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#1
06-28-2008, 11:29 AM
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91' W124 300D Automatic shifting hard. IP proportioning valve??
Hi
My transmission shifts quite hard from 2->3, 3->4. 1->2 is perfect. Downshifting (4->3 etc) is smooth and the shifting points is good. Kickdown also etc works fine. It shifts smoother when accelerating really slow. I have measured the vacum going to the tranny: At Idle: 11"Hg to tranny for prop. valve, (20"Hg from vacuum pump to IP prop. valve.) Full throttle: 0"Hg (as expected) Is 11"Hg of vacuum enough vacuum on a W124 diesel? The vacuum pump is new and i found no vacuum leaks. The proportioning valve is adjusted for max vacuum to tranny. Any toughts? 
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#2
06-28-2008, 06:05 PM
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With low vacuum, mine shifts hard with a slight clunking sound. Each time I've had slammy shifts, it's been low vac, with a leak in a valve or line.
__________________
'91 300D 2.5 Turbo 330K '00 VW TDI Golf, 190K '67 BMW R50/2 '73 Norton Commando Interstate
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#3
06-29-2008, 01:06 AM
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What brand of Vacuum Pump?
And how new?
And , I don't think 11 inches is enough...could you be experiencing any leaks? (Older, cracked from the heat hard plastic lines...same for the rubber connections.)
__________________
'84 300SD sold 124.128
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#4
06-29-2008, 09:10 AM
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The pump was installed about a month ago. Don't know the brand yet (don't have the car right here).
Have done a quick check for leaks and didnt find anything. Tried plugging all the other lines and just running one from the pump to the IP valve.. Maby I should do a more thorough test. Is seems that the vacuum coming from the vacuum pump (20"Hg) is good, but the vacuum from the IP prop. valve to tranny is to low. Is there a chance that the prop. valve is leaking? may be i should try to tweak the amount of air the prop. valve is leaking into the system by partially blocking the inlet line for the prop. valve?? Does anyone know what the vacuum directly from the vaccum pump is supposed to be?
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#6
06-29-2008, 11:41 AM
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Have a look at http://www.peachparts.com/shopforum/diesel-discussion/225697-w124-vcv-20inhg-9nihg-out-ok.html#post1890896
Should be 12" at VCV. but 11 is fine. Adjust the VCV on the side of the IP (pull it forward to make softer shifts). There's 2 bolts - one above and one below, size 10mm.
__________________
1983 240D Silver/Blue "Sadie", unknown miles. 100k miles on WVO single tank, converted to 2 tank about 10k miles ago, FPHE, Injector Heaters, Aux Fuel pump. Alcohol/Water injection. Frantz oil bypass filter 1992 300D 2.5 Turbo Green/Tan "Jade" 267K miles Stock. 1992 300D 2.5 tan/tan "Rocky" on 2 tank WVO. Pressure actuated Turbo "rat's nest" surgery completed. 197k miles
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