1983 300SD Won't shift past 2nd - PeachParts Mercedes-Benz Forum

angerthosenear · #1 02-14-2016, 10:42 PM

I got a 1983 300SD Turbo Diesel with ~240k miles on it. Recently I have been having transmission issues.

About a month ago my transmission would not shift out of 1st (yes 1st, not the usual 2nd gear start). It would exceed 4000rpm @ 25mph or so yet not shift to 2nd. Occasionally it would jump to 2nd gear and I could get going a little bit faster. Got it home, drained the transmission (fluid dark) and torque converter, replaced the filter, gasket, and refilled. Worked fine until this week.

Last week/early this week, 2nd -> 3rd slipped some until the car warmed up some. Tried adding a bit of Lucas to see if that would help with the slip, no dice. Took it to a local lube place and had them flush the transmission. Came out a bit dark again (but not too bad). After that the slipping mostly went away and the car kept working fine.

Yesterday car is back to square one. Car would mostly work from 1st to 2nd gear. But refused to get out of 2nd gear, over 4000 rpm @ 45mph, but wouldn't shift. Decided to try draining and changing the fluid once again. Did a basic drain of the transmission (didn't include torque converter this time around since it can be a pain to line up that drain plug), fluid didn't seem bad.

I read that sometimes the Lucas additive can make the fluid a bit too thick and can prevent the pistons from moving, so tried running it without any additives (as it should be). No change whatsoever, 1st and 2nd work great, wouldn't shift to 3rd.

Tried the Trans-X stuff that some people here have shared some success with, since I'm at a wall I give it a whirl. This time I dropped the pan and changed the filter again. The filter I pulled out was somewhat degrading inside, luckily it didn't come apart and get inside the deeper parts of the transmission. Swapped the filter with a new one, and filled again. Tried with the Trans-X again.

During the test drive, same as usual, except it did shift to 3rd for ~25 seconds. Took 3rd up to 75mph, but then wouldn't shift to 4th at all (just like 2nd to 3rd issue). But once I went back to 2nd gear, I couldn't get back to 3rd again. So here I am now.

Various other info:
1. Bowden cable adjustment, didn't work.
2. Pulling line off modulator hoping for some hard shifts, didn't work.
3. Reverse and Drive (1st or 2nd gear start) work fine and engage quickly.

As long as it doesn't involve 3rd or 4th gear, everything seems peachy.

Possible issues?
K1 and K2? 2nd->3rd and 3rd->4th aren't slipping (since they don't work at all), but could it be these pistons are broken/stuck and refuse to work at all?
Honestly, apart from that I can't think of anything, drive engages and it certainly has the power so I doubt it's the B2 piston (which would be bad if there was no drive at all, correct?).

The transmission is a 722.3? I found the ATSG for the 722.3 and 722.4 and looked through it.

Anyone know the part numbers for the 722.3 for the K1 and K2 pistons? Or, is it the same as the 722.4 as seen here:
722.4 K2 Spring Part Number

I don't want to start ripping apart the valve body if I don't have to since it seems like a huge pain to deal with. Certainly would like some insight first.

So any thoughts to what this might be? Thank you immensely for your help.

sixto · #2 02-15-2016, 01:15 PM

1262704477 722.xxx Transmission K-1 spring kit

From what I read, the K1 and K2 springs although different take the same revised replacement. Do your own homework!

You don't need to remove the valve body to replace the K1 and K2 springs. Remove 3 screws and loosen the 4th so the cover pivots out of the way.

Sixto
83 300SD

angerthosenear · #3 02-15-2016, 02:07 PM

Quote:

Originally Posted by sixto

1262704477 722.xxx Transmission K-1 spring kit

From what I read, the K1 and K2 springs although different take the same revised replacement. Do your own homework!

You don't need to remove the valve body to replace the K1 and K2 springs. Remove 3 screws and loosen the 4th so the cover pivots out of the way.

Sixto
83 300SD

From both our links, the K1 and K2 have different part numbers. I don't see anything about a revised one that works for both. I've always seen the K1 and K2 pistons/springs have different part numbers. Or is the difference in the part numbers for a difference in the springs? I cannot seem to find anything in this regard. But I did find info that someone did use K1 in the K2 as far as springs go.

I'm aware of the covers for the springs so I don't have to take apart the valve body.

However! Would replacing these allow for 3rd/4th to work? From what I see the spring help if it flares. Would replacing the pistons help if the gears don't work at all? Or is it one of those things where you just have to take it apart to find out.

Trying to get all ideas together before climbing under my car again this weekend.

angerthosenear · #4 03-30-2016, 08:20 PM

Replaced the K1 and K2 springs.

Same as before, 1st and 2nd work great. It will not shift into 3rd (or skip 3rd to 4th).

From all of the searching I've done (read: hours), I find tons of information about bad quality shifting (flares/skipping/etc), but nothing about fixing a transmission that does not shift at all. Maybe I'm using the wrong search terms or something.

Any ideas on what it might be?

Thanks.

Bandit240 · #5 03-30-2016, 08:59 PM

I'm following this thread close as my own 84 300SD is starting to act up during shifting. It doesn't want to go into 4th and is kinda jumpy from 2-3.

angerthosenear · #6 03-30-2016, 09:03 PM

Quote:

Originally Posted by Bandit240

I'm following this thread close as my own 84 300SD is starting to act up during shifting. It doesn't want to go into 4th and is kinda jumpy from 2-3.

For 2-3 does it do a weird stutter action where it pulses between the two?

Glad I'm not completely alone!

Mxfrank · #7 03-30-2016, 10:39 PM

Your problem appears to involve 1st, 2nd and 3rd gears, is that correct? The B2 band is common to those gears, you may want to check the B2 piston. Hopefully, this archive link will work:

https://web.archive.org/web/20150901014400/http://www.mbz.org/articles/transmission/b2/

Stretch · #8 03-31-2016, 12:30 AM

Going from 2nd to 3rd is the engagement of the K1 clutch and release of the B1 brake band.

If however you are actually in 3rd when you think you are in second then it is a release of the B2 and an engagement of the K2

The next best stage is to get hold of some pressure gauges and make some measurements - compare readings with data in the FSM / ATSG manuals.

DrewGerhan · #9 03-31-2016, 08:28 AM

I've got a used automatic from my 81 SD that I am parting out. Shifted great, no slipping, no flaring. Torque converter too. I can deliver just about anywhere in Ohio if needed. Make me an offer! It needs to go.

angerthosenear · #10 03-31-2016, 01:13 PM

Quote:

Originally Posted by Mxfrank

Your problem appears to involve 1st, 2nd and 3rd gears, is that correct? The B2 band is common to those gears, you may want to check the B2 piston. Hopefully, this archive link will work:

https://web.archive.org/web/20150901014400/http://www.mbz.org/articles/transmission/b2/

I think this is next on the list. But shouldn't 3rd still work if B2 is jammed up since 1st and 2nd work?

Quote:

Originally Posted by Stretch

Going from 2nd to 3rd is the engagement of the K1 clutch and release of the B1 brake band.

If however you are actually in 3rd when you think you are in second then it is a release of the B2 and an engagement of the K2

The next best stage is to get hold of some pressure gauges and make some measurements - compare readings with data in the FSM / ATSG manuals.

I'm aware of the usual 2nd gear start.

Since I can use both 1st and 2nd, would this help rule out any issues with the B1 since it isn't engaged for first? So the issue might come down to the K1 being faulty in some way?

I'd be checking the governor pressure correct? Since modulator is only for softening the shift from what I've read.

Lower than normal pressure might allow 1-2 to work barely, but fail when trying to go 2-3?

Quote:

Originally Posted by DrewGerhan

I've got a used automatic from my 81 SD that I am parting out. Shifted great, no slipping, no flaring. Torque converter too. I can deliver just about anywhere in Ohio if needed. Make me an offer! It needs to go.

Sadly I'm in Texas.

---

Thanks all.

lowpresh · #11 08-05-2020, 01:29 PM

Quote:

Originally Posted by angerthosenear

I think this is next on the list. But shouldn't 3rd still work if B2 is jammed up since 1st and 2nd work?

I'd be checking the governor pressure correct? Since modulator is only for softening the shift from what I've read.
.

did you check pressure? any luck? conclusion? resulution?

we who follow your footsteps in the snow of aging transmissions would appreciate an update on the probability of light in the end of this tunnel

thankx