4l60e cracked case for 3rd time

[Hipster]

It just seems the 2 are so far apart that's a bit of a reach. Have either of you seen this before? The poly trans mount still has some give.

.... and the engine and trans are bolted together as one piece. They either need to float together or mounted solid together. There's plenty of info all over the net. Visit some racers forums.

Yes, I have seen it albeit in hot rods that have transmissions that have long tailshafts like a Mopar 904 or 727 automatics or an 833 4 speed.

Mount all three locations with similar materials. If you lock the trans down tight and have sloppy engine mounts when the engine torques over under throttle you're twisting the trans case. Yes, damage is more prevalent when you introduce hard hitting shift kits or launching off a clutch dump.

 

[Supercharged111]

I guess when you consider the narrow span of the trans mount and making it more rigid it makes sense. All but my Camaro has stock motor and trans mounts, and the Camaro has poly on both ends. I just haven't seen any threads in my time of folks complaining about wrecking trans housings with rubber motor and poly trans mounts.

 

[thinger2]

Did they whack the trans mount together with an impact each time?
Never use an impact on a trans mount.
Dont know if that is the problem but it can cause case cracks and thread pulls and uneven torque loading.
Might be worth a look.

 

[El Tigre]

Trans case is aluminum with one mount. Poly engine mounts won't break an engine block.
Re-read Hipster's post above....

 

[stutaeng]

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i didnt take pics before i tried to jb-weld the crack its wraps around the top and gos from driver to passanger side mount seems to be good also does anybody have the part number for that adapter between the trans and transfer case?

Can't really see the last photo, but aren't poly mounts like really colorful and/or glossy? Yours does not look like that. Here's an article that talks about possible causes:

https://www.autoserviceprofessional.com/articles/5865-cracked-gm-tranny..."A cracked or broken transmission case is most often the result of abnormal external torsional forces acting on the transmission case."

I'm trying to picture in mind what this means, LOL.

You said you had a different engine and transmission already installed, so those are not likely the cause. You said you had the transfer case looked at also...(but still a slim chance any of those 3 items could still be it!)

You said you replaced the wheels at some point, right? Was that before you discovered the crack? Maybe get those checked for balance? I'm assuming you got it aligned after the torsion bar cranking? Are any of the mounts (engine and tranny) original OEM (like from a junkyard?) or new aftermarket? I've heard here members say the new aftermarket Chicom mounts are junk...

So that's only leaving driveshafts, frame and rear tranny crossmember. May be worthwhile to take it to a reputable shop and get the entire suspension inspected. U joint wear is fairly common. Maybe do a carfax to see if you discover anything the PO didn't disclose?

I wonder if whatever anomaly you are having caused the engine to wear out? Knocking? Not sure if that's possible...

I hope this helps.

 

[red98]

Can't really see the last photo, but aren't poly mounts like really colorful and/or glossy? Yours does not look like that. Here's an article that talks about possible causes:

https://www.autoserviceprofessional.com/articles/5865-cracked-gm-tranny..."A cracked or broken transmission case is most often the result of abnormal external torsional forces acting on the transmission case."

I'm trying to picture in mind what this means, LOL.

You said you had a different engine and transmission already installed, so those are not likely the cause. You said you had the transfer case looked at also...(but still a slim chance any of those 3 items could still be it!)

You said you replaced the wheels at some point, right? Was that before you discovered the crack? Maybe get those checked for balance? I'm assuming you got it aligned after the torsion bar cranking? Are any of the mounts (engine and tranny) original OEM (like from a junkyard?) or new aftermarket? I've heard here members say the new aftermarket Chicom mounts are junk...

So that's only leaving driveshafts, frame and rear tranny crossmember. May be worthwhile to take it to a reputable shop and get the entire suspension inspected. U joint wear is fairly common. Maybe do a carfax to see if you discover anything the PO didn't disclose?

I wonder if whatever anomaly you are having caused the engine to wear out? Knocking? Not sure if that's possible...

I hope this helps.

Take truck to local bodyshop, pay $100 to put it on the frame rack and make sure its straight, that would eliminate frame as a possibility. No clue how a tweaked/bent frame would cause 3 tranny cases to crack but if the frame is suspect get it checked.

 

[Hipster]

Can't really see the last photo, but aren't poly mounts like really colorful and/or glossy? Yours does not look like that. Here's an article that talks about possible causes:

https://www.autoserviceprofessional.com/articles/5865-cracked-gm-tranny..."A cracked or broken transmission case is most often the result of abnormal external torsional forces acting on the transmission case."

I'm trying to picture in mind what this means, LOL.

.

It goes along with what I mentioned about sloppy engine mounts and a super tight trans mount not allowing the trans to torque over and move with the engine when you hit the go peddle. In that case, the trans case is trying to absorb and take that torsional force. Eventually you'll find the weak spot. Flex an aluminum casting enough times and it will eventually fail. I didn't look at the photos closely, or saying that it's definitely the issue, but something to look at and poly mounts can be black.

He did mention it was cranked. Some say they ride ok that way or "It's not that bad" and some of us know once you pass and inch and a half or so the truck rides like a jackhammer. Riding down the road impact after impact with that energy being transferred to components of the truck. The Op needs to be honest with himself here on what cranked a little, not really beating on the truck, etc. is.

After 3 trans cases you can conclude the trans case is a symptom, not the problem, and I'm sure getting pretty expensive. I also mentioned vibration because when you have the same repeated failure something else is usually at play and harmonics and vibration can be extremely destructive.

 

[VictoryRedK1500]

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this is how the truck sits. new wheels and tires....but the stock wheels and tires where on when the original trans cracked.. i talked with a local speed shop and they seem to think that it could be the driveshaft. but they dont work on trucks(a policy they have) i forgot to mention that i noticed the crack after i got off the interstate. we normal drive the wifes car on trips just to save gas. but that day she was not around and off i went.
normal driving for me around town would be 55-65. interstate 75-80ish around here... would the extra speed cause a vibration you would normally not notice at a lower speed like a driveshaft out of balance?
i never noticed any vibrations. maybe some tire noise but the truck does not shake or rattle. it really is a good driving truck.. thats why im such at a lose. u joints and everything i grease at 3000 miles with oil change and i use the green lucas grease... is that the right grease?

 

[VictoryRedK1500]

It goes along with what I mentioned about sloppy engine mounts and a super tight trans mount not allowing the trans to torque over and move with the engine when you hit the go peddle. In that case, the trans case is trying to absorb and take that torsional force. Eventually you'll find the weak spot. Flex an aluminum casting enough times and it will eventually fail. I didn't look at the photos closely, or saying that it's definitely the issue, but something to look at and poly mounts can be black.

He did mention it was cranked. Some say they ride ok that way or "It's not that bad" and some of us know once you pass and inch and a half or so the truck rides like a jackhammer. Riding down the road impact after impact with that energy being transferred to components of the truck. The Op needs to be honest with himself here on what cranked a little, not really beating on the truck, etc. is.

After 3 trans cases you can conclude the trans case is a symptom, not the problem, and I'm sure getting pretty expensive. I also mentioned vibration because when you have the same repeated failure something else is usually at play and harmonics and vibration can be extremely destructive.

thank you for helping!
what trans mount would you recommend?
and you are 100 percent correct. i dont wanna put a new trans in until i find out what is going on!! something is going on that nobody can pin point........ YET!
yes i have it cranked up some but im not riding the bump stop or anything. i want a smooth riding truck nothing that knocks your teeth out riding over a speed bump hahaha .. it still has a rake look to me on flat ground, im cranked up to clear a 16x10-24mm offset on a 285/75 and still ended up trimmed bumper to clear

 

[thinger2]

It goes along with what I mentioned about sloppy engine mounts and a super tight trans mount not allowing the trans to torque over and move with the engine when you hit the go peddle. In that case, the trans case is trying to absorb and take that torsional force. Eventually you'll find the weak spot. Flex an aluminum casting enough times and it will eventually fail. I didn't look at the photos closely, or saying that it's definitely the issue, but something to look at and poly mounts can be black.

He did mention it was cranked. Some say they ride ok that way or "It's not that bad" and some of us know once you pass and inch and a half or so the truck rides like a jackhammer. Riding down the road impact after impact with that energy being transferred to components of the truck. The Op needs to be honest with himself here on what cranked a little, not really beating on the truck, etc. is.

After 3 trans cases you can conclude the trans case is a symptom, not the problem, and I'm sure getting pretty expensive. I also mentioned vibration because when you have the same repeated failure something else is usually at play and harmonics and vibration can be extremely destructive.

Yep, somehow that casting is either getting cracked during the install or is taking some type of a load that it cant withstand.
And it really doesnt take much to crack cast aluminum.
I also wonder if it could be something that could be easily overlooked.
Like maybe a bolt that is a bit too long or an end tapered bolt that bottoms out before it torques and causes a crack?