'87 300SDL, 300D shift points - PeachParts Mercedes-Benz Forum

DslBnz · #1 09-09-2003, 07:16 PM

When I put the pedal to the floor of my SDL in 'D', she climbs to about 4900 rpm in every shift.

When I keep my foot pressed to the floor in '2' or '3', power lets off around 5100 rpm, but climbs up to about 5300 rpm (5150 rpm +- 150, right? I think it's the overboost protection). How would I get my SDL to shift later than it shifts now?

My sister has an '87 300D turbo that shifts at 4600 rpm for every shift, too. Doesn't even make it close to the dots on the speedometer.

I have seen these six-cylinders shift normally in excess of 5000 rpm. Why can't mine do that?

william rogers · #2 09-10-2003, 03:37 AM

I have my 81 SD set to shift at around 4200 at full throttle,I don't mind running my MB V8 up to near red line but anything past 4200 on the diesel just seems uneasy to me. you set the shift points by adjusting the Bowden cable there are lots of post in search about it........
William Rogers......

DslBnz · #3 09-10-2003, 04:44 PM

I know what you mean. I had an '84 300SD, and she did not like to go beyond that 4200. The engine sounded like it was maxxed out and might explode if taken much farther.

The six cylinder OM603 is different. It is much more quiet and sounds much less stressful than the OM617 at those revs. It even sounds really envigorating when it gets above 4500 rpm. At least mine does. It has an extra gutteral sound that kicks in and makes it sound like a mean German gasoline six, in a diesel. Kind of like the CDI's when they get wound up.

Around town, it does sound like a diesel, though.

I didn't know that the cable could let the actual revs climb higher than a set engine speed, I just thought it made the shifts later and harder (for towing), or softer and earlier (for regular driving).

Could it be an adjustment on the modulator valve, or something? Of course I thought all that was was make shifts softer, smoother, and piled more wear on the transmission.

I appreciate your response, Will. Thanks, at least someone is willing to take a stab at this.

** I have done a search, and I didn't find what I was looking for. But I will keep trying, and will repost if, and when, I might find a solution. This rpm adjustment isn't super important to the functionality of my car, but it would be a convenience.

william rogers · #4 09-10-2003, 04:57 PM

I don't think that the tightest setting on the bowden cable would over ride any type rev limiter,sound like pretty touchy business trying to exceed factory set limits on a stock engine of any type.mordren MB diesels are already reving high compared to truck or marine diesels...........
William Rogers.......

DslBnz · #5 09-10-2003, 08:40 PM

Yes, but the factory set limit is 5150 (+-) 150 rpm according to MB repair manual. Mine shifts at 4900, and my sister's shifts at 4600.

My SDL will hit it's redline in '2' or '3' as opposed to leaving it in 'D', which only goes to 4900. It doesn't even make it up to the shift point indicator dots on the speedometer.

I do not want to overrev the engine, and to do so would be to disable the overboost protection unit. It would melt the pistons, and turn the engine into scrap (courtesy of the turbo). Obviously, that would not be wise.