I thought pushrods were supposed to be straight??
08-27-2011, 03:21 PM
#21
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instead of the pushrods taking the initial hit from the motor over reving then the motor holds and transfers the torque hit through the main shaft, hurting your main shaft and bearings. the main shaft my be able to take the sudden jolt but the bearings cant.
think of it this way, you are going 90+mph in 3rd and shift to 4th, but accidentally hit second. 2nd gear is made to go to maybe 80mph...maybe, then you have 10mph that the engine can not compensate for. the motor will immediately got to 6200 rpms (redline) and stay there, and force the car to go from 90 to 80 instantly, locking up the rear end and putting a tremendous amount of force on the bearings that are trying to slow down the car so the motor can function. that is why the tranny is then the weak link. easiest way to prevent this from happening, get an aftermarket shifter. i have a Pro 5.0 and love it.
think of it this way, you are going 90+mph in 3rd and shift to 4th, but accidentally hit second. 2nd gear is made to go to maybe 80mph...maybe, then you have 10mph that the engine can not compensate for. the motor will immediately got to 6200 rpms (redline) and stay there, and force the car to go from 90 to 80 instantly, locking up the rear end and putting a tremendous amount of force on the bearings that are trying to slow down the car so the motor can function. that is why the tranny is then the weak link. easiest way to prevent this from happening, get an aftermarket shifter. i have a Pro 5.0 and love it.
Last edited by raven154; 08-27-2011 at 03:32 PM.
08-27-2011, 05:29 PM
#22
This thread is sooo full of fail, good and bad.
I love the pushrod carnage! Those are some crazy pics
Dude the transmission can EASILY EASILY take the shock of a 3-2 downshift, or any downshift for that matter. You really think that is much pressure? How do you think that pressure relates to a 7k RPM clutch dump on slicks?? Do you seriously think a down shift is harder than slamming the clutch during an upshift or a launch? The bearings and gears will easily handle the forces applied to them. You said something about the speed of the gears...The gears don't give a **** how fast they are turning, they are made to spin and spin fast, they could handle a 6-1 downshift at 200MPH without a problem if you could get it into 1st, the rest of the car may explode though lol. And the bearings can also take immense amounts of load.
On a downshift the first weak link is the tires, they break loose, there is very little load on them when the weight shifts to the front of the car, which if the tires break loose they cannot apply enough pressure to the rear end or trans to break them. Next the motor redlines, and the valves float and hit pistons. The weak pushrods bend saving the vavles and saving the pistons. So hardened push rods would be bad in this scenario. Hardened pushrods would make the valves hit the pistons harder and break the heads of the valves of and end up going through the piston.
I love the pushrod carnage! Those are some crazy pics
Dude the transmission can EASILY EASILY take the shock of a 3-2 downshift, or any downshift for that matter. You really think that is much pressure? How do you think that pressure relates to a 7k RPM clutch dump on slicks?? Do you seriously think a down shift is harder than slamming the clutch during an upshift or a launch? The bearings and gears will easily handle the forces applied to them. You said something about the speed of the gears...The gears don't give a **** how fast they are turning, they are made to spin and spin fast, they could handle a 6-1 downshift at 200MPH without a problem if you could get it into 1st, the rest of the car may explode though lol. And the bearings can also take immense amounts of load.
On a downshift the first weak link is the tires, they break loose, there is very little load on them when the weight shifts to the front of the car, which if the tires break loose they cannot apply enough pressure to the rear end or trans to break them. Next the motor redlines, and the valves float and hit pistons. The weak pushrods bend saving the vavles and saving the pistons. So hardened push rods would be bad in this scenario. Hardened pushrods would make the valves hit the pistons harder and break the heads of the valves of and end up going through the piston.
08-27-2011, 08:39 PM
#24
You have no idea what you are talking about... The motor will easily go over 6200 rpm, because that is fuel dependant rev limit, the engine will still over rev. You arent locking **** up from 90-80 instantly, and the trans will hold it easily, the valvetrain probably not so much...
If you were racing, chances are you are at 6000 or so before you shifted, which means the motor will see ~8100rpm if the clutch doesnt slip and no speed what so ever is lost.
If you were racing, chances are you are at 6000 or so before you shifted, which means the motor will see ~8100rpm if the clutch doesnt slip and no speed what so ever is lost.
08-27-2011, 10:32 PM
#25
Next the motor redlines, and the valves float and hit pistons. The weak pushrods bend saving the vavles and saving the pistons. So hardened push rods would be bad in this scenario. Hardened pushrods would make the valves hit the pistons harder and break the heads of the valves of and end up going through the piston.
08-28-2011, 01:29 AM
#26
Wow the amount of bs info in this thread is ridiculous lmao I dare any one of you to go and do a misshift from 2nd to 1st at the drag strip and see what happens. I'm sure the pushrods will cushion the hit 
you will grenade your t56 my friend and if you're lucky there won't be any engine damage from over revving. SMH
you will grenade your t56 my friend and if you're lucky there won't be any engine damage from over revving. SMH
08-28-2011, 05:27 AM
#27
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Im gonna guess that the rear was on its way out to begin with, and when hit with the shock of being engine braked lokced it up. Meanwhile all that force had been transfered to the engine, spinning it to 8K+. And the trans was caught in the middle. between the rotational force of the engine, and the axle locked up and immovable.**
**This is complelety off the wall and should not be taken in anyway as a professional opinion. Nor a fully educated one.
08-28-2011, 02:56 PM
#29
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On the ls1 revving above 6500 the lifters can pump up and can cause valve float which can make a valve hit a piston bending pushrods. I highly doubt that downshifting from 4th to 2nd will break the transmission if you bend a pushrod. Corvettes that road race or autocross shift like that under extreme conditions and are fine.
08-28-2011, 05:22 PM
#30
The way you worded it earlier made it sound like you were saying the high RPM caused the damage, if that were the case high revving engine cars would blow transmissions everytime they drove. The wheel hop thing does make sense however.
08-30-2011, 05:37 PM
#31
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Putting aside the different merits of missed shifts and resulting damages, I pulled the other valve cover and luckily this was the only bent pushrod. I rounded up a spare one and replaced the bent one and put it back together. After a warming up at idle for a little while it was running pretty good but the Check Engine light was still on. Took it for a short cruise and rechecked everything and then checked the codes. P0300 random misfire and a knock sensor code were in history. Cleared those out and drove around some more and the light didn't come back on. Woo hoo!
It's running pretty good now. I guess I got lucky and this was the extent of the damage (so far). I'll drive it around for a little while as a daily driver and take it from there.
It's running pretty good now. I guess I got lucky and this was the extent of the damage (so far). I'll drive it around for a little while as a daily driver and take it from there.
08-30-2011, 06:01 PM
#32
So that makes you an expert? Im quite sure I have alot more knowledge on the subject than you. Wheel hop probably was what broke your ****, ive missed gears and had tons of **** break over the years and have worked on a ton of these cars. You will not destroy your inputshaft bearings from a downshift. Was your pilot bearing destroyed? You still havent commented about the rpm, your motor will not hang at 6200 rpm and lock the rear, i can tell you that from personal and professional experience.
08-30-2011, 06:12 PM
#33
Putting aside the different merits of missed shifts and resulting damages, I pulled the other valve cover and luckily this was the only bent pushrod. I rounded up a spare one and replaced the bent one and put it back together. After a warming up at idle for a little while it was running pretty good but the Check Engine light was still on. Took it for a short cruise and rechecked everything and then checked the codes. P0300 random misfire and a knock sensor code were in history. Cleared those out and drove around some more and the light didn't come back on. Woo hoo!
It's running pretty good now. I guess I got lucky and this was the extent of the damage (so far). I'll drive it around for a little while as a daily driver and take it from there.
It's running pretty good now. I guess I got lucky and this was the extent of the damage (so far). I'll drive it around for a little while as a daily driver and take it from there.
So that makes you an expert? Im quite sure I have alot more knowledge on the subject than you. Wheel hop probably was what broke your ****, ive missed gears and had tons of **** break over the years and have worked on a ton of these cars. You will not destroy your inputshaft bearings from a downshift. Was your pilot bearing destroyed? You still havent commented about the rpm, your motor will not hang at 6200 rpm and lock the rear, i can tell you that from personal and professional experience.
haha 