Differential fill plug

[pttsls5]

72 differential fill plug seems to be leaking. It takes a 5/8 open end wrench on plug but no room to swing wrench ( because of spare tire bucket and half shaft). Is there a tool out there that I can put on my ratchet ( socket/ crows foot or otherwise) to remove without taking spare tire bucket off. On replacement do I put teflon on threads? I've also heard that the original rear pumpkin's crack. Could the leak be coming from a crack? Where do I look? How do I tell ? Can the seal from the rear cover pumpkin to diff go bad after 36 years? Would probably put in 336 gears if I have to do this repair. Is this O.K. for a 454 with auto trans? Sorry for all the questions. Thanks.

 

[bill81vette]

drive the rear of the car up on ramps/jack-stands and crawl under it to see how to accomplish the task.if you have to remove the spare tire and the carrier so be it.I would clean the area with some brake clean and inspect the housing to find out if there is a leak/crack.the seals could very well have gone away!!

 

[Sean77]

cracking

The typical cracking is usually at the "ears" on the end cap where the spring mounts to. The tire tub doesn't take long at all to remove.

 

[Hib Halverson]

Yes! You can use 5/8ths crows foot wrench on a 3/8ths-drive extension to remove the fill plug.

63-79 axle housings are susceptible to cracking but the problem area is usually not around the fill plug. If you believe there is a crack in the fill plug opening, you need to inspect that area to confirm. It is usually unnecessary to seal the fill plug with Teflon tape as it's a tapered thread, but if the fill plug opening is not cracked but does leak, Teflon tape may help.

After 36 years, it is possible that the gasket between the two housing parts is faulty.

 

[White75]

Don't know if it's any different from a 75 and 78 but I took a 12 point socket on a foot long extension and my ratchet and didn't have to remove anything.

 

[Hib Halverson]

"White 75" is thinking when I'm not!

He's right, you can always put a 12-pt socket on a square head.

 

[mkapp7879]

Why not pick up a 5/8" 8 point socket?
Always seemed like the best tool for the job to me.
Sears has it.

 

[GTR1999]

Why not pick up a 5/8" 8 point socket?
Always seemed like the best tool for the job to me.
Sears has it.

That is all I use, 8 PT 5/8 sears socket. Jack up the RH side, pull the tire, reach in with an ext and you should get it. Those are 3/4 NPT threads in a 72 so use some PErmatex high temp thread sealant on it.

Leaks from a diff come from
1- pinion seal
2- pinion yoke splines
3-side seals
4-cracked rear cover threaded holes from using too long a spring bolt
5- over fill- blow out the vent
6-rarely the cover gasket
Cracked housing, this is usually a major event from abuse where the posi explodes, oil leaks would be the least of the concerns at that point.

 

[pttsls5]

Thanks eveyone!!

I spent the last few days and cleaned all fluid from the differential and inspected it carefully. I didn't see any major cracks but the diff was painted 16 years ago so it may hide a hairline crack. I found that it is definately coming from the fill plug area as this is the only area that was oily today. I tried the 8 point and 12 point sockets but they just slipped over the edges ( rounded from age I guess). So now I have a set of crows foot wrenches and will pull plug tomorrow. I did add the GM special posi fluid 2 years ago when I had the spare tire bucket off, maybe I over filled? Will use the High temp thread sealant after checking for cracked threads on the diff. Will let you know what I find and thanks again to everyone.