I have had this problem for a little bit now. There is a fairly loud engine knocking(very noticably by ear) and whenever i startup after about 15 secs it will begin. When you rev the engine in park the knocking just gets faster and a little bit louder but when you put the car into drive it goes away while in drive not moving. When i accelerate you dont hear it while in drive but when you start to slow down or just let off the gas it comes back. I tried using better fuel but no difference. I unplugged the knock sensor and took it for a ride and didnt really see any difference. Was just wondering could it be the knock sensor or am i looking at something different. Thanks for anyhelp

 

Cracked flex plate

 

Funny, but happened to me. Make sure the shift linkage is correct too...

 

Dont really know anything about the flex plate. How much would it cost to get replaced and where is it located. Anything additional would be great. Thanks

 

Flexplate connects the Torque Converter to the engine. Its a round metal disc, between motor and tranny. Can be picked up at most auto stores for $30 +/-

 

what does it take to replace it. do i have to drop the tranny to get at it. i think i have my old one off my 89 305 tbi. Im a little new at all this and just wanna get my car running up to par so i can start with mods instead of repairs.

 

Hey I have had a similar problem, going on six or eight months now. Mechanics couldn't find anything, but they replaced the tranny mount and motor mounts, which were worn anyway. (Tranny mount was broken actually.) Still makes this weird knock/rattle for about 30 sec. when cold, goes away instanty when put in drive, with a bit of a chirping sound. Sound is intermittent, mechanic said it's definitely not the motor. How long can you drive with a cracked flexplate? Is that an expensive fix? Otherwise, the car is awesome, super smooth with good power. Love it.

Have searched these forums looking for an answer, first time I've found a post describing my problem. More info please.

 

Okay, replying to myself here, a new B&M flexplate is right around 100 bucks, with a TCI being somewhat more. I'm assuming labor in the 100 dollar range, unless you do it yourself. Sometimes, the car doesn't make "the noise" at all, making me think it ain't that serious. However, I will most likely get a new flexplate this month and see if that takes care of it.

 

Make sure the torque converter bolts are tight.

 

You can get a B&M, or just a stock one at autozone for $40. It could be serious. It could cause damage. I'd replace it.

Since you have to take the tranny out to do it, if you ever planned on replacing the converter, now is a good time.

Figure around $200-250 labor at a local shop. Prolly around $500+ at a dealership. If your car is in good shape it will come right out. If its like any of the parts cars i've bought, and crossmember bolts snap, stuff doesn't wanna come out, etc then expect to pay more.

-- Joe