Hi all,

I have a 91 300D 2.5 Turbo with 73000km on it. I just acquired the car a few months back at 65000km. I am fairly sure the tranny fluid has never been changed and will be changing it soon (along with the filter). I would like to put synthetic in the transmission like I have just done now for the engine. Last night, I put Mobil 1 15W50 in the engine based on what I've read in this great forum, and I am pretty sure I already notice a difference (after driving about 150km) in the idle clatter sound. It seems to be a bit quieter at idle than before (it had Quakerstate 15W40 from the dealer of the PO in it). So, good news with the engine oil.

I've got a couple questions though:

1) The transmission is very happy to upshift and go into as high a gear as it can, and won't downshift until I give a lot of pedal travel. It works fine, and shifts well, but basically I am wondering if I can adjust the shift point slightly so that it upshifts a little bit later. I do notice there is a cable just above the valve cover that curves around and goes to the tranny (and it is adjustable). Will this cable to what I want, or is it even possible to adjust the shift points a bit? Also if this is adjustable, would it change the upper shift point (when flooring the pedal), because I don't want that RPM to go any higher.

Let me rephrase that a bit.. very simply, what I want is for the transmission to downshift without having to push the pedal down so far. If I am going about 80km/h I have to kickdown to make it go into third, and I think that's a bit excessive because the engine is only running at about 2000rpm then, and when I do kick it down it takes off nicely.. is it possible to adjust what I want here?

2) When accelerating fairly lightly (so it will shift from 2 to 3 at about 2300 rpm), it sometimes flares a little bit.. maybe 200 rpm. I always notice when it happens. It does not happen if I am giving less throttle or if I give more throttle, and seems to only happen around one throttle position (and then it doesn't always happen either). Is this anything to worry about right now or should I just leave it for now?

3) Upon changing the oil, it appears that both the front and read main bearing seals leak slightly. For 12000km of driving I had to add approximately 1.5 L of oil. Is this common on this car? I know the rear seal would be a bear to change, so I'm hoping it doesn't get any worse with the Mobil 1 15W50 synthetic oil.

4) What transmission fluid should I use? If I go with synthetic, is the Mobil 1 a good choice again? I've read in here a lot of people using that in their transmissions.

5) The PO always took the car to the MB dealer, but I'm not sure if the 48000km service was ever done (which in the book includes the ATF change, timing chain check, etc...) ... Any other specific recommendations I should check at this point in the car's life?

Thx for your help!

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1991 MB 300D 2.5 Turbo (207000km) (now gone)
1993 Audi 100 CS Quattro (300000km)
1999 VW Jetta TDI (290000km)
2002 Audi A6 3.0 Quattro (150000km)
2005 MB E320 CDI (34000km)

first, welcome to the forum. im sure youll learn alot here and soon youll be able to pretend to be an expert just like i do! Im assuming youre in Europe because of the km measurements, its good to have people on the forum over there, then again, maybe youre just a metric system enthusiast. and with a '91 300D 2.5 with only 45000 miles on it? i envy you.

1) thats interesting, thats the exact opposite of what everybody elses transmission problem is. most cars shift up too late. if youve never owned a diesel before, its possible that youre just not used to it. diesels run at a lower rpm range than gassers. cruising at 2000-2300 rpm is about right. as for the kickdown, its activated by a button on the floor directly under the throttle pedal, you can probably feel it when you push the pedal all the way down. the kickdown is the only way the tranny downshifts at speed (unless you use the shifter) so theres no way to kickdown without putting the pedal to the floor. the only way i can think to make it kickdown at a lower engine speed is if you adjusted the throttle linkage to reduce the amount of travel it gets when the pedal is on the floor, but the downsides of that are obvious. these engines and transmissions were designed to get maximum fuel milage, so they run at the lowest rpms possible. the kickdown was designed for merging and high speed passing (although i use mine all the time because my turbo doesnt work).
A good and easy way to check if youre transmission is tuned right is to start from a dead stop (with plenty of empty road in front of you) and punch the pedal all the way to the floor, including the kickdown button. there are 3 sets of orange dash marks on your spedometer, placed at approximately 30mph, 60mph, and 90mph (50, 95, and 145 kph) if my memory is right. these marks are where the transmission is supposed to shift to 2nd, 3rd, and 4th respectively. this is not affected by a lack of vacuum when the pedal is all the way down. if thats where it shift, then your tranny is fine.

2) i dont know what you mean by "flares a little bit...maybe 200 rpm", but maybe the answer above applies to this question as well.

3)its hard for me to get anxious about a diesel engine leaking/using oil, but since yours only has 45k miles on it, that is a little concerning. you said 1.5 liter after 12000km (appx 1.5 qt after 7500mi) that would be ALOT for such a young engine. mine only uses about .5qt after that, and ive got 4x as many miles. but you also said you only bought the car 8000km ago, which makes me assume that you dont know for sure what it was filled to at the last change. the manual calls for only 7.5qts or 7liters of oil i believe. this puts the oil level directly in between the max and min marks on the dipstick, about 1qt more than min and 1qt less than max. so if it was filled right at the last change, then it was filled 1-1.5 liters short of the max fill mark. if youre measuring that 1.5 liter loss from the max mark on the dipstick, then its probably just a .5 liter loss or less. or maybe you already though of that and you really do have a problem, what do i know. also you should probably change your oil more often than every 7500mi.

4)i dont really know anything about synthetic trans fluid, but if you used a trans fluid with more lubricity, it will make your trans shift sooner, and maybe you dont want that.

5)your vacuum lines, they dont have many miles on them, but theyre still old and will probably start falling apart soon since the car is being used more than it was under the previous owner.

gosh im sorry, i can be very long winded. hope i didnt waste too much of your time.

later

__________________
1991 300 D 2.5 Turbo, 220k
also in the family:
1981 240 D 185k
1991 350 SD 185k
2006 S 500
2005 SLK 350

Thanks for the info. I am actually in Canada, not Europe. And yes, we use metric here for the most part.

It does shift a bit earlier than the marks on the the speedo (it will shift into 4th at about 135 instead of 145 for example). This is with the pedal all the way to the floor including the kickdown switch. Not that it really matters much, it's fine the way it is, but I thought if it was easy to adjust then I would do that.

By flaring a bit, I meant that sometimes during the shift between 2nd and 3rd, the engine rpm shoots up a bit before it catches. Only sometimes.

I've been driving a diesel for the last 5 years (a Jetta TDI) but switched to the Benz because of the comfort and a deal I couldn't pass up. Of course that car had a 5 speed manual...

Anyway the transmission is fine for the most part, I was just hoping for some opinion on the shift points.. but if it's relatively normal then that is fine.

I'm not sure if it burns oil, but it does definitely leak a bit from what looks like the front and rear crankshaft bearing seals. I'll see if it's any different once I have had synthetic oil in there for a while. I suppose this trouble could have been caused by the car sitting a lot and not being used much for the last 5 years or so. Maybe the seals went a bit funny during all that sitting time.

__________________
1991 MB 300D 2.5 Turbo (207000km) (now gone)
1993 Audi 100 CS Quattro (300000km)
1999 VW Jetta TDI (290000km)
2002 Audi A6 3.0 Quattro (150000km)
2005 MB E320 CDI (34000km)

Mobil 1 ATF in the transmission. ("runs cooler , longer")
THE CORRECT viscosity Mobil 1 gear lube in the rear end. (same)

'might want to throw Redline "Water Wetter" in the coolant after you
flush.

If you switch to Delvac 1 (Mobil's specfic fully synthetic Diesel oil) and
do a "baseline oil test" you may be able to run 10K miles between
oil changes (with regular oil testing).