75 280 transmission jerking - PeachParts Mercedes-Benz Forum

VickMorrow64 · #1 08-09-2010, 08:50 PM

Hi
This is my first post

I have a 75 280C and the the tranny fluid was very low - I purchased some quarts and filled until I started to get a reading. When I put the car in reverse and back out of garage then put it in drive the car makes a tremendous clanking/banging sound. Seems to shift fine while driving.
Is this clanking vacuum related? If so , where do you suggest I check?

Also the tires chirp when I go from reverse to drive - seems idle is a little high. I removed the extra large air cleaner but could not find any of the adjustment screws (idle and air/fuel)- does anyone know where they are located on this model.

Also is there anyway to tell what carb this car has? I was told Solex4a's came on these - are there any identifying marks?

Any help is appreciated

mbbuff · #2 08-10-2010, 08:33 PM

Idle speed can definitely cause the jerking/tire chirping between drive and reverse. If it has the Solex 4 bbl. carb. (looks like a 4MV Rochester Quadrajet, if you're familiar with them) on it, the idle speed adjustment is not easy to set "correctly", but once set should never need messing with. The "real" idle speed adjustment is located on the vacuum governor. Some folks use the idle stop below the governor as the speed adjustment. This is not correct, but will do if the governor is bad or not adjusted properly. The idle fuel mixture screws are on the carb. base (very difficult to see/adjust) in the front of each primary throat. If it has the stock "huge, flat" air cleaner, it is more than likely the stock unit. An easy way to tell is to look at the choke. It's an electric (one wire) unit with a small coolant line going in each end. Fuel inlet is in the front, center. A small vacuum dashpot on the outside rear.

Can you better describe the clanking/banging sound? This concerns me, as there should be no such sounds upon gear transition from reverse to drive. Have you checked the motor mounts, and the driveshaft flex discs? Is there any vibration when driven.....during acceleration/deceleration/steady throttle?

mercmad6.3 · #3 08-15-2010, 05:32 AM

Sounds like the flex disc to me also,and the center bearing support.

Before adjusting the carb,check all the engine vacuum lines for leaks.

VickMorrow64 · #4 08-16-2010, 09:36 AM

Thanks for the replies will drive it some this week and get back to you.

I used to have a rochester quadrajet 650 in my old buick gsx - looks similar just not as large. I am familiar with the sound generated from center bearing/support and drive axles(when they are going bad) and neither appear to be the noise that I am hearing. I am not familiar with the flex disk noise - so that could be the one. I'll need to check motor mounts and vacuum leaks as well.

mbbuff · #5 08-16-2010, 05:17 PM

Definitely sounds like a Solex carb. With a little luck no one has messed with it too much. They can be troublesome if someone has warped the top/body. Does it look like the vacuum governor (big vac. dashpot) is in tact, hooked up and working? Do you have a vacuum tester/hand pump?

BEFORE YOU DRIVE IT ANY FURTHER, I highly recommend you get it up on a lift and physically check the flex discs for cracks/distortion, and look for anything else in the drivetrain that could be causing the noise/clank/banging. If a flex disc fails, especially a front one, (even at slow speed) you can potentially suffer some serious drivetrain destruction. Definitely worth an early look, IMO.

VickMorrow64 · #6 08-17-2010, 09:07 PM

I'll get it on a lift this weekend. Don't have a vaccum tester. Did drive it some yesterday and it was a little rough going from 1 to 2 then much smoother shifting going from 2 to 3. I punched it down and felt the kickdown working but then nothing happened - barely gained any speed - lucky to go 45mph. A guy is working on the interior and when he is done I plan on examining all vacuum lines before driving it home. Any thoughts?