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Old Aug 21st, 2008, 18:48   #3
Clan
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There could be a number of things causing the same problem . Once you get up to 50 mph it should change up with the aid of the centrifugal weights in the primary unit and rpm reduce is this the case?

The cases with probability first assuming it was working properly before this fault developed ..
1 . Broken air valve head in Vacuum 4 way valve , There are two rubber valves in this , one at each end , if you dismantle and find one broken it can be superglued back on and you will get another year or two of extra useful service from it ..
2 , Accelerator kickdown switch on cabe faulty ..
3 , brake switch stuck on , on master cylinder .
4, Vacuum pipe seals where the 2 pipes enter the centre of the primary unit drum
5 , Primary unit diaphragm hole
6 Tachometric relay faulty near brake servo
7 , Have you had some welding done ? Melted front to rear vacuum pipes inside inner chassis members ..

This is really a specialist job , if there are any people left who can remember how they work ! A DAF specialist would be a good first stop ..
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