Rear Differential Cover - best way to remove?

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  #1  
Old 10-22-04, 07:37 PM
splashchris
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Rear Differential Cover - best way to remove?

All,
Tomorrow, I will attempt to remove the differential cover on my '95 Chevy G20 van in order to change the fluid. I've purchased a new gasket, and enough gear oil for my particular differential (10-bolt, 8.5").

The problem I anticipate is figuring out how to get the cover off once the bolts have been removed. Yes, this should be a very straight forward scenario; just remove all 10 bolts, pry the bottom loose to release the fluid, and off it comes.

Sounds easy, but in my case the emergency brake cable AND the solid brake line has been run directly infront of the differential cover (about a third of the way down from the top). Both lines appear to obstruct my ability to move the cover far enough away from the ring/pinion gears in order to remove it from the vehicle.

Any advice on how I should approach this potential problem before I get under the van? I'm not so worried about the emergency brake cable, as it has some (very little) flexibility. My major concern is the solid brake line running between the two rear wheels. I know I shouldn't be messing with it and moving it around.

Thanks in advance for any and all suggestions.

Chris
 
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  #2  
Old 10-22-04, 07:43 PM
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The cable and line(s) should both have brackets on them holding them to the diff. cover. Take the bolts out and push them up over the top of the diff. They'll both move easily enough, barring an extremely rotten line.
 
  #3  
Old 10-22-04, 07:55 PM
splashchris
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there are brackets

Yes, there are brackets (one for each) attaching the lines to the differential cover. I noticed that when I took a preliminary look earlier. Had no idea I could move them without damage.

Thanks for your suggestion, and for such a quick response! I will do as you advised with the hold-down brackets.

Chris
 
  #4  
Old 10-22-04, 08:29 PM
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Follow the brake lines along the differential housing. You should find little strips of metal welded to the axle tubes. They are bent over the brake lines to hold them in place. Pry the end of them up just enough to slip the line out from under them. That will give you more flexability to move the lines out of the way. When done put the lines back and gently press the tabs back to hold the lines in place. If you should break one off just get a large nylon ty-wrap and go around the axle tube to hold the line in place.
 
  #5  
Old 10-22-04, 08:40 PM
splashchris
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Thanks again, Car Nut. I'll check for those welded tabs. Anything to give me more room with the lines is a good deal!

I've been spoiled with new cars the past few years. Since getting laid off last year do to a corporate buy-out I have learned the lesson of downsizing - sold the new cars and bought another Chevy. Oh, to own a car that I can repair again

Chris
 
  #6  
Old 10-23-04, 04:56 AM
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I'm surprised you were even able to buy a gasket for that. They just don't use gaskets on them any more. A bead of silicone is the standard way to seal those now. Just let it dry for an hour or so before filling it.
 
  #7  
Old 10-24-04, 02:25 PM
splashchris
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All - Thank you for the suggestions and responses regarding the cover removal, etc. I was able to get past the lines using car nut and pmg's input. I really appreciate it and hope to return the favor.

Desi501 - While the general procedure may be to use silcone versus a gasket, something isn't clicking in my head.

For example, how cost effective or efficient would it be for a vehicle to be sitting on a lift in someone's shop for a few hours - waiting for the silicone to dry (cure) before filling the differential with gear oil? Unless, of course, that's how shops increase their profit margins these days, by charging the customer the extra hour(s). Normally, this would be a one hour job.

With the gasket, all you have to do is apply a bit of spray-tack, pop the cover on, torque the bolts, fill it up, and drive off.

Chris
 
  #8  
Old 10-24-04, 03:53 PM
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Chris -
Glad to hear the job is accomplished. To answer your "curing" question, I've personally never found it necessary because there is no fluid pressure in the diff. Same as with a gasket - silicone it, pop it on, fill it up and out she goes. As long as both surfaces are clean and dry - no problems.
 
  #9  
Old 10-24-04, 05:00 PM
splashchris
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Thanks, pmg. I get it now

What prompted this whole discussion was the slight clunking sound I was hearing from the rear differential. I just changed the u-joints earlier in the week, so I know they're good.

My G20 is a 6,600 lb. Mark III conversion van with towing package, etc. It's in excellent shape, inside and out, but has 116,000 miles on it. There's no telling what maintenance the previous owners did. If it tells you anything, "59K" was painted in white on the differential cover. When I drained out the old fluid it was quite dirty and smelled old, but I found no debris in the oil and the gears looked great - smooth surfaces, no burning, etc.

I wanted to be sure I would have no issues in the future. I filled the differential with a mix of 60% Lucas 80/90 gear oil and 40% Lucas Heavy Duty Oil Stabilizer. This was done at the advice of the powertrain shop that did the driveshaft u-joints.

Chris
 
  #10  
Old 10-24-04, 07:39 PM
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I forgot to remind you to check to be sure the vent is open any time you are working on a differential.

I pulled the fill plug on a land rover last week and there was pressure in the differential. A good way to push fluid past the seals.

I found the vent plugged solid.
 
  #11  
Old 10-24-04, 08:54 PM
splashchris
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differential vent

Car Nut - Is there a way I can check to see if it's clear now, or am I too late? I'm going to assume that since it is a vent, it would be located near the top portion of the differential - to allow pressure to equalize without having the fluid squirting out. I'll poke around under the van tomorrow and take a look.

One other question:
I took several pictures of the gears while I had it apart, just in case I needed to refer back. Can't figure out how to post them here. Is there a way to determine from the pictures if it is a limited slip or an open rear end? The reason I'm asking is because the clunking sound (possibly clutch chatter?) I mentioned above seemed most prevalent when making low speed turns and sometimes when shifting into reverse.

I know I could jack up the rear end and spin the tires, but no jack is available at the moment to support the weight of the 6,600 lb. beast.

Chris
 

Last edited by splashchris; 10-24-04 at 09:42 PM.
  #12  
Old 10-25-04, 08:00 PM
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The vent on GM differentials will usually be on top of one axle tube. All it is is about a 1/4" or 5/16" tube that sticks up with a metal cap. If they are clogged it is usually from gunk caked around the metal cap. The metal cap should spin if you turn it. I don't remember if the tube is pressed or screwed into the axle housing. Clean it off and you will probably see a hex or some flats if it screws in. If so you can see if it will screw out for inspection. You can always spray some brake clean under the cap if you want. If it won't come out I am willing to bet it is clear if the cap spins.

Unless someone removed it GM limited slip diffs. have a tag on the fill plug to identify it. If you have pictures a limited slip will have clutch packs behind the side gears on the axle ends. They will have springs on both sides of the smaller (spyder) gears. The springs press out on the clutch packs. If you have limited slip see if one wheel will turn freely with the other wheel on the ground. If so it is worn out and must be rebuilt to work again. If it is worn out it won't hurt anything except it will not work.

If it does work and you want to keep it working I would drain and refill ASAP with GM fluid and their friction modifier additive. I have found the GM stuff to be better than anything else.

The sound you describe sounds like clutch chatter that the additive prevents.

The 59K on the cover leads me to believe either the fluid was changed at 59,000 miles or it had 59,000 miles when it came from a salvage yard.

Let me know what you find.
 
  #13  
Old 10-26-04, 05:40 AM
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Originally Posted by pmgheritage
Chris -
silicone it, pop it on, fill it up and out she goes. As long as both surfaces are clean and dry - no problems.

The parts store told me the same thing. But for $1.79, I know that next time I have to change the diff fluid that $1.79 gasket will pop right off, no scraping. I thought it was worth it.
 
  #14  
Old 10-26-04, 12:37 PM
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about silicone...

just for future reference...silicone is an aerobic type of sealer and therefore needs air to cure...specifically, it needs the water molecules in the air. so...when using silicone you can lightly mist it with water before assembling parts to speed up the cure time.

my .02 worth...
 
  #15  
Old 10-26-04, 09:08 PM
splashchris
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Personally, I've never liked any kind of sealant/sillicone gasket material. A buddy of mine used to build race engines and always said that if the motor is machined properly, and all bolts are torqued to specs, you should never have to put anything on a gasket to help seal it. Sure speeds the removal process The only exception is the front and rear manifold flanges (where the rubber gasket meets the heads. I always put a dab of high-temp sillicone there. Never had a leak anywhere - valve covers, oil pan, etc.

Could be an old wives tale, but it's worked for me.

Car Nut - Got your message, but was busy today. I'll check for the vent tube tomorrow morning and post back what I find.

Chris
 
  #16  
Old 10-27-04, 04:12 AM
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Well the times are changing alot of engines are put together using sealants instead of gaskets as are differentials.They call it assembly adhesive.Also try putting a head gasket on certain Chrysler engines without the adhesive it wont last if it gets out the door that is.
 
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