69 f-100 t-18 tranny. 3 speed with granny gear (4 speed) very quiet transmission except after driving a couple of miles. I get this kinda rattling bearing noise from the front of the tranny. At first I thought It was the motor 300 I6 but that was not it. the tranny is not hard to shift either before or after this symptom. when It does make this noise I do not feel any vibrations coming from the tranny nor on the clutch pedal. I am wondering since this happen only after a warm up if the previous owner changed oil and replaced with wrong oil. The oil was topped off when I did get the truck and looked clean. the u-joints, carrier bearing and yoke are all tight. the differential is also topped off and clean it appears to be the same oil as in the tranny. It is getting annoying and that it scares me if something might happen.
Update: now that I have driven it on a long distance trip it is quiet except for when slowing down from 55 to 45 to 35 ..... but does not get noisy when traveling just when I have to slow way down. it is strange thought maybe it would make noise going down steep hills while coasting it does not. Shifting does seem to be more difficult now going from 3rd to second when I turn off the main highway onto a side street like the synchronize is bad. Another f-100 enthusiast said it could be just the pilot bearing. I have no idea
Any thoughts out there would be appreciated. thanks
update: I found out that when the previous owner changed fluid , he put 80-90 gear oil. he did not realize that would be to thick of oil. I have drained and refilled with 50wt and the noise has stopped and shifts almost effortlessly . so hopefully that it is fixed!!
"Success is the ability to go from one failure to another with no loss of enthusiasm" Sir Winston Churchill.
well still no avail. . the only thing it did change is making it easier to shift at higher speeds. still the growling sounds are there. I guess the next thing to do is look at the clutch. I have been told that the wrong clutch could have been installed.
I am at a loss.
"Success is the ability to go from one failure to another with no loss of enthusiasm" Sir Winston Churchill.
It does not matter what gear it is in. It is after driving for a short distance . I can drive to a destination 20 miles away as soon as I go down the street about 5 minutes after warm up and start shifting gears 2nd to 3rd everything is fine then if I have to slow down the noise starts or if I speed up. I can shift gears from 3rd to 4th and same noise I can down shift same noise. If I use the clutch same problem. if I get up to 50 mph it is really loud. if I stop and idle it stops. I can start moving again everything is ok for about 15-20 feet then the noise starts.if I idle and not use the clutch no noise If i use the clutch at idle no noise. at first I thought it might have been the throwout bearing on the clutch. I have eliminated that, then some said it could be a bad pilot bushing.if I am at idle and bring the rpm's up to 1500 to 2000 no noise with or without the clutch. I also have checked the differential fluid all is clean and full, checked the axle seals all clean, no leaks. while truck was in the air I rolled the axles no roughness actually pretty smooth. disconnected drive shaft turning the pinon all ok, nice and smooth. checked the drive shaft all in good condition including u-joints. carrier bearing also good. so I have no idea what to do now except to take the tranny out and inspect the clutch and pilot bushing. The funny thing is if I start driving i after it sits for about an hr or 2 I do not have this problem until I get ready to shift or the truck is warmed up.
something is taking the heat and causing the problem. like something expanding and not getting any lubrication or......
I am about to the point of having to tear down this tranny , however I cannot due to time constraints (work) .I was thinking about just swapping out and put a c-4 or c-6 in it , but I do not know how hard that would be. for a temporary fix until restoration. I am trying to keep the truck original as possible.
"Success is the ability to go from one failure to another with no loss of enthusiasm" Sir Winston Churchill.
If the noise is there only when the clutch is depressed you're looking at a t.o. bearing. Noise in neutral, clutch out (louder in the lower gears and when letting off the gas): front bearing. Noise continously louder in the taller gears: rear bearing. Noise all the time in every gear, speed variant: could be mainshaft, countershaft bearings.
sounds like the main shaft,counter shaft bearings. Bummer, oh well another project for the truck. wonder how long I can keep driving it this way... hmmmm.....
"Success is the ability to go from one failure to another with no loss of enthusiasm" Sir Winston Churchill.
The thing is you don't know how long it's been making the noise. You could just have toasted front and rear bearings. You don't know if the previous owner ran it low on oil. Just no way to tell without tearing it apart. The symptoms I listed are just basic symptoms.
Your description of noise under decel does not fit well with a transmission issue. A trans problem will usually make more noise under power and almost always have atleast some difference in sound between 1,2,3,R and 4th gear (direct).
That I have done. I thought that may have been the problem, but everything is smooth back there.
I did take the rear end apart and did a through inspection of bearings, gears etc.... all are ok . no problems. took the top off the tranny all looked ok from what I could see after draining the oil I just put in. . took off the drive shaft played with the output on the tranny hardly any play at all, just what would be normal wear. took the drive line out gave it a through inspection, looked at the carrier bearing and gave it an inspection all looked good. So now it leaves either the tranny bearings or clutch.
"Success is the ability to go from one failure to another with no loss of enthusiasm" Sir Winston Churchill.
Not going to find much pulling the cover off the trans or trying to wiggle the output shaft.
Maybe I'm just not following what you mean by "makes noise when you slow down". Can you describe exactly what you're doing when it makes noise?
Bad pilot bearing symptoms are usually pretty easy to diagnose because it's erratic. It doesn't Always do the exact same thing, but there will be "whirring" noise of sorts that only happens during shifting, but not all the time. The other symptom is clutch feel will be inconsistent. Sometimes you will get a little chatter, other times it will be nice and smooth. Bad pilot bearing can also cause bearing noise in the transmission that's sometimes there and sometimes not going down the road. It will sound like a light churning noise as it's the sound of the input and cluster gears center distance changing rythmically from the clutch disc being clamped off center by the pressure plate.
slowing down . letting your foot slowly off the accelerator., like keeping constant light pressure until I stop. I have not heard any noises If I suddenly let my foot of the accelerator. coasting at lower speeds like coming up to a stop light waiting for it to change it continues to make the sound. and it is a constant sound, not intermittent. I have no trouble duplicating the sound. the pattern on ring and pinion is very nice. just even wear almost like they were new.
"Success is the ability to go from one failure to another with no loss of enthusiasm" Sir Winston Churchill.
Helical gear toothforms are symetrical. Hypoid toothforms are the complete opossite, a lot like a buttress thread turned into a gear.
That's why when you get a whine only under decel the differential is the suspect. Everything else in the vehicle will make the same noise under positive or negative acceleration.
It is getting annoying and that it scares me if something might happen. 
. the only thing it did change is making it easier to shift at higher speeds. still the growling sounds are there. I guess the next thing to do is look at the clutch. I have been told that the wrong clutch could have been installed. 
