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Discussion Starter · #1 ·
Hi!
I have a strange issue with my Turbo R 3-Speed:
It's never wanted to change down under part load, say 2/3 throttle. Whilst checking the dump valve in the intake elbow, I discovered that the one-way valve (part UR 20876) in the vacuum line between the manifold and the dump valve (and that also branches off towards the vacuum modulator of the gearbox) wasn't working properly, so I removed it and plugged the vacuum line. Suddenly the started changing down under part load - all good I thought. Today I replaced the one-way valve with a new one, and now the down-changes have disappeared again...

What's the explanation for this?

I got a Pierburg valve, optically identical to the original one. The arrow is pointing towards the dump valve.


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Discussion Starter · #2 · (Edited)
Can anyone with a 3-speed tell me if their car changes down under part load?
Lots of info on tuning TH400s around, but all for making the cars (not Bentleys...) go faster on the drag strip...
 

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Yes mine does. Hard to know when I'm flooring it as throttle is so light but pretty sure it changes down. Will test tomorrow to be more accurate.
 

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Mine does too, but I don't have a turbo.

Are you sure the rest of system is good/tight?
 

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Discussion Starter · #5 ·
Mine does too, but I don't have a turbo.

Are you sure the rest of system is good/tight?
I think the rest of the system is OK, but I'm not 100% sure.
So, if you're cruising along at say 50mph and then apply 2/3 throttle or so,it'll shift down a gear?

Es
 

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Check completely the linkage, you need a minimum play, but remember if too much play at each point, when you add the play is important. Check play from the pedal and put a little oil and check all the system is straight and not bended.
 

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Discussion Starter · #7 ·
Hi Jean,

There is some play in the throttle linkage, which isn't really surprising considering how complicated it is, but that shouldn't affect the part load gear changes.
As far as I know, those can only be affected by the modulator, which is connected to engine vacuum, and the governor, which is speed regulated.

Es
 

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Play is absolutely necessary, just make sure between the begening ( accelerator) and the end ( engine) there are not too many small plays or a part bended.
Best is to be 2 to check.

Check also if you kick down is working

You maybe right for what you say for the main causes, you know better than me I see.
I am always to start by simple causes and uprgade to compicated.
 
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