Strange Transmission Shifts - PeachParts Mercedes-Benz Forum

rrgrassi · #1 01-31-2007, 03:25 PM

Here's one for the tranny guru's....

When cold, tranny hits all the gears fine.

When at operating temp, 1-2 is good. 2-3 feels like it is either hunting, double shifting, or going from 2-4, back down to 3. 3 to 4 is good.

Keeping the selector in S does not change the behavior.

The 3-2 valves have been removed, and the EGR disabled. It loes have lock and HVAC vacuum issues, but those have been disconnected and plugged. The car has no problem shutting down.

The tranny was rebuilt or replaced by the PO at 185,000. It is due for a fluid/filter change. Fluid is bright red, and does not smell burnt. It does feel like the selector bushings are getting weak as well.

Thanks!

Rob124 · #2 01-31-2007, 03:44 PM

I'll be interested in the replies to this post. This is usually described as 'flaring'. I've experienced the same problem on mine, and seem to have mostly eliminated it with an adjustment to the Bowden Cable. I've backed out the adjustments I made to the vacuum amplifier and modulator, because they didn't help. I wouldn't rule out the possibility that the Bowden Cable adjustment just hides a wear issue, but I'm encouraged with the result so far. I switched to synthetic ATF 2,000 miles ago, and hope that makes a little difference.

Brian Carlton · #3 01-31-2007, 03:53 PM

I'd also be curious to see if the Bowden cable could help you with that.

Tighten it three turns (counterclockwise) and see what it does.

rrgrassi · #4 01-31-2007, 04:23 PM

I did that last night, and all it did was make the upshifts later depending on how farthe pedal is mashed.

I do have the Black/Blue vacuum damper out of the car. It seems to be a one way valve, but was hooked up the HVAC.

The Modulator does hold vacuum and the VCV holds vacuum until you move the rack. The VCV and tranny are hooked up to the first vacuum port from the vacuum pump on the main line, and the other working systems are on the 2nd port.

rrgrassi · #5 01-31-2007, 04:27 PM

I wonder if I have a weakening K-1 valve.

Brian Carlton · #6 01-31-2007, 05:29 PM

Quote:

Originally Posted by rrgrassi

I wonder if I have a weakening K-1 valve.

I believe that's your next step. A change in the K-1 usually does wonders for the 2-3 shift.

rrgrassi · #7 01-31-2007, 05:51 PM

Thanks Brian. I'll change the K-1 at the fluid and filter change.

I'll probably get to see what is "sans-a" this time.

BTW, what does the black and blue vac damper get connected to?

Rob124 · #8 01-31-2007, 11:32 PM

FWIW, I changed my K1 springs tonight. So far, so good. I'll have to see if it permanently cures the 2-3 shift anomalies.

rrgrassi · #9 02-01-2007, 09:41 AM

Let me know how that works for you!

sailor15015 · #10 02-01-2007, 11:06 AM

I'm in the same boat you are. I've got almost the same miles and my tranny was rebuilt due to what I believe was a mis-diagnosed vacuum issue, due to what was written on the repair bill. I need to adjust my vent valve on top of the ip because all the shifts are a little soft but the 2-3 tends to run away a little bit more. I'm due for a fluid/filter change in about 8k miles, sometime in early spring and I'm going to install the K-1 spring kit then.

Is the K-1 not replaced or updated in a rebuild? Could it be worn out alread, in say, 50-70k miles?

rrgrassi · #11 02-01-2007, 11:14 AM

I have no idea what the life expectancy is on a K-1 assembly. I do know that it is a some plastic, rubber and a metal spring. I'm surprised that plastic and rubber last that long.

I still want to know where the black and blue one way restrictive vacuum valve connects to.

Biodiesel300TD · #12 02-01-2007, 11:31 AM

Quote:

Originally Posted by rrgrassi

I still want to know where the black and blue one way restrictive vacuum valve connects to.

Its a check valve for the door lock system. It should be positioned so that you can suck air through the side that goes into the cabin, and so the side you can't suck air through towards the main vac supply line.

rrgrassi · #13 02-01-2007, 11:44 AM

Quote:

Originally Posted by Biodiesel300TD

Its a check valve for the door lock system. It should be positioned so that you can suck air through the side that goes into the cabin, and so the side you can't suck air through towards the main vac supply line.

Now I'm confused...

Does it go before the check/splitter that hooks up to the yellow lock line and the yellow/gray vacuum keeper line? The check/splitter, I think it's white, does work. When I disconnect it, the locking system does maintain vacuum.

It seems to me that if it hooked up before the splitter, then the locking system and vacuum keeper would get no vacuum at all from the main line.

Thanks!

Rob124 · #14 02-02-2007, 09:15 AM

My tranny shifts flawlessly since I installed the new K1 springs. What an improvement for a simple job! I used a couple of deep-well sockets to easily slide the two halves of the new spring assembly together. My understanding is that the new springs are stiffer than the originals--it's not just that the old ones were worn out. Go for it!

rrgrassi · #15 02-02-2007, 10:37 AM

Yep, that's my next step along with the fluid/filter change.