Just hoping to get a quick checklist of things to troubleshoot for in an 87 300 SDL that won't shift up to 4th. The trans shifts a bit sluggishly when cold and when on the highway I don't think it's ever getting out of 3rd.


OOPS.. I forgot to ask.. is there a better place to post transmission questions? ie a transmission topic?

try disconnecting the kickdown switch. It's the button underneath the gas pedal and a small 2 prong plug. If it's that you're in business.

You're more or less in the right place. Tech Help is another good one and may get a few more views/hits than diesel discussion for general transmission problems.

__________________
1982 300TD 210K miles ("The Replacement" aka "The Anvil") - SOLD
1979 300SD 245K miles (never ending project)
2007 Pinarello F3:13
1995 Ducati 916 (SOLD, sniff)
1999 Ducati 900SSie (SOLD)

Another note.. The trans fluid looks fine, nice and red, not burnt smelling..
What would explain the slushy shifting when first starting out..??

When I first got my 300 SD, I didn't think it was getting out of third. The First to Second shift is barely noticable, and it cruises at a very high RPM. That's the way if is I guess. Can you shift up to 4th if you do it manually? Mine is a little sluggish when cold too. I still need to fiddle with the shifting to smooth things out.

Hmm, well I just assumed the revs were too high for 4th.
I guess a better diagnostic question might be, what should rpm be in 4th at say 60mph?

transmission fluid is designed to work at a certain temp range. As transmission gets older it will be more temp sensitive. That's the extent of my knowledge of why. My TD has a mind of it's own and seems to shift differently every time I drive it. Probably the humidity here .

I'm guessing the rpms should be about 2500 in 4th at 60. I know at about 80mph I'm north of 3000 but haven't driven my SDL in ages to know exactly where it's at.

__________________
1982 300TD 210K miles ("The Replacement" aka "The Anvil") - SOLD
1979 300SD 245K miles (never ending project)
2007 Pinarello F3:13
1995 Ducati 916 (SOLD, sniff)
1999 Ducati 900SSie (SOLD)

I wish I could tell you, my tach has never worked. Actually, I finally got around to trying the cigarette butt in the plug trick last weekend. Now it works maybe 20% of the time (haven't had it on the freeway working yet) Maybe it needs more butts...?

probably . I had to repack mine when I had intermittent function. I used folded thin cardboard

__________________
1982 300TD 210K miles ("The Replacement" aka "The Anvil") - SOLD
1979 300SD 245K miles (never ending project)
2007 Pinarello F3:13
1995 Ducati 916 (SOLD, sniff)
1999 Ducati 900SSie (SOLD)

Is there a table of speeds / revs / gear for these trannys?

In this era, the 4-sp transmissions started out in 2nd.

It required manipulation of the gear lever (from D) to get them to start in 1st.

Normal highway revs in 4th are around 3-3.5K at 70-75mph.

Lots of folks think this is high, but it's not for a Mercedes.

Many confuse the 2nd gear start as a no-shift-to-4th problem.

__________________
Kent Christensen
Albuquerque
'07 GL320CDI, '10 CL550. '01 Porsche Boxster
Two BMW motorcycles

hmm, ok I feel better about it.. thanks all, I'll go take a drive and test the hypothesis..

I read on here that someone had a similar problem with the tranny not shifting into 4th, although his acted as if it wanted to shift but wouldn't drop over the edge. He solved it by changing the two fuel filters. It turned out it was all down to fuel starvation at high(ish) revs.
cheers
Adrian