anyone have a mercedes 300td?

[TBurow]

i have an 84 mercedes 300dt, and have a question about rpms at 60 mph. what rpms do theese things turn at 60, the one i have runs close to 3200 at 60, seems high for a diesel, i feel 4 shifts and shifts firm, but seems like there should be an extra gear.

 

[NCovey]

That sounds more like it should be doing 70 at 3200. Does it have the correct size tires? I don't remember the one I have running that high at 60, but it has been awhile since I drove it-Nicholas

 

[JMachemer]

my father has a 1976 300D and it the engine screams at 60+ mph. I don't know what RPM it is turning though - i could ask him. But it sure would be nice if it was a 5 speed auto. It would cut down on a lot of yelling and help the vocal cords.

 

[WDixon27]

they buzz pretty high at modern hwy speeds with no lock up converter, i don't remember if they have a overdrive, i don't think so as they usually have a real boring diff ratio to compensate, much beyond 70 and they usually start sucking oil pretty good so if you gotta fly for a good distance keep a eye on the level

 

[TBurow]

yeah this thing runs great but is pretty much crap on the highway, i dont want to toast an engine just to not get run over on the e-way, so it will be for sale soon as the title comes back, anyone interested?

 

[MOates]

I've got an '87 300D Turbo sedan. According to the specs, it has a 2. 65 rear end, and the 4 speed slushbox is 1:1 in 4th. It'll run about 2400 rpm at 60 and about 2800 rpm at 70.



One thing to remember, these beasts were sold and set up for back in the day when we still had a 55 mph speed limit, and as has been noted, they don't have lockup torque converters.



I've noticed on mine during the winter, for about the first 10 miles until the transmission fluid gets good and warm, it turns about 200 to 300 rpm less for the same speed.



The condition of the transmission cooler, the transmission itself, and the vacuum and other adjustments might have a lot to do with it as well. About 10 months ago I checked out another '87 with the same number of miles as mine. The transmission was much tighter and shifted so smooth you could barely feel it, and it only turned 2400 rpm at 70 mph. I took the hint and started doing some work on mine.



One easy mod you could try to see if it makes any difference would be to add an aux transmission cooler, see if colder transmission fluid makes any difference. With the factory radiator cooler, the fluid can't be any lower than what engine coolant temp is - ie, 170 to 180 F.

 

[WDixon27]

you could see what ratio diff it's got, i've seen em go as low as 2. 24 and you may be able to score one that's a better highway gear, it's also possible that someone put one that's less highway friendly for better off the line speed and that's why it sucks on the road

 

[TBurow]

i just fixed the vac lines and adjusted the cable, it shifts great just needs more speed. any change in gear ratio or taller tires and it would be even slower to accelerate.

 

[MOates]

Yep, the '85 and earlier 300's and larger models, with the OM616/617 engines, weren't noted for being barn burners. Even the '87 I have, with the 6 cylinder 3 L OM603 engine, rated for over 120 mph straight from the factory, was only rated for 140 HP/200ft-lbs.

 

[WDixon27]

double check that it's actually getting into 1st gear, the old cars were bad about starting in 2nd and it feeling normal, 1st is almost a granny gear and on a slow start it will just take off in 2nd till you put your boot in it, that slows some down, i have a theory about some of the slowness being a worn timing chain retarding the pump timing but i haven't had the chance to test that as a while back we stopped working on mercedes, a good valve adjustment can help too

 

[bigkid59]

For what it is worth, I checked my 1985 300SD and at 3000RPM it is showing 71-72 MPH. I have read that it has a 2. 88 axle ratio.



I just bought this car off of eBay a couple of months ago and I am really happy with it. All I have done to it so far was to install a new set of Bridgestone Touranza LS-T tires and that made all the difference in the world.

 

[tony597fitter]

You can always adjust the ALDA screw.

Check out Schuman Automotive /Forums - Powered by vBulletin

there is alot of good info here. Check out the super turbo section. It gives you a few ways to get some more power out of it. I know on my wife 83 300sd adjusting the ALDA screw seemed like it was double the power.

 

[Motorhead]

Your '84 has stock a 3. 07 rear axel ratio. I would check your speedo against another car or GPS. The only other explanation is that someone put an EARLIER third member in it. The NON turbo 300's ran about a 3. 40 ratio and a 240D ran a 3. 6 I believe.
The easiest way to check to see if you have the 3. 07 is to jack up the rear of the car, keep one wheel from turning, mark the driveline and other wheel and count the revolutions of the driveshaft to one revolution of the rear wheel.
Should be a little over 3 turns of the driveshaft to one turn of the wheel.

 

[2broke2smoke]

, i feel 4 shifts and shifts firm,

4 shifts?



hmm ...

1-2

2-3

3-4



makes three



you sure the fourth shift isn't going back from 4th to 3rd?



probably not but i thought i'd throw it out ...

 

[TBurow]

yeah, i just caught that, i meant it shifts firmly and i know it upshifts into all 4 gears. got the title yesterday so its up for sale.

 

[TBurow]

or trade for anything interesting.

 

[Motorhead]

It shouldn't be very hard to sell. Guys want them for greasers. I have a nice '77 240D that I have planned to transplant a turbo 300D engine into and possibly change over to veggie oil. I have owned several and the '82 to '85 turbodiesels were hard to beat.

 

[Misenheimer]

It shouldn't be very hard to sell. Guys want them for greasers. I have a nice '77 240D that I have planned to transplant a turbo 300D engine into and possibly change over to veggie oil. I have owned several and the '82 to '85 turbodiesels were hard to beat.

I think that the front end is a little light for the 300 engine. They needed to upgrade for power but a six was too heavy for the 126 chassis so they made a five till a light weight six could be brought out. The aluminum head six is a POS as far as I am concerned, the parts are a lot more expensive and it is harder to work on.

I have three of the 300sd and had a 300td wagon, they are great cars for looks, ride and reliability. Mine turns 3300 at 80 and will cruise as long as you want and still get 24 mpg with occasional burst of over 90+ . It is low on hp which makes it slow around town but I try to just use it for long highway trips.