CLassic 1983 Mercedes 300SD

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Hello everybody, my names Daniel and i just recently got this car about 1 month ago from a used dealership. My problem is that when i press on the accelerator either a 1/4 or more down i get a horrible vibartion coming from my rear when the car is going between 15mph and 25mph, you can feel it even more with the more you press on the gas. It sounds like a thumping, rumbleing sound that might be coming from the back tires. But after i pick up speed it stops making the horrible sound. And also when you light press on the gas and slowing picking up speed you cant hear the sound. I just got the car not that long ago and gave it an oil change (2 times cuz the oil was so damn black, i guess that happens to diesels. Anyways i might have pushed the car to hard by pressing the gas to much and even starting it in 2nd gear and punching it (I wanted to hear that turbocharger roar) I think thats where i went wrong, now im getting that noise, and worrying that it might by my tranny, or something in my rear end. Can someone plz help me find out what my problem is, I dont think that it might be major cuz i added more AT fluid and the Gunk* bottle to clean the AT fluid etc. And its not that loud anymore (i think). I dont know about the previous matience but the engine sounds fine (but it sounds like it needs a timing adjustment but I might be wrong, it revs at 33-3500 at 80mph.

Can somebody plz help me out?

posted by  smokendabuda

Hi and welcome! :thumbs:

It could be a number of things. My initial thought was one or both rear wheel bearings, but you mentioned that the noise stops after a certain amount of time or when a certain speed is reached. This makes me thing it's more of a transmission problem, as this car is a rear wheel drive (or atleast I'm assuming it is, as most Mercs are), I would have the rear axle and diff setup checked out by a Mechanic, I would suggest however, that you check the axle oil level and fill as required, it should use Transmission fluid, but it's vital that you check which fluid is the correct fluid. This can be done at home by yourself and it should only require a hex tool to remove the bung (the type you get in a set of about five or six and slot into a 19/21mm spanner/wrench?). If you carry this out and the noise persists, I suggest you go with having the Mechanic check out your transmission...good luck :thumbs:

By the way, turbo's dont roar...they whistle...and does your Merc even have a turbo? :hi:

posted by  Cliffy

Hahaha LoL,
Axil oil? Never heard of it, but ill be sure to check it out in the chiltons shop manual. Hmm I never thought about the bearings or axel, it could be because i fishedtailed (whatever you call it) a couple of times and it mighta put too much stress on the axels or something esle back there. I just dunno cuz it goes away after i go past 25, but maybe the noise gets quietier the faster i go?? Cuz i dont know if my brain is playing tricks on my but sometimes it sounds like i can BARELY hear it.

Oh boy did i screw up.

And ya its turbo charged, ild post a pick but i dont know how!

posted by  smokendabuda

Replaced the gear oil in the differential, had rear bearings inspected and repacked ?????
Cliffy said"rear wheel bearings, but you mentioned that the noise stops after a certain amount of time or when a certain speed is reached." Which is a good point, BUT,
You just may not be able to hear it anymore :2cents:

posted by  lectroid

Very true Lectroid, also, it might still be atleast one rear wheel bearing. If the noise disappears when you round a bend, the weight of the vehicle is shifted, so if you turn a corner say...left, and you hear a loud noise, chances are it's your right, or off side bearing that's worn. It works the opposite way if it's the other bearing, obviously lol.

And yes, getting the back end to go out can be known as 'Fishtailing' but I suspect it wont be an easy tak in a car like that lol...especially as it's a diesel! :thumbs:

posted by  Cliffy

What I meant was, as the speed/rpm of the wheels increase, you won't hear the noise as prevelant as in the lower speed/rpm,and as such with the differential. Sometimes I don't spleak to splain :laughing:

posted by  lectroid

Ya it was pretty easy to fishtail, all i had to do was decrease my speed and stear hard and floor it in 2nd gear (p.r.n.d.3.2.) and the shift of the weight and the tires rotating would be enough for me to do a 360. (did it only once though cuz it was damp.). At first it sounded like it came fromt he right tire, but now i think its coming from the back (i cant sey both cuz i dont know ifs its actually coming from the tires. Hmm I dont think you can hear it from the outside, but inside its a loud vibartion with more gas applied.

But do you think that a bearing can make that much vibartion?? I dunno ill spray that ****er down with some wd-40 and see what happens, I need a damn owners manual!

thank for your input guys i REALLY appreciate it.
and lectroid i love your sig man, kerrys a koward.

posted by  smokendabuda

I dunno ill spray that ****er down with some wd-40 and see what happens,

Don't do that! :banghead: You need to have the bearings and rear end checked. Also, it could be nothing more than universal joints.

posted by  lectroid

Did you try Gas-X? :hi: :laughing:

posted by  DodgeRida67

What bout this:
get the car up on stands, or a hoist, and follow the driveshaft up towards the transmission. there's 2 pieces up there that can cause exactly the type of vibration you describe. the first is a rubber 'donut' between the transmission output, and the drieshaft. if its loose, the rubber is degraded, or the little centering bushing is worn, you'll get a lot of vibration out of it. second item is that your car uses a 2 piece driveshaft, with a carrier bearing about 12" behind the tranny. if that bearing, or its mount are bad, you'll get vibration. If worn, both the 'donut' assebmly, and the carrier bearing/mount are remove and replace items, neither are rebuildable.

Is it more likely that i can be that???

HOw much do you think that it might cost for the bearings or for the rubber donuts??

posted by  smokendabuda

I called the donut shop and they said they don't have any rubber donuts :screwy:

:laughing: :orglaugh: :laughing: :orglaugh: :laughing:

posted by  DodgeRida67

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