Barking tires, vacuum control valve?

[John Winn]

Hello Group,
I just had my 84 300SD in the shop for a plethora of things and one of them was the transmission shifts really hard, especially when cold..Barks the tires in fact from 1-2 and the rear end clunks from 3-4. The owner of the shop told me the "vacuum control valve" on the injector pump is inoperative and they wanted $200+ to replace..Being already at 1000.00 in repairs it had to wait..Is this an easy part to change and is it expensive? Is it the same device that shuts the car off? What can I screw up doing it myself? Thanks all for your help! John

[stevebfl]

The part they are talking about most likely is the vacuum proportioning valve MB# 123 070 00 46. MB list $143. Might be cheaper here.

It is a commonly misdiagnosed device but they do go bad. The replacement is very very easy. The adjustment is very, very easy for me. But a mess can be made if you don't have experience. The system runs on a fragile balance between a metered source and a controlled leak (the part in question).

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician