Hello, I recently have noticed a "clunk" sound coming from the drivers side in the rear end. I assumed it was the axle bearing and seal so I replaced it. The bearing was really bad, but after the reinstall I still have the same noise. If I rotate the drivers side rear wheel you can hear an obvious clunk sound. I do not hear that noise when rotating the passenger side rear wheel. I did notice that the passenger side wheel bearing was also sounding like it was time to be replaced. I have a feeling that something inside the 3rd member is causing this noise and also caused the bearings to go bad. It is a 1964 f100 with a 9 inch (no inspection cover in the back) and 3.89 ratio gears.

Any ideas on what could be the issue?

Thanks in advance

 

A clunk inside the housing could be a few teeth off the ring gear, or the bolt holding the spider gear shaft if loose and letting the shaft move hitting on something.

 

 

No unfortunately you'll have to pull it.

You sure it's not a u joint clunk?

 

Yes, I pulled the drive shaft and hear the same exact noise. I did notice there is some wear on the piece that the driveshaft connects to from where the U-joint connects. I can take a picture and post it tomorrow if needed. It does seem to sound like gears not meshing together or something in the 3rd member but not positive. I got a quote to rebuild the 3rd member for $250 but I am unsure if that price includes the parts.

Thanks again!

 

Have you tried any salvage yards. That is just a 28 spline center, if it is the original housing. They were in Ford cars and trucks for decades. It's just a matter of pulling yours out and bolting another one in as long, as the pinion yoke is the same. Finding a 3.89 might be difficult though. Craigslist is a good place to check also. As far as rebuilding yours $250 would be a good price if it includes the parts. But I bet that price doesn't include any new gears if you need them. Used ones are usually in the $75-$200 range.

 

I believe I am just going to get the entire 3rd member rebuilt. I noticed on the yoke that there is a bit of wear around where the U-joint makes contact. I will attempt to upload a picture soon, is wear on the yoke something I should be concerned about?

 

Where on the yoke? Sounds like maybe the pinion bearings might have a problem

 

 

Nothing wrong with that, have seen dozens like it, machined thin at the factory.

 

Rebuilding it is better than getting stuck by the road side because of something like mine.

Might think about replacing the bearings as well

 

Oh that's rough! I finally got the parts in and the 3rd member is getting dropped off tomorrow afternoon. Hopefully everything goes smoothly. Thanks again everyone for all the help!

 

It sounds like I get to buy a lot more parts than I planned. I currently have a 3.89 ratio in the rear while running a 292 y block, 3 speed manual tranny, and 235/75r15 tires. I want to get some better gas mileage, should I go with a 3.25 or 3.50 rear end ratio? I'm worried the 292 won't have the torque for 3.0's or even 3.25's.

Any opinions?

 

 

Sometimes I like to round up to 10 mpg. It came with an open 3.89 9 inch from the factory