Can a bad 700R4 knock??
 

Hear is the deal. I have a 89 Formula 350 with 133k on the chassis for about 2 weeks now I have noticed a knocking or a pinging sound coming from under the car when I drive.
I beleve it is the transmission but I want to be sure before I have it rebuilt. Any input would be great. Here are the symptoms-
knocking sound is only heard when:
The car is in drive and moving forward with foot on the gas (sound starts at about 1000rpm).
Knocking sound is not heard when:
The car is in park or neutral even if I rev it up.
When the car is in reverse.
When the car is in drive with foot on brake even if I give it gas (power brake it)
I have heard a sound like it before and it turned out to be the bolts were loose where the flex plate bolts to the torque converter.
I have checked everything mounts, u-joints fluid, everything is ok. Does this sound like I need a new tranny or is it something I over looked, it still shifts fine and it does not slip. Any info?

did you check the tranny mount ?

at 133k Its prolly bad anyway.



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60 Ranchero - Project ( Money Hole )
85 Sport Coupe LG4 - Daily Driver

Livin' the Stereotype

That very likely is not the problem. It sounds like the problem is RPM dependent, but only while moving. You may have a cracked flexplate. My bellhousing bolts backed out after installing the tranny, and one day I got a hideous *BANG-BANG-BANG* sound that emanated from under the car. There was an inch of bolt threads visible on one side... yikes, to say the least. Now, I get a constant 3000+ RPM driveline vibration that drives me nuts. I'm pretty sure that at this point, it is a cracked flexplate. You may have the same problem.



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91 Trans Am WS6
Bright White
5.0 TPI auto
Flowmaster 3" 2 chamber catback
Trans Go shiftkit
2000 stall converter

Built on Wednesday

I'm with 'MrJ', I think its a flexplate.
You need to check up near the hub, right outside the crank bolts. Look for any tinny hairline crack. At worst it will be all the way around hub.
You've said that you had the flexplate bolts come lose before, this is usualy terminal for the flexplate.

KNOCK - KNOCK - KNOCK - KNOCK I've broke four to this day. One of them was a TCI believe it or not (lost a flex bolt on that one).

Ron

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'82 Trans Am
'81 Camaro Z-28
'94 Vette LT1 Coupe

[This message has been edited by ronterry (edited January 19, 2001).]

Re: Can a bad 700R4 knock??
 

Just going through some old post, It was a cracked flex plate. Man it sounded like a spun rod bearing.