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Curious bout what this does to my clutch...

B

bradleyheathhays

NAXJA Forum User
Location
Lexington, KY
Had an incident recently where I left the lights on to my '96 XJ 4.0 and killed the battery. During the jump it wouldn't start unless I gave it some gas and wouldn't stay running less I gave it gas as well. Computer eventually relearned idle after a couple times driving but to keep it running at stop signs I continued to give it gas at the same time as braking...which got me wondering. When you power brake a 4.0 what does that do to the clutch. If you can rev the motor without the wheels turning wouldn't this wear down the clutch? I'm just generally a little undereducated on how the clutch comes into play other than when shifting gears.

Thanks
 
With you fut pushed down this pushes the throwout forward against the splines on the clutch housing which pulls it back off of the clutch disc (which is splined to input of transmission) and disconnects the transmission effectively from engine. With pedal pushed down a properly functioning clutch is not making contact with the engine so nothing bad will happen giving it gas at a stop. However, not the same can be said for the classic rev it up and drop the clutch...
 
Oh yeah and forgot to mention for theories sake...clutch cover is bolted to flywheel which is bolted to crankshaft so clutch cover is always at engine RPM. Throwout bearing is on the input shaft but is on a bearing surface so it is around it just never engaged with it so it spins freely.
 
How many pedals does this Jeep have?
 
bradleyheathhays said:
Had an incident recently where I left the lights on to my '96 XJ 4.0 and killed the battery. During the jump it wouldn't start unless I gave it some gas and wouldn't stay running less I gave it gas as well. Computer eventually relearned idle after a couple times driving but to keep it running at stop signs I continued to give it gas at the same time as braking...which got me wondering. When you power brake a 4.0 what does that do to the clutch. If you can rev the motor without the wheels turning wouldn't this wear down the clutch? I'm just generally a little undereducated on how the clutch comes into play other than when shifting gears.

Thanks
Click to expand...
Power braking a manual trans? That takes skill, and is a bit dangerous at a stop sign. Better to disconnect the battery and wait 15 minutes for the the computer memory reset than take the risk of an accident.

Power braking an auto will heat the fluid quickly but isn't hard on anything internally unless you are hitting the converter stall. That causes rapid fluid heat up and can cause damage.
 
Based on you saying you had to hold the brake while you revved, I'm guessing you have an auto. If so, you do not have a clutch, you have a torque converter http://auto.howstuffworks.com/auto-parts/towing/towing-capacity/information/torque-converter.htm. Beyond heating up your fluid a bit more than necessary, you're probably fine.

If you have manual, and you either put the clutch fully in or put it in neutral, that should be fine too. If you didn't press the clutch didn't fully disengage (as evident by you needing to hold the brakes to not roll forward), you added some wear to the clutch, but if don't think you would have damaged anything, especially if you didn't smell something.
 
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