Bellhousing dowel pin issue

Discussion in 'Transmission & Driveline Topics' started by 1934chevycoupe, Jul 16, 2021.

  1. big gear head

    big gear head Veteran Member

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    I got my Lakewood bell housing within about .001 perpendicular with the crank and run out within .004 total. I had to put a .010 shim under the bell housing in 2 places to get it right and I made my own offset dowels to get the run out where I wanted it.
     
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  2. badazz81z28

    badazz81z28 Veteran Member

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    Hardly nobody checks parallel alignment, concentric is good enough according to many. It's telling that Jody is the only place that I have ever seen to offer shims for it. Not saying it doesn't help and to get perfection isn't required, but I think it's overkill and not necessary. You worry about the face of the bell to the block, but neglect the face of the transmission to the bell and in some cased the front/mid plate to the body of the transmission. Many flat surfaces that may not be exactly flat to each other. You are just going down a rabbit hole.
     
    Last edited: Jul 18, 2021
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  3. 1934chevycoupe

    1934chevycoupe Veteran Member

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    when i asked SST last week, they said don't worry about the parallel, but i can see where it would effect the centerline runout. i can also see where the face of the trans would also need to checked. where does it end? thanks for the reply
     
  4. Fbird

    Fbird Veteran Member Lifetime Gold Member

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    it doesn't.....ever....lol
    The more you CHECK = higher rate of success on the end product. Everything has an acceptable tolerance and still performs as designed....but you get 2 or 3 things OUTSIDE acceptable limits...your success % goes down. The goal might be to have no vibrations at 120 mph? Your going to be checking alot of things. Better yet.....no vibrations at 150 mph... Yeah your going to speed balance the rotors and the wheels and alot of other things.
     
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  5. mrluckies

    mrluckies Veteran Member Lifetime Gold Member

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    Having worked in design and production, I also don’t fully agree that the measurement is entirely necessary…if all parts are stock. especially with the newer stuff that has better manufacturing results.

    However, one reason it’s important to check runout is for when you have an engine block that had been line bored. When you do this, you usually machine a little material off the main caps and then install them on the block. Then proceed to bore the opening back into tolerance. This raises the crank centerline on the block slightly and will cause the runout to be off and the need for the bellhousing to be raised slightly. On my friends block, he was off and the bearing started to mark his input shaft.

    on older combinations, the factory used brass bushings in the crank instead of bearings. Brass bushings usually deal with slight misalignment better than roller bearings. I don’t think a roller bearing is entirely necessary here anyway. The input shaft is only spinning in the crank when the clutch is pushed in, so you’re not transferring any real load.

    also, I think those plates you can buy to check runout on a t-56 bell are not very accurate for this measurement. As mentioned, the tolerance stack between parts adds up. If the checking plate isn’t the same as your transmissions front plate, then you’re not getting an accurate reading. But most people don’t want to take their front plate off the trans to check it properly. The front plate is drilled and pinned to hold that alignment to the trans just like the bellhousing is “pinned” to the engine block. The checking plate doesn’t have this advantage. There’s a couple thou tolerance on all the bolt holes alone, maybe not .010, but again it all adds up. If you’re off 6 thou on the plate in one direction and 8 thou on the bell in the other, they cancel out and you’re only 2 thou off total. But if they are in the same direction, you’re now off by 14 thou. Older bellhousing alike for a Muncie, don’t have this issue as the hole is a circle on the bell.

    Again I do recommend checking, if for no other reason than the block might have been line bored. But I don’t think those checking plates make sense. At their price, there’s no way they have super tight tolerances like a real lab tool would have.
     
  6. big gear head

    big gear head Veteran Member

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    With the old Muncie and Borg Warner 4 speed transmissions this wasn't as important because they have a ball bearing in front. These bearings can tolerate the misalignment somewhat. The newer transmissions have a tapered roller bearing in front and these must run true or the bearing will be damaged. This is why it is more important to get the bell housing in line when installing a Tremec transmission. This will also help with quicker shifts when using the older transmissions.
     
  7. camarochevy1970

    camarochevy1970 Veteran Member

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    But to an earlier comment, you know there is no way the OEM's are taking those measurements on every car they build, and they are running the same design Tremec transmissions
     
  8. 1934chevycoupe

    1934chevycoupe Veteran Member

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    I asked SST that very same question, and was told that the OEM T-56's arn't as tight ( not their description ) as the aftermarket Magnums
     
  9. black_aerocoupe

    black_aerocoupe Veteran Member

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    A Tremec GM-application T56 Magnum is a TR6060 (with large front end bearing package; not all TR6060s are.)
    The OEM T56 can be built with pre-load instead of endplay at the different bearing shim positions. The bigger bearing package TR6060 vs. the small bearing package TR6060 and T56 is a rabbit hole discussion, frankly, which can't, and won't be addressed fully with a phone call to a kit vendor. And given you're not even fired up, it's not relevant here.

    If your bell, block, and pilot alignment are within tolerance, the "tightness" of the T56 or TR6060 is not an issue and you won't hurt the maindrive tapered bearing, nor the mainshaft pilot bearing. Unless of course your clutch pilot bushing/bearing is completely trashed and you continue to drive or abuse it.

    Did your original effort use a Tremec bellhousing for 98-02 LS1 F-body?
     
  10. badazz81z28

    badazz81z28 Veteran Member

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    Yeah, its called production line work...when you build cars on a production line, you know there will be some variance car to car and that will show up later under a warranty claim. The cost and time to check and verify each one is not worth the gain. Its better to just throw them together and if stacked tolerance is not in your favor, it will come in for repair...which Im sure is less than a percent. You can throw a T56 on a car all day long and odds are you will be just fine. I did it for years using the T56 on 4 speed bellhousings, but because to get 100% of the performance advertised, of the cost and time involved, a private owner is more invested to check and encouraged by Tremec. I have dial indicated all my bellhousings for the last 10 years and they have all been off little requiring correction. I also believe it is the engine...when I swapped my quick-time and magnum from the LS1 to the LS7, there was a big difference in the measurements requiring different off-sets. When you use a roller bearing and tapered bearings, you want it closer than you would with ball bearings and bronze bushings.
     
    Last edited: Jul 25, 2021

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