Merry Christmas Eve!

About a week ago, my 81 300SD developed a delay when up shifting from 3rd to 4th gear. The upshifts from 1 to 2 and 2 to 3 are fine, and it downshifts fine, but that 3 to 4 upshift is delayed. ATF level is fine. Fluid is bright red, no burnt smell. It's not my daily driver so I haven't really delved into it. I'm thinking it could be the K2 spring, but I need to check the simple things before I dive in that far. I'm thinking to check the things that control the timing of the upshifts, so the bowden cable will get checked. I think the kickdown switch is ok because it would cause delayed upshifts in every gear if it was stuck. Am I missing anything else to check? I'm thinking perhaps vacuum, but if I remember correctly, vacuum controls the quality of the shift and not the timing. Looking forward to getting your thoughts.

Daughter's car had that problem after it wasn't being driven regularly. After a few weeks f driving it regularly, the problem went away never to return.

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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

Kerry, the thing is I'd driven the car most of the day that Sunday and the problem didn't start until that evening.

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

Your vac bleeds off to zero for upshifts so it would not be a vac leak, especially if your other upshifts are OK. There is a table which shows which shifts are effected by K1, B2, etc. You might spot it in that table.

The 3/4 upshift is where problems show up in transmission hydraulics, because there has to be enough pressure and volume for both clutch packs to engage. A delayed shift could be caused by a damaged K2 accumulator spring or a clogged filter. So a good place to start is to drop the pan and replace both the filter and the spring, both pretty simple jobs. Do a full fluid change while you're at it. Some say Type F fluid is better for this condition than Dexron, not sure I'd go there. If that doesn't do it, it wouldn't hurt to try a magic additive. Look for something that claims to have viscosity improvers and seal expanders. When that doesn't work, you'll have to tackle the most likely cause, which is either a worn clutch or defective seal in the K2 pack. Repairing this requires tearing down the transmission.

I've read up on the K2 spring and think it might be that. I'll try that when I change the fluid and filter.

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

Does delay mean that the 3-4 shift is initiated at a road speed that is higher than you feel is correct?
OR
Does delay mean that the shift is completed in a slow, sloppy, or flareing manner?

By your further comments, it would seem that the first instance is the case. If that is so, look to the balance between the throttle pressure (control/Bowden cable) and the governor pressure. Either high throttle pressure or low governor pressure will cause a shift to be initiated late.

Accumulators and their springs are not involved in shift timing, but do affect shift quality.

I have the non-beefier version of your trans in my 92 300D. Same setup and internals.

Mine shifted like trash when I bought it. 1-2 were on time, but shifted hard from vacuum leaks and disconnected lines. 3-4 took forever and didn't flare or shift sloppy but was extremely late and almost at 50 MPH. Adjusted the bowden cable and kept playing with it until it was right. Fixed the problem.

I'm fixin' to say this is your problem and NOTHING inside the valve body. That is however dependent that it just shifts "late" without slipping or slop like Frank has mentioned in the post above (I'm really not trying to reiterate like a parrot, but this has been my experience and bet this is yours!).

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

X3 on the bowden cable. I bought a 300SDL with a supposedly bad trans with no 4th gear, tightened the cable up and shifted like and dream till I sold it.

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'85 300D ~ 381k, HD Bilstien shocks, 27.50x8.50x14R General Grabber AT2 tires, 4 E-Code headlight upgrade with 90/130w bulbs, boost turned up, new timing chain, and injectors. SOLD

'85 CJ7 ~ OM617 swap, Tarus electric fan, T5 trans, Dana 300, 4.88 R&P, Mile Marker locking hubs, ALDA removed, AMC 20 rear disk brake conversion, Aussie locked with 33's and 5" Rough Country lift.

It's more of the latter. Like when I'm accelerating on an onramp, I'll take my foot off the accelerator or back off on the accelerator and it'll stay in 3rd instead of the usual upshift into 4th. After a few seconds, it'll finally settle somewhat sloppily into 4th. I've got video which I'll try to upload and share. Funny thing is last night while I was driving it to warm it up to check the fluid level and make the video, it did a proper 3-4 upshift one time, but not afterward.

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

Late sloppy/flared shifting is internal. Late smooth transitions are Bowden cable adjustments.

Before ruling out anything:
I, myself, and everyone else in this thread would like to see a video. It will bring clarity to your situation instead of guessing and throwing ideas around.

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

Interesting comment, would this apply 1 - 2 shifts on 722.435, I suspect the VCV unit or modulator may be faulty on mine.

Thanks,

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David


1996 Mercedes S124 E300TD - 129k - rolling restoration project -

1998 Mercedes W210 300TD - 118k (assimilated into above vehicle)

As far as I know they all pretty much share the same design. You need vac only to prevent clunky downshifts. So I would say the answer is yes.

To test the vac modulator you can unplug the plastic line going from the VCV to the tranny. Plug up the exposed nipple on the VCV and hook up the Mityvac to the plastic line going to the vac modulator (with the Mityvac inside the cabin). Drive around with no vac and you should see smooth upshifts and clunky downshifts. Then drive around some more but pump up the vac and hold it while you come to a stop (you can pump up the vac and hold it as soon as you shift into fourth gear). If the vac modulator is not leaking you should now experience smooth downshifts. I tried this on my 1981 300SD and it worked perfectly.

You should measure about 15 inches of vac between the VCV and the vac modulator and it should immediately bleed off and go to zero as soon as you hit the throttle; if not you can pull the plastic dome off the VCV and adjust it with the screw. There is a specified gap at the stop - like in points - when the VCV is fully closed so be aware of that .

(Apologies if hijacking thread, link below to continue on existing thread http://www.peachparts.com/shopforum/diesel-discussion/379453-k1-k2-b1-722-4-valve-replace-4.html)

Thanks for the detailed reply.

This is my current temp set-up in order to bypass the VCV on the left of diagram, the T piece is also blanked off.

The modulator still receives vacuum controlled in part by the accelerator linkage and vacuum box attached to the pump, it's only a trial and error and easily reversed.

No real difference, under moderate to hard acceleration from stand still the small thump into 2nd is non-existent but soon returns under light load.

I will try your recommendations, thanks again.

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David


1996 Mercedes S124 E300TD - 129k - rolling restoration project -

1998 Mercedes W210 300TD - 118k (assimilated into above vehicle)

How does it shift at WOT?

__________________
'85 300D ~ 381k, HD Bilstien shocks, 27.50x8.50x14R General Grabber AT2 tires, 4 E-Code headlight upgrade with 90/130w bulbs, boost turned up, new timing chain, and injectors. SOLD

'85 CJ7 ~ OM617 swap, Tarus electric fan, T5 trans, Dana 300, 4.88 R&P, Mile Marker locking hubs, ALDA removed, AMC 20 rear disk brake conversion, Aussie locked with 33's and 5" Rough Country lift.