Tranny hunting for fourth gear and other issues. - PeachParts Mercedes-Benz Forum

muleears · #1 11-17-2012, 08:43 PM

I have been searching K1 and K2 and B2 piston threads and haven't found what I'm looking for. My son's (new to us) 86 300SDL has the following shift problems: Under hard acceleration (kick down engaged) the 1>2 shift is ok, the 2>3 won't take place unless I left off slightly on the accelerator, and the 3>4 shift it "hunts" for 4th. When I say hunts I mean the RPM's vary up and down with no change in the accelerator position. It eventually shifts but usually I need to left off some for it to shift. I have also noticed some stacking (double shifting) of the 2>3 or 3>4 shifts (can't remember which) under slow acceleration.

My question is, will a superior shift kit help this situation? Or am I looking at a different problem entirely? I don't have a flaring issue, the shifts are reasonably firm and (other than when "hunting") occur at the appropriate RPM. Both bowden cable and modulator seem to be adjusted properly.

A wild guess is 250K on the tranny, the fluid level is correct, but don't know when the last service was done. Planning one this week with Dexron III.

Any input is appreciated.

Doktor Bert · #2 11-17-2012, 09:11 PM

Verify detent cable adjustment is correct....

muleears · #3 11-17-2012, 11:33 PM

Quote:

Originally Posted by Doktor Bert

Verify detent cable adjustment is correct....

When you say detent cable, do you mean the bowden cable that controls the shift points? I am not familiar with that term. Thanks for the advice.

Doktor Bert · #4 11-18-2012, 11:17 AM

Yes....

muleears · #5 11-18-2012, 12:58 PM

Quote:

Originally Posted by Doktor Bert

Yes....

It seemed to be ok, but I will research and check it out. Thanks.

wantamb · #6 11-18-2012, 01:05 PM

I just fixed the same issue on my 82 300d turbo yesterday night.

What did you do to your W123 today in 2012? - Page 66 - Benzworld.org - Mercedes-Benz Discussion Forum

I used two of K1 spring kits(part number 126 270 44 77) for both k1 and k2.

muleears · #7 11-18-2012, 02:45 PM

Just went for a drive and here is what I found. Under light acceleration all shifts were soft but positive at 2000-2200 RPM's. Moderate acceleration, 3/4 pedal, shifts took place at 3500 RPM's and were firm. Full acceleration, 1>2 was about 3000 RPM's, 2>3 was above 4000, the 3>4 appears to not want to shift above 4000 and it "hunts" or surges until it shifts.

Actually I don't know why I'm worried about this, it will never be driven as hard as I'm driving it now to test it. Under normal driving, shifts are at the appropriate speed and firmness. I guess I'm just worried that passing someone it will start hunting on me and not upshift.

vstech · #8 11-18-2012, 10:14 PM

when was the last filter/fluid change?
how is the fluid level at FULL operating temp of the transmission fluid. after a LEAST a 20 minute drive, on PERFECTLY LEVEL surface?

muleears · #9 11-19-2012, 05:01 AM

Quote:

Originally Posted by vstech

when was the last filter/fluid change?
how is the fluid level at FULL operating temp of the transmission fluid. after a LEAST a 20 minute drive, on PERFECTLY LEVEL surface?

No idea when the last service was. Fluid is red and clear. Checked it when we bought the car, after our test drive, which wasn't 20 minutes. I'll take it for a good run this morning and check it again and get you a definitive answer. Thanks for the help.

muleears · #10 11-19-2012, 02:50 PM

Quote:

Originally Posted by vstech

when was the last filter/fluid change?
how is the fluid level at FULL operating temp of the transmission fluid. after a LEAST a 20 minute drive, on PERFECTLY LEVEL surface?

vstech, I thought you had found a simple solution. I drove the car about 18 miles parked it and checked the fluid and it was a quarter inch below the low mark. I thought Bingo! What a stupid mistake I had made. But I added the correct amount and I still have the same surging, hunting tranny. Not sure what to do till after we do the service this weekend. I guess I'll check back then.