7.5 differential fill plug


Elijah1989

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I’m at a loss here. Differential Gasket was leaking so I put on a new gasket. Went to undo the fill plug and nothing. I put some PB blaster on it and let it soak. Tapped on it a few times and soaked it again. My impact wrench wouldn’t ever budge it.

I would love to be able to drive it again but wouldn’t dare do it with no oil in it. What are my options here? I’m in the verge of stripping the 3/8 plug on it. Any ideas or info would be amazing and appreciated.

Thanks.
 


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sgtsandman

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You could try heating it with a torch. If you don't have an acetylene torch, a propane torch often works in a pinch with a couple of heating a cooling cycles. I had to use that method to break a wheel from the hub recently.
 

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I would try a hammer impact driver. They come in 3/8" and 1/2" drive same as a ratchet. Heat can help.
First pic in the link;
 

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Slather it in antiseize before heating it. That will draw it into the threads. In addition to the rust there is thread sealer on the plug that acts as thread locker.
 

scotts90ranger

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simply remove the speed sensor on top of the axle and add fluid, I think the 7.5" holds like 2.5 quarts?
 

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simply remove the speed sensor on top of the axle and add fluid, I think the 7.5" holds like 2.5 quarts?
If it is there. Most of the 7.5s I've owned from that era did not.
 

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Try all the above ideas first. Then, if necessary, use a hammer and punch. Should be videos on YouTube. But, basically, you hold the punch at an angle on the side of the plug,almost tangential to the plug. Tap with the hammer to make the plug rotate.

Absolute last resort would be to drill it out and use an "easy out". If you have to do that, put some grease on the drill bit before it breaks through, to maybe catch the chips. I would still do a thorough cleaning inside after that.
 

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I hope it's been removed before, when 7.5's first came out we had trouble getting the fill plugs out because the factory used water as a coolant when they tapped the hole. Everyone would use a 3/8 extension to remove the plugs and we twisted off a few before I broke down and bought a 3/8 square socket with no hole and ball in it for 1/2" drive so I could use a 1/2" breaker bar on it. I'd try heating around the plug first and avoid drilling it out unless nothing else worked. If you drill it I'd remove the rear cover and thoroughly clean it out, one metal chip and the bearings are toast.
 

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I've ran across a couple that were stubborn... heat... 1/2 to 3/8 impact adapter... 1/2 ratchet and a pipe is necessary.

If all else fails... pull an axle... jack that side of the vehicle as high as you can get it... add recommended amount of lube through the axle tube.
 

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I've ran across a couple that were stubborn... heat... 1/2 to 3/8 impact adapter... 1/2 ratchet and a pipe is necessary.

If all else fails... pull an axle... jack that side of the vehicle as high as you can get it... add recommended amount of lube through the axle tube.
How you gonna put the C-clip back in?
 

Uncle Gump

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lol... I guess I forgot about that part. I better have more coffee.

Maybe someone makes a cover with a fill plug on it. I have seen them on an 8.8 cover I believe. If not... put one in the existing cover.
 
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Dirtman

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The old dodge 9.25" rears had a simple 3/4" hole in the cover with a rubber plug. Simple and effectve to add on if it's driled at the proper level.
 

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86merc5.0

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I've seen 7.5 diff covers with fill & drain plugs. This fix would only hurt your wallet ( not sure on prices ), but would make future maint much easier. The new rear diff cover could also be counted as a modification.
 

scotts90ranger

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If it is there. Most of the 7.5s I've owned from that era did not.
In '87 or '88 they went to RABS, my base/fleet model '90 had a sensor, pretty sure all second gens do at least.
 

19Walt93

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I wouldn't give up so easy, heat up around the plug and put either never seize or crayon wax on the exposed threads and let it cool, then try again. If it still won't come out heat around the plug again and try with the case hot- just hot, not glowing red. It's worth getting a 1/2 drive socket with a 3/8 square instead of just using a 3/8 extension so you can put some torque on it.
 


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