Well, I got my new radiator in, fan shroud in, new mirrors on, coolant flushed and replaced, carb tuned and drag link replaced today. No more overheating at all, I've never seen this truck run so cool, I'm excited. I took it for a long ride, about 1.5 hours and everything was smooth as butter! I was driving back home and all of a sudden I started hearing a bang bang bang bang from the rear end as I'm driving. It was decently quiet when under load, but coming to a stop with the clutch in its quite loud. I'm not even sure where to start with this, it seems to be in the drive shaft or rear end...not u joints. There is play in the driveshaft when truck is in neutral and back wheels are on the ground. Does anyone have any ideas what just happened? I don't have a shop manual yet, its on its way from Amazon...is the play in the driveshaft normal? Also, (excuse my ignorance, but i just dont know), are there parts inside the driveshaft itself that can fail and lead to a noise like this? Thanks!

 

Block the rear wheels, set the e-brake, and drop the driveshaft. You can check the u-joints much more accurately off the truck, although it sounds like your problem will be obvious. If the joints are OK, see how much play there is in the diff by rotating the yoke. If the yoke moves in and out visibly, or you can wobble it, you've lost preload in the pinion. Check back after investigating!

PS, have you checked diff oil level?

 

I can be up there in a couple of hours with my trailer to take the truck off your hands , Eric.
As Ross mentioned. Sounds like driveshaft/rear end noise. The u-joint wear will be evident without dropping the shaft. Was there any squeaking noise before the clunking (indicating dry ujoint(s)?
Please do not go under the truck if jacked up without it being properly supported on jack stands. We want to keep new members around a while.
After checking ujoints and differential level, and play in the driveshaft, you might have to remove the cover to check condition of the gears. It's also possible a rear axle bearing is gone, so check for play and noise before removing the cover.
If differential is bad and it's a Spicer I might be able to help you out with another from a 54.

 

I will let you know what I find today...truck is not for sale, so no need for that. I'm going to go out and take a look in the daylight.

 

If you say the noise is coming from the rear of the truck, it probably is. But, anytime you change something and a new problem surfaces, back track. Make sure the noise is not something related to the fan shroud installation. A soft or loose motor mount that allows the engine to shift could allow the fan to contact the shroud.
Drive shafts normally have radial movement which is the backlash in the differential. Pull up and down on the shaft near each U joint and you should get no movement. Before you do anything, try to determine if the noise is related to the speed of the truck or the speed of the engine.

 

Well, I took the driveshaft off, u joints were good. Took tires off and diff cover. Found this (picture below) stuck in the teeth!!

 

Can't see pic

 

Ouch, do you know where that came from?
Is there any damage to the teeth?

 

Appears to be the head of a grade 8 bolt. If you're lucky you didn't break anything worse. Time to investigate where it came from, and why.

 

What size is the bolt head? There aren't too many small bolts in the diff, I'm thinking it must be a bolt for the ring gear.

 

Im looking through LMC to try to identify the rear end in this...its a 52 f1 with 239 v8. If you look close, it appears to have "44" on bottom right, does this help with identification? I need to figure out what it has in it, not too sure its stock...

The bolt head size is 11/16

 

Havent found where it came from yet...all bolts are present in ring gear

 

I see pic now, ouch... No Bueno

 

Yep, it's the stock Dana 44. Should be a 3.92 ratio.

Most D44's used a pin to retain the pinion cross-shaft (between the spider gears), but some used a bolt. But not that big of a bolt. Any pieces laying in the bottom?

The ring gear bolts show to be 3/8" which would normally have a 9/16 head, but maybe larger head for this application. Can you tell what the diameter was? There are only the 10 ring gear bolts and the big bolts on the bearing caps in there. Spare parts???

 

Awesome, good to know. There is still a "clunking" coming from rear differential with drive shaft off and bolt removed...i don't see where the bolt came from...very interesting. The only place I can see play in the differential is outlined in the picture below, which looks like 4211, 4215, and 4230 on the diagram above. I am sorry, but I dont know much about differentials, but I am learning at the moment. What would be the plan of attack on fixing this guy? Everything else actually look really good, doesn't appear to have damaged any of the teeth or anything else.