Rear Axle: Noisy rear diff

[evilhawk]

I changed the differential oil in my 59 Hawk and since then its been making some noise. Its a dana 44 with twin traction and makes a pretty good banging noise at take off and sometimes around corners. The oil I put in is Valvoline High Performance gear oil 75-90w (it has friction modifier). From what I understand, the wrong oil can cause a lot of noise. I am thinking it could be an issue with the spider gears or yoke, but am not sure how to check. Has anyone here experienced anything like this?

Also when I drained the old oil it seemed low, but it never made any sounds until after I drained and refilled.

[StudeRich]

IF you used the Proper GL Spec GL-5 for Limited Slip Differentials, it is NOT enough Friction modifier for a complete Fill, it still takes the 4 OZ Bottle of Friction modifier to get the Clutches working properly and quietly.

It still MAY be possible that if you run it very long Low on Oil, that there is damage to the Pinion Bearings, which will make a Wah, Wah, Wah sound, but the limited slip issues are usually, but not ALWAYS the wrong Lube.

[evilhawk]

I think its the right oil. It said on the bottle "where an API-GL5 or MT-1 fluid is specified". Ill try adding friction modifier. The rear end doesnt make any other sounds besides the clunking noise.

[swvalcon]

A noise when turning and sometimes where you can feel the clutches slip is a problem with the oil most times. If it where me I would be sure I have the right oil and drain what you have and just start over.The least that would happen is everything would be a little cleaner.

[evilhawk]

What oil would you recommend? Is any GL-5 for limited slip ok?

[swvalcon]

I've never had a problem if I used oil that said for limited slip. I think today I would use a something like Amsoil or Mobil one type. Maybe add some additive to it if I wanted to be sure. How long has it been that the cover has been off and a good cleaning and inspection done on it. The gasket is not much money and not hard to do plus piece of mind knowing what everything in there looks like.

[karterfred88]

What oil would you recommend? Is any GL-5 for limited slip ok?

I would think in todays world, since they are all formulated to a specification, brands would not matter much. I'd add the additional modifier, see what happens, a little too much, shouldn't hurt it any. I wouldn't drain it, just add some first, to see if that cures it. When these things were built, the "modifier" was whale oil, long outlawed, so todays "modifiers" may give a different result from the those in 1959, on a one to one basis. Also todays "limited slip" units have somewhat different designs than our old TT units, with spring packs, different clutch materials etc., so some experimenting make be in order. GL5 is simply a hypoid lube spec-nothing to do with limited slip differentials, has to do with the ring and pinion loads only.

[Mike Van Veghten]

I've used the same oil in posi rear ends with no problem for many years. I switched to full synthetic a few years back with similar quiet results.
Not sure what would cause your noise.

Mike

[StudeRich]

I've never had a problem if I used oil that said for limited slip./Cut/

It does not matter what "they say" on the bottle or what Brand it is, what matters is the GL rating, I run the other way from ANY that have multiple GL Specs, I have seen GL-4, GL-5 all on the same Label!

GL-5 is the ONE that can be used for modern Limited Slip Units, but for older designs it is best to play safe and Add an additive like Jeep recommends for their Dana Axles.

[studegary]

I always recommend adding a small bottle of GM limited slip additive to a change of Twin Traction lubricant.

[BILT4ME]

On a non-Studebaker vehicle, I found that the Eaton limited slip diff I had was noisier and would tend to pop in and out harder if I did NOT have the friction modifier in it. The friction modifier allowed it to open and close more easily and thus, quieter.

If it were me, I would use the off-the-shelf GL-5 and add the friction modifier. There may be others that disagree, but I run 4x4's with big tires and limited slips and that's what works for me (unless it's a Detroit Locker....)

[evilhawk]

So I did add modifier and it seemed to help at first, but then the car started to bang around corners pretty loud again after a short ride, so I drained out the fluid and refilled with a 4oz bottle of modifier and 75w 90 limited slip oil and drove it again. It was still banging pretty loud so I added more modifier and went for another drive. This time it banged so hard when taking a left turn that it shook the car and it felt like the rear end was coming out! So I limped it home and crawled underneath, but didnt see anything out of the ordinary. So now the diff cover is coming off so I can inspect the gears. I am expecting to see damage. I dont know the history of my car, but I know it had a rough life so I wouldn't be surprised if the rear end is trashed.

[BILT4ME]

Were you totally off the throttle when going around the corner? If so, the "bang" is when the gears/plates/cones release to allow the axles to turn different speeds.

Next time, go into the corner and accelerate. You should NOT hear banging, but the chirping of tires.

If you find an intersection where someone's sprinklers are soaking the roadway, you can check it by decelerating through it and by accelerating through it. The water on the road will allow the tries to slip a little more.

The very first time my pickup with a LS in the front diff came loose, it sounded like someone hit it with a sledgehammer. I thought I broke an axle shaft. No, that's they noise they make when they're tight. The more you drive it, it will loosen up a bit and you will get used to the noise. Only run enough friction modifier that it requires. Running twice as much will actually burn the clutches and junk it because it will release and slip too much and cause heat, and burn the clutch plates/cones.

If you want it to be quiet, change it out to an open diff and send the original one to me........

[TWChamp]

"The very first time my pickup with a LS in the front diff came loose,"

I thought limited slip didn't come on the front of vehicles because it would be hard to steer on ice and snow. My 1971 Scout only has L/S on the rear.

[evilhawk]

I think I let off the throttle when going around the corner. Also, I think I have way too much friction modifier in it. Ill drain and pop the cover off and have a look inside when I get a chance. Do you guys know how much modifier is required? I think someone mentioned a 4oz bottle with limited slip 75-90w.