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Discussion Starter #1
I know this is a bronco site but im not having much luck on the fte forum so I tought I might give it a shot here

So I have a 1990 f150 4x4 with the 4.9 and the M5R2. I have this noise that happens when going down the highway like a grinding/rattling noise around 45mph and up then when you pull it into neutral it becomes a loud grrrrr noise (like the sound a wheel makes while you spin it on a soild shaft with no bearing and then it wobbles) and it only happens when decelerating clutch in/out makes no difference . I checked the trans fluid and it looked good but while under it I noticed the yoke on the rear was loose like it had some wobble in it so I thought the noise was coming from there. I tore into the rear and fixed all that (bad pinion bearing) and now the noise continues.


I know what a throw out bearing going out is like and this sounds nothing like it. does this sound like a transmission issue or a transfer case issue

the transmission and transfer case both shift smooth and don't grind going into and out of gears


this was what I did yesterday

and this is what I did today

So tonight I raised up the rear put it in gear and let the tires spin so it made the noise and poked around under the truck and noticed the noise seems to be a louder from the tcase but I can defiantly hear it coming from the transmission too still not 100% on witch is causing it.


so pulled the rear drive shaft and noticed that one of the caps on the u joint was able to spin inside the yoke that slides into the trans so I pulled it apart and the head of the u joint can be pushed in and out with little resistance (1 finger) but there doesn't seem to be any wobble to it. so I went back to the truck and put it in 5th and no noise with no rear drive shaft so then I stick it in 4wd hi with the hubs unlocked and the same noise comes back


since the yoke is most likely trashed im going to try throwing a couple tacks on the u joint and yoke tomorrow and see if the noise continues u joints were good other then that seems the yoke is some how wore over sized on that one ear.

I also dropped the fluid in the trans and it looked good I changed it less then 500 miles ago this is mostly a play truck so it was about a year ago and there was some metal flakes on the magnetic plug

any more ideas to narrow down the problem will be greatly appreciated.
 

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Discussion Starter #2
ok so tonight I pulled the tcase and then got in the truck and stuck it in 5th and ran it up to about 3k rpms and it made no noise.

so I cracked open the tcase and the oil pump retainer was still intact like it was suppose to be. so I kept digging, the shift forks still look good so I pulled out the main shaft and the only thing I can see that could be making the noise is there seems to be some play in the needle bearing and brass bushing at the bottom of the planetary gears when I put the main shaft in I can rock it back and forth a little it looks like it should be a pretty snug fit to me.

I snapped some picts so you guys could give me some advice.









idk if you can see very well but there was gold flakes in the fluid that was still in it.



pict of the bottom of the shaft that goes in there

it doesn't appear to be scored up much in there but I guess that if the oil pump is still working it could prevent it from getting to bad for a while.

so does this look like it could be the culprit? the noise did sound more like a bearing noise then a gear grinding noise.

my theory is that since the yoke was loose on the rear it was vibrating and caused this to happen. Does that make since to anyone elts?
 

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Discussion Starter #3
is it possible to have the trans not make the noise because it doesn't have a load of any kind on it?

I have another 1356 t case that came with the truck as a spare but its not set up for a slip yoke so I guess I can try putting that one on and hook up the front drive shaft and see if the noise continues.

oh and thanks for the super glue idea I never heard of that im gunna give it a try first if I ever get this noise figured out
 

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Discussion Starter #4
well I threw my spare t case on and the noise was back so I bit the bullet and pulled the trans tonight but that thing whooped my ass pretty good coming out so I didn't get around to pulling off the top as much as I wanted to. so Ill see what I find tomorrow.
 

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Discussion Starter #5
well I pulled the trans and swaped in another one and changed the slave because it was in sad shape. but the noise continues so im giving up on it. im going to drive it until something breaks or becomes more obvious im getting ready to move to Alaska and the truck is going to be shipped. very frustrating
 
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