vibration like a power sander when in drive...
 

...but not in reverse or neutral while parked!

Howdy! I just inherited a pretty nice '79 300SD to go with my '79 300SD! I'm pretty excited because it shares the same earlier chassis number, so we can share parts! I have not driven it yet, just got it started this afternoon after charging the (Sears Diehard battery...THE SHAME!), and noticing that the cold start knob had popped it's lid! I reached up and found the lid, so that's miles behind me. :D

The previous owner was having trouble starting it. I wonder why? ;) They did not think it ran, but have owned it since new, and took great care with it.

Once I got it started, I put it in drive, and this HORRID vibration starting, not like a diesel engine sway, but more like a floor sander that shook the steering wheel, the seats, the whole cabin, and worst of all, ME!

:eek:

It stops when I put it in neutral or reverse, so I'm wondering if it might be a simple motor/trans mount, or if the tranny is crying!

What do you all think?

This car is a sweetie, leaky a little but really nice looking inside and out. I keep peeking at it from the windows in different parts of the house.

P.S. After charging the battery and solving the cold idle knob problem, it started pretty well in 9 degree weather! That's more than I can say for my other one.

I have the service records. It was serviced very regularly, has had two new timing chains (wow!), two new climate control servos, and a plethora of window regulators (thank goodness!)but no mention of any tranny work or motor/trans mount work.

Think buzz saw, think crop duster!

I've missed you! Glad to see you are all still here!

Sounds like a flex disk / drive shaft problem.

Did I understand correctly? When you put the car in drive, it vbibrates? Are you saying that you are not moving down the road, but simply sitting still with transmission in drive? If so, I don't think you have a flex disk or drive shaft problem.

If the severe vibratin happens when you're idling in drive, it's most likely motor/trans mounts. If it happens only after pickin up speed, it could be driveshaft 'U' joint or flex joint.

Happy Motoring, Mark

Sorry, I misread his post. I thought he meant moving in drive.

I'd go with motor mounts / trans mounts suggestion.

Yes, you understood me correctly, it happens while sitting still in the driveway, shifting into drive with my foot on the brake. When I shift back to neutral or reverse, it stops. It's really something!

I'd go along with earlier posts. I think it is engine and transmission mounts. My 300CD vibrated (less than you are describing) when in drive, and my mounts were not all that bad. After replacement it was significantly smoother.

I hope this is your problem A relatively cheap and DIY repair.

Good luck.

Thanks everyone, I'll switch out the mounts and let you know if that cured the weird vibration.

That sounds like mounts, huh...

The engine is probably touching the frame, and that would really cause a ruckus!

Well, the vibration is gone. I guess it wasn't the mounts, but perhaps a combination of two things I recently did.

After changing out the starter, which required letting down the exhaust system. I noticed that the 'muffler shop' exhaust had been rubbing up against the transmission. When I put it up again, I made sure that it wasn't touching. That seemed to completely change the vibration into near nothingness.

The other thing that happened on a fluke was after filling up this 'new' car to full for the first time, I noticed that when I took a hard left, fuel was spilling out onto the pavement! This car had been idling much rougher than my other car. I realized that the fuel cap was missing the white plastic part! So, I switched it out with my other car and the idle became quite nice! Of course my fuel filler drain tubes were plugged and the entire filler area was full of diesel fuel. It's dry as a bone now.

I'm not sure why that would affect the idle unless some vacuum was involved, but there you have it. You'd think a full fuel tank would create its own vacuum?

I'm a firm believer in 'magic mechanics'.

The car just purrs like a kitten now. Thanks for the help. I'm now experiencing the dead battery 'on occasion' complex. I'm certain that my brushes on my voltage regulator are exhausted. I took the one out of the other car and will swap it tomorrow.

P.S. for all the '79 300SD owners, it is a five minute job. Just take off the air cleaner, get a mirror and a flashlight, unclip the wire harness pull it off, then get a small ratchet with a screwdriver blade, there is lots of room and it comes right out! No need to lay on the ground for this one!

I was getting a 12.4 when the car was running, but on the car with the good one, I get a 14.4. So, that's a sure bet (isn't 16 the norm?)! The funny thing is today it was dead twice and I got jump started by little itty batteries and the car just fires right up! I'm amazed by the stories by P.E. Haiges and running all of those miles with a dead battery! I think my battery which I recharged 2 weeks ago when I first had it go dead is just starting the car until it runs out of juice! I thought for a bit that my rear defroster was the cause, but it was just taking more battery juice. I don't have a stereo installed and had I, I would have noticed earlier about this problem. I have not noticed any battery light or dimming but I don't drive at night too often. Tonight when I put the charger on the battery, it was completely drained. It's a brand new battery so I'm quite sure it is the brushes.

Of course I checked the archives here before becoming so sure of myself. Thanks everyone!

HI ya Patsy.

Good job, definitely get the brushes replaced and this will all be behind you. Remember, the idiot light seldom comes on when the alternator isn't charging, but it has to be there to complete the circuit.

Glad to see you're still poking around the Shop ;).

Hi Mike! Nice to see you as well. :) I just came inside from swapping out voltage regulators. Sure enough, the one that was seemingly having problems (the black one) had brushes that I had to get the magnifying glass out to see! It was a real Bosch VR, and was much smaller, and of a different design than the 'made in Brazil' regulator that I got from the ivory car. I questioned swapping them out, because the Brazilian one had a big box on it, but it was the same size internally, and had much longer brushes.

I was waiting for some kind of chaos when I fired the black car up, but it seemed to run even better (I swapped air filters too!).

Oddly, or not, both cars have a broken 'leg' on the air filter mount (the back one)! I smell a recall (or pot metal)!

It is now putting out over 14 volts.

I stole the starter from the Ivory car today too! The poor thing! I also have eyes on that vacuum pump I rebuilt a few years ago. The black car seems to be going through all of the same things I already repaired on the ivory one, but the body is so much better, I can't resist!

I had better check out some 'two for one' deals.