74 C10 rear end interchange

[oldearl]

Hello All, it's been a while since I logged in here. Lots of great information when I use the search. All of your expertise is very much appreciated.
I am looking to find out what other square body year rear ends fit a 1974 C10 long bed ? Is it 73 to 79 without changing anything ?
It seems the poor old girl is asking for more money to be put into her.
The issue is when I put the auto transmission in gear she sorta locks up until I give her more throttle, it makes a popping noise then moves very slowly . I did jack up the rear so that the wheels were off the ground. I can spin both wheels with the trans in park.
Thanks in advance
Old Earl

 

[Tonimus]

If you're going like for like axle and doing the whole axle, I believe all the square body rear ends are set up the same.

 

[75gmck25]

All of the 1/2 ton square-body rear axles should bolt right in, but the driveshaft yoke may be different. Not a problem if you have a local place that can change it if necessary.

 

[oldearl]

Thanks Tonimus and 75gmck25 for at least answering my questions.
Until the weather clears and the ground dries out all I can do is research and ask about the rear end. I will have to see what is broken inside of the rear when I can pull the cover off.

 

[Ricko1966]

I didn't answer because I do not know enough about interchange on the rearends,to tell someone what is a straight swap. I don't believe the above information is complete enough,but do not know for sure. I do know for sure some squares were 10 bolt some were 12 bolt and some were 14 bolt,so even if they bolt in the same you probably need a different length driveshaft. You have to take into account,how many lugs the different rearends have, as well as what brakes and backing plates,the backing plates will determine what ebrake cables you can use,and the brake package may require other swaps there's a lot more than you might think,to swapping rearends. I can take apart a rearend replace all the bearings,etc and put it back together,just as fast or faster than pulling the rearend bolting another one in hooking up e brake and getting the brakes to work. So unless one is really ,really blown up I repair them,even if I have to replace a diff,gears etc.

 

[Fat 454]

Hi - all the above is great advice, however it is very hard to provide accurate advice "remotely". From what you describe, it may be that you have problems with the transmission and / or torque converter mounting?? You should not be able to spin the wheels with the transmission in park.
I would suggest the following to start -
Axle / Diff - first things to check are the wheel stud pattern and diff cover bolt pattern. If you have a 74 C10 you "should" have a 5 stud wheel, and 12 bolt heads on the diff cover. Also the drive shaft yoke will probably be the smaller size ( 3/8" v 1/2" - I can't remember off hand ).
If you have an 8 lug wheel and 14 bolts on your diff cover, it will be a heavy duty C20 / 30 axle
I would jack up the truck on axle stands and whip off the diff cover to assess the state of the internals. If anything is broken it should be obvious. You can then decide to repair or swap.
Transmission - If the diff appeares OK, I would ( mark both prop shaft and diff yoke to line back up before taking apart ) un-bolt the end of the drive shaft from both the transmission and the diff., rotate the wheels to check if anything is binding, and then start the truck and engage drive. If there are still odd sounds, it is likely that you have an issue with either the transmission internals and / or the torque converter where it bolts on to the flex plate of the engine.
If that is the case, you will need to drop the transmission and inspect. There are transmission experts on here that can advise you further on that, as it is a huge area on its own.
Good luck - post pics...

 

[idahovette]

If you pull the drive shaft and start the engine and put it in drive, you run the risk of pumping all your ATF out on your floor, through the tail shaft housing.