What could slow a car down when changing gear?

[Scots_Man]

Hi,

Does anyone know what could be causing this problem?

When I accelerate, then dip the clutch to change gear (manual), the car feels like it is slowing down quite rapidly - almost like the kick you sometimes get with turbo cars/dump valve.

I can rule out the braking system as I have checked the calipers and handbrake shoes - all working perfectly and not sticking on.

I notice the problem more so if the car is cold. I don't think it is to do with the electrics (plugs, leads, etc) as I have checked them. I haven't looked at the fuel system yet, and thought I would check if anyone had any solutions before I did this.

Many thanks,

Gary

 

[paulcallender]

Okay try this: do a gear change, but 'stop' half way through and leave the clutch in. If you're clutch is disengaged, the only thing that can slow you down is a hill, or a brake binding issue (or a tree/etc).

I suspect however you're changing gear wrong. Do you lift off the accelerator during changes? How much clutch are you using? How much force are you applying to the gearshift?

 

[tom7035]

I think a binding or seizing flywheel spigot bearing/bush could cause this effect, but another symptom you would have is difficulty engaging first gear from rest.

 

[paulcallender]

I think a binding or seizing flywheel spigot bearing/bush could cause this effect

Only if you take your foot off the throttle during changing.....Am I doing it wrong, by keeping my foot on the throttle when changing gear in manual cars????

 

[tom7035]

No Paul, this is the correct method in order to maintain corresponding engine/road speed, but very few drivers actually do that. This may be the case with Gary.

 

[TimN]

Don't want to be alarmist but you may have a problem with your thrust bearing. As you depress the clutch you may actually be moving the crankshaft forward before the clutch disengages thus placing stress on the con rods and pistons. Hopefully this isn't the case as I would expect the engine to konk out or definitely show signs of struggling. To check and eliminate it this, ask someone to press and see if any movement on the pulley on the fron of the crankshaft can be detected.