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  1. #1
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    Question about 2.5 Diffs and the 3.3 Diffs 2 Screw 4 Screw and Indentification?

    Hello again, So I have one Truck that is a 2.5 and one that is all 3.3 (Upgraded all except engine) and I was looking at my Diffs on the 2.5 which have 2 Screws holding the cases together where mine have the 4 screws then I seen online a set of 2.5 Diffs that have 4 Screws holding the cases together. What other Identifiers would seperate the sealed 3.3 diffs from the non sealed 2.5 diffs since it appears the newer 2.5 now come with 4 screws in the cases?
    I just want to make sure I have the Sealed Cases and not the 2.5 cases unless the newer 2.5 cases are sealed to and just a Upgrade to the 2.5 T-Maxx.
    Is there any way to tell them apart now without havung to Dissassemble them?
    I know the 3.3 Sealed Diffs have A seal on the Diff Carrier along with Special Seals where the axle shafts go through the carrier part internally which the Older 2.5 Diffs did not but I do not really want to open them up that far just to look at the parts.
    I have noticed my diffs are quite free as far as resistance from left to right wheel so I may be wanting to run thicker Silicone oil in it.
    I have seen so many different Thicknesses in Gear oil SOme are in wt. some cps. how is one to convert say 500,000 cps to a Normal wt oil we are all familiar with? is 500,000cps similar to say 500wt or would it be more like 50wt? and what is a decent gear oil to get a really Stiff almost posi like rear end but still allow the vehicle to be able to turn?
    I do not want to Spool it but I want to get a Nice stiff Diff. Right now it acts like I am running no Gear lube at all it is Quite Free in my 3.3 Truck where my 2.5 actually is quite stiff as far as Left to right but Spins nice and free from the input shaft which is almost exactly what I want on my 3.3 but I have no way to explain or show you this via the forum.

  2. #2
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    Sounds like you have the pre-2002 unsealed diffs.
    In 2002 the diff case was changed from 2 screws to 4.
    So it is possible to have an unsealed diff in a 4 screw diff case.

    From 1999 to 2007 the diffs were the same internally, regardless of engine size.
    Unsealed carrier/pinion,with no gasket, and filled with grease
    .
    In 2008 the 3.3 Maxxes (like the 4908 for example) were issued with sealed diffs.
    I dont believe the 2.5 4910 model ever had sealed diffs, But they do have 4 screw diff cases like 3.3

    The best way to identify what you have is to open up your diff and see
    if you have oil or grease in them and a rubber seal. You can also indentify through bearing size.
    The pre 2008 diff cases use 10x15 bearings while the 2008 and newer have 8x16 bearings.

    So if your looking for sealed diffs, order the 3.3 diffs, not the 2.5's.
    Bash, Crash, Upgrade, Repeat..

  3. #3
    RC Turnbuckle Jr. Nitronaught's Avatar
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    +1 ^^ Excellent info as always NitroTrout!!!!!

    Cudos!
    Founder of H.U.A.
    Hop Ups Anonymous

  4. #4
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    <---Humble student with great teachers. Thanks Nitronaught! ::salutes::
    Bash, Crash, Upgrade, Repeat..

  5. #5
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    Thanks, ya I think the Original Diffs 2002 2 Bolt came with Both Trucks..
    I have the Newer Diffs (Post 2008 Non Sealed though) in the 3.3 which are the 4 Bolt ones with Shiny Phillips Head screws not the Black Hex Head ones, Now Out of Curiosity since I have the Post 2008 4 Screw Diffs and I am sure they have grease not oil internally can I get the Seals, Carrier, X-rings, Gaskets, etc and Then clean up the Ring-Pinion and the Spider Gears free from grease then fill up the Carrier with Proper wt. Silicone Oil or do I need to Buy completely new ones?
    BTW the Sealed 3.3 Diffs does the Silicone run throughout the Diff (Ie ring-Pinion) or does it just stay specifically in the carrier Spider gear assembly itself, I ask as I noticed in the Explosion View it appears there are X Seals ( I think they call them that) along with a Seal between the carrier and the Ring which appears to seal the carrier from the ring-Pinion area.
    Actually I do not think complete 3.3 Diffs are that Expensive from what I have found and I think it would actually cost more to get the Seals and Oil not to mention time involved to clean and re assemble them.
    Maybe the Rebuild as sealed 3.3 Diffs would be an Idea if I wanted to have a Set as Backup in case I blow one up or strip one out etc.
    Last edited by spudler_t; 11-16-2012 at 10:37 PM.

  6. #6
    RC Turnbuckle Jr. Snook Man's Avatar
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    You can not add the X-ring seals to the older style diffs because there is not enough room inside the spyder gear cup. The sealed diff use a different design on the ring gear, it has a recess machined into it to allow extra clearance for the pinion x-ring seal and the spider cup has a deeper recess to allow for the other pinion seal. If you add the x ring seal to the old style cup and ring gear they act as a thick shim would and cause the spyder gears to bind terribly. As with most all sealed diffs the diff oil/lube only goes in the diff cup with the spiders. The ring and input beveled pinion just use any standard grease of your preference.
    No slipper/tall gearing/power = broken parts.

  7. #7
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    @Snook Man Wow again you have Helped me with a Question, When I mentioned Carrier I was talking about the Unit the Spiders are held in with, but great to know Ring is different too. looks to me be much easier and cheaper to find a Set on-line and just buy them all ready to go.
    Thanks to for the info about the Silicone Oil, I have not actually found any articles showing or explaining how to swap out different weights to modify the amount of Diff Slip so I was not sure about if the entire diff was filled withtheh silicone or not although I was leaning towards only the Carrier being filled as I noticed the X-Seals look to seal that section fromtheh rest of the Diff whichwouldl not be needed nor wanted if the entire diff was filled.
    By Chance could I get Some opinions on what Weight of Lube People use in there sealed diffs (if changed from stock) and how much does it seem to Stiffen up. I am a real fan of Stiff rear-ends had a Mopar and a Firebird and Spooled booth, did not like the way it would sometimes pull to one side on hard take-offs which I find my T-Maxx does something quite terrible, always to the right too.
    I have seen I believe 10K,20K,50K,100K,500K Weight Diff oils and was thinking that is such a huge range from 50K-500K Is massive in Viscosity Terms, so I kinda wanted an Idea as I would just because get the 500K and use it but maybe that may be way to thick and keep the truck from turning at all, I mean heck I could just Spool it if i wanted Turning problems.

  8. #8
    RC Turnbuckle Jr. Snook Man's Avatar
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    For general all around use in a stock TMaxx I like somewhere around 30K in front and rear. 500K in the diffs will tighten them up considerably and like you said they will tend to pull to one side with hard acceleration and at the shift point.
    It’s best to have a few different wt diff oils on hand to experiment with if possible.
    No slipper/tall gearing/power = broken parts.

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