Rear Gear Oil change it or leave it alone??

[lngfish]

This P30 has about 80K on it. The rear gear oil level is fine. It smells OK and does not look dirty at all, but it looks original by the color. This is all guessing I know. But maintenance records show this has never been done.

The only plug I see on it is on the rear pumpkin cover with all the bolts, I forgot to count how many.

This is the hole I used to check the level about a year ago.

My understanding is to renew the oil you need to remove the rear cover to drain the old gear oil.

My understanding is it takes 80-90W gear oil.

I see Carquest carries 75-90W and this will work, if I decide to renew the gear oil.

My under standing I will need 7+ pints so I need 8 quarts.

The things I am not sure of are.

1. Is there a gasket there that needs to be replaced or is it sealed on with a sealant? Silicone?
2. Can this gear oil be just sucked out or siphoned out somehow?
3. I ponder why a drain plug was not installed on a GM product like a P30. I guess they want you to put an eye on the gears like changing an automatic transmission filter/fluid.

I may do this next or I may not. All depends on what sort of feedback I get. I know this gear oil runs out to the rear bearings and all that seems fine to me.

Just getting caught up on some PM since I haven't driven it much in the last few years and I will be taking a trip when I get the stuff that may break down on the hwy. I have the gas leak fixxed at regulator, the new fuel pump installed and all new Gates belts installed and tightened back up a few times.

Tell you what, the brakes sure work allot better with a fresh gates belt on the PS Pump!

Let me know what to do with the gear oil please.

Thanks allot I like this site from the experienced folks here!

Steve


Thanks!

Steve

[ClydesdaleKevin]

If the oil looks fine and smells fine, it isn't absolutely necessary to replace it, but a quick and simple way to change most of it is with a simple transfer pump...looks kind of like a grease gun with a rubber hose on one end.  You stick it in the opening of the filler hole, try to get the hose to go down as far as possible into the bottom of the gear case, and pull on the handle, which sucks the old gear oil into the pump.  Then you push on the handle to force the old gear oil out of the pump and into a container to bring to a recycling center.  You'll have to repeat this procedure a bunch of times until the transfer case and axle are as empty as they are going to get.  Then you simply top it off with gear oil and replace the plug!  Easy peasy lemon sqeezy!  This is what I'm going to do when I change the oil here shortly and grease all the fittings, before leaving NY.  I was putting it off until I had the rear suspension fixed on our rig, which now sits 10 inches higher and will be easy for me to get to the rear diff.  We have 110 K on the rig, so I figured it would be a good time to do it.  80k is also a good time to change the rear gear oil.

You won't get every last drop out of the rear axle and diff case, but you'll get most if it if you are careful to make sure the hose is going down as far into the bottom of the case as possible.

I doubt you'll need a whole 8 quarts though...but I could be wrong.  Save your receipts and just bring back what you don't open.

The alternative to my simple and easy method is to remove the cover...and yep, a new gasket is required!  And if you go this route, you should put a light film of RTV sealant on both sides of the gasket.

I don't know why they didn't add a drain plug, but I have seen aftermarket rear diff covers that fit our axles, even fancy chrome ones, with drain plugs!  If I was going to remove the rear cover on ours, I'd go ahead and get a new cover with a drain plug...probably even a fancy chrome one...so the next time I wanted to change the rear gear oil would be a lot easier.  Or you could clean and paint your rear diff cover after installing a drain plug to the stock cover.

Depends on your budget, and how much time you have to play with it.  I'd recommend changing the oil at 80k if it has never been changed, but that's just me.  And you can get an inexpensive transfer pump for around 15 bucks.

Kev

[lngfish]

Thanks Kev,

I meant 7+ pints or 4 quarts.

Yeah I'll have to look for a transfer pump, plastic for $15 or look into a gasket.

I think they want you to look inside at the gears is all.

Plexiglass Cover and a plug would be ideal ! 

Kidding,

Steve

[Lefty]

I never put RTV silicone on any rubber or cork gasket... doing so can cause the gasket to squish out. I do recommend using Permatex High Tack Gasket sealant.. it comes in a small spray can. Just spray a couple light coats on the surface where the gasket will go, as well as on both sides of the gasket. Wait a few min between coats until it's sticky, and assemble.. In 20yrs I've yet to have a gasket leak after using it.
As for changing the oil, I would recommend doing it at least once a year if for no other reason than it's cheap, easy, and can keep a very expensive rear end from failing. I use 85w/140w though on HD rear ends, and the lighter 70w/90w on cars & light trucks.

I would remove the rear cover and drain it completely, then refill until you can touch the oil after inserting your pinky in the inspection hole. It's not necessary to fill it until oil emerges from the hole, just fill it till you can touch the oil.

Another thing I do when I remove the rearend cover the first time is epoxy a magnet onto it so it can capture and trap any metal particles that might be present, before they can do damage... just clean it off each time when you change the oil afterwards in the future.

A common mistake is over tightening the bolts causing the gasket to over compress.. this can cause leaks, as well as bend the bolt holes inwards.. be sure to check the cover when you have it off and flatten the bolt holes out if needed (same as on a transmission pan flange). Be sure to tighten the bolts in a alternating cross pattern, and only tighten them to the specified spec using a torque wrench.

[lngfish]

Lefty,

By your reply I take it these P30's are HD rear ends?

I like the maganet idea also. Where do you epoxy it on the very bottom?

I guess no chance of oil breaking down the epoxy. Won't the magnet stick anyway to the iron of case? I guess epoxy is back up.  I know transmissions have them in them.

Thanks for all the inputs.

Steve

[Lefty]

The magnet will stick to the iron case, or to the steel rear end cover.. but I epoxy it in place on the rear end cover towards the bottom as a precaution to prevent it from becoming dislodged... just make sure you place it so it doesn't hit anything with the cover on.

[cncsparky]

IMO, you should pull the cover.  The heavy metals settle at the bottom and its good to get in there with a rag and wipe out the old oil and gunk.  You will need a gasket and a good scraper, the old one doesn't always remove easily!  I plan to do mine this fall, will replace with Amsoil synthetic tho I'm not sure which weight to go with yet.

[legomybago]

Permatex Spray Tack....excellent product. Ive had same results. If you need to use rtv on anything....another great product is The Right Stuff or Permatex Black.

[lngfish]

I'm back, been away a bit.

It is funnie I originally posted this thread but only got to doing this job yesterday. I picked up the Lube from Amazon; Lucas 75W-140 for $39 w/free shipping, and the 10 bolt gasket from Rock Auto. Lucas is 100% synthetic and they have good products. Mobil-1 75W-140 rear lube was twice the cost.

I parked on a slight front down incline, butt-up, chocked 4 wheels, emergency brake and park-ON, I raised back of vehicle with rear-jacks and I had about 18 inches below pumpkin to work.

Job went well. When I was done I scraped all dirty surfaces and sanded them and primed and painted them black.

I measured what I took out and got 2.5 quarts or 5 pints. It looked semi dirty but not dark, but brownish. Smelled ok. There was no gasket just black RTV. I reassembled with gasket and RTV. I felt no sludge and there were no metal particles. Ring rear was smooth as heck.

Ring Gear is huge. Could not see pinion. Cover is stamped DANA with some numbers. Little Tag on one bolt on exterior has designation 456 and another number. I assumer 456:1 ratio.

Previously I had found it will take 6.7 pints but I forget where I found that bit is information.

I know just fill till you can just feel the oil or until it dribble out.

The reason I ask and it may be academic is my RV sags in the rear. I was thinking this may change the quantity but I'm not sure about it.

I do think that what was in there was a tad low at 5 pints wouldn't you agree?

But obviously plenty for lubing up the gear and bearings at rear and I assume the wheel bearings too.

If I was about a quart low, if my memory serves me correctly, I guess over the years some leaked out somewhere?

I see no leaks at the Pumpkin so that makes me think where.

Or perhaps 5 pints is correct, not sure.

Does anybody know the factory spec quantity for Rear Lube on a DANA rear on a Chevy P30 1987? (456)

Thanks for reading,

Steve

[lngfish]

Thanks,

Looks like P30 BOM is stamped on axle, doubt I'd find that. I'll just start filling it till it runs out. Great site anyway!

What I did find on my was a tiny tag "removable" on one bolt, 41-9  456 and on cover numbers stamped 30809 and 333 5

Those must be part numbers for the cover, the last 2 numbers.

Steve

[lngfish]

Finished up.

It took 3 quarts and 12 oz. or 6.7 pints.


I just wanted to add that I used that black Permatex RTV.

Put it on like Indians put on war paint, does not have to be thick.

I put on all surfaces thin.

Do not add oil till RTV has set up for 24 hours.

I had no leaks.

Steve

[Rickf1985]

I used to run a 4x4 shop and we were changing gear oil in the trucks we ran every week since we were in water up to the windshields. We never used gaskets, a small bead of RTV and slap the cover on. Didn't wait to fill it either. Never had a leak. The factories have not used gaskets for many years now, Just RTV sealants. Be careful you do not overfill it, the wheel bearing are lubricated by the oil that runs out there on turns but they are not submerged in oil all the time. The fill procedure is to fill to the hole and let any excess run out and then put the plug in. I do not worry about letting the excess run out since it would be such a small amount but the vehicle is supposed to be level and having the nose down can add a lot of oil since it all runs into the pinion cavity.

[cncsparky]

Here is my rear oil change.

http://www.classicwinnebagos.com/forum/index.php/topic,9139.msg50201.html#msg50201

[lngfish]

OK Rick,

Understood about the possibility of some overfill with nose down a bit. I was thinking same thing.  Looks like I put in .7 pints more than next fellow who posted pics who put in 6 pints.

One thing I noticed is one axle is higher than other. Ever notice that?

My figuring on the extra .7 pints extra being OK was the "settling" down of the rear on the leaf springs.
I guess mine sags 3 inches or so, never measured the sag on it but it does.
When I get to a level surface I will crack the plug if you think .7 pints is a problem.

Let me know.

Anyway, road tested it with this 75W-140 Lucas in it, 100 Synthetic and it was very quiet back yonder.

Steve

[Rickf1985]

It should not be a problem, that is not grossly overfilled. The settling down on the springs is all above the axle and has no effect on the differential and the only way one axle would be higher than the other is different size tires side to side.

[lngfish]

OK Rick,

Thanks.

I must of been looking at the axles upside down or something, oh I was.

The left one looked higher to me but I guess it wasn't.

Mirage I guess or it was closer. Who knows. It fooled me in any event.

Gotcha on the sag, makes sense. I hadn't thought about what you said the suspension is not the coach.

I was a lil low on gear lube when I drained what was in there. I think I took out 2.5 quarts or 5 pints and 6.7 went back in and it was ready to dribble out so I stopped filling it.

So I was a quart low.

I guess normal to loose some at 80K.

I'll leave in the 6.7 pints as I read it takes 6.7 pints.

It does seem and quieter however driving not that I remember gear nose before.

One of those things if you do something it is always better huh?

[Rickf1985]

I seriously doubt you were hearing any noise from the rear before, if you were you have bearing issues. You would have seen metallic oil when you drained it if that were the case. The oil level is considered good as long as you can touch oil when you put your finger in and down at the first joint in your finger. Roughly 1/2 inch. Any lower fill it to the edge of the hole. It does not have to be running out, if you see it at the edge then it is good. When that differential is turning it is moving a lot of oil and the gear goes all the way to the bottom of the case so a half inch will not starve it but is considered the lower limit.

Just curious, have you checked the rear wheel bearings? The heavier oil could mask noise from there, not likely but possible. Those bearings are overlooked most of the time.

[CJ7365]

A little confused on your post so far as type of oil your using

you said you understood the rear diff take 75-90

Then you bought and put in 75-140

Just wondering if it matters which weight of oil to use???

[lngfish]

75-140 covers 75-90 but I think better?

[tarifachris]

I changed today my Dana 70 gear oil. The old oil was dirty and smelled, but zero metal particles in the old oil or sump.  The bolts are 9/16 - I filled it with 3.5 quarts Oil (7pints). Most time consuming is cleaning all the parts and bolts and clean the sump! 0.1 quarts will not drain and you have to clean and remove it by hand. I used a gasket, because I didn't want to wait to let it dry and to save the 20 minutes cleaning off of the old black RTV the next time...


The torque for the bolts is 30 ft/lb and you should use the following pattern:

[Rickf1985]

Wow, Synthetic and a reusable gasket! The whole shebang. Gear oil is something that really only needs to be changed every 70,000 miles or so since it is sealed and contained and unless something goes bad like a bearing the oil does not go bad. It certainly will not hurt to change it more often as that is the only way you get to see the gears and also the oil to see if there is metallic in it that would tell you a bearing is going bad but definitely is a nasty job. And that gear oil smell stays with you for a long time.

[tmsnyder]

That Imperial is some unit.  You won't have any problems with that rear end, especially now.