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post #1 of (permalink) Old 02-28-2002, 09:53 PM
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Synthetic or fossil for rear end

Should I go with synthetic gear oil or traditional oil, I know the synthetic will find a leak faster, but is it really that much better, my drag buddies say yes....thanks


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post #2 of (permalink) Old 02-28-2002, 10:32 PM
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Re: Synthetic or fossil for rear end

Lower friction coeficient, better lubrication when cold (or warm for that matter), more resistant to breakdown under load, and if you go synthetic on all driveline fluids (both diff's, t-case, trans) you might even pick up a mile or two per gallon...really! The only drawback is price, and because it flows better, it may find a leak better...but you were gonna fix all the fluid leaks anyways...right?


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post #3 of (permalink) Old 03-01-2002, 05:49 AM
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Re: Synthetic or fossil for rear end

i guess if you were running a dragster or formula car, the syn would give you the extra edge you need to hold together and be competitive BUT for your application i think you are spending needlessly. how many years has the conventional oil been working for you?

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post #4 of (permalink) Old 03-01-2002, 07:09 AM
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Re: Synthetic or fossil for rear end

I say go with a synthenic. I run royal purple but it is 10 bucks a QT. Redline, mobil 1, and vavoline all make the synthenic gear oils and are much cheaper. I just couldnt find enough of one when i did my rears. Synthenic is great stuff. I have seen a rear that was put together using synthenic. It was givin to the customer and he broke it in. With no gear oil in it. It was then driving on the road 10 miles before it locked up. That is what made me go with synthenic.

Can someone please bring me a hammer my 33's just ate my fender again. Damn i need more lift.
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post #5 of (permalink) Old 03-01-2002, 10:40 AM
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Re: Synthetic or fossil for rear end

Something that has not been brought up. Do you have a clutch type limited slip? If so do not use synthetic. It can definitely affect the way the clutches work. If not, then it is a matter of choice. I personally prefer a good quality standard gear oil, but I change my oils on a regular basis and the cost factor is important to me. I have not had any adverse effects from standard gear oil in many years of diff setups, tranny and transfer case buildups. If you live where there are temperature extremes then synthetic may be a good choice. A lot of it will depend on your situation. Good luck. Nickmil.

post #6 of (permalink) Old 03-01-2002, 10:49 AM
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Re: Synthetic or fossil for rear end

<font color=blue>Do you have a clutch type limited slip? If so do not use synthetic. It can definitely affect the way the clutches work.</font color=blue>

I have been running Mobil-1 synthetic in the rear diff of both our daily drivers for over 100,000 miles now with no problems. In fact, Mobil-1 is better for LSD's than dyno-oil due to it's heat tolerance. I have even called Mobil-1 and they recommend it for all LSD's. You still need the friction modified though.

Even at 148,000 miles, the LSD in the Trooper locks up tight, and the TJ has 105,000 on it now, it still works well also. I'd highly recommend running Mobil-1 in those applications.

For my daily drivers, I only run Mobil-1 (Redline isn't available up here), but in the wheeling rigs I only use Dyno-oils as they get changed out a LOT more frequently. I typically buy it in the 5 gallon bucket to save some cost as well.



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post #7 of (permalink) Old 03-01-2002, 05:58 PM
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Re: Synthetic or fossil for rear end

Do you have a clutch type limited slip? If so do not use synthetic. It can definitely affect the way the clutches work

Thanks jeepn for saying that. The royal purple i run can go right in with no friction oil.

Can someone please bring me a hammer my 33's just ate my fender again. Damn i need more lift.
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post #8 of (permalink) Old 03-02-2002, 10:21 AM
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Re: Synthetic or fossil for rear end

Check out Amsoil.
I use it in my CJ-7 and my Ford F-150 4x4
F-150 has LSD, no additives needed.
I am more than pleased with their products to say the least.
I would recommend to anyone. I re-searched alot about synthetics before I switched.

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