Engine revs jumping after rear axle beam replacement

[julia2026]

After having the rear axle beam (differential) replaced, when I press the clutch during gear changes – e.g. from 3rd to 4th, 4th to 5th – while the clutch is pressed the engine revs jump up to around 2500 rpm. Generally, this also happens sometimes while driving: if I put the gearbox in neutral and just press the clutch pedal, I can use the clutch pedal to rev the engine as if it were the accelerator.

What could be causing this? I'm genuinely running out of ideas where to look.

2017 Ford Transit 350 L3H3 RWD TDCI 130, 1996cc Diesel, Manual, RHD (UK).

[metalworker0]

all i know

the clutch pedal has a switch on it that detects when you press on it .. so it can increase revs as you lift it off again .. an anti-stall feature .. but its not 2500 revs.. more like a hundred

cant see how the back axle would be involved

but that extra hundred revs may be enough to trigger something else, like the throttle valve in the manifold, (which is there to make a vacuum and suck more exhaust gas into the egr)

or could be turbo leaking oil and you are getting mini runaways .. all guessing - would be a first warning if that .

try unpluging the switch to see if it goes away .. then you'll know its somehow related to it.. not the cause .. but related .. meaning causing something else to react.

throttle is fly by wire and clutch is not part of it like the old pedal boxes where all levers were suspended on a common shaft

all the best.mark

[dumper]

My 65 plate had two switches on the clutch pedal one at the top it raise the revs for anti stall and a switched at the bottom of travel and it returned to tick over until you lifted the pedal to drive off this only happened when in gear

[julia2026]

try unpluging the switch to see if it goes away .. then you'll know its somehow related to it.. not the cause .. but related .. meaning causing something else to react

Hi Mark.

You've hit the nail on the head! A week ago I replaced the clutch master cylinder with a new one, because unplugging the old one made the problem go away, and the mechanic said the clutch master cylinder was at fault and needed replacing.
Unfortunately, after fitting the new clutch master cylinder, the problem is exactly the same. If I unplug it from the clutch (there's a 6-pin connector there), everything works as it should — but it has to stay connected, because if I switch the van off, I won't be able to start it again afterwards (the clutch pedal being pressed is what allows the van to start).

So we're back to square one. But thank you so much for your time and willingness to help. If you have any other possible ideas, please let me know.
Thanks again.

julia

[julia2026]

My 65 plate had two switches on the clutch pedal one at the top it raise the revs for anti stall and a switched at the bottom of travel and it returned to tick over until you lifted the pedal to drive off this only happened when in gear

Thank you for the valuable advice. I’ll see if anything can be done about it and ask my mechanic. I really appreciate all your help.
Kind regards.

[metalworker0]

try unpluging the switch to see if it goes away .. then you'll know its somehow related to it.. not the cause .. but related .. meaning causing something else to react

Hi Mark.

You've hit the nail on the head! A week ago I replaced the clutch master cylinder with a new one, because unplugging the old one made the problem go away, and the mechanic said the clutch master cylinder was at fault and needed replacing.
Unfortunately, after fitting the new clutch master cylinder, the problem is exactly the same. If I unplug it from the clutch (there's a 6-pin connector there), everything works as it should — but it has to stay connected, because if I switch the van off, I won't be able to start it again afterwards (the clutch pedal being pressed is what allows the van to start).

So we're back to square one. But thank you so much for your time and willingness to help. If you have any other possible ideas, please let me know.
Thanks again.

julia

Well its complicated .. the clutch pedal and throttle pedal switches also reset things like cruse control etc .. beyond my understanding .. and controlled by modules and bcm pcm .
it may be that the system requires a relearn , or you have the cruise control or other functions like hill start assist left on.. that should not be left on. etc

You could try reading the owners manual .. as to the operation of these .

it may not be you, but anything like a faulty switch or wiring that can cause this . even the abs system is wired into this, as it detects the speed of your vehicle .. now some of that abs system is on the rear axle

just giving you an idea where to look

all the best.mark