sschevy400

So what now huh....When the car is in reverse it will knock/tap. Cant locate it at all. Must be the trans?

What do you guys think?

As soon and you put it in park or drive, the noise stops. Place it back in reverse and it comes back. It will tap faster with engine RPM also. some days it there...some its not.

Any ideas? thanks guys

dr.fiero

I'm thinking motor or trans mount. Torques in the opposite direction in D vs R of course.

Pop the hood, do a partial (not all the way!) brake stand in drive, then do it again in reverse. See how much the engine tilts over each way (should be about equal).

edit: oh yeah... heh... if it does move too far over, I'd start with checking the fan shroud for signs of hits.

sschevy400

Yea i thought of that...but electric fans.
I just tried it and the motor moves about 1 1/2 inches in drive and reverse when giving it quick stabs of the throttle with the brake held.

BtownZ28

I vote trans mount- replace it and see what happens.

dr.fiero

E-fans, ah yes! Oops.

So, when you did the mini brake stand, did you get any noises?
If not, you've narrowed it down to half the trans, or the driveshaft (etc).

I'd lift up the back end, then run it backwards. See if the noise is still there.

jagevileye21

iTrader: (3)

My car does the same thing when I put it in reverse (a loud bang) and I have new polyurthene trans mount. Now I'm leaning more towards torque converter being slightly loose, u-joints or bad yoke.


Jay

sschevy400

No no noise this time. But it does come and go. It doesnt bang hard, its just taps. I can put my hand on the trans and feel it....almost like the flexplate is rubbing. But then next time, it wont do it at all.

I'll try a trans mount and see what that does

should i get a poly? or a stock one?

dr.fiero

Your call, but... they're so cheap... I'd toss in a poly from Energy Suspension or whoever floats your boat.

But the way you're saying comes and goes - I'm starting to lean away from it being a mount.

jv9999

iTrader: (1)

I vote for a cracked flex plate.

el_muerte

make sure it's not the exhaust hitting the transmission, i had a similar problem... strange knocking sound that comes and goes, changes with engine speed, and comes from transmission area.

gavin.priestley

Hey guys im new here, and I know this is kind of an old thread, but I'm having a problem with my bird, like when the car is cold, the engine is fine, but as soon as the engine reaches normal temperature and I put it in reverse or drive I hear a kind of knocking/lifter sound. But then if i put it back in Park, the noise goes away. I just changed the oil, replaced the oil pump with a HV one and put a new oil filter too. When me and my dad were down there he noticed a bad bearing on the crank, so we replaced that as well, it was the only bad one, so idk now, idk is it the lifters?

GeneralDisorder

iTrader: (1)

Crank bearings feed rod bearings - did you check those too?

It's not usually a great idea to roll bearings into an engine once one has "gone bad". Do you have any pictures of the bad one?

GD

86LG4Bird

iTrader: (1)

Don't rule out an exhaust manifold leak.
Since the exhaust is somewhat restrained by its mounts to the chassis, a "barely-there" exhaust leak could be opened up when the engine+transmission torques over one way in reverse, and closed up when in neutral or torqued over in a forward gear.