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  #1  
Old 04-25-2004, 10:00 AM
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Speed vs. RPM '85 300D (in lieu of repair)

Good morning .....

I'm the proud new owner of an '85 300D (USA model). I bought it specifically for an 8000 mile, around the states trip. But now, after driving the car for the last several weeks I'm falling in love with it and can see keeping this car for many years to come. It's built to such high standards ... just amazing.
Anyway, my area of concern is a pessimistic speedometer. She reads slower than actual speed but operation is smooth as silk and consistant. No noise.
Does anyone have any rpm vs, speed data for this car in top gear (4 speed auto)?
A second concern ... the transmission was rebuilt (by a well known local German auto garage here in Phoenix) 20k miles ago and shifts/performs flawlessly) but I'm concerned that it may have been an off the shelf exchange and has a wrong speedo drive gear in it ... is that possible?
The data will be fine if someone has it and would be greatly appreciated.

Thank you
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Old 04-25-2004, 01:14 PM
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Thank you for the info. Will report back on results. Yes ... I have already noticed that the seats are lacking and plan an upgrade (maybe before I take my trip in late May).

The previous owner passed on 3 years ago and the car sat garaged till I happened along. He was the type of owner that brought it in for service at the first sign of a malfunction and I have $8000 in service slips. The vacuum system was overhauled, the transmission, front end, New Behr radiator and complete hose kit, constant oil changes and valve adjustments, KYB shocks, etc. etc. Most of this work was done between 110,000 miles and 140,000 miles. I bought the car several weeks ago and it has 155,000 now.

I did a detailed inspection, and I mean detailed .. up on a lift at a friends shop and I couldn't find a single mechanical flaw, loose part, or leak. Every hose, wire loom, etc. is in place. I happened on a great example and I know it. I'm a nut on care and attention so it will stay this way.
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Old 04-25-2004, 01:35 PM
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My 80 300SD with a 3.07 ratio rear shows 70 @ 3000 rpm.

AFAIK it is correct. Not sure why it would be the same as dieseldiehard's with the 2.88. Must be a difference in the tires.

FrankinAZ sounds like you got a real nice one
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Old 04-25-2004, 02:06 PM
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The speedo in my '83 300DT reads low (80mph is really 72mph) but the odometer is right on... hmm...
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Old 04-25-2004, 04:39 PM
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Let me thank you for the responses. Thank you.

I just came back from a (the first) good test drive. The speedometer is exactly on the money with your pre-conversion specs and I believe your figures to be deadly precise. It must be the feel of the car that made think it was off, keep in mind that my daily driver is an xtra cab late model Ford pickup.

after a 65 mph, 20 mile cruise down the highway with the air on (it's approaching 90 degrees here today) my oil pressure was 1.5 bar at idle in gear .. normal??

Thank you,
Frank
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Old 04-25-2004, 04:48 PM
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Quote:
Originally posted by FrankinAZ


after a 65 mph, 20 mile cruise down the highway with the air on (it's approaching 90 degrees here today) my oil pressure was 1.5 bar at idle in gear .. normal??

Thank you,
Frank
Normal. Should peg 3 Bar at about 1000rpm and stay there till the rpm's drop again.
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Old 04-25-2004, 04:54 PM
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Thanks WW ... yes, above idle she stays pegged at 3 bar.
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Old 04-25-2004, 05:21 PM
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Quote:
Originally posted by dieseldiehard
FranklinAZ, the '85 300D / TD are wonderful cars with great reliability if a little maintenance is done when necessary. They are pretty safe cars also. I have driven my '85 300TD cross country and the only thing I disliked was the soft squeaking seats which have now been updated with the later version spring bottoms, and I wish I has done that at the beginning!
The transmissions are unique in those years (84, 85) and there have been reports that indicate they are not as robust as the transmissions used in prior years (yours has been rebuilt already, proof maybe that is true?)
It is not likely that there is anything other than one drive gear in them, because the US cars in those years all had the 2.88 ratio differentials so I wouldn't be concerned that the shop made a mistake in that regards.
Enjoy!
I agree that there may be a possiblity that the transmissions in those years were not as robust. My '85 had the A/T rebuilt at only 108K and my concern at the moment is that now I have over 116K on the rebuild. I hope they used the more robust parts in the rebuild.
I wish my seats were soft and squeeky. They are squeeky but hard.
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Old 04-25-2004, 07:51 PM
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Originally posted by dieseldiehard

One thing more, I have never seen a Mercedes that the speedo reads low in.

FWIW, I have two -- both W123s, an '82 300cd and an '82 300td. I've clocked mileposts and found them both to be about 3 mph pessimistic at 70 mph. I also have documentation concerning the coupe from the Town of Brookfield, Wis., Police Department! They claim I was doing 81 when I thought I was traveling at an only slightly illegal 77. The verdict of the court: defective speedometer, a lighter rap on the knuckles than the justice system's alternative in Wisconsin, speeding 16-19 mph over posted limits.

Yes, I know mileposts aren't always 100% accurate, but I've taken the measurements repeatedly and they seem pretty consistent for both cars.

Russ Maki
Ixonia, Wis.
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Old 04-25-2004, 07:59 PM
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True, mileposts are not totally acurate. Use the speedometer check signs for that.
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84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012
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Old 04-25-2004, 08:18 PM
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I use GPS to verify. That's the sure-fire way. 5% too low on SDL, 3% low on 350SD. However 4% too high on my sister's 300D.

I don't know about you guys, but my speedometer really seems to be inaccurate when it comes to WOT. The speedometer is playing catch-up a lot. When I get to 5000 rpms in third gear, and keep it steady, the speedometer is still climbing 80-85 in less than 3 seconds, even though I am not really accelerating.

As far as the 2.88 vs 3.07. The 2.88 has a really high stalling torque convertor. Let off the pedal at 70 mph, and the '85 300D will drop off more revs than the '83 300D with the 3.07. My TC doesn't completely lock until I am practically at redline in 4th gear. 350 has a 2.82 that locks late as well.
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  #12  
Old 04-25-2004, 08:28 PM
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The PO of my car actually had the speedometer checked by a speedometer shop. My car's actual speed is only about 2-3 mph slower in the higher speeds than what the speedometer shows.
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84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012
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