Lately I've noticed a small drip right in the middle of the rear sway bar on my '72 Supreme. It started about a month ago, and it's after I park it. By small I mean it's just enough to see it, but not enough that it's a constant drip. There is very little residue on the rear axle housing, but I'm guessing it's coming from the pinion seal. With a such a negligible leak, how concerned should I be about fluid loss, checking the fluid, and the time frame for when I need to replace it? I usually drive it every 7-10 days to work and back (40 mile round trip), and an occasional cruise.

Thanks!

 

You probably have time to wait as there isn't oil pressure on the seal but. keep an eye on the leak to make sure it doesn't get worse. In the meantime check that the vent tube isn't clogged.

If you've never replaced a pinion seal, familiarize yourself with the procedure before disassembly. There is a one way only pinion bearing preload crush collar, if it is overtightened on reassembly the differential will need to be disassembled.

 

I would leave it alone for now and monitor it.

 

Would a clogged vent tube cause back pressure and allow diff fluid to weep around the seal?

 

How often should I check it?

 

My vent tube seems to be MIA, but I did check the hole with a pick and I didn't feel any blockage.

 

A clogged vent could cause seepage. The broken vent tube should be addressed to prevent water intrusion. Eyeball the drip each week, can be done with aluminum foil on the floor or a metal pan to see how much drips. Put the seal replacement on the list of to do's.

 

Copy that. I've already done the research for a new tube, and just have a question. I see a collar on the tube, so does it just fit around a boss on the housing, and R&R is simply a matter of popping it off and sliding a new one on?

Also, it seems there are two different size tubes. .375 and .452. How would I know which one I need?...and something about a base piece?
https://classicoldsmobile.com/forums...nt-tube-43667/

 

Clean up the area, retorque the bolts, tape it off, and use the product in the picture along the seal area at the bottom of the differential. Apply 2 to 3 light coats. Let it cure, then finish up with black paint. This product will stop the leak, weeping.

 

Thanks for that, but the leak isn't from the gasket, I think it's from the pinion seal.

 

You indicated the leak hits right in the middle of the rear sway bar. The differential cover seal is extremely close to the rear sway bar on my car. Revisit this area to see if there is weeping/leaking at the seal.

 

Yup, but there is no runoff from the gasket area on the housing.

 

If it's pinion, look for oil slung on the mufflers and the hump area of the underside. I apologize for leap frogging to the cover seal, but there is a good possibiity for a leak there as well, especially if the diff fluid is showing up on the rear sway bar.

Happy Motoring!

 

The vent plugs into a hole in the tube. What you see is all vent. Push the new one in until the larger part bottoms against the tube.

You can pry the old one out and measure the base to verify the diameter.

 

Dave - I don't recall how long you've owned your '72 Supreme. In the time you've owned your '72 Supreme, have you ever had the differential cover off and changed the fluid?

 

I have checked diff fluid level by removing the fill plug and sticking either my pinky finger or a bent piece of wire into the hole to use as a dipstick. If my pinky touches fluid, I know there’s plenty.

 

Completely agree w/ your method & hopefully Dave has already done that to ensure the fluid is at the correct level. The reason for my question is: (1) An OEM rear differential fluid should be changed at a minimum of ~100,000 miles; and, (2) the differential should be visually evaluated @ 100,000 miles for any conditions of wear, cracking, etc. If it has NOT been cracked open, it should be cracked opened, fluid changed and gears evaluated.

 

Norm, thanks for the input. I've had it 5 years now. It had 98,000 miles on it when I bought it, and I'm at 113,000 now. I haven't changed the fluid, but I do know it has been changed at some point based on the fact that the gasket has been replaced. Unless a PO decided not to change the fluid when he changed the gasket, I'd say my fluid is good.

 

So is this the complete unit?

 

I'll let you to your own decisions. I change my differential fluid in all vehicles @ 60,000 miles - all vehicles, all differentials including transfer cases.
You have zero idea when (and, honestly if) the PO changed the differential fluid. If he did, might I suggest he/she wasn't a very bright individual if they left the vent hose unattached; and, how long you been driving around with no vent tube? The vent tube releases/dissipates heat and condensation from the differential. It is there to remove pressure which could build up from the heat. If the differential fluid is low, you'll have a greater amount of heat; albeit, a greater amount of heat can prematurely wear/crack the rubber of the pinion if that heat is not allowed to vent/dissipate. You say you can get a pick into the fitting? You need a vent which can breathe. Again, I'll let you to your own decisions. It takes 1/2 - 1 hr to change diff fluid. Be sure you have a proper vent with a proper vent hose. Good luck.

 

I hate to guess since I don't own a '72 Supreme and I don't know what rear end you have. Even if I were to guess based on my '71, there is always the chance they changed the location &/or style of the diff vent tube even on the same rear end. Part numbers work better than pictures though in this case I'd suggest.

 

See my pic in #6 above. That is looking at the passenger side from the rear. It looks like the vent is in the correct location. I will pull the old tube tomorrow and measure the diameter so I can order the right size.

 

Read this thread in its entirety. Note the year they changed the size of the vent hole. I noted they mentioned part numbers, as well.

Issues With Axle Vent Tube

 

As long as the hole is clear and unobstructed, wouldn't it serve the purpose of allowing the axle to vent?

 

I never suggested the vent was NOT in the correct location. I said I don't know the location of your vent tube on your car; and, I don't know the size and what remains of what should be the base unit into the axle or the actual tube which inserts into the base.

 

I currently have some residue on the diff housing, so Ill clean it up and see what happens.

 

Dave - I am not going to debate this w/ you. You have a micrometer to measure the diameter of the non-existent vent hole? Make an informed decision or fly by the seat of your pants.

 

I'm gonna replace it Norm....I'm just understanding what is meant by "base" and "vent tube" Is there supposed to an actual tube that connects to the vent? And what is the base?

 

Did you read the link I provided in Post #23?

 

Since the link I provided is the EXACT same as the link you already provided, it should be clearly apparent you need the larger size vent tube:

GM # for the larger vent tube is 01236317

 

Dave, the picture you posted it the entire vent assembly. It’s essentially a tube with a hole in the center and a cap on top to prevent debris and water from entering.

If the PO replaced the gasket, then the fluid came out during the process.

 

Personally, I'd go to a NAPA store and get it from them. Let NAPA pay the shipping and if it's the wrong one, you take it back to NAPA. I hate buying some of these type parts on-line since so many of these vendors are clueless what they're selling.

 

Dave - I said I didn't want to debate the vent hole (tube) w/ you. I was tired and a tad 'cranky' before retiring for the day - apologies.
Allow me to realign my mental inadequacies.
The size of the vent hole is important and needs unencumbered access to the atmosphere. Just simple/basic physics here. Heat is produced inside the differential as the gears turn. Heat is absorbed by the differential fluid. A highly viscous (90 weight) differential fluid will absorb far more heat than a light weight (less viscous) differential fluid. The heat inside the differential needs to be released. Excess heat is released at the interface of the liquid/vapor barrier - between the fluid and the atmosphere above the fluid inside the differential housing. The heat in this atmosphere will condense and form moisture (water). It's this heat/moisture which needs to be dissipated/released; otherwise; the heat will continue to reside inside the differential increasing the amount of moisture and retaining this higher than normal temperature. The most likely 'cause' of increased moisture exiting the vent tube is low differential fluid, but can be exacerbated by a restricted vent hole. If not enough fluid, the atmosphere above the fluid is greater (increased) than normal forming more condensation and this moisture needs to be released. A smaller (normal) less atmospheric volume of air above the fluid will yield less condensation and dissipate heat better. Therefore, fluid level is important. If you restrict this vented orifice, heat builds, heat is retained (bad things happen), moisture/condensation builds. This heat can wear the pinion rubber and form cracks/degrading the rubber. The housing is not under pressure when the vent hole is open - e.g. open at the correct size and unobstructed. If its diameter is less than normal (the orifice restricted) you'll increase the amount of heat retained in the housing i.e. less area for the heat/moisture/condensation to vent and a far better chance you'll see increased moisture/water escaping a small vent tube opening than a proper (normal) sized vent tube opening. It's like a pressure cooker - you keep making the hole smaller the pressure will increase and with an increased in pressure comes an increase in temperature. So, ensure your fluid level is always correct, as well.

 

Good morning Norm - Apology accepted. I understand the importance of the vent tube, but until I get a new one, just the open hole would serve the purpose, correct?

Also, I found a NOS on ebay with the correct part number, but the description says it's 3/8. I've messaged the seller to confirm the diameter. Or, based on the part number, is it, without a doubt, .452?

 

Dave - You're a good guy.
Honestly, I don't know the true diameter of the vent tube you need. So hard to evaluate if you don't have the correct literature. I 'might' be able to find the OEM correct diameter if I can locate the correct Parts Number catalog. Who knows if the original picture you posted is correct with a 0.452 hole? Maybe we'll find some indicative/informative information elsewhere. Like I said, 1/2 the time these vendors are clueless on what they're selling.

EDIT: BTW, yes, you're completely fine until you get it replaced.

 

I don't know - I need to play some golf. I researched several other sites with the part number you need (01236317) and they present information like Swiss Cheese regarding the hole diameter. As stated, the correct Part Number is 01236317. What these guys list is beyond belief.

 

The seller got back to me...it's .452. I've ordered it.

 

Got the vent tube today and it's done

 

Good job, Dave. Did you stick your finger in the fill hole to ensure the fluid is to spec?

 

Norm - When I stuck my finger in the fill hole I got nothng, so used a piece of coat hanger wire as a dipstick and from what I can tell, I'm right at the "fin".

Here's a pic to help...the yellow is to point out the mark I made to show where the level is, and the red is the outline of the fin. As you can see, I'm right at the fin.