my 300sd is not getting 1st gear i have checked the vacumm line and all seems fine. will this possibly improve if i change the filter and fluid. i do not think it has ever been changed by the p/o and i havent driven it that much so i havent had the urge to change it. i have found that it is starting in second by testing it in drive and then testing it in second. same take off. too keep up with traffic at take off i have to floor it to the kickdown switch. has anyone else had this problem. any info would be greatly appreciated.

if you are saying that the tranny starts in second and
that you have to floor it (the kickdown switch) to get
into 1st, there is no problem. almost all mercedes
autos rest in 2nd and start off in 2nd.

don

All automatic Diesels with the 722.x transmission I've seen and driven start in 1st. My TD does, I can clearly count all 4 gears every time I accelerate under 5mph.

Wherever you put the shift selector it will (should) start out in first gear. Might want to check the Bowden cable to make sure it's hooked up and adjusted right. It's the cable that comes off of the linkages on top of the valve cover and goes down toward the transmission.

__________________
1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k

My 1980 300SD does the same thing. It always starts in second, unless I put the selector in 1 or hit the kick down.

My 1979 300SD always starts in first, then shifts smoothly to second as I suspect my 80 model should.

There is a box that I think controls this IIRC. Time to get my book out and chase this down.

I have got the shifting sorted out now on the 80 execpt for this.
The 79 shifts perfect.

I'll try and post what I find.

__________________
1980 300SD Manganese Brown Metallic Clearcoat 248k
1979 300SD White 148 k
1984 300D Silver project car for daughter
1982 300D wrecked
1980 300SD 310K not running

The owner's manual in my 77 300d clearly states that it is designed to start in 2nd unless you engage the kickdown switch or drop the shifter into L and then back into D before starting out, or leaving it in L.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

i know that it is supposed to start in first because my dad has a 300sd same year,same model and everything and his starts in first.

My 1979 300CD does the same thing, and the owners manual states the same thing, that it starts out in 2nd, unless manually put there, or the kickdown switch is engaged...

jdblann you are absolutely correct! The 722.120 transmission that the 116.120 (all W116 chassis SD's) uses will sit at a traffic light in second to 'prevent crawling' and should automatically engage the kickdown for you so that you drive away in first.

The circuit that controlls this is the 'Overboost Protection Circuit". Its function is to have 1st gear, and to make sure you don't have the engine over a certain level of boost pressure below 2000 rpm in 1st gear (too much torque for the tranny).

The 'relay' that controls all of this is located in the right side of the passenger footwell. If you ever hear a clicking noise when your stopped and let off the break it is the relay engaging the kickdown for you.

If you would like to troubleshoot your car using the mercedes wiring diagrams use the 1980 MY as the electronics are the same, but the diagrams were redesigned to make them MUCH easier to use.

Everyone else out there I believe can be helped with these articles, but I have no first hand knowledge of any trannys other than the 722.120.

http://transmission.articles.mbz.org/

HTH

John
'79 300SD

Tymbrymi you posted:

=========================================
If you would like to troubleshoot your car using the mercedes wiring diagrams use the 1980 MY as the electronics are the same, but the diagrams were redesigned to make them MUCH easier to use.
==========================================

Where does one find these diagrams?

Thanks

__________________
1980 300SD Manganese Brown Metallic Clearcoat 248k
1979 300SD White 148 k
1984 300D Silver project car for daughter
1982 300D wrecked
1980 300SD 310K not running

is that relay black and located near the cc amp?

jdblann -- You can get the electric manuals off of the W116 CD manual. Its about 100 bucks from mercedes, 5 bucks for a burned copy on ebay, or you can download it. I can send you the pdf if you would like.

kmaysob -- The CC circuitry (so far as i know) is solely located in the drivers footwell. The Overboost Protection circuit is located on the right wall of the passenger well. The relay is black. It may have a silver sticker on it somewhere (maybe, fuzzy memory)

John
'79 300SD

I fixed It! Took the relay out. It has four tiny screws which allow
one to get at the electronics. Found a burnt trace. I found a small wire
to make a jumper. Soldered it and put it back in and now first gear
starts!!

Thanks for your help, Tymbrymi. I had read there was a relay, but I didn't know where to start to look for it.

__________________
1980 300SD Manganese Brown Metallic Clearcoat 248k
1979 300SD White 148 k
1984 300D Silver project car for daughter
1982 300D wrecked
1980 300SD 310K not running

i cannot find this relay you speak of. i found one that i thought was it but i dont think it was. i got it working a little better. i found that one of the throttle linkages was bent. i fixed that but still cannot find the relay. do you have a pic of it?

kmaysob:
you have a 1983, w126 with a 722.315 transmission. jdblann &
Tymbrymi have w116's with 722.112 tranmissions. different
beasts. i believe that within the transmission itself is a
spring that can be adjusted to always start the car in 1st,
but i am not sure of this.

don