Why do tranny cases crack or fail?

Discussion in 'Transmission & Driveline Topics' started by sponge003, Jun 13, 2010.

  1. sponge003

    sponge003 Veteran Member Gold Member

    1,511
    1
    Jan 10, 2009
    Concord, NC
    Hey,

    Looks like my glide case is cracked, pulling tranny today and hope to have pics sometime soon.

    Question for the knowledgable tranny people here.........

    What are some of the reasons why a case would crack? I will be looking at things when I pull it and am looking for some areas to pay close attention to!

    Thanks

    sponge
     
  2. 1WILDZ

    1WILDZ Veteran Member

    1,320
    5
    Jun 14, 2002
    Rockland County, NY
    I'm going to say a bad vibration will crack a case
     
  3. sponge003

    sponge003 Veteran Member Gold Member

    1,511
    1
    Jan 10, 2009
    Concord, NC
    Didnt feel anything abnormal during runs or burnout when it happened.
     
  4. Cardinal

    Cardinal Veteran Member Lifetime Gold Member

    8,245
    13
    Jun 22, 2003
    Endicott, NY
    Things that can cause the case to crack:

    1) Internal transmission failure.

    2) Drive like vibration which usually (can) causes a blown driveshaft = broken transmission. JD, youngest son, broke three TH350 till I told him we had to fix what was wrong with his 83 S10 with a 350 SBC, TH350 and stock 7.5" 10 3.73 rear end. He had changed all of the bearings in the rear but the offending vibration was still there. We pulled a rear end out of our S10 parts pile, put that one in, problem solved. The truck has been in an "off road adventure" with the previous owner. We suspect tht it bent the rear end housing = created a vibration = blown drive shafts & transmissions.

    I had a vibration in a 12 bolt rear with new GM axles in it (replaced them because the previous owner ran it with bad bearings which put wear marks on the wheel bearing surface of the axles). The faster I went, the worse the vibration. While heading from the speed shop in Windor, NY back to home in Deposit, at about 80 to 90 mph the driveshaft parted company, broke the ears of the Muncie M20 and left a arched dent in the floor board where the driveshaft tried to come into the car. Took chunks of concrete out of Rt 17 too! Found that the bearing surface on the new GM axles had too large a radius between the bearing surface and the axle flange which cause the axles bearings to "sing". Got my money back and put as pair of used axles out of a totaled Chevelle. Problem solved.

    3) Solid motor and trans mount when the frame isn't tied together. Body of vehicle flexes twisting the enging and transmission. The weakest link is the transmission case = cracked case.

    4) Flexing the frame and/or body. Good friend of mine has an XR7 with a big HP small block Chevy in it. He broke the trans in half power braking it. Come to find out the XR7 has a four link suspension from the factory. The four link in effect bends the car in half front to back. Weakest link was the TH350 and it broke in the middle of the trans right where that checkerboard pattern is cast in the case.
     
  5. mrdragster1970

    mrdragster1970 Veteran Member Lifetime Gold Member

    .

    If it fails is one as mentioned.
    Usually those are obvious, windows the case and the bell is fine.

    A chassis issue is very very common with real cars.
    The motor, trans and chassis are all moving, if there is not enough give,
    something has to go, and it's usually the bell, or case near it.
    That's why a lot of us do not even bolt in the trans.
    Even with a poly or stock mount, there's not enough give with a flimsy car.
    The trans is not going to fall out, and the extra movement has saved many cases over the years.
    I've even see some guys not use a trans mount. I've never done that,
    I felt better with the trans at least sitting on the mount, even if it was not bolted in.
    I'm talking 7-8 second guys that don't bolt in the trans,
    so it's not some 15 second kid that don't know better.

    Find out what's going on, or upgrade to a race set up,
    and I bet your issue goes away.

    When you jack up a corner, does the car go up square??
    Flex is a bad bad thing when starting with a real car.

    .
     
  6. sponge003

    sponge003 Veteran Member Gold Member

    1,511
    1
    Jan 10, 2009
    Concord, NC
    Regarding chassis flex for my car

    Poly motor and tranny mounts
    Subframe connects welded in + solid body bushings
    when I jack up the car the whole side left or right will basically come up off the ground.

    Vibration never felt anything on any pass

    thinking when the $ is available go to a HD case and be done with it.

    keep it comin guys!!
     
  7. 79camaro2001

    79camaro2001 Veteran Member Lifetime Gold Member

    4,757
    0
    May 4, 2003
    Monroeville, PA
    Where did it crack is a good start on figuring out what cause it to crack.

    You never said where it cracked.
     
  8. 74RAT

    74RAT Veteran Member

    3,400
    0
    Dec 28, 2003
    ft. stockton,tx,usa
    here is one that sometimes isn't considered.
    pinion/front yoke angles. but,, i'm sure you've gone through all that already,, referring to complete drive line angle under load from crankshaft to pinion.
    anyway,, just some thoughts below not assuming anything.

    a u-joint is not really designed to be loaded when at an angle of more than about 3*-4*. it can set up a speed change or velocity change of the u-joint at the caps from the drive part to the driven part. which transfers to the yokes/shaft/pinion/axles,etc...... a vibration of sorts for sure.

    hence why they came out with the c/v or constant velocity joints for the front wheel drive cars where the front spindles turn way angled from the drive/half shafts. they don't change speeds during rotation at severe angles.

    it's like using a ball end type universal joint vs a u-joint type socket/ratchet drive adapter to tighten your fasteners. like on 3/8" drive or 1/2" drive ratchet tools.

    i went to the ball end type tools back in the early 90's. can use an impact on them too. just an example of them not binding at angles so bad.

    i'd with you and think you'd be feeling a vibration though. other than that,,, flex as mentioned. just thoughts. hope it helps.
    andy
     
  9. sponge003

    sponge003 Veteran Member Gold Member

    1,511
    1
    Jan 10, 2009
    Concord, NC
    I was trying to get the tranny out today to be sure where it cracked.

    Leak is between cooler lines and servo area.

    Tranny will not be out soon unfortunatly I am having vertigo issues for the last 3 weeks and now it happens only when I lay down. crawled under the car and the room went for a spin, I will have to wait to get it out until I can actually do the work without spinning around in my head.
     
  10. sponge003

    sponge003 Veteran Member Gold Member

    1,511
    1
    Jan 10, 2009
    Concord, NC

    I have not measured driveline angles yet as I have not really modified anything from stock other than cal tracs for traction, still multi leafs ect

    Dont assume I have done anything right at all!!!
     

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