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Auxiliary transmissions

Discussion in 'Heavy Haul Trucking Forum' started by m16ty, Nov 28, 2016.

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  1. Nov 28, 2016 #1
    m16ty

    m16ty Road Train Member

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    We've got a 1985 Mack RD822, E9 500hp engine, Mack 12 speed trans. We have acquired a Spicer 1241c auxiliary trans that we were going to install. The more research I do on this trans, the more I'm worried it won't hold up.

    The guy I got it from says it will hold up fine but I talked to TTC (the people that currently build this trans), they say I'm crazy but they also offered to sell me one that will hold up.

    Has anybody had any real world experience with the Spicer 1241 or have any idea of how much torque it would take?
     
    m16ty, Nov 28, 2016
    m16ty, Nov 28, 2016
    #1
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  3. Nov 28, 2016 #2
    51.50

    51.50 Heavy Load Member

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    If it has twin counter shafts, it will hold up. If it's a single counter shaft, it will not. A Mack Quadraplex transmission is a married main / auxiliary trans with triple counter shafts.
     
    51.50, Nov 28, 2016
    51.50, Nov 28, 2016
    #2
  4. Nov 28, 2016 #3
    noluck

    noluck Road Train Member

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    I have no clue, but I think the e9 only puts out 1450 to 1650 flbs. So I would think it woud. But again I have no clue or experience with either an e9 or a spicer aux.
     
    noluck, Nov 28, 2016
    noluck, Nov 28, 2016
    #3
  5. Nov 28, 2016 #4
    m16ty

    m16ty Road Train Member

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    It has the double countershafts.

    Yes, the torque rating is 1650 ft lbs on the engine but when you figure the output ratio of the main transmission, you end up with a possible 24,000 ft lb in low gear.

    The guy at TTC recommended a Fuller AT1202.
     
    m16ty, Nov 28, 2016
    m16ty, Nov 28, 2016
    #4
  7. Nov 28, 2016 #5
    truckdad

    truckdad Road Train Member

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    I had a 1241 in my 72 Pete. As I recall the 8341 single countershaft had an 830 lb torque rating. The 1241 has 1200 lb ft rating. The 1241 will do fine as long as you avoid abusing it in overdrive. Use direct when doing rough stuff or under as a second choice. Use OD when rollin empty or when using little power and minimal torque.
     
    truckdad, Nov 28, 2016
    truckdad, Nov 28, 2016
    #5
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  8. Nov 28, 2016 #6
    wore out

    wore out Numbered Classic

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    I would go with the fuller 1202. It's been moons ago before I started driving but we had a couple 13 speeds with the 1241 behind them. Wasn't a sturdy combination on either box
     
    wore out, Nov 28, 2016
    wore out, Nov 28, 2016
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  9. Nov 28, 2016 #7
    51.50

    51.50 Heavy Load Member

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    24,000?
     
    51.50, Nov 28, 2016
    51.50, Nov 28, 2016
    #7
  10. Nov 28, 2016 #8
    m16ty

    m16ty Road Train Member

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    Yes. Engine max torque (1,650) times main trans low gear ratio (14.44:1) equals 23,826 ft lbs of torque on the input shaft to the auxiliary.

    Now this would require being hooked to a darn near immovable object, main trans in low gear, and engine reved to max torque rpm but it is theoretically possible.

    The good part is, even a 1880 driveline isn't good for that much torque so you'd probably ring out the driveline before something else broke.
     
    m16ty, Nov 28, 2016
    m16ty, Nov 28, 2016
    #8
  11. Nov 28, 2016 #9
    M_T_Noggin

    M_T_Noggin Bobtail Member

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    If we are on the subject of aux trans I will tell you of my experience with them. I worked in a shop where we looked after off highway log trucks. We repowered some trucks from Cummins 903 V8's to 12V71's. The trans were updated to Spicer SST 6 mains and 1241 aux. When they went to work all off them experienced transmission failure's. Spicer sent a fellow from Los Angeles with his tools and lots of parts. I was delegated to help him remove and update the trans, and I will never forget what he told me. He said the trucks were leaving the top of the mountain, using an engine brake or retarder, and the torque from the weight of the load coming from the back of the trans to the engine/retarder was causing the problem. These trucks were on the jake or retartder for miles down a steep mountain road. They kept changing the lube specs until they ended up with 30 w. engine oil for the aux. After his updates there was no problems. I personally ran RT 12510/ 1241 aux 400 cats for years with no problems.
     
    M_T_Noggin, Nov 28, 2016
    M_T_Noggin, Nov 28, 2016
    #9
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  12. Nov 29, 2016 #10
    Mack427

    Mack427 Medium Load Member

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    I'm surprised you need the aux box behind the 12spd they have a stupid lo hole and reverse in compound low, it pretty much comes with a aux trans bolted on the front end
     
    Mack427, Nov 29, 2016
    Mack427, Nov 29, 2016
    #10
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