Transmission tugging? - PeachParts Mercedes-Benz Forum

seabrighter · #1 09-16-2007, 03:03 PM

I just bought an '83 300D turbo about a month ago. It's running on Biodiesel, and the previous owner had already changed all the fuel lines and filters. I'm still taking it out on short drives until I fully understand any issues it might have. So far my biggest issue is, of course, vacuum lines. My door locks don't work, engine runs for about 8 seconds after pulling out the key, and my transmission shifts pretty hard on the 1-2 and 2-3. I've read a little about the relation of these things on the forum and I have a MityVac coming in the mail to help troubleshoot.

Yesterday I took the car on our first long drive, about 80 miles round trip. I had to climb a couple long inclines, and I noticed things getting a little jerky. I could barely hold 55mph up the hill, downshift was not kicking in, and it seemed to "tug" a lot. It wasn't a transmission "slip." I've had a car with a slipping tranny, and this was not it. It was more like the car was being tugged, as if pulled by a rope. It did this in 4th gear, but when I downshifted manually into 3rd, the tugging was more noticeable.

I would kind of describe this movement like the way your car feels when it is being blown around by the wind. It was like gusts of wind coming from head on, except I know it wasn't very windy. Also, all gauges read normal when this is happening. Tachometer is constant, oil pressure, even speedometer not fluctuating much.

Is this more of an engine thing? A turbo thing? I'm a little worried about the sluggish uphill because it is fairly hilly where I live. Any pointers on where to start with this problem would be great!

pawoSD · #2 09-16-2007, 03:16 PM

Check your transmission fluid level, that could cause something like that. Or, if the trans fluid is proper, I'd check to see if the engine is running properly....tugging could be a cylinder not firing properly....does the engine make good power? How is the 0-60 acceleration? It should be about 12 seconds for that car. Does it idle smooth? Little to no smoke? Etc....

A 300D turbo should be able to take most hills at 90mph no problem, they are a quick little car. Ours easily tops 100mph....

300SDog · #3 09-16-2007, 03:38 PM

Hard shifting i understand is healthy sign. You dont want it smooth as butter or it'll soon be flaring in between shifts. Am getting used to newly purchased 1980 w116 300SD automatic myself, learning to feather my foot off the pedal when anticipating the tranny to shift. Also I often shift manually in between D and S feathering the pedal, never use L. Dont gas it between shifts and it wont kick like a mule. Hope I aint stating the obvious here if you're aware of this already. But another thing you wanna do is visually inspect the flex-disc and tranny mounts underneath, could be the engine and tranny rocking around and yanking on the driveshaft.

pawoSD · #4 09-16-2007, 03:53 PM

I usually let off the throttle a bit at shifts too....especially the 3-4, I usally just let off completely for a moment like its a stick shift. It appreciates it. I also usually hold it in 3rd and shift it to 4th when I really want it to.

Dumping on the power when its trying to shift just wears out clutches.

seabrighter · #5 09-16-2007, 04:00 PM

Quote:

Originally Posted by pawoSD

Check your transmission fluid level, that could cause something like that. Or, if the trans fluid is proper, I'd check to see if the engine is running properly....tugging could be a cylinder not firing properly....does the engine make good power? How is the 0-60 acceleration? It should be about 12 seconds for that car. Does it idle smooth? Little to no smoke? Etc....

A 300D turbo should be able to take most hills at 90mph no problem, they are a quick little car. Ours easily tops 100mph....

I haven't really timed the 0-60 accel. I feel like it's pretty good, but then this is the only one I've driven. I'll time it next time I'm getting on the freeway. The idle is not the smoothest. It makes the car shake a little when I'm at a stop. I was told this is normal for a diesel, but maybe not? What about the air filter? I looked at it today and it's pretty dirty. Think changing it would help very much? (I'm gonna change it anyway)

pawoSD · #6 09-16-2007, 04:14 PM

A little shaking is normal for these engines, it takes a bit of work to make them idle super smooth.......a real dirty air filter could indeed inhibit some performance, its good to replace it. I do every couple years.

Another thing not yet mentioned is fuel filters. The little pre-filter on the line going into the engine, and the "spin-on" filter behind the power steering pump (looks like an american car oil filter) could be plugged up, if so, you'll definatley have a loss of power at higher speeds, and potentially rough starting and idle as well depending how plugged they are. About $11 to replace both, so its easy/cheap maintenance.

Once all that is looked at, if its still doing what you described, I would bet its a transmission or possibly a vacuum issue.

Brian Carlton · #7 09-16-2007, 04:17 PM

Quote:

Originally Posted by pawoSD

A 300D turbo should be able to take most hills at 90mph no problem, they are a quick little car.

This is factually incorrect. With 125 hp, the vehicle is very close to using every available pony to run 90 mph. If the grade is greater than about 1%, the vehicle will slow down.

On a decent grade (4% estimated), the vehicle won't hold 70 mph. You can't raise a load at high speed without horsepower.

pawoSD · #8 09-16-2007, 04:24 PM

Quote:

Originally Posted by Brian Carlton

This is factually incorrect. With 125 hp, the vehicle is very close to using every available pony to run 90 mph. If the grade is greater than about 1%, the vehicle will slow down.

On a decent grade (4% estimated), the vehicle won't hold 70 mph. You can't raise a load at high speed without horsepower.

I went up a fairly long/steep (3-4%) grade today in my SD and I was going over 90 when I began the hill, and with the pedal to the floor I didn't fall more than a couple mph over the course of the entire hill (kept it over 90)......so I guess I was using every last HP.....but it still did it remarkably well. Thats on dino diesel with new injector nozzles....perfect timing, and not much weight in the car (1 person and no stuff and fuel tank on reserve....)

With a bunch of stuff, full fuel tank, and my old nozzles....it worked pretty hard to hold 85 up that hill....so I guess my nozzles improved things.

I'll agree 90 easily is a bit overstated......

I just like to imagine they have more power than they do....

benzforlife · #9 09-16-2007, 06:52 PM

i have never had my sd strain on hills, if i mash the pedal it just keeps climbing

the tugging sounds like low tranny fluid to me.

seabrighter · #10 09-16-2007, 09:54 PM

Quote:

Originally Posted by pawoSD

A little shaking is normal for these engines, it takes a bit of work to make them idle super smooth.......a real dirty air filter could indeed inhibit some performance, its good to replace it. I do every couple years.

Another thing not yet mentioned is fuel filters. The little pre-filter on the line going into the engine, and the "spin-on" filter behind the power steering pump (looks like an american car oil filter) could be plugged up, if so, you'll definatley have a loss of power at higher speeds, and potentially rough starting and idle as well depending how plugged they are. About $11 to replace both, so its easy/cheap maintenance.

Once all that is looked at, if its still doing what you described, I would bet its a transmission or possibly a vacuum issue.

Well, I got a lot done today. I changed the rear brake pads (my first time doing it on any car, thanks to the MBDIY!). I changed the air filter, and I replaced a few missing screws on the interior. I checked my tranny fluid, and it was a nice clean red and plenty full. I checked my oil, that was not so pretty, so I'm going to get that changed right away. I also pulled my driver's side door panel off and checked vacuum lines. They were fine, so that's 3 out of 4 door locks that I've checked now. I'm hoping the MityVac will help me find this vacuum problem quick, but I'm sure I'll be asking this forum how to use it! I'm appreciating all the input though.

barry123400 · #11 09-16-2007, 10:14 PM

It would not hurt to eliminate the fuel filters as the cause of your problem on the hills. Especially if you have no ideal when they were last changed.
The engine is asking for more fuel on the hills and the filters may not supply enough constant volume if very dirty. Yet still preform pretty well normal at lower power loads. Probably the first place to go unless there is some other positive indicator. A previous member mentioned it as well. General maintenance item anyways.

kerry · #12 09-16-2007, 10:15 PM

The 'tugging' sounds to me like fuel filters.

#13 09-16-2007, 10:22 PM

Quote:

Originally Posted by kerry

The 'tugging' sounds to me like fuel filters.

I agree, that does seem to describe the feeling of a partially clogged filter.

The rest of you guys need to define "hills" a little better. Holding 90 mph on an average mid-west freeway "hill" is one thing, holding 90 mph on a 4% grade at 9000 feet above sea level is something else. Mine will do 90 on the first and (maybe) 70 on the second.

DeliveryValve · #14 09-16-2007, 10:29 PM

I had this Symptom in my car a couple of times. First It turned out to be one of the rubber fuel lines getting air into it and the second time it was the filter.

benzforlife · #15 09-16-2007, 10:54 PM

maybe its the in tank filter, the up hill grade makes the fuel fall back and if the filter is clogged that would greatly affect suction.