Read Diff leaking?

[willfxp]

I noticed that there is a ring around my rear diff. The center of the diff cover was its normal dirty color, but around near the edges looks like it was wet with some dirt splattered on it. I usually notice this around the oil pan screw. Is there a leak? Or just normal and I've never looked at it before? I just came back from some snow, if that makes any difference. I have about 75k miles on it. I've never had the fluids changed yet when I bought it at 60k.

 

Thanks!

[k1500chevy97]

I say go ahead and change the fluid in the rear and replace the gasket while you are at it . You bought it used so you really dont know if the previous owner has changed it yet .

I change mine once a year or about 18k miles

 

There is a guide on this site that show how to do it . Clcik here

[willfxp]

That's true. Forgot about that. Never done this before. Will have to do it at my dad's house though.

Thanks!

 

-w

[gnutruk]

Yeah, change out the diff. fluid for sure.

 

There's a magnet stuck on the diff. cover to catch metal shavings and "fuzz." After 75 K it will probably be fairly thick on there, assuming the previous owner never removed the cover.

 

You will need a new gasket. DO NOT try to re-use the old one. GM part # for the 10-bolt diff. cover is : 26066456

 

The gasket will cost you about $5.00 or 6.00, and that is very cheap insurance.

 

If you have the G80 locker rear diff., you will need to use the special GM fluid. That stuff is expensive, but the Eaton G80 has carbon plates, and requires special friction modifiers which are in the fluid. Some folks here use various other synthetic brands, and have reported good results. You will have to make your own judgment call on that one. There has been a LOT of discussion about this.

 

Rear diff. with G80 10-bolt takes about 2-1/2 quarts. The spec. and amounts called for ought to be in your owners manual.

 

PROCEDURE :

 

1. Remove spare tire to gain better access (not necessary, but suggested).

 

2. Lift truck on jackstands (again, not necessary, but makes things easier).

 

3. Remove fill plug, which is on the upper right front of the diff. housing, forward of the axle.

 

4. Remove drain plug on bottom of the diff. housing and drain fluid into a suitable container.

 

5. After the fluid is out, remove the 10 bolts holding the rear cover. You may have to “persuade” the cover to come off. DO NOT DO ANY HARD PRYING ON THE REAR DIFF. COVER. Believe it or not, you can tweak the cover, and then it won’t “seat” well again. I put a piece of hardwood against the edge of the cover, and then hit the hardwood with a hammer to get things moving. After that you can pry it gently.

 

6. Scrape off the old gasket. At 75 K, yours will be a bit rotten, but some pieces will seem like they're glued on.

 

7. Clean off the fuzz that'll be stuck on the rear magnet, and generally clean off the crud etc. that's on the cover and inside.

 

8. Briefly admire the beauty of an exposed rear differential, all those neat gears and things.

 

9. If you're in a cold climate, take a break, go inside, get warm, then do this: Or hot chocolate.

 

10. Put the new gasket in place (I seem to recall that the notch is at the top). Some folks apply gasket sealer, but it isn't necessary.

 

11. Put the rear cover back on in the same orientation you took it off. Tighten down the 10 bolts just snug.

 

12. IMPORTANT : Be sure to re-install the clip that holds the brake line on that upper bolt.

 

13. Do the final tightening of the 10 cover bolts. Tighten in a crosswise pattern, torqueing them to 30 ft lb (40 N-m).

 

14. Replace bottom drain plug. Torque down to 30 ft lb (40 N-m).

 

15. Pour the gear lube into the fill hole. A small funnel that just fits into the hole will be helpful.

 

16. Fill to about one inch below the fill hole. A nice trick that was mentioned by someone else here a long time ago was to take a standard type of 90 degree bend Allen wrench, and dip that into the hole to check your level.

 

17. Re-install the filler plug. Torque down to 30 ft lb (40 N-m).

 

18. Replace the spare tire, lower vehicle, and go for a test drive. You want to get your diff. warm – maybe three or four miles.

 

19. IMPORTANT : After you return, let the diff. cool back down. Then, re-torque the 10 cover bolts. When you got the diff. warm, everything swelled a little bit, the gasket “set,” and so the 10 bolts will have loosened just a smidgen when they cooled. If you re-torque them now, you will not have another leak. While you’re at it, you might as well check the torque on the drain and fill plugs, too.

 

20. For the future: after a moderately long drive some day soon, crawl under there and feel the rear diff. cover. Rear diffs. naturally warm up a bit in use, but they never get hot. The cover should never get so hot that you can’t put your hand on it. If you can’t keep your hand on that cover, then you have got serious problems inside that diff. and you need to take it to the rear diff. doctor.

 

21. After everything is cleaned up and put away, do this again :

 

gnutruk

[chvythndr]

Wow, good post gnutruk.

[willfxp]

Great post! Thanks.

 

I followed those steps and everything seems to have went smooth. I didn't go with the GM fluid though. They were $38 /quart! Local autoparts store had three brands, ranging from some purple stuff (~$7), Mobile1 ($9), and Red Line ($10). I went with the Red Line.

 

What kinds of problems can I expect if I didn't do everything right? If I used the wrong fluid, if I didn't have everything tight? Didn't completely take all of the old gasket off, etc?

 

Thanks!

[JayMan]

Great post! Thanks.

 

I followed those steps and everything seems to have went smooth. I didn't go with the GM fluid though. They were $38 /quart! Local autoparts store had three brands, ranging from some purple stuff (~$7), Mobile1 ($9), and Red Line ($10). I went with the Red Line.

 

What kinds of problems can I expect if I didn't do everything right? If I used the wrong fluid, if I didn't have everything tight? Didn't completely take all of the old gasket off, etc?

 

Thanks!

Yeah, that Goodwrench stuff must have gold or diamonds inside for what they charge.

 

If you have an open carrier differential, feel free to use any 'ole synthetic GL-5 gear oil.

 

If you have the RPO G80 GovLok "locker" then you must use a fluid that claims suitable for "limited slip" service, or the G80 may stop working.

 

When I first serviced my axle, at 600 miles, I thought I'd try a commercial gear oil, since I have pails of the stuff in my shop. I had about 10 quarts Exxon SGO 75W-90 leftover in a 5 g pail, which meets the Eaton Dana extended warranty and extended drain for HP-40 tandems.

 

Everything seemed fine till 3 months later in the first snow. The "locker" was slipping and chattering like crazy. I called Exxon and they were horrified: the additive package to meet Eaton Dana E500 specs is NOT compatible with "limited slip" clutches! In time I could expect glazed clutches.

 

 

They suggested I drain ASAP, find a cheapie 80W-90 (I would need to flush things), and some LS additive. I refilled with 3 tubes of CRC Trans-X PosiTrak LS additive and NAPA 80W-90, which was luckily on sale for $1.69 a quart.

 

I drove around and the G80 came back to life. About a week later I drained and refilled, but using only 1 tube of LS additive and the NAPA cheap lube. Things seemed fine, so I drained and refilled with 1 tube additive and Mobil 1 Gear Oil.

 

Otherwise, the only problem I foresee, asides from using the wrong fluid and buggering up your G80, is not getting all the gasket off the axle housing and the sheet metal cover. You have to take your time to carefully scrape all the gasket material off using the proper scraper, and be careful not to warp the sheet metal cover in any way.

 

A quick tip: make sure the axle vent tube is open. If the axle vent tube should become plugged and/or kinked, pressure will build up inside the axle and create a leak. Those seals and gaskets are NOT designed to hold pressure of any sort!

 

I've seen a plugged vent wreak havoc by causing leaks from the sheet metal cover, the shaft seals, and on HP-40 tandems the hub seals. It doesn't take much to plug or kink the vent tube.

 

Not a major operation, so there isn't much to go wrong, with the exception of the above. Most important is to NOT overtighten the bolts or you'll warp the sheet metal cover and guarantee leaks. I have an assortment of torque wrenches from 1/4 inch up to 1 inch drive, and religiously use them on fasteners.

[100R1]

Good info above.

 

I can only add a little helper on cleaning the diff. cover

 

3M makes a scotch bright pad that attaches to your rotary / die grinder / dremel / electris drill ETC>

 

What use to take me atleast 30 minutes to clean the gasket flange takes 2 or 3 minutes and does a lot cleaner job.

 

It works wonders on RTV silicone goop and paper gasketing. No gouging the pan from gasket scrapers or knives.

 

Who makes GM's grape juice ? Gm does not. why pay piper at the Stealership?

As long as you meet OR exceed the factory requirements you are covered for any warranity issues.

 

Is GM's Mfg by Royal Purple?

 

I use Red line 75 -90W in my G80 3.73 '01 Yukon And I tow A travel trailer.

[willfxp]

Yeah, I have the G80, so I made sure the stuff I bought said LS somewhere on the bottle. I was surprised that the purple stuff had it and the Mobil 1 didn't. Oh well.

 

My friend helped me to take off the old gasket. Using a dremel is a good idea. I'll keep that in mind when I do the front diff.

 

I didn't have a torque wrench, but my friend works on cars a lot and guessed how much pressure to use. I hope that works

 

Thanks!

[JayMan]

Yeah, I have the G80, so I made sure the stuff I bought said LS somewhere on the bottle. I was surprised that the purple stuff had it and the Mobil 1 didn't. Oh well.

 

My friend helped me to take off the old gasket. Using a dremel is a good idea. I'll keep that in mind when I do the front diff.

 

I didn't have a torque wrench, but my friend works on cars a lot and guessed how much pressure to use. I hope that works

 

Thanks!

Actually, the Mobil 1 Gear Oil does claim suitable for Limited Slip service. I have a bottle in front of me:

 

" ... exteme pressure limited slip additive package ... prevents chatter in limited slip differentials ..."

 

I have to keep using a tube of CRC as I must have glazed the clutches in my G80 by using the wrong fluid. Without the CRC additive, the G80 still slips a little. I doubt you'd have to use additional additive.

 

Good tip on the Dremel tool. I KNEW there was a reason why I bought one!

[willfxp]

Actually, the Mobil 1 Gear Oil does claim suitable for Limited Slip service. I have a bottle in front of me:

 

" ... exteme pressure limited slip additive package ... prevents chatter in limited slip differentials ..."

 

I have to keep using a tube of CRC as I must have glazed the clutches in my G80 by using the wrong fluid. Without the CRC additive, the G80 still slips a little. I doubt you'd have to use additional additive.

 

Good tip on the Dremel tool. I KNEW there was a reason why I bought one!

Hmm... I didn't see anything referring to LS... I would have rather bought Mobil1 than RedLine.

 

Are all gear oils as thick as RedLine? That stuff was sure thick!

[JayMan]

Are you sure? I read it right off the back of the bottle.

 

What do you mean by "thick?" Did it seem really goopy?? Just curious. A 75W-90 gear oil at room temp will have the approximate viscosity of a straight 50 motor oil.

[gnutruk]

Great post! Thanks.

 

I followed those steps and everything seems to have went smooth. I didn't go with the GM fluid though. They were $38 /quart! Local autoparts store had three brands, ranging from some purple stuff (~$7), Mobile1 ($9), and Red Line ($10). I went with the Red Line.

 

What kinds of problems can I expect if I didn't do everything right? If I used the wrong fluid, if I didn't have everything tight? Didn't completely take all of the old gasket off, etc?

 

Thanks!

Glad it went well. All that other info. and tips from JayMan and the other folks are real good. Sounds like you got all the essential things, and did all you could with the tools you had available. Start shopping for a torque wrench before too long. Some of the things you will do in the future will REALLY require that bolts be correctly torqued back up. Got a birthday coming up? Maybe someone who loves you will surprise you with one of them, especially if you’ve carefully checked out the different models, and “accidentally” leave the brand, model number, and store that has it out on the kitchen table.

 

Torque wrenches: a medium sized topic in its own right. I recall there was some discussion about torque wrenches before Christmas over on the Parts And Suppliers page on this site (or whatever the page is called).

 

Torque wrenches: DO NOT GET THE “NEEDLE” TYPE OF TORQUE WRENCH. That’s the sort that has a “tension” bar that moves a pointer across a scale placed horizontal across the bar plane. They are just no good – inaccurate, too affected by temp. changes, and hard to read. About all you can really use them for is to throw at rabid skunks that wander into your yard.

 

Of course, that’s just my opinion.

 

What you want instead is a so-called ‘clicker’ type. This is where you set the desired torque by releasing a lock on the handle, and then twisting the handle to the desired setting of the scale that’s on the bar of the wrench. When tightening the bolt, when you reach the set torque, the wrench give a loud “click,” indicating that you’ve reached the needed setting and to stop pulling.

 

As always, Craftsman (Sears) is a good solid tool. Other brands too, probably. Snap-On is going to be among the best available, but expect it to be pricey. There are more modern torque wrenches out there now, having digital read-outs, etc. Hell, for all I know, by now some of them might have integrated internet access, so you can track the progress of your stock portfolio AND do remote programming of your TV-VCR, while hot oil is running down your arm.

 

Ok, I went a little too far there.

 

Anyhow, when you get your brand new, shiny torque wrench, be sure to start a new thread about that, because believe it or not, you have to take good care of torque wrenches. These modern types aren’t just some box wrench you can throw in your tool chest and forget about. Torque wrenches should be treated as precision instruments, or semi-precision instruments, anyhow. For example, you DO NOT want to store a torque wrench out in your garage where it gets freezing cold in winter and torrid hot in summer. Torque wrenches are very sensitive to temperature changes, and if exposed to wide swings, they can go inaccurate on you. Then, you have to get it re-calibrated. Also, you do not EVER want to drop a torque wrench. Ever.

 

Ok, moving on.

 

Yeah, the GM fluid is priced just crazy. You go into the parts dept. for some of these items, and it’s like, “GO AWAY, WE DON’T WANT YOUR BUSINESS. PLEASE BUY THE COMPETITOR’S PRODUCT INSTEAD.” But it seems, in the last analysis, that the GM fluid is the “safe buy,” since GM and Eaton formulated it specially for the G80’s. So, should you take out the Red Line and go GM? I don’t know, really. Only thing I would say is that if you did that, you could probably re-use the gasket, if it came off clean, no rips or pieces missing, since the one you got is so new.

 

If you didn’t totally remove all the old gasket, you might start to leak fluid. Just watch around the cover plate to see that it stays dry. If not, tighten the 10 bolts to 30 ft lb (40 N-m) using you new torque wrench. FOR SURE, NEVER OVER-TIGHTEN A BOLT TO TRY TO STOP A LEAK. Worst way to approach the problem. Instead, re-do the entire operation from scratch. 100R1’s scotch pad idea sounds like a winner.

 

gnutruk

[Bulldog]

If you don't have the G80 RPO then what kind of rear end do you most likely have?

[JayMan]

Very good points on torque wrenches. In my shop, I have around $1,800 worth of them. They're kept in the "environmental" part of the shop where I keep the computer and other delicate stuff.

 

One more pointer: never store a torque wrench at any value. You MUST back the torque wrench off to "zero." Leaving it set at a torque value will completely bugger it up.

 

Not sure about 1995-96 trucks, but mine is a 10 bolt, I think 8.6 inch R&P. The R&P is the same for an open carrier or the RPO G80, it's the carrier guts that are different.

 

Other folks I know use Mobil 1 Gear Oil in their G80 "lockers" no problem. You can do an entire axle service for less than the cost of one bottle of Goodwrench Synthetic. Man am I in the wrong line of work: $26 a quart.