages with the spring in them and wondered the reason for it.

Charlie

#6 05-01-2009, 04:27 PM

The bucking has to do with throttle linkage. You can add a damper but adjusting (and later removing) the ALDA eliminated all bucking in mine.

winmutt · #7 05-01-2009, 05:11 PM

Or perhaps replace your tranny mount and rear diff mount.

Number_Cruncher · #8 05-01-2009, 05:18 PM

I don't know if Bajaman's motor car was originally a manual car, or has it been converted?

Looking on the Russian parts site, many MB diesels, W123 & W124 are fitted with an accelerator damper when fitted with manual gearboxes. Perhaps it should have a damper?

Stevo · #9 05-01-2009, 06:53 PM

I notice the difference, my 85, Euro manual, has the damper (little 'shock' type thing) and my 79, 240D does not. It makes shifting a little smoother in the 85, particularly first to second.

I am not sure the original poster was talking that type of "bucking". The springs in my 85's clutch disc are getting a little older (118K) and I can feel the difference when I drive my 79 with 45k on the clutch, no "bucking". It definitely feels like the clutch springs in the 85 are causing the "bucking" or "horizontal bounce". It only happens in first at very low RPM, easy to control, not something that happens much.

moon161 · #10 05-01-2009, 07:03 PM

Mine will buck pretty easily. I've trained my right foot to get to 20 mph w/o bucking, then you're pretty much good. My damper and motor mounts are both thrashed. Both are fine on the replacement engine. S'pose I could borrow the damper from it.

OM616 · #11 05-02-2009, 06:45 PM

Quote:

Originally Posted by Bajaman

Does anyone know if there is a clutch with stiffer springs available? It is very easy to get my 4spd stick wagon into an oscillatory bucking mode. For example, if I abruptly let up on the go peddle and then get back on it, the car will buck violently until I dampen it by letting off the go peddle again. This seems like the stiffness of the springs ( or perhaps I have a broken spring) in the clutch may be one of the culprits. Any other slop in the drive train is also obviously not going to help this situation. All the driveline rubber is new, diff seems tight. Thoughts?

Question; Am I correct in understanding that this is a 617 that was converted from an auto to a manual?

If so, with the car in neutral and at idle, if you very slowly step on the gas petal, (as just to increase the idle speed not to rev the engine), does the engine speed increase smoothly to say 3000 rpm, or is there a phase where it the speed will oscillate, for lack of a better term, (It would be as if you were pumping the throttle)? Then when the throttle is increased to a point the engine speed will steady out and increase?

Bajaman · #12 05-02-2009, 09:37 PM

Yeah, I put the manual gearbox in last March. Charmalu, the tranny does move around a bit under torque, I used the heavy duty 617 auto mount. I have the 240 mount as well (one with hole in it). OM616, accelerator response is normal.

OM616 · #13 05-02-2009, 10:18 PM

I asked because my 300D manual can be touchy on the bottom as well because the internal Idle adjustment is set for the automatic. I will get into that IP soon. there is just no room!!

The basis of my questions is, when I was adjusting my 616 IP, I went too far with the internal Idle governor and it wanted to balk. After readjusting it all was good.

The Idle governor setting for the automatic is such that the engine will idle down fast. This is desirable with an automatic, but is not good with a manual. I have found that if the idle governor is too strong that the engine will want to balk at very low speeds and will idle down too fast during shifts.

If all the external possibilities are not causing the problem, you may need to get into the IP and change some internal settings.