Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Synthetic for differential ?

Discussion in 'The Garage' started by kick, Jul 19, 2004.

  1. kick

    kick 1/2 ton status

    Joined:
    Dec 19, 2002
    Posts:
    385
    Likes Received:
    0
    Location:
    FL
    I want to use a synthetic gear oil in the differential of my 1990 V10 The owners manual calls for a 80/90 I have been using castrol 80/90 regular oil plus additive. I notice all synthetics are 75/90 will this work in my Blazer ? Even though it is a lower viscosity, I'm in FL so I need the higher viscosity due to the heat. Royal Purple ? Castrol ? Amsoil ? Any recommendations ? Thanks
     
  2. pauly383

    pauly383 Daddy383 Staff Member Moderator

    Joined:
    Jul 22, 2001
    Posts:
    16,217
    Likes Received:
    1
    Location:
    Mesa , Arizona USA
    Hossbaby50 runs synthetic in his , but he runs super thick stuff . I am in AZ and personally myself run 85/140 regular /forums/images/graemlins/k5.gif
     
  3. GMCLegacy

    GMCLegacy 1/2 ton status

    Joined:
    Jan 24, 2002
    Posts:
    620
    Likes Received:
    0
    Location:
    Grand Haven, MI
    what is your reasoning behind switching to synthetic?
     
  4. Pookster

    Pookster 1/2 ton status

    Joined:
    Nov 21, 2000
    Posts:
    3,195
    Likes Received:
    0
    Location:
    NYC, NY, USA
    Synth is the way to go, if you can afford it. Some people run synth- acutally GM runs synth now standard in the diffs on most newer trucks. Reasons:
    - Lower operating Temp from less friction
    - Better startup temp (doesnt get as thick in lower temps)
    - More resistance to thermal breakdown
    - Better Fuel economy.

    Reasons Not to-

    If you offroad, do a lot of water crossings, and you commonly get water into your diff, then synth, while still better, is a very very expensive option.. around 7-10 bucks a quart for synth, vs about 10 dollars for a gallon for regular stuff.

    Recommendations: I run Mobil 1 in the rear diff, and I run regular stuff in my front diff- My front diff doesnt exactly see all that much action other than being offroad, or in snow.

    Im running Quaker State Synthetic in my rear diff of my other truck. It was the only synth I could find on the shelf at the time. It wasnt my first choice, but it is still better than conventional- Lower pour point, and higher viscosity at high temps. I dont think you could go wrong using Amsoil or Royal Purple either.
     
  5. Hossbaby50

    Hossbaby50 3/4 ton status

    Joined:
    Sep 1, 2001
    Posts:
    8,972
    Likes Received:
    0
    Location:
    Peoria, AZ
    Paul is right. I run synthetic. I run Redline Shockproof Heavy mix gear oil. It is AWESOME stuff. My gear oil is 75/250W. It works great for keeping the lockright quiet and the gears happy.

    You can get lesser weights then the heavy that I run if you want. I highly recommend the Redline oil though. I run it front and rear. The only downfall is that it is $8 a quart and is hard to find.

    It is WELL worth the money and hassle though.

    Harley
     
  6. bigburban383

    bigburban383 1/2 ton status

    Joined:
    Dec 30, 2003
    Posts:
    1,242
    Likes Received:
    0
    Location:
    Michigan, Royal Oak
    The current trend is synthetics in gear boxes and differentials. If the manufacturers are using it, its for a reason.
     
  7. afroman006

    afroman006 1/2 ton status

    Joined:
    Aug 21, 2002
    Posts:
    2,876
    Likes Received:
    0
    Location:
    College Station & Kingsville, Texas
    I'm running mobil one synthetic in my 14 bolt and I guess I like it. I dont remember what viscosity it is, whatever they sell at auto zone lol. What viscosity should I run with a detroit locker in about 90-100 degree temps? (florida is arctic compared to south texas /forums/images/graemlins/whistling.gif)
     
  8. jon v

    jon v Registered Member

    Joined:
    Jul 8, 2004
    Posts:
    22
    Likes Received:
    0
    Location:
    Hesperia, CA, USA
    Synthetics don't carry heavy loads. They are good for high temps and have lower pour points as well as high oxidation rates, thats why new trucks come with them (ie some fords 75w-140 no service diffs). They are good for new stuff cause a lot of the new diffs run real hot when you tow with them. I run Lubrication Engineers Almasol gear oil. My truck is a 79 jimmy, stock 10 bolt front, 12 bolt rear. I use a high end 90W viscosity (ISO 320) straight weight, Lubrication Engineers #605 Almasol. It carries better than an 1100 Newton shock load. OEM spec is 80w-90, but thats good any where in North America. I live in the Mojave desert, 110F in the summer. Axle rebuild shops out here pretty much use straight 140w, and they don't like synthetics, seen too much wear too fast. Ask Bucky at O & R 4x4 shop in Bloomington CA. I've drained water off this almasol stuff, and kept using it it separates out so well. It's a high refined parafin oil. I found it from pro trophy truck racers, and on that honda s2k website. Also, mag-hytec in Van Nuys CA recommended it to me when I bought a new diff cover for my other truck. /forums/images/graemlins/cool.gif
     
  9. Hossbaby50

    Hossbaby50 3/4 ton status

    Joined:
    Sep 1, 2001
    Posts:
    8,972
    Likes Received:
    0
    Location:
    Peoria, AZ
    One of the reason I run the Redline Heavy Shockproof synthetic is that it won't press out from between the gear teeth under heavy shock loading like can be seen in offroading and such.

    It is also stated to make your diff run 75* cooler then with standard gear oil and have very high viscocity to heat.

    The other main reason I run it is because my LockRight locker doesn't make a sound with it in there. Most of the time you can here lockright ratcheting and stuff with standard gear oil. Not with this stuff.

    I have dropped my cover a few times in the past year and every time I do I just reuse the same oil. It always looks pretty good when I pull it. I just toss it back in and keep on trucking.

    The last thing I will mention about the Redline Heavy Shockproof is it is really easy to tell if it is contaminated. Normally the oil looks like Pepto Bismol (redish pink) and if it gets contaminated it turn green and looks nasty.

    Harley
     
  10. bigburban383

    bigburban383 1/2 ton status

    Joined:
    Dec 30, 2003
    Posts:
    1,242
    Likes Received:
    0
    Location:
    Michigan, Royal Oak
    I would probably guess if you did put synthetic in a brand new gear set it would fail. I know when an engine is totally rebuilt (machined etc.) using typical equipment would require you to run the engine with regular non-synthetic oil to break in the surfaces.

    The vette comes from the factory synthetic ready. They use different processes when machining to allow the use of synthetic straight up.

    So the moral of the story is you should break in a new rear-end with normal lubrication, then later change over to synthetic lube.
     
  11. Hossbaby50

    Hossbaby50 3/4 ton status

    Joined:
    Sep 1, 2001
    Posts:
    8,972
    Likes Received:
    0
    Location:
    Peoria, AZ
    Yep, I put 500 miles on my new rear gears with standard cheap 85-140. Then switched to Redline.
     
  12. SUBFAN

    SUBFAN 1/2 ton status

    Joined:
    Mar 23, 2003
    Posts:
    2,334
    Likes Received:
    0
    Location:
    Davenport, Ia
    [ QUOTE ]
    The last thing I will mention about the Redline Heavy Shockproof is it is really easy to tell if it is contaminated. Normally the oil looks like Pepto Bismol (redish pink) and if it gets contaminated it turn green and looks nasty.


    [/ QUOTE ]


    /forums/images/graemlins/thinking.gif /forums/images/graemlins/thinking.gif /forums/images/graemlins/thinking.gif /forums/images/graemlins/thinking.gifThen I could leave 'pretty drops in everyones driveway /forums/images/graemlins/histerical.gif /forums/images/graemlins/thinking.gif /forums/images/graemlins/histerical.gif
     
  13. kick

    kick 1/2 ton status

    Joined:
    Dec 19, 2002
    Posts:
    385
    Likes Received:
    0
    Location:
    FL
    I've been reading about synthetics for a while. My Blazer has 162,000 miles and the heat here in FL. I was using castrol 80/90 plus the additive when I lived up north. I've been using Castrol 10-30 full synthetic in the motor with good results for about 60K. It keeps my engine oil pressure where it's supposed to be between 30 and 40 psi. So I figure it's a good idea to use it in the tranny and diff.
     
  14. Diesel Dan

    Diesel Dan 1/2 ton status

    Joined:
    Feb 27, 2002
    Posts:
    798
    Likes Received:
    0
    Location:
    Warren, Ohio
    [ QUOTE ]
    Synth is the way to go, if you can afford it. Some people run synth- acutally GM runs synth now standard in the diffs on most newer trucks. Reasons:
    - Lower operating Temp from less friction
    - Better startup temp (doesnt get as thick in lower temps)
    - More resistance to thermal breakdown
    - Better Fuel economy.


    [/ QUOTE ]

    This is an interesting subject /forums/images/graemlins/thinking.gif.
    My brother in-law has been working at GM dealerships for over 20yrs as a heavy tech. He has seen more rear axles burned up since they switched to synthetic.
    Could be a low grade synthetic? Dunno at this point.

    The other thing, which I have heard from several others also, is synthetics don't like clutch style positractions. He loosened up a gov-loc in late model HD as much as possible and it still chattered. Switched it over to reg lube and it went away and the customer was happy.

    Another guy I work with builds $30K street rods on the side. His last one has a Ford 9" with factory style posi and had it filled with synthetic. 3 bottles of additive later still chatter severly, switch to reg oil with additive-still chatters but not as violently. He will have to pull the diff to replace the clucths. Heard similar story from others with street rods.

    Now, my opinion. I run sythetics in most of my vehicles, most are open diffs and were broke in on straight oil. If you are gonna fill a new diff with synthetic then soak the clutchs in a reg. oil/additive solution. Similar to soaking new trans clutchs before installation. Clutchless LSDs shouldn't need any extra precautions.
     
  15. kick

    kick 1/2 ton status

    Joined:
    Dec 19, 2002
    Posts:
    385
    Likes Received:
    0
    Location:
    FL
    Thanks, I think I'll stick with the regular 80/90 oil + the additive on this oil change. I use synthetics in the motor and tranny with good results. Thanks
     
  16. 84_Chevy_K10

    84_Chevy_K10 Banned

    Joined:
    May 30, 2001
    Posts:
    17,669
    Likes Received:
    0
    Location:
    IL, USA
    Leave the additives out.
     
  17. kick

    kick 1/2 ton status

    Joined:
    Dec 19, 2002
    Posts:
    385
    Likes Received:
    0
    Location:
    FL
    I mean the GM limited slip additive.
     
  18. K5MONSTERCHEV

    K5MONSTERCHEV 1/2 ton status

    Joined:
    Jan 27, 2003
    Posts:
    3,254
    Likes Received:
    0
    Location:
    Castro Valley, CA
    If you want to wate money on special gear oil, run Red Line. It has some crazy PSI rating, so the R and P never touch.
     
  19. DaPlumber

    DaPlumber 1/2 ton status

    Joined:
    Apr 4, 2003
    Posts:
    212
    Likes Received:
    0
    Location:
    Holland Oh.
    It's all about the seating of the rings!!!!!

    Yes, You can add synthetic to a new gear set!!


    On a new motor, I recommend using a quality mineral-based oil for break-in purposes. As a general rule. On street setups, the rings should seat within the first three or four times the engine is brought to temperature. After the rings have seated, change to a synthetic. It is not recommended to break in an engine using synthetic, as the film strength of the oil may not allow proper seating of the rings.
     
  20. 4xcrazy

    4xcrazy 3/4 ton status

    Joined:
    Oct 31, 2003
    Posts:
    9,472
    Likes Received:
    5
    Location:
    Olympia/Lacey, Washington
    wow, i really hope he got his gear and oil setup figured out by now,,,,,, :doah:
     

Share This Page