Syntec gear oil

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daredevil

daredevil

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I just put a rebuilt cone type 4.10 gear in and put two quarts of castrol syntec in the rear. It says its good for open and limited slip rears because it has friction modifiers in it. With a clutch type i would be worried but I,m thinking it should be ok with out an additive in a cone type rear. Whats your thoughts on this?
 
Not trying to be smart,but they recommend using the additive with any sure-grip.I,d add it for piece of mind.My 1.978 cents.:-D
 
pettybludart said:
Not trying to be smart,but they recommend using the additive with any sure-grip.I,d add it for piece of mind.My 1.978 cents.:-D
Click to expand...

I think this is because dino oil doesnt have friction modifiers though.http://www.smokinvette.com/corvette/articles/a-study-of-automotive-gear-lubes-part-1/ this is a pretty thorough test of the top gear lubes and the following paragraph states they have the nessasary additives for sure grips. Review Candidates
The cross-section of gear lubricants tested includes those offered by original equipment manufacturers (OEMs), motor oil companies and specialty companies. All gear lubes, with the exception of Mopar Synthetic and Torco SGO Synthetic, are recommended by their manufacturers for limited-slip differentials and are therefore expected to contain appropriate limitedslip- type additives. Mopar limited-slip additive was added to Mopar Synthetic and Torco Type G limited-slip additive was added to Torco SGO Synthetic at the recommended levels to ensure equal testing. Each gear lube tested is listed in the following chart along with the performance specifications identified on the respective bottles. Batch codes are also listed.

Gear lubricant specifications are established for minimum performance levels. The active API gear lubricant specifications are API GL-4, GL-5 and MT-1. API GL-4 designates the type of service characteristics of spiral bevel and hypoid gears in automotive axles operated under moderate speeds and loads. These gear lubes may be used in select manual transmissions and transaxles. API MT-1 designates lubricants for non-synchromesh manual transmissions and transaxles. API MT- 1 is independent of API GL-5. API MT-1 calls for a higher level of oxidation stability, copper corrosion resistance and seal compatibility, which is not provided by API GL-4 or GL-5. Not all gear lubes meet API MT-1 performance standards.

API GL-1, GL-2, GL-3 and GL-6 are inactive. API GL-6 is identified by Lucas, Red Line and Torco as a performance specification. However, the test equipment is obsolete.

The U.S. military has established separate gear lube specifications. The most current military specification is MIL-PRF- 2105E, which supersedes the previous specification, MIL-L-2105D. MIL-PRF-2105E combines the performance requirements of MIL-L-2105D, API GL-5 and all but one parameter of API MT-1, thereby adding improved oxidation stability, copper corrosion resistance and seal compatibility to extreme-pressure axle lubricants. An additional gear lube standard, SAE J2360, mirrors MIL-PRF-2105E and is a global standard used by oil companies in countries where U.S. military standards are not applicab What I understand this to mean is that of all tested hereonly mopar synthetic and torco dont have the additives
 
Why add it? Whats it going to do? Is it going to reduce gear wear or posi wear? I think it just lets the posi slip more to prevent tire chirp and clunking in turns. I prefer all tire chirp and clunking in turns as long as my posi is locking. Trans slip shortens clutch life in automatics, wouldn't posi slip shorten posi life?
 
While it's true clutch slippage in an auto trans shortens it's life, clutch chattering in a sure grip shortens life by galling the clutch discs. Trans. friction discs are made different than sure grip clutch discs. Sure grip discs don't have friction material. They are metal on metal so it is necessary to have a little slipping.

I had my doubts about using just plain gear oil too because for the last 50 yrs. they said you have to run friction modifier but the last differential I rebuilt (clutch type sure grip) I used just gear lube in that said it had the modifier ingredients. I figured I'd test drive it and if it chattered I'd put some modifier in it. It worked fine. I took apart about 2 yrs. later to touch up the gear mesh cause it had a little gear whine and it looked just like the day I put it together new. It had no clutch chatter or abnormal wear so I see no reason to add more modifier.

BTW: I used Valvoline lube in mine but Castrol should be fine as it's good quality lube.
 
I have about 45K miles on the sure grip in my 68 Barracuda with Mobil 1 synthetic gear lub and no additional friction modifiers. I have never had any issues with clunking, tire scuffing or roughness.
 
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