rear differential cover bolts

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When i went to change the rear diff gear oil, the fill plug was completely rusted up ( i always check the fill bolt first). There is no drain bolt on this rear end. The previous owner towed a boat and the rear has seen salt water, so there is rust on the bolts.

Are differential cover bolts hard to get out when rusted? Or do they come out okay since they are not open on the back side?

My option is to leave the rear end alone and just drive it until if fails without changing gear oil.

Or remove the rear cover and replace it with one that has a fill bolt on the cover.

I don't want to have a bolt shear off in the diff body trying to remove the cover.

I tow with this truck.

What would you do in this situation?
 
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Clean them off and see what you're dealing with. Typically ,the screws are a female torx head. You'll need a gasket. I'd spend the money on a cover with a drain plug.
 
Originally Posted By: spasm3
When i went to change the rear diff gear oil, the fill plug was completely rusted up ( i always check the fill bolt first). There is no drain bolt on this rear end. The previous owner towed a boat and the rear has seen salt water, so there is rust on the bolts.

Are differential cover bolts hard to get out when rusted? Or do they come out okay since they are not open on the back side?

My option is to leave the rear end alone and just drive it until if fails without changing gear oil.

Or remove the rear cover and replace it with one that has a fill bolt on the cover.

I don't want to have a bolt shear off in the diff body trying to remove the cover.

I tow with this truck.

What would you do in this situation?


This is very common where I am, and I'm no where near the water. Road salt does the same thing.

What type of fastner is it? Square? Torx? Hex? Make sure you use the right tool.

Take a stiff steel brush, and clean it up.

Get some PB blaster, WD-40 (yes it helps), and Liquid wrench or go to Family Dollar/Ask the old lady for Acetone nail polish remover. Mix(don't need much, maybe 2 oz of each) it up 50/50 with some used or cheap ATF, spray down the plug. I use a dollar tree spray bottle, it is all deformed but it works for years. Maybe pick two products. Let it sit overnight.

Get a Yellow mapp torch, heat the iron around the plug. Take a candle and melt it into the threads.

Try working the bolt out. Impacting, banging on the breaker bar is better than brute force sometimes. A weak impact helps too. You don't want to destroy the fastener.
 
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The plug is high up on the front of the axle, its a square type, there is not enough left to get a grip and its rusted solid. Its not coming out.

They way it looks i'm not even considering trying to get the fill bolt out. Its the diff cover bolts i'm worried about. There is no drain plug so the only way to dump the gear oil is to remove the cover. I'm worried about bolts shearing off in the body of the diff. I recently had transmission pan bolts shear off.
 
Pictures would help. Is the fill plug the recessed 3/8" square style or is it an actual bolt head?

I would think you could siphon some out through the fill hole, but you certainly don't want to proceed with the cover until the fill plug issue is resolved. Let the cover bolts soak for some time, but they should come out issue free.

If all else fails, get a new cover and have one of these installed. https://www.jegs.com/i/Currie/272/95070/10002/-1
Have a second one installed as a drain plug and get some easy Toyota style diff drain and fills.
 
Clean them good with a wire wheel/brush and then soak them with PB blaster a couple days ahead of when you want to remove them. I have done a lot of them and never had a screw break. The importance of cleaning them is so you dont round the head out. I always clean them once they are out and then put some anti sieze on the threads for next time. A 1/4" impact driver should get them out.
 
Originally Posted By: spasm3
The plug is high up on the front of the axle, its a square type, there is not enough left to get a grip and its rusted solid. Its not coming out.

They way it looks i'm not even considering trying to get the fill bolt out. Its the diff cover bolts i'm worried about. There is no drain plug so the only way to dump the gear oil is to remove the cover. I'm worried about bolts shearing off in the body of the diff. I recently had transmission pan bolts shear off.

Diff bolts should be encircled with RTV, and the chances of breaking off are slim. I know on a Ford 8.8 it is a pretty heavy duty bolt, because it provides some support to the case.

If they do break off they should be easy to take out, you will have plenty of access to heat and drill out.

A welding place can put a nut on the plug easily, that can be an option too. Once it is welded it will break any rust bonds. Maybe $25-30 to do something like this. I have a guy that I hand a $20 for this work. Takes him 3 minutes.

An easy out may be an option too. If it is 3/8" square drive you can probably get a big one in there, less chance of breaking off.

If you have to leave the plug in place, make sure you can find a rear end cover with the fill plug that can fill to proper level. They are quite pricey too.
 
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Buy the cover … you will love it.

The G2 normally has a “tattle tell” port (in addition to drain and fill plugs) …
There since the capacity goes up a bit … you can still get the oil level to the bottom of axle tubes …
 
I had this problem on the GMC in my sig-bought a cheap steel cover, drilled it, had my welder weld a bung in it, and painted it with Rustoleum primer & black spray paint. It's been on & fine for almost a year. The key is getting the fill plug level correct, needs to be right below the bottom of the axle tubes.
 
Ok here are some pics. I'm not going to mess with the fill bolt, i'm just not.

I'd rather add a new cover as suggested above that has a fill bolt.



How much chance of these bolts shearing?

 
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Originally Posted By: bullwinkle
I had this problem on the GMC in my sig-bought a cheap steel cover, drilled it, had my welder weld a bung in it, and painted it with Rustoleum primer & black spray paint. It's been on & fine for almost a year. The key is getting the fill plug level correct, needs to be right below the bottom of the axle tubes.


Yes … If you go homemade … be careful how you read this … target is this picture:




See ports on G2
 
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I didn't have any problem with the diff cover bolts on my F-350 after 10 winters of road salt here in MN. Soak them with PB Blaster or something similar, and use a good 6 point socket.
 
Hard to give you a probability of shearing. Best for someone with GM rear end experience in the salt belt to chime in. Transmission pan bolts are small diameter.
For starters I would take wirebrush and spray the bolts down.

Since it is gasketed you can try to tighten 1/8" turn to break things. Then loosen a bit more. Once it breaks a bit and leaves a gap, spray each bolt with penetrant.

You can also heat the diff case where the bolts are.

If you don't force things with a long breaker bar(take it slow) you should be ok.
 
Originally Posted By: KD0AXS
I didn't have any problem with the diff cover bolts on my F-350 after 10 winters of road salt here in MN. Soak them with PB Blaster or something similar, and use a good 6 point socket.

Not surprising, because RTV always makes itself into the threads.
 
Thanks 4WD i like the look of that cover , has drain as well as fill ports!

The fill port on that cover though looks higher that the illustration on oil level.


There is a small set screw, perhaps thats a plug for oil level?

81GSzsekVnL._SL1500_.jpg
 
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The diff cover bolts usually come right out even when rusted, use a small cordless impact and rattle them out or tap the wrench with a small dead blow, impact loosens them, turning torque has a greater chance of breaking them.
I would not mess with the OE fill plug. It will come out with persuasion but your asking for a PITA that you don't need.

BTW I like that G2 cover, I never used one but it appears well done.
 
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Yes … that’s the little “tattle tell port” … with the truck level just fill with gear oil until that weeps a bit … done …

With that vertical fill cap … I can squeeze oil in from the bottle … check level … and used a clear straw to pull a bit of oil out …
(Delvac 1 was clean as new 2-1/2 years later)
With a machined on machined face … they seal very well … you will need to figure on longer bolts …
Take the cover to the parts house with one of your old bolts (with pattern)

On my small truck (G80 locker) it added one quart to fill …
 
Since it's been going for years a few more weeks or months won't hurt. I'd go slow and steady:
- Clean up the area with a wire brush/wheel
- Tap with a ball peen hammer
- Heat it up a little with a hand torch
- Tap some more
- Soak with Kroil (#1 penetration oil IMO)
- Repeat 1-2 times

Do this every weekend for a few weeks

In a month or so give it a go. I have found for bad bolts and nuts like this if you actually start with tightening a little then back off it works better. Tapping is better than brute force. Go back and forth between tightening and loosening. clean out/around the area with brush and Kroil as you go.

You could also buy one of these new covers. But buy it from a place with a good return policy and do not open i. If the above works just return it. If not, your prepared and not in a desperate place....
 
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