Recently, the axle and pinion seals were replaced in my '71 Cutlass open diff. with 2:56 gears. The mechanic replaced the old lube with newer synthetic lube, but I wonder if he should have used something similar to VP Fuels VP Classic Gear Oil GL-4 SAE 80w-90 instead? They claim their formulation is superior for applications with 'yellow metals' like bronze or brass. Is this even a consideration for my diff., or am I okay keeping the newer synthetic lube? The pinion seal had to be replaced a second time, and still weeps somewhat but doesn't drip. Could this be a lubricant issue?

 

If the rear is a Open Non Posi rear...You can use ANY rear diff lube and be fine.
Gear lube does not make a difference on a seal . The seal should retain WATER . The seal surface on the yoke is either compromised ...or the retaining spring on the seal lip is not tight enough . It can be tighten some by twisting the spring to a tighter loop then reinstall it on the rubber inner lip .
I would say the yoke seal surface has some pitting or a lip ridge worn into it relaxing the seal contact.
You can also use a .020 or .030 shim on the top of the bearing under the yoke and this will move the seal surface to a different location for the seal to ride. Cheap fix that has worked in the past for us.


Jim
JD

 

Synthetic will leak where dinosaur juice won't (or didn't) simply due to the synth having smaller molecules vs regular oil. This situation rears its head when no leaks were observed prior to the switch to synthetic and now you have a leak.

Since your seals were replaced and you have an open diff you are OK using the 75/140 synth. Unless it still leaks.
If it leaks with new seals you could try switching back to regular old school 80/90. The VP oil sounds like it's designed for stick transmissions due to brass & or bronze parts. Nothing to worry about on an old school open diff. (limited slips are a slightly different story).

In general, you shouldn't simply replace a seal if the metal sealing surface has a groove worn into it from the old seal. If a new seal is installed in the same spot it will likely continue to leak, thou slower. Oversized seals can be found for many applications.(Google BDI Inc. to find a branch near you).

If there is room on the component the seal can be set deeper or shallower to avoid the groove thus the seal will ride on a "new" surface.

Another option is to install a speedy sleeve over the worn metal. But It needs to be installed/prepped correctly to work.

Spray welding and re-machining is the last option reserved for an obsolete or a very expensive part.

Dam good tip on twisting the spring, Jim. Learned something today!

 

Any 90w will work fine, you don't need anything special. They sell a redi sleeve for your pinion that will fix your leak.

 

Make sure the leak is from the seal and not the pinion splines. The splines between the pinion and the yoke had a small amount of sealer from the factory. Most rebuilders that I have seen do not put any kind of sealer in this area. Axle fluid will leak from the splines and appear to be coming from under the pinion nut or washer. I always apply a thin cover of RTV to the inside spline on the yoke before final assembly.

 

I have seen pinion and axle seals leak due to plugged vent in rear diff. Once fluid is warm, builds pressure and free's itself

 

Some GL-5's are not recommended for use with yellow metals such as bronze due to a higher sulfur content. GL-4's are ok around yellow metals. Since there shouldn't be any yellow metals in the differential, I don't see a problem. I would be careful to use the correct version in a manual trans though.

Leaking...syn vs. dino? Some say yes some say no, I lean toward yes particularly if a part is worn.

Good luck!!!

 

"Spray welding" is ok for stationary mounting surfaces such as bearings axle bearings. Its usually too abrasive or porous for a sealing surface.

 

The sleeve for an 8.5" ring gear is NATIONAL 99170, very easy too install. Cost is around $20

 

Many of my friends use sticks that release incense smoke. These things can weatherize the smell of a dog/cat

 

While incense may nullify the stink of an animal, it will NOT eliminate carbon monoxide from engine exhaust.

 

Though not as relevant as incense, any sealer on axle/wheel bearing? CW507CR to be specific.

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No, there is a mechanical seal on the axle.

 

Agreed, that is a sealed bearing with internal lubrication. The axle seal is inboard of the bearing and keeps the oil from getting to the bearing area.

 

Thanks guys. I found some silicone like sealer residue while wiping out housing bore, like it was on outer circumference of bearing. Could not determine if it had been apart previously.

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