1. J Body Driver

    J Body Driver Member

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    Just finishing my winter up grades. Rebuilt rearend (8.25) suregrip put in new Spicer clutch pack and 3.55 crown and pinion gears. Put new Radial TA's 275/60R/15 on rear. This car is a original E58 so it has a 727 tranny. Questions is.......Took car for test run and speedo is way off, how many tooth speedo gear do it need to fix problem? Thanks
     
  2. 4speedjim

    4speedjim Well-Known Member

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    Theres dozens of graphs online to give you the right count by gear and tire size. It will be around 33.
     
  3. BudW

    BudW Moderator Staff Member

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    Your vehicle should have been built with either 205/75R15 or 215/70R15 tires. Your door jamb sticker would say for sure.

    205/75R15 have a diameter of 27.11 inches (688.5 mm)
    215/70R15 have a diameter of 26.85 inches (682 mm)
    275/60R15 have a diameter of 27.99 inches (711 mm)

    I really need to know which tire size came on the car to begin with.
    Also, I need to know what previous gear ratio was.


    I have a suspicion you will have a hard time trying to find the correct plastic replacement speedometer gear – once the tooth count is determined. Finding an older metal/plastic gear will be fairly easy – but that would require replacing the existing speedometer cable, speedometer gear housing and gear, as an assembly.

    Getting a gear a tooth larger and smaller, is helpful, to dial it in.
    Then you can sell the gears you don't use.
    BudW
     
  4. 4speedjim

    4speedjim Well-Known Member

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    Theres long and short shaft also. Ones electronic, the other analog. I don't remember which is which or the years they switched. Id guess the short ones are for the electronic speedo, to make room for it. I bet Bud knows.
     
  5. BudW

    BudW Moderator Staff Member

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    In 1988 (I believe), The Dodge truck family (pickups, vans and Dakotas) had a new sensor added for the fuel injection system – the VSS (Vehicle Speed Sensor). What Dodge did was add a screw-on sensor between the speedometer cable and metal speedometer gear housing. The cable nor the housing was changed and part is fairly easy to change.

    Matter of fact, if you needed to add a vehicle speed sensor (VSS) to your Mopar, this is an easy way to do so (for fuel injection, or whatever).
    The VSS sensor part number is 5233152.

    There is another location to place an “in-line” VSS and that is at the cruise control servo. That part number is 4439097. It matters not what direction the VSS spins (so it can attach to either cable). There are also a few different versions/styles of this one.


    In, 1990 (I believe), Dodge did away with the speedometer cable altogether – going with an electric speedometer head. The electric speedometer head (in trucks) was not the most reliable part Dodge has used, before. The VSS sensor looks close to the same sensor (above), for it still screws to outside of the metal speedometer gear housing – but sensor does not have a provision for speedometer cable to attach to it, any more.
    Again, the metal/plastic speedometer gears are still the same Chrysler has used sense 1966.

    In 1993, the system changed. The speedometer housing hole is still in transmission and still being used, but the sensor changed drastically and Dodge started to use a short (metal) shaft version of the speedometer gear.

    The short shaft gears are found in most (older) transfer cases (4x4’s) and is commonly used in Jeeps (as well as the ’93 and up truck speedometer gears).

    The Jeep community has made aftermarket short shaft gears – just the same way that the muscle car community has made the long shaft gears aftermarket.
    The long shaft housing is still a far more popular part to locate.
    The plastic gears/plastic housing gears has zip, zero, nada support so our gears are very hard to find – especially for those who do don’t use the more popular gear sets (aka: the 2.2, 2.4, 2.6 & 2.8 differential gear ratios. Red means harder to find).
    Matter of fact, I just now performed a quick search on eBay for a plastic speedometer gear and only found 1 (one) plastic gear vs. 1,040 older style steel/plastic gears.

    Examples of long shaft gear, a short shaft gear (Jeep) and a typical FMJ gear (in order):
    Long Shaft.jpg
    Short Shaft.jpg
    Plastic.jpg
    Note: I wish I had that collection! All pictures stolen from eBay.

    VSS pictures (for reference)
    VSS.jpg
    VSS b.jpg
    I couldn't find a picture of the '93 design - but have one in my garage, somewhere. It has a plastic housing (like the older geared housings), has same electrical connector but also has speedometer gear on other end.
    BudW
     
  6. volare 77

    volare 77 Well-Known Member

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    I have a new green 34 tooth gear for sale here on the Parts for Sale section.
     
  7. 4speedjim

    4speedjim Well-Known Member

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    79-86 gm truck 4 speeds use the same (I believe) speedo gears from our 883 OD.
     
  8. BudW

    BudW Moderator Staff Member

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    I know GM did use the A833 w/OD for several years – but I’ve never seen one, so can’t comment.

    A lot of ‘60’s-‘80’s Dodge truck 4-speed transmissions and GM manual transmissions were built in same plant. Somewhere in the ‘90’s (I think – going by memory), Chryslers New Process transmission plant merged with GM’s Muncie plant to form New Venture transmissions (which went belly up about a decade ago, or so).
    A lot of GM and Chrysler (bigger) manual transmissions share tons of parts.

    Currently, GM and Chrysler are designing a 10-speed automatic transmission together, that each company will use when ready.
    BudW
     
  9. 4speedjim

    4speedjim Well-Known Member

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    The case and gears are the same. The cover and forks are the same. The tail, input shaft bell bolt pattern differ. A rebuild kit, bearings seals shims shafts are all the same. I don't think it wise to attempt putting the gm in a mopar and vis versa, but internally theyre identical.