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wtjosaas' 1970 Firebird

2018 July
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TWO LANE BLACK TOP

Rear differential oil

Question

The rear pinion seal on my Firebird Formula has started leaking..Going to replace seal..Figure might as well change the rearend  oil also..Was thinking of going synthetic any thoughts??...

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3 hours ago, TWO LANE BLACK TOP said:

The rear pinion seal on my Firebird Formula has started leaking..Going to replace seal..Figure might as well change the rearend  oil also..Was thinking of going synthetic any thoughts??...

Well first off if you prefer, I have a really good, think chemical company, seal swell if you wanted to try that?

in general I don’t like synthetics for rear axles because of the tooth pressures. Synthetics tend to not have as good of an EP package as std. gear lubes. Shear in a gear lube is rarely an issue.

Edited by Last Indian
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First off Thank you for the input...

I did think about a seal swelling additive . Have used them before in Industrial applications..Mostly in gear boxes..Self contained hydraulic units etc.. at an aluminum foil mfg.. Rolling mill where I was the lead Millwright / Industrial mechanic.. Before it shut down..Had mixed results on the effectivness..I'm just going to go ahead and  replace the seal..Going to do it myself so..Getting the crush and preload correct is NO problem...I caught it early the oil level is only about a 1/4 inch below the filler plug..If that low..I agree with you on the synthetic..Reaffirmed kind of what I was thinking..Has 90,000 miles on it...Going to change it anyway and Go back with petroleum based gear oil with the limited slip additve...

Edited by TWO LANE BLACK TOP

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1 hour ago, TWO LANE BLACK TOP said:

First off Thank you for the input...

I did think about a seal swelling additive . Have used them before in Industrial applications..Mostly in gear boxes..Self contained hydraulic units etc.. at an aluminum foil mfg.. Rolling mill where I was the lead Millwright / Industrial mechanic.. Before it shut down..Had mixed results on the effectivness..I'm just going to go ahead and  replace the seal..Going to do it myself so..Getting the crush and preload correct is NO problem...I caught it early the oil level is only about a 1/4 inch below the filler plug..If that low..I agree with you on the synthetic..Reaffirmed kind of what I was thinking..Has 90,000 miles on it...Going to change it anyway and Go back with petroleum based gear oil with the limited slip additve...

I would suggest that before you unbolt the pinion nut you do the following. After you drain the diff. I would use gear marking compound on the ring gear and roll the ring and pinion through some revolutions and then take a few pictures. Now you know what the original pattern looked like. This way when you put the assembly back together you have a benchmark to compare to.

Also if you don’t plan on doing this for a month or so I might be able to get you some  special rear gear lube. It’s a test axle lube we would run in a axle test when we didn’t want to test or break the gears, we would be testing other components. I usually go back around the beginning of December for patent advisement on applications I still have and to see friends. At that time I could see if I can get some.

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Last Indian,

I am in no big hurry...As long as I have it done before middle of Jan. Was planning to take it to Carolina beach...(4hr drive) As far as checking the gear pattern to get a baseline..That is absolutely sound advice..Will do that..The test lube you are referring to. What is it exactly?? Also is it something that will last for a few years under all types of driving conditions and temperatures??  With no issues..OK for use in limited slip differentials??

Edited by TWO LANE BLACK TOP

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17 hours ago, TWO LANE BLACK TOP said:

Last Indian,

I am in no big hurry...As long as I have it done before middle of Jan. Was planning to take it to Carolina beach...(4hr drive) As far as checking the gear pattern to get a baseline..That is absolutely sound advice..Will do that..The test lube you are referring to. What is it exactly?? Also is it something that will last for a few years under all types of driving conditions and temperatures??  With no issues..OK for use in limited slip differentials??

Two Lane, the gear lube I mentioned was a phenomenal lube. It was a custom blend for our test work. I ran it 80,000 miles in a 4/11 Camaro rear end and it was still in it when I sold it in 2004 (22 years). In making a call to my old blending contacts at work that fluid has changed, so it’s thinner and no limited slip additive. 

That said they’re are three ways you can go.

1. You can use the update lube from my company and add a Lucas Oil limited slip additive, the down side of that is getting the ratio right can be a little tricky.

2. This would be my choice. Use Lucas Oils Heavy Duty 80/90 gear lube. This is good for limited slip. 

https://lucasoil.com/products/gear-oil/gear-oil/heavy-duty-80w-90-gear-oil

3. Obviously what ever other oil you wanted to choose.

The Lucas Oil is good stuff. My good friend from work who I’ve built several cars with and he was my tech for the last 20 years at work who helped me put a lot of my designs together and help me test them says it’s really good.

Edited by Last Indian

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Last Indian

Thanks for the input..

Use Lucas products in our racing ventures..have had no oil related problems..of anykind..So that is what I'm going to use....

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