Th350 bad or rear end bad?

[travisr1988]

So I have an issue that I originally thought was the trans,  but my dad says it could be the rear end. There's a grinding noise like brakes lightly touching metal to metal coming from the trans, however, it could be rear end and the sound is just transfering through the trans. The trans will likely be rebuilt anyways, but I don't know what rebuild kit is the best quality or best bang for my buck.

Trans issues: does not shift into second at very light throttle like in parking lots (waits until I snap throttle at above 15-20mph to go into 2nd)...shifts hard sometimes, soft others...leaks like crazy sometimes, not at all others...vibrates and makes awful howling and grinding noises. The grinding like dragging brakes gets louder with speed until I mash on it (then I can't tell because the truck gets louder) and is there in all gears except park, reverse and neutral, is there at any speed and gear but goes away completely in neutral at any speed, no noise when not moving, none on reverse (then again reverse is never over 5mph).

[Captain Swampy]

I guess I would pull the brake drums off and have a look. Pull the rear cover off if the brakes are OK. If you need a trans, I would swap in a 700R4. The lock up converter and overdrive will do wonders for your MPG.

[Greybeard]

What he said^^^^

Start easy, move to the harder stuff as the easy things are ruled out. Don't overlook anything that moves. Don't overlook the wheel bearings.

[travisr1988]

I checked the diff fluid today, its old but not metal shavings, and not very low, but I topped it off. I also replaced the o ring on the trans dipstick hopefully that will stop it from leaking there. Haven't had a chance to drive it again though.if it were brakes then putting it in neutral while I'm motion wouldn't make a difference, which is why I rules out brakes. The noise goes away instantly when I put it in neutral.


Oh on a sidenote, I'm running 3.42:1 rear diff, 700r4 would lug the motor as several people have told me. heck my brothers truck has 3.73s and the 700r4 lugs his motor at 75mph; he gets max 14mpg at 70, but 17mpg at 85 in his '66. I also don't have funds available for a 700r4 swap, whereas rebuilding either the th350 or the 12 bolt is cheaper.

[Greybeard]

Yup, if the noise goes away when it's moving in neutral I might assume it's the tranny. However, as you mentioned it could also still be the rear end but since you gave it a look-see, probably not. The gears can grind when under load but be as quiet as a mouse when freewheeling. BTDT. Has the truck ever sat for an extended length of time, like years? 14 bolts are rather inexpensive and nearly bolt right in except for the shock mounts, u-bolts, and spring plates (might need adapter bushings for the brake line ends too if it's a metric unit). OH and new rims. 

[travisr1988]

It did sit for a couple years. There are 2 distinct noises and the local trans shop thinks I should focus on the rear end because of the noises. First noise is the light grinding like disc brakes dragging...this goes away in neutral. Second noise is heard when driven by a wall and is a loud howling noise. Last time I took it around the block it made a new noise that sounded like a freespinning bearing after I got on it and let off. How can I narrow down where the noises are from if they only occur under load?

[Greybeard]

Uhm...

I used to hold tight to the steering wheel on a deserted road, hang my head out the open door as low as possible and nail it. Might have to do it a few times to really tell whether it's coming from the front or rear.

I once had a noise that sounded like I was dragging a chain under my truck. It drove me nuts for many months! It was louder when under load than when coasting. It was just a noise no vibs or anything else. It turned out to be the spring pack clamp on the right rear spring was loose, and since it was a riveted connection and I was too lazy to fix it right a few feet of good duct tape and all was quiet.    Sometimes things can come from the damdedest places.

[travisr1988]

Hmm, well my floor is holy, there's a golf about 3x6 on the driver side of the trans hump the p.o. made to run the trans cable...at 18 he didn't know any better. I could uncover that and give it a try. I'd have my girl drive it while I located the sound but she can't turn or stop it without power steering or brakes.

[Captain Swampy]

Buy a pinion seal, a tube of black RTV, and a few quarts of 80w90.  Pull the cover, take out the spider pin and C clips. Pull the axle shafts so you can inspect the wheel bearings and the surface of the axle shafts. If the surface of the axle shaft where the bearing rides, you either need a different shaft or a special bearing that moves where it contacts the shaft. Take the drive shaft off. Rotate the yoke (pinion) and see how it feels. Does it have a rough feel? Any movement up,down, in, or out? You should be able to inspect it pretty well at this point. If anything feels funny, pull the carrier. Make sure you keep everything on the correct side for re-assembly (shims). You can take the yoke off and remove the pinion to inspect the  bearings now.