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+-- Forum: Tuning (https://www.superturbodiesel.com/std/forumdisplay.php?fid=6)
+--- Forum: Drivetrain (https://www.superturbodiesel.com/std/forumdisplay.php?fid=9)
+--- Thread: trans shifting hard (/showthread.php?tid=711)
trans shifting hard - heavyD - 09-23-2009
shifts perfect when cold. when its up to temp shifts hard on light throttle ok on full throttle. my stupid p.o.s. benz service manual doesnt have half the things that i need like any info on the trans,[/u] adjusting the trns vac modulator or what the vac switch on the firewall does that is connected to the vac modulator. vac modultor is round green thing near fuse box 617.952 1985 123
RE: trans shifting hard - europower - 09-23-2009
On what gear is the hard shift?
Are you familiar with transmission vaccum tuning on Mbenz diesel models at all?
Have you adjusted anything? any loose hoses anywhere in the system?
Ep
RE: trans shifting hard - heavyD - 09-23-2009
the car runs fine when cold shifts perfect. i think the problem is related to the vacuum transducer switchover valve. this appears to alter the vac acting on the modulator as the car warms up. it seems to allow more vac to act on the transducer making the harder shift then necessary. it seems this system to control the trans was only used on later models?
RE: trans shifting hard - mcb - 10-15-2009
(09-23-2009, 08:05 PM)heavyD the car runs fine when cold shifts perfect. i think the problem is related to the vacuum transducer switchover valve. this appears to alter the vac acting on the modulator as the car warms up. it seems to allow more vac to act on the transducer making the harder shift then necessary. it seems this system to control the trans was only used on later models?
It is possible it is related to a leaking EGR valve. When the car is cold, no vacuum is allowed to act on the EGR valve. When the car warms up, a thermo switch opens up allowing vacuum to act on the diaphragm in the EGR. If the diaphragm is leaking you will have reduced vacuum to the rest of the system which can cause a hard shift.