shift points on a 300SDL - PeachParts Mercedes-Benz Forum

banshee350 · #1 12-18-2005, 03:17 AM

My car shifts very early.When starting out at a easy pace it shifts out of 1st before the speedo reachs 10mph 2nd is at 25 3rd at 30 and 4 th is some time before 40 .We only got 22mpg this was around town and freeway but most was freeway.I think if the tranny shifted later and the motor stayed in its power range the mileage would be better.If I shifted it manualy it shifts firm and has much better acceleration.The way it is now the motor is lugging .It seems to stay in 4th all the time unless you totaly floor it.has any one had to adjust the vacuum controls to make it shift better.I would like it to stay in 1 till 20 2nd to 30 and not go into 4th below 45 or 50 unless you are at a cruise.Also would like it to down shift under part throttle acceleration is this posable with this tranny.

t walgamuth · #2 12-18-2005, 07:50 AM

you can adjust the shift points higher. i am not sure how on this model, but i am sure it is easy to do.

but shifting to a higher gear should be giving better mileage rather than the opposite. and 22 for mixed use is excellent in an sd or sdl.

tom w

TX76513 · #3 12-18-2005, 07:58 AM

SDL's can be tempermental in getting that perfect shift that matches your driving style. At the top of your screen is a DIY tab - go down to transmission adjustment. I believe the procedure is for a 123 but the process is close enough for you to get an idea. Before you start adjusting things please take a minute and look for vacum leaks, probably the leading cause of shifting issues. PM me and I will give you some problem areas to look at.

Good Luck!

Brian Carlton · #4 12-18-2005, 09:12 AM

The '87 has the exact same problem. It shifts way too early and is a complete dog around town because of this and because of a needed ALDA adjustment.

Now, the '86 is setup perfectly. You won't get the dreaded 3-4 shift until above 40 mph unless you are just barely opening the rack. If you step into it a bit, the 3-4 will be delayed to over 50 mph. And, if you mash it, the 3-4 won't occur until 60 mph or so.

All of this is related to the Bowden cable from the linkage down to the trans. The cable needs to be tightened a bit to delay the shifts. I need to do it on the '86 as well. But, I'm not fond of working in the cold.

Hit Man X · #5 12-18-2005, 01:40 PM

Another point I'd like to make, I never drive any of my vehicles in 4th around town. At speeds less than 50mph I do not see the need for the direct or OD gear (dependant on the vehicle).

Also there's less wear on the trans.

t walgamuth · #6 12-18-2005, 01:48 PM

would you think there is less wear on the tranny? this doesnt seem correct to me.

i think that you are just burning extra fuel and wearing out everything that much quicker. it's a diesel for heavans sake. it loves low rpm.

sorry to sound negative. that is not my intent.

tom w

Brian Carlton · #7 12-18-2005, 01:51 PM

Quote:

Originally Posted by Hit Man X

Another point I'd like to make, I never drive any of my vehicles in 4th around town. At speeds less than 50mph I do not see the need for the direct or OD gear (dependant on the vehicle).

Also there's less wear on the trans.

I agree. I leave the SDL in 3 around town. High gear is just too tall and the engine is running too slow.

It might be a diesel, but it definitely doesn't like 1300 rpm.

I don't believe wear is affected one way or the other.

Hit Man X · #8 12-18-2005, 01:54 PM

Quote:

Originally Posted by t walgamuth

would you think there is less wear on the tranny? this doesnt seem correct to me.

i think that you are just burning extra fuel and wearing out everything that much quicker. it's a diesel for heavans sake. it loves low rpm.

sorry to sound negative. that is not my intent.

tom w

Just no constant 3-4 and 4-3 shifting to get around in traffic.

t walgamuth · #9 12-18-2005, 01:55 PM

1300 rpm just fine.

he told me so.

tom w

Brian Carlton · #10 12-18-2005, 01:56 PM

Quote:

Originally Posted by Hit Man X

Just no constant 3-4 and 4-3 shifting to get around in traffic.

Actually, wear is reduced. If it shifts to "3" and stays there, it's preferable to 3-4 and then 4-3 and then 3-4 repeatedly.

t walgamuth · #11 12-18-2005, 02:04 PM

i see that. just less shifts. i thought he meant that running in fourth was somehow slipping and wearing the tranny out.

yeah, i agree with that.

tom w

Hit Man X · #12 12-18-2005, 02:08 PM

That's what I attempted to say.

I pretty much am always in 3rd gear from 15mph rolls up to about 50mph. There seems to be enough power like that.

t walgamuth · #13 12-18-2005, 02:13 PM

i suppose the 350 is a little more torquey and therefore loves low rpm more. usually aroung town i just squeeze the throttle and get pretty respectable urge wo down shifting. this 350sdl is the happiest combination of engine and diesel i have owned in an automatic benz.

tom w

Hit Man X · #14 12-18-2005, 02:16 PM

I stumbled upon a 1991 350SD on Friday when I looked at the other '85 SD to clean up then resell. I wish those motors were not so hit or miss or I'd have considered picking it up. It was black with a grey interior, needed a head. The No 17 cracked on it as it was ran without coolant!

banshee350 · #15 12-21-2005, 03:19 PM

The reason I want to change the shift points is that it is realy slugish unless you floor it to get it to down shift.You can watch the tach and see that it is running up to the stall point of the converter when ever you try to accellerate. Lugging the motor and putting that much load on the trans cannot be good on the clutchs.All the cars that I have done tranny rebuilds on get shift kits so that they shift with a positive feel.Soft shifts = sliping clutchs and bands = unneeded wear.