Pilot bushing vs bearing

Discussion in 'Transmission & Driveline Topics' started by 76z28, Apr 15, 2019.

  1. 76z28

    76z28 Veteran Member

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    What are everyone's thoughts on these?
    I am going to a t56 magnum soon and want some input as there seems to be a lot of controversy over this.
    I will be using a quicktime bell housing and as much as I don't want to do it(because the engine will still be in the car), I will be dial indicating the bellhousing to ensure it is within the spec of .010" concentric alignment.

    What would be best in my situation?
    I am running a 489 mark iv big block.
    Also does anyone have a part number for either?

    Thanks!
     
  2. big gear head

    big gear head Veteran Member

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    You should be OK to use the bearing with that transmission. I prefer the bushing, but there are a lot of bad bushings out there, so you have to be careful. I'd try to get it within .005 or less. .010 seems like a lot to me. I got mine to .002. and perpendicular within .0015.
     
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  3. 76z28

    76z28 Veteran Member

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    Do you know of a decent roller bearing?
    The manufacture recommends .010 total, or .005 on each side. I am going to shoot for less, but we will see. I would rather run a sealed bearing, but don't know what I should be looking for.

    What is parallel alignment?
    Is that the bellhousing face measurement relative to the block?
     
  4. big gear head

    big gear head Veteran Member

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    You might see if the GM roller bearings will work. There might be one of them that will fit your crankshaft.

    Perpendicular would be the face of the bell housing to the crankshaft center line. Set up a dial indicator on the rear of the crank and measure the face of the bell housing where the transmission bolts on. Turn the crankshaft and see how far out this surface is. If this is out then your transmission may develop problems. You can correct this with shims between the bell housing and the block. This is as important as the concentricity of the hole and should be fixed before checking the hole.

    These things matter more with the newer transmissions that have tapered roller bearings than they did with the old transmissions with ball bearings.
     
  5. 76z28

    76z28 Veteran Member

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    I see.
    Where can I buy shims to resolve if it is out of perpendicularity with the crank?
    I will see about a roller bearing that will work and go from there.
    I have read many horror stories about it.

    What is the benefit of a roller vs a bushing?
     
  6. big gear head

    big gear head Veteran Member

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    Jody's Transmissions has the shims. If you are worried about the bearing then just use a good bushing. Jody has those too.
     
  7. Jeep43

    Jeep43 Veteran Member

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    I don't see the benefit of the bearing over a simple bushing.

    I use a quicktime bell on a mustang application and it dialed in within specs out of the box. They are nice pieces.
     
  8. big gear head

    big gear head Veteran Member

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    Quick Time is probably the best. The Lakewood can be a real pain to get dialed in.
     
  9. C4Racer

    C4Racer Veteran Member

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    I just did this. Took several steps and it’s not easy to do even with the engine on a hoist. I would seriously pull the motor. Unless you have a lift. Then maybe it’s ok to do in the car. Pulling the motor is a few hours. I spent way more time than that messing around with alignment.

    Do parallel first. I didn’t and it then once I dialed that in the concentric moved a lot and I had to remove and re-orient the dowel pins. Twice.
    And my parallel was only off .008 to start and I used .005 shims. McMaster Carr. Paper thin.

    I ended up with .001-.002 parallel and .008 total concentric. Best I could do with standard dowel pins. I didn’t think it was worth chasing the last few .001.

    I used a QuickTime. Recommend it. It’s expensive but worth it. Tap the trans mount bolts all the way thru before you try mounting the trans. They don’t clean up the powder coat very well. I stripped a bolt for the adapter plate for alignment - which I also recommend. Worth the $80.

    Anyway I had that bellhousing and flywheel on and off more than half a dozen times and did a trans mock up once before doing it on the car. I couldn’t imagine doing all that laying on my back under a car. Unless it’s on a nice lift. Then maybe.
     
  10. big gear head

    big gear head Veteran Member

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    I'm doing this in the car right now. I made my own .014 offset dowels and I cut a 1/2 inch hex on them so that I can use a socket to turn them without pulling them. I also made shims. I have it within .0015 perpendicular and now I'm working on concentric. My helper hasn't been available to turn the crankshaft for me, so I haven't been able to finish it. This is much easier with the engine out of the car, but it can be done in the car.
     

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