722.357 automatic transmission adjustments - Page 2 - PeachParts Mercedes-Benz Forum

tyl604 · #16 11-07-2014, 09:58 AM

I believe you read James Dean's post backwards. The tranny does not need vac to upshift. If you disconnect the vac from the modulator and the tranny is OK, it should upshift smoothly. I believe he was asking if it slipped or otherwise did not upshift properly with no vac which would indicate problems with the tranny.

However the downshift with no vac will be harsh. It must have vacuum to downshift smoothly.

To test you can unhook the tranny vac line from the engine and hook it into the Mityvac. Drive around with no vac and you should see upshifts smooth. When you get ready to come to a stop sign, pump up the vac on the Mityvac and you should get smooth downshifts.

So:

no vac - smooth upshift
vac - smooth downshift

JamesDean · #17 11-07-2014, 10:02 AM

Quote:

Originally Posted by tyl604

I believe you read James Dean's post backwards. The tranny does not need vac to upshift. If you disconnect the vac from the modulator and the tranny is OK, it should upshift smoothly. I believe he was asking if it slipped or otherwise did not upshift properly with no vac which would indicate problems with the tranny.

However the downshift with no vac will be harsh. It must have vacuum to downshift smoothly.

To test you can unhook the tranny vac line from the engine and hook it into the Mityvac. Drive around with no vac and you should see upshifts smooth. When you get ready to come to a stop sign, pump up the vac on the Mityvac and you should get smooth downshifts.

So:

no vac - smooth upshift
vac - smooth downshift

Yep that is what I was asking.

With no vac the tranny shifts hard.

However, in my experience both the up and the down shifts were hard. Hard in the send that they were very distinct and there was no flaring/slipping.

My 91 300D (722.418) is like that. When I had my vac leak it would shift hard both directions. Now that I plugged up all but 2

of the HVAC ports on the valve tree it shifts beautifully.

Stretch · #18 11-07-2014, 10:04 AM

Quote:

Originally Posted by JamesDean

Not to contradict you, I know some have had problems with the EPC but in my 7-8 years of usage I've not had any problems related to starting it up in Windows. That covers 7 and 8, 8.1.

I'm glad to read a positive story for once!

Vilnis · #19 11-10-2014, 10:17 AM

Unfortunately i didn't had a chance to get under the car last weekend, will do it this weekend. However I played with mityvac, connected to the modulator to see what VCV gives to it during the drive.
It looked like I need to leak down little bit less vacuum, so I turned VCV counter-clockwise. All shifts became much smoother, I almost don't feel 1-2 shift, but then 2-3 slips and 3-4 is little bit harder then 1-2 shift.

Can this (2-3 shift) be improved with modulator or Bowden cable regulation?

JamesDean · #20 11-10-2014, 10:25 AM

Quote:

Originally Posted by Vilnis

Unfortunately i didn't had a chance to get under the car last weekend, will do it this weekend. However I played with mityvac, connected to the modulator to see what VCV gives to it during the drive.
It looked like I need to leak down little bit less vacuum, so I turned VCV counter-clockwise. All shifts became much smoother, I almost don't feel 1-2 shift, but then 2-3 slips and 3-4 is little bit harder then 1-2 shift.

Can this (2-3 shift) be improved with modulator or Bowden cable regulation?

Adjust the module one notch (I cant remember the direction, but you want less vacuum) and see how that works out. It might make the 1-2 shift a bit more noticeable but it should take care of that 2-3 slip.

Vilnis · #21 11-10-2014, 10:33 AM

Quote:

Originally Posted by JamesDean

Adjust the module one notch (I cant remember the direction, but you want less vacuum) and see how that works out. It might make the 1-2 shift a bit more noticeable but it should take care of that 2-3 slip.

But that slip is caused by inner problem? Something like pistons or break bands?

JamesDean · #22 11-10-2014, 10:35 AM

Quote:

Originally Posted by Vilnis

But that slip is caused by inner problem? Something like pistons or break bands?

Too much vacuum can also cause the transmission to flare. To verify you can disconnect the vacuum to the transmission. This should cause the transmission to shift firmly in all gears. There should be no flaring/slipping at all.

If you have flaring or slipping then you have internal problems.

If you have no flaring and no slipping then you have too much vacuum going to the transmission causing the 2-3 flare/slip.

Vilnis · #23 11-10-2014, 11:49 AM

Quote:

Originally Posted by JamesDean

Too much vacuum can also cause the transmission to flare. To verify you can disconnect the vacuum to the transmission. This should cause the transmission to shift firmly in all gears. There should be no flaring/slipping at all.

If you have flaring or slipping then you have internal problems.

If you have no flaring and no slipping then you have too much vacuum going to the transmission causing the 2-3 flare/slip.

Is there a method to equalize all shifts? If I will turn VCV back 1-2 and 3-4 shifts will be hard again. Or this will go away with the modulator adjustment, not VCV?

JamesDean · #24 11-10-2014, 11:58 AM

Others might be able to comment more than I but you might be able to fine tune the shifts with the modulator more so. Give it a try and see how they do. Generally the 1-2 shift in most Mercedes of this vintage is harder than the rest.

Beyond that there are some springs that can be changed in the transmission valve body that can help fix some of the shifting issues.

Superior Transmission - Superior K722A-G
Superior Transmission - Superior K722A-D

Vilnis · #25 11-10-2014, 01:55 PM

Wow, that is interesting, thanks.