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Thread: definitive answer on gearing for our trucks ... (i'm a noob and dont understand it)

  1. #1

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    definitive answer on gearing for our trucks ... (i'm a noob and dont understand it)

    OK I'm still searching on this but again I'm at a loss... here is the info from this site


    All trucks 79-96 came with what Mitsubishi would call a 8 inch differential in the rear

    GEAR RATIOS
    D50/MMs came with 3 different possible gearing options
    3.545 used in certain 2 wd trucks let you achieve optimal fuel mileage
    3.909 most common gear ratio used in about our trucks most 4 X 4 came with them for sure
    4.222 rarely seen in the D50/MMs only seen so far in 4 X 4 so far primarily seen in Dodge Raiders/Mitsubishi Monteros
    4.625 never came in the trucks only seen in the Monteros/Raiders swaps into our housings

    LIMITED SLIP DIFFERENTIALS & IDENTIFICATIONS OF THEM
    LSDs or different gears can be swapped out of various vehicle depending upon which diff you have if you have the 7.5in diff a rear diff
    out of any FOUR CYLINDER MM/D50, Montero/Raider will work

    If you have a LSD factory you will have an orange sticker in the door jam and on the differential housing its self talking about the use of LSD additive inside of that housing If you cant find those stickers but still wanting to make sure you do or don't have an LSD you can jack the back of your truck up and spin one wheel then watch the other side to see if it spins in the same direction

    Now if you have a 4 X 4 MM/D50 the rear differential out of a Starion/Conquest will work Starions 1983-1987 (1986/87 wide-bodies all came LSD, narrow-bodies with LSD are more rare) used a 7.5" diff, which will work in the FRONT of a 4cyl truck/rig. Starions 1988-1989 used a 8.0" diff, which will work in the FRONT of a V6 truck/rig. (thanks Robert) If you have a V6 powered truck any first gen Montero/Raider with a V6 will change differentials with your trucks 2nd generation Monteros wont work with the 8in housing available in our trucks I was told the Monteros have a high pinion design compared to the trucks low pinion design

    ---keRby
    mopar_1986_power_ram50


    The Starion LSD from years 83-87 will fit the front diff of the 4cyl MM/D50 trucks/Monteros.
    The Starion LSD from years 88-89 will fit the front diff of the 6Cyl MM/D50 trucks/Monteros.

    The Montero LSD from 83-89 4Cyl will fit the 4cyl MM/D50 trucks rear diff.
    The Montero LSD from 89-91 6Cyl will fit the 6cyl MM/D50 trucks rear diff.

    Not all early Starions had LSD, special order and 85.5.
    All wide-body Starions had LSD.
    Not all Montero's had LSD, check for orange sticker inside drivers door jamb.

    Kane
    MainstreaM


    just to clarify no truck or monty has a 7.5" rear diff.only the front is a 7.5".the rear is a 8".the 4 banger monty and the v6 has a 8" rear for the gen 1.the early years 7.5" starion lsd can be swapped into the front 7.5" diff,with a spacer.



    so I read this.. a few times and I'm just dumbfounded by it... I did the formula 336 x 60 x 3.909 / tire = rpm to work out differences in tires and rpms using different gears.. coming to conclusion that the 4.625 should do pretty decent in my 2.6 4x4 with 33" tires...

    OK... now the info I'm completley lost on is what I need.. I hear the words... "gears" "ring and pinion" "differential" "gear set" "pumpkin" blah blah blah ....


    All I want to know is what to buy .. I think from alllll the reading that it HAS to com from a 4 cylinder montero

    "The Montero LSD from 83-89 4Cyl will fit the 4cyl MM/D50 trucks rear diff."

    ... I've not found a single 4cylinder montero with an lsd and these gears??

    and... not a single thing is mentioned about front gears except lsd from the cars... I just want the gears so I can use 33" tires without killing to truck... lsd in the rear would be nice but up front I don't really care.. I'll occasionally play in some mud nothing too major...

  2. #2



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    OK: Ring and pinion. They are a mated set and can never be used 1 with out the other one. They are never replaced 1 at a time. Always as a set. Otherwise they will self destruct.
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    The drop out. That is the part you see bolted to the differential housing and holds everything in place.
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    Carrier. That is the part that holds the differential gears and ring & pinion.
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    Spider gears, AKA the differential. That is why when you turn one wheel one direction the other one goes the other way. With out it you will have axle bind when turning a corner. When going around the corner the outside tire must travel further then the inner one.

    Click image for larger version. 

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    Pumpkin. The bulge in the rear housing.
    I hope this helps. But You can find more on the workings in the manual section, under UTI training manuals. It's good info to scan through.
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  3. #3

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    So only a LSD out of a 4cyl montero will work in my 4cyl pick-up?

    Could somebody please explain why the 4cyl and 6cyl are different if they all have the same mitsu 8 inch differential?

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    I believe you can use the diff from either from what I can decipher from the info. Says they both had the same 8" rear end.
    Josh
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  5. #5

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    I'm wondering this too since all the gears I wanted I've only found from the 6cyl

  6. #6

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    The V6 trucks have a bigger differential i think it's a 9 inch housing vs 8 inch for the 4cylinder trucks, the 4wd drive have a 8 inch housing in the front v6 or 4

  7. #7



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    The 6 cyl monteros with the 4.625 gears are a 9" diff in the rear - the lowest gears(highest numerically) available for the 8" rears are a 4.22 set - found in 1 ton 2wd and some v6 pickups. If you swap the rear gears, you will also need the front diff 4.625 gears, or 4.22 if from the v6 truck.
    Pennyman1
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    Living the D-50 lifestyle since 1980

  8. #8

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    Alright well then Im 100% lost. Using gearing calcs. I saw 4.625 as the best for a 33"

    What should i get then? 4.222 but where and what would i use up front

  9. #9

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    To keep it short and sweet i have a 2.6 5-speed in a 1989 4x4.ram 50. i want to put on 33" tires. what gears can i get to keep it from being bogged down and what vehicle / year and engine size can i get the front and rear gears from.

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