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Mysterious knocking sound, what could it be, Read pg2. and on

basically, The first day I started to have problems. I get into my truck, I take off Getting onto the highway. As my truck downshifts It just stays I let off because I didnt want to hurt my truck. it then shifts back to 3rd. just cruising at 50mph the truck downshifted again. so I let off. I get off the first exit, Turn around And start to go home. As I'm driving home The truck was making the Odd noise at a medium-high rpm 3-4kish I have no tach so.. Anyway I continue home. As I get on my street. the truck then starts to Have this Knock it has now. Which I really Really hope isnt my Motor.
so Maybe my description could help someone give me some ideas maybe
 
I would be real suspicious of the transmission. The TH350 does have a vacuum modulator if I remember right, so if the engine was having bad problems, it might cause a low vacuum condition that would make the transmission downshift.

Can you hear the noise when sitting still? Such as revving up the engine in park?
You need to try to find where is it coming from. And that is hard to do when driving.
 
Fordum said:
I would be real suspicious of the transmission. The TH350 does have a vacuum modulator if I remember right, so if the engine was having bad problems, it might cause a low vacuum condition that would make the transmission downshift.

Can you hear the noise when sitting still? Such as revving up the engine in park?
You need to try to find where is it coming from. And that is hard to do when driving.
Click to expand...
when I have the truck started I dont hear it at idle. yes it still makes the noise in park when you rev it up. when I have the hood open and my head over the block. It sounds like it's coming from the back of the engine, Towards the Flexplate and Torque converter area. I have not been under the truck with someone else on the throttle though.

edit, also drove around for 2 days while the Vacuum line to the vacuum modulator was disconnected. as for the super hard shifting.
 
flexplate....

takes 2 mins to check and sounds like your issue. ive changed mine twice.


get under there and look at it were the holes are for lightening. thats werer it is prone to crack. then blip the starter and look at the other side.

CIMG0827.jpg
 
NorCal_Chris said:
flexplate....

takes 2 mins to check and sounds like your issue. ive changed mine twice.


get under there and look at it were the holes are for lightening. thats werer it is prone to crack. then blip the starter and look at the other side.

CIMG0827.jpg
Click to expand...
okay i see thecracks on the picture. Ill get under there when i can have someone in the truck to blip.
 
nah, just do it yourself
take a look at it with a good flashlight
then turn the key just enough to get half a rotation o the engine
climb back under and look again, this way you are looking at a different side of the flexplate. Maybe mark it the first time so you know ur not looking at the same spot :) Check your bolts too, mine as well. Should be 3 of them, I think 15mm.
 
K85 Octane said:
nah, just do it yourself
take a look at it with a good flashlight
then turn the key just enough to get half a rotation o the engine
climb back under and look again, this way you are looking at a different side of the flexplate. Maybe mark it the first time so you know ur not looking at the same spot :) Check your bolts too, mine as well. Should be 3 of them, I think 15mm.
Click to expand...

I did go under there, and I moved it with my hand, It was tough but I did about half of it.

I didnt see any cracks. and I dont think I can get a ratchet in there
 
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