Hi all - the 4WD in my 78 F150 isn't functional. The front driveshaft spins when shifted into 4WD, but the second I lock the manual hubs in, all I get is a violent "THUNK THUNK THUNK" sound. Pretty sure the problem is in the front axle.

Do you think I'm on the right track? I've not yet pulled the cover off the front axle. I'm looking for advice on:
- steps to take to properly remove the cover and check for a problem
- what to look for
- how to replace what's wrong

A mechanic quoted me $1400.00 which is more than I paid for the truck so I want to DIY if possible.

Thanks for the help!

 

one or both of your hubs are broken

 

 

Thanks Jklnhyd! You sound pretty confident in your assessment. I've pulled a few hubs before, but those pics are very helpful. Much appreciated.

 

X2 on the sounds like a blown hub, axle u joint, snapped axle or a broken ring and pinion. Have some one stand beside the truck and confirm the thunk thunk is coming from either one hub or the other. Or it is coming from the pumpkin.

What were you doing when the sound or the problem first started? In 4H or 4L stuck in the mud, or one a big boulder, steering full left right and gouging on the go fast pedal? Are you sure you have not broken a front axle u joint, have you looked? You can see that easy enough.

Remember when you take the hub apart that the outer nut has NO edge pin and the inner HAS a edge pin that the middle washer must line up on after you torque the inner nut and back it off 90 degrees.

Get the hub apart, insp all that, then insp the short shaft for being broken or stripped. Then the axle the u joint. Then pull the caliper, caliper mount and the spindle and pull and insp the inner axle.

If all that is good, cross you fingers and pull the front differential cover.

Jklnhyd great walk thru on the pics.

 

See parts catalog pic.

D8TZ-1104-F .. Free Running Hub Assy. / Obsolete

All the parts of the hub assy were available by themselves.

Applications: 1978 F150 4WD/Bronco from production date 8/1977 / 1979 F150/4WD/Bronco before production date 11/1978.

Production date printed on the upper corner of the Certification Label, glued to the B pillar below the striker plate.

1979 F150 4WD/Bronco from production date 11/1978 used a Warn hub.

 

Green Sales has single pieces like part #1A055, 1A052 amd 1A028. When I had to do some repair to my F250 they had very good prices, versus the dealership.

Green Sales Company - Obsolete Ford parts, Lincoln, Mercury parts Green Sales Company, supplier of obsolete Ford parts and Lincoln / Mercury parts. Our Ford parts inventory represents all Ford and Lincoln / Mercury products from 1950 to the present.

 

Thanks all. I'm going to get it up on jack stands and try to figure out where the "clunk" is coming from. The info is appreciated, and I will update soon.

 

I would do a drive in a slow figure 8 and see if you can locate it that way 1st.

 

I can give that a shot. But it is a very violent noise. I've found that the hubs are very hard to unlock after this sort of "testing"

I didn't actually do anything to cause the failure (although that may have been fun ) I bought the truck, and knew that 4WD had an issue going into the purchase. I'm just trying to diagnose now...

From what Numbersdummy said, it seems like my truck is NOT a Dana hub. I assume this makes it harder to find replacement parts...

Both UJoints seem to function fine, but that's just me under the truck watching em spin. I've not yet driven it while engaged, to try to hear where the noise is coming from.

 

Make sure you drive is on dirt or grail, NOT PAVEMENT! I told you where I got my hub parts, Green sales had all I needed a while back.

Then jack stand it and tear into the hubs, short shafts u joints and axles and then pop the cover.

 

Thanks! I thought you meant that they had some of the parts. Good to know they have all of em. I will tear into it, and keep updated.

 

I said they "HAD ALL I NEEDED, a while back NOT "all you might and will need".... Figure out what is broke, then go parts hunting. There are a lot of part sources on here.

 

I would say it's easier to pull the cover and take a peek than pull the hubs, just imo. If you do pull the cover, make sure you can get the fill plug out first.

 

That's the plan right now. Also - I just found something curious: I wanted to check the fluid level in the transfer case... pulled the check plug... can't feel a thing! No signs of leaking. It may not have been filled for 20 years! The previous owner said he never put it in 4WD, so he didn't really have any idea.

As long as the transfer case isn't shot, do you guys think that might be a big part of my problem??

I have not really driven the truck; I'm just flushing all fluids, new plugs, wires, filters, etc. Just checking things as I go; hence discovering a dry transfer case.