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#1
08-22-2008, 04:27 PM
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another vacuum/hard shifting issue 83sd
do these vacuum pumps go out slowly?
my sd needs to build vacuum in the morning and doesn't shift from 1st to 2nd for 30 seconds or so. also it shifts hard, with a bit of a bang. other vacuum operated components seem fine. (climate) do I need to start fumbling with the actuator on the tranny? or can that vacuumpump indeed 'go out slowly'? (it seems to get worse over time) when flooring the pedal it shifts smooth though, at high revs. thanks for info! 
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#2
08-22-2008, 04:56 PM
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I would hook up a mity vac to your main vac line and see how much vac it's pulling. Withthe car running it should be between 18"-25". If you are lower then that either the pump is going bad or the break booster is leaking. You can test that by removing the vac line from the booster and reading the mity vac again. If the number jumps to the range above then the booster is leaking, if there is no change then the pump needs a rebuild.
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Andrew '04 Jetta TDI Wagon  '82 300TD ~ Winnie ~ Sold '77 300D ~ Sold
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#3
08-22-2008, 05:01 PM
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The shifts point are controlled by the vacuum control valve which in turn is controlled by the location of the rack/accelerator linkage. Since diesels require heat to function well, when the engine is cold the accelerator must be pushed down further to get the same horsepower. Hence the lengthened shift between 1-2 when the engine is cold and the harsher shift since more vacuum is bled off by the VCV as the accelerator is pushed farther.
This is not to say that there might not be a vacuum problem somewhere, but just to comment that the change in shift patterns between cold and warm is entirely normal.
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1977 300d 70k--sold 08 1985 300TD 185k+ 1984 307d 126k--sold 8/03 1985 409d 65k--sold 06 1984 300SD 315k--daughter's car 1979 300SD 122k--sold 2/11 1999 Fuso FG Expedition Camper 1993 GMC Sierra 6.5 TD 4x4 1982 Bluebird Wanderlodge CAT 3208--Sold 2/13
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#4
08-22-2008, 07:47 PM
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I agree with Kerry as well. There is defintely some warm up time needed to get the best performance out of these diesels and their transmissions. But you might also think about changing the ATF and the filter. Some times that can help shift quality.
__________________
Andrew '04 Jetta TDI Wagon '82 300TD ~ Winnie ~ Sold '77 300D ~ Sold
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