722.303 2-3/3-4 Shift Flaring - PeachParts Mercedes-Benz Forum

JamesDean · #1 10-11-2010, 10:19 AM

Hey everyone,

I'm trying to adjust out some shift flaring on my one SD.

Mileage: 142k
ATF: less than 20k

Some notes:
1) K1 spring kit has been installed
2) B2 has been replaced
3) Throttle Linkage connection to pedal is adjusted so pedal is firm and throttle response is quick.
4) EGR switchover valves are removed and lines are plugged.

When cold, 2-3 will always flare 1k rpms, sometimes 3-4 as well

When warm, 2-3 will seldom flare, 3-4 does flare

I might have the vacuum modulator adjusted too much as the 1-2 shift is very docile and gentle.

I turned it two clicks to the right last night trying to lessen the vaccum to quell the shifts. This might have been the incorrect direction.

Any thoughts?

kerry · #2 10-11-2010, 10:23 AM

Have you tried removing the vacuum line to the modulator to see what happens? If flare disappears, then you have too much vacuum going to the modulator.

JamesDean · #3 10-11-2010, 10:29 AM

Kerry, I was going to pull the vac line on my way home from work today and see what happens. I suspect there is too much vacuum. My 1-2 shift (which was always a bit of kick is very very tame)

kerry · #4 10-11-2010, 10:57 AM

If it improves with the vacuum removed, you can attach a Mity Vac to the transmission line and run a hose out at the cowl, leaving the Mity Vac visible thru the windshield. You can then read the exact vacuum going tot he transmission as you drive around.

JamesDean · #5 10-11-2010, 09:37 PM

Ran it with the vac unpluged. Nice non-flaring shifts. However I think its shifting quickly through them.

1-2 shift is at like 7-9 mph
2-3 shift is at like 12-13 mph
3-4 shift is at like 20 mph

Its in final drive before 25mph when at like 1/4 to 1/2 pedal.

kerry · #6 10-11-2010, 09:48 PM

Adjust the bowden and leave the vacuum line unhooked. That's what I did with my W116.

JamesDean · #7 10-11-2010, 09:52 PM

Like permanently unhooked?

I'm know that hard shifting like that isnt exactly good for the flex discs...

I think I'll get the shift points right first, then hook up vacuum again..and adjust modulator pressure....once its stops raining and I can lay on the ground without getting all wet.

kerry · #8 10-11-2010, 10:01 PM

Mine weren't hard, just nicely firm.

JamesDean · #9 10-12-2010, 10:19 AM

Well..this isnt a good sign.

I'm getting a 3-4 up shift flare with the vac disconnected.

Either I have to replace something in the transmission (maybe similar to K1 spring kit but for 3-4?)

Or

I have the bowden cable adjusted too much and its causing this...

tangofox007 · #10 10-12-2010, 11:03 AM

Quote:

Originally Posted by JamesDean

Either I have to replace something in the transmission (maybe similar to K1 spring kit but for 3-4?)

The Superior Shift Kit has options for that issue.

JamesDean · #11 10-12-2010, 03:32 PM

http://www.superior-transmission.com/Product_Page.cfm?ID=19

Quote:

1. This Shift Correction Package services early and late 722.3 and all 722.4 Mercedes transmissions 1980 to 1990, Diesel models.

2. The Superior kit softens the harsh 1-2 shift.

3. The K722A-D Shift Correction Package offers options on firming up the 2-3 and 3-4 shifts from normal to firm to even firmer.

4. This kit also offers an even softer option on the 1-2 shift.

5. The kit offers a simple solution to correct stacked 2-3 shifts.

6. Proper installation will stabilize shifts of this unit.

7. This package supplies needed parts to set vacuum properly.

Stacked Shifts...is that when the tranny shifts very quickly though the gears?

babymog · #12 10-12-2010, 04:35 PM

"stacked shifts" is when the transmission changes more than one gear at a time (such as going from 1st directly to 3rd).

JamesDean · #13 10-21-2010, 09:11 PM

got the kit in, havent had time to install it.

I've been manually shifting into 4th.

I've noticed this:
If speed is increasing and I upshift, the shift is less firm than it is if I am at a constant speed...

When at constant speed/rpm (say 40mph) it'll shift like the rest of the gears...

I'm sure that means something..but not sure what.

whunter · #14 08-07-2012, 08:38 PM

Quote:

Originally Posted by JamesDean

got the kit in, havent had time to install it.

I've been manually shifting into 4th.

I've noticed this:
If speed is increasing and I upshift, the shift is less firm than it is if I am at a constant speed...

When at constant speed/rpm (say 40mph) it'll shift like the rest of the gears...

I'm sure that means something..but not sure what.

How was this resolved?

.

JamesDean · #15 08-07-2012, 08:48 PM

Quote:

Originally Posted by whunter

How was this resolved?

.

Sorry about that Roy,

I haven't fulled finished this up. But I did install the kit. I put in the highest K1/K2 springs the kit offered. That combined with a new B2 piston made the 1-2 shift almost unnoticeable at a moderate acceleration.

I think I might be low on ATF due to my inability to properly install a pan and pan gasket.. but without vacuum, there are no more flares in the shifts, all are nice and firm.

With vacuum, if only applying a small amount of pedal, all shifts are nice and just about undetectable. When applying full throttle, no problem either, nice firm ****s. When applying say anywhere in between I occasionally get a 3-4 flare up.

I'm still working it out, this car is a long-term restore so its not driven daily [even though it needs to be

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