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Originally Posted by N0DIH My Cad (91 4.9 Dev) has an interesting, although scary problem.
When you are in neutral or park, doesn't matter, although more prevalent in Park, and you rev the engine, all of a sudden BANG! it sounds like you just revved into the parking pawl (that tone, like when you put it in park and let the car roll into the pawl). The engine torques up when that happens. It is taking a lot of power when it does it. The bang sounds like someone just hit the engine/trans with a 20 lb sledge hammer, HARD. It will scare the crap out of you.
It strikes me as coming from around the chain belt for the transaxle, but it is hard to tell. All it takes is rev it up to around 1000-1500 and it will do it randomly, only once, and I guarentee you will take your foot off the gas!!!
Is the chain slack and whipping or catching on itself? Is the parking pawl loose?
It never does it driving. Only while you parked or in N and revving it, when you are working on it.
No, I don't practice doing it, but obviously it isn't a good thing.
Thanks!
Tom |
This is a sure sign of a worn sprag clutch. The clutch overruns normally when when the engine is revved in neutral the sprag has to overrun at a faster speed and as it wears it will sometimes momentarily engage and jerk the componenets it is attached to in the trans.
There is no solution except to pull the trans and replace it.
Stop revving it up in neutral. Now that you know that it does this do not do it again. The trans may live for tens of thousands of miles. It is not necessarily a sign of am impending trans failure...but...if the sprag breaks the trans will loose drive and it will have to be rebuilt at that point. The next time you rev it up and it grabs like that it may break the sprag clutch so.....
It isn' the chain or anything like that...it is the sprag clutch for sure.