Transmission oddities - PeachParts Mercedes-Benz Forum

Jason Beal · #1 12-02-2008, 02:11 PM

1994 c280, 722.4 transmission. 128k miles, serviced regularly. The transmission won't let go of second gear (even after warm up, which works correctly btw) all the time. Often it will hold until 3500-4500 rpms before it shifts. If I bring it up to 2500-3500 rpm and let off the throttle it will shift (like driving a stick.) If I go really light on the gas pedal sometimes it will shift as it should. Vacuum leaks have been addressed, and there was no metal in the pan the last time I dropped it. From what I've read, this sounds like the governor is sticking.(I've searched and read posts about cars that won't shift at all out of second, but nothing like my issue. ) Any ideas? It hasn't gotten worse, but it certainly isn't getting better on it's own. Although one afternoon it shifted flawlessly for three stops lights, lol.

I want to be clear that I'm not talking about the car holding gear when it's cold. In this case, it simply will hold the gear all the time.

Thanks.

johnjzjz · #2 12-02-2008, 05:38 PM

if you pop off the small boot on the modulator ( the key adjustment area ) and trans fluid is present than the vacuum signal is being affected - the day it worked it might have gulped the oil out of the line for a few minuets - check it out - jz

Jason Beal · #3 12-02-2008, 10:58 PM

Quote:

Originally Posted by johnjzjz

if you pop off the small boot on the modulator ( the key adjustment area )

Is this on the side of the transmission? Thanks.

Edit: Also can a faulty MAF cause shifting issues?

Jason Beal · #4 12-04-2008, 05:43 PM

Does this transmission have the k1 spring problem that causes the 2-3 shift issue? Anybody know?

I cleaned the MAF last night and it smoothed out my idle (curious to see if it helps with my gas MPG) but did nothing for the shifting issue. Adjusted the modulator on the side of the trannie and while that firmed up my shift I still have second gear holding before it shifts.

compress ignite · #5 12-04-2008, 05:53 PM

JB,

I HIGHLY recommend these three Posts/Articles:

It's CRITICAL... how you set your transmission's vacuum system on your diesel MBZ...

http://peterschmidtransmission.com/

http://www.continentalimports.com/ser_ic20242.html

Further thought:Kickdown switch underneath the Accelerator Pedal might be bad.

And yes it has the K-1 (Along with half the rest of the Alphabet.)

I'm not as "up" on the Transmission as I should be...

If you can interface with STEVEBFL he may be able to assist you further.

hey_allen · #6 12-07-2008, 06:15 AM

If you get to feeling like really diving into the deep end of the transmission troubleshooting and want the rebuild manual, you can get it from ATSG.com for $25.

If you opt to buy the paper copy, you'll still get access to download the electronic version so you can play with it on your computer while you wait for the dead-tree version to arrive.

Happy wrenching, regardless!