Please Help-broke Tranny....
Thread Starter
Melting Slicks
Joined: Dec 2001
Posts: 2,765
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From: Dana Point Ca
Please Help-broke Tranny....
I am at a loss for words and hope that some more experienced guys could help me. Friday night I shifted hard from 1st to 2nd and thought I blew up the diff. The car has 3:90 gears with 387 rwhp and 367 rwtq, not alot of power compared to some. I just got a call from WCC and I broke the output shaft coming out of the tranny and basically need a new transmission! The car is an 04 with 12k miles. I am PISSED at this point. Is this common? I thought these cars were A LOT stronger than this? I don't know if GM will warranty this. I asked John the head mechanic with a ton of experience and he says he doesnt see it as a defective part. I snapped so hard it broke the diff case. How can blower guys with 600 rwhp not have this problem and my car on 20's does? 
Le Mans Master
Joined: Jan 2001
Posts: 5,786
Likes: 6
From: Lafayette Colorado
The differential output of the C5 has always been a weak link, but I have not heard of one breaking less than a year old. Definatetly get it replaced under warrenty. If you buy the 300M harden output shaft, I am sure the dealership would not mind installing that one rather than another POS GM one.
Keith
Keith
Team Owner
Joined: Sep 2001
Posts: 23,283
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From: Lake Elsinore, CA
Sorry to hear that. I'm not too surprised though considering your combo of the M12 with 3.90's puts my MM6 with 4.10's to shame when it comes to final drive ratios. Your 1st is 11.58 while 2nd is still a beefy 8.07. The SM rates the MM6 at 450 lb.ft.and the M12 at 400 lb.ft. With 20's and that torque multiplication, that's a lot shock for the output shaft and diff to absorb. The wind-up can be pretty severe. The stiff suspension has very little give as well. Below is a pic I snapped of a buddy's tranny output shaft when we pulled the drivetrain a couple of weeks ago.
Le Mans Master
Joined: Dec 2003
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From: Atlanta metro Ga.
Originally Posted by Patches
Sorry to hear that. I'm not too surprised though considering your combo of the M12 with 3.90's puts my MM6 with 4.10's to shame when it comes to final drive ratios. Your 1st is 11.58 while 2nd is still a beefy 8.07. The SM rates the MM6 at 450 lb.ft.and the M12 at 400 lb.ft. With 20's and that torque multiplication, that's a lot shock for the output shaft and diff to absorb. The wind-up can be pretty severe. The stiff suspension has very little give as well. Below is a pic I snapped of a buddy's tranny output shaft when we pulled the drivetrain a couple of weeks ago.
So Ed, are you going to assist in the re-install?
Thread Starter
Melting Slicks
Joined: Dec 2001
Posts: 2,765
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From: Dana Point Ca
Originally Posted by kromberg
The differential output of the C5 has always been a weak link, but I have not heard of one breaking less than a year old. Definatetly get it replaced under warrenty. If you buy the 300M harden output shaft, I am sure the dealership would not mind installing that one rather than another POS GM one.
Keith
Keith
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Le Mans Master
Joined: Jul 2002
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From: Slave to the evil empire
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St. Jude Donor '04
Originally Posted by Patches
Sorry to hear that. I'm not too surprised though considering your combo of the M12 with 3.90's puts my MM6 with 4.10's to shame when it comes to final drive ratios. Your 1st is 11.58 while 2nd is still a beefy 8.07. The SM rates the MM6 at 450 lb.ft.and the M12 at 400 lb.ft. With 20's and that torque multiplication, that's a lot shock for the output shaft and diff to absorb. The wind-up can be pretty severe.
So you broke the output shaft on the transmission and it in turn broke the case on the rear diff?
time for a DTE strut brace as well DTE brace
Thread Starter
Melting Slicks
Joined: Dec 2001
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From: Dana Point Ca
Originally Posted by runamuk
So you broke the output shaft on the transmission and it in turn broke the case on the rear diff?
time for a DTE strut brace as well DTE brace
Team Owner
Joined: Sep 2001
Posts: 23,283
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From: Lake Elsinore, CA
Definitely go for the DTE brace and the hardened diff output shaft. I don't think anyone has come out with a hardened tranny output shaft yet - at least, I haven't heard of one.
Best of luck on the repair.
Dan - yes, we are tenatively scheduled to reinstall on 10/2.
Best of luck on the repair.
Dan - yes, we are tenatively scheduled to reinstall on 10/2.
Melting Slicks
Joined: Nov 2000
Posts: 2,380
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Sounds to me like events happened in reverse of what you were told. You probably broke the differential first, causing the casing to rotate in place and take out your tranny output shaft as a result. Don't ask how I know. 
And yes, in this case a differential strut would've helped. May not have saved your differential, but would've saved the tranny for sure. I haven't had any breakage since installing one (not the DTE one, but the prototype of the first one on the market about 2.5 years ago.)
By the way, I did have my tranny rebuilt with a hardened main shaft. The 4.10s also have a hardened output shaft.
Good luck. Nasty breakage.
And yes, in this case a differential strut would've helped. May not have saved your differential, but would've saved the tranny for sure. I haven't had any breakage since installing one (not the DTE one, but the prototype of the first one on the market about 2.5 years ago.)
By the way, I did have my tranny rebuilt with a hardened main shaft. The 4.10s also have a hardened output shaft.
Good luck. Nasty breakage.
Last edited by The One; Sep 22, 2004 at 05:38 PM.
Thread Starter
Melting Slicks
Joined: Dec 2001
Posts: 2,765
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From: Dana Point Ca
Originally Posted by The One
Sounds to me like events happened in reverse of what you were told. You probably broke the differential first, causing the casing to rotate in place and take out your tranny output shaft as a result. Don't ask how I know.
And yes, in this case a differential strut would've helped. May not have saved your differential, but would've saved the tranny for sure. I haven't had any breakage since installing one (not the DTE one, but the prototype of the first one on the market about 2.5 years ago.)
By the way, I did have my tranny rebuilt with a hardened main shaft. The 4.10s also have a hardened output shaft.
Good luck. Nasty breakage.
And yes, in this case a differential strut would've helped. May not have saved your differential, but would've saved the tranny for sure. I haven't had any breakage since installing one (not the DTE one, but the prototype of the first one on the market about 2.5 years ago.)
By the way, I did have my tranny rebuilt with a hardened main shaft. The 4.10s also have a hardened output shaft.
Good luck. Nasty breakage.
Melting Slicks
Joined: Mar 2003
Posts: 3,116
Likes: 10
From: Macomb MI
I have broken enough of those parts to be amillionare just in scrap metal.
The mainshaft can be replaced in your tranny with a hardened mainshaft from LPE. You will also have to have the front and rear main bearings replaced also asa they will get detroyed on rebuild. If, it busted the rear housing on the case, thats replaceable too, but look at places like Karshop or local tranny rebuilder to get one way cheaper than the GM $300 bucks.
Unfortunately...The diff case if broke is toast..Time to find a donor 3.42 and and put your gears in it.
Phil
The mainshaft can be replaced in your tranny with a hardened mainshaft from LPE. You will also have to have the front and rear main bearings replaced also asa they will get detroyed on rebuild. If, it busted the rear housing on the case, thats replaceable too, but look at places like Karshop or local tranny rebuilder to get one way cheaper than the GM $300 bucks.
Unfortunately...The diff case if broke is toast..Time to find a donor 3.42 and and put your gears in it.
Phil
Thread Starter
Melting Slicks
Joined: Dec 2001
Posts: 2,765
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From: Dana Point Ca
Originally Posted by RoadRebel
I have broken enough of those parts to be amillionare just in scrap metal.
The mainshaft can be replaced in your tranny with a hardened mainshaft from LPE. You will also have to have the front and rear main bearings replaced also asa they will get detroyed on rebuild. If, it busted the rear housing on the case, thats replaceable too, but look at places like Karshop or local tranny rebuilder to get one way cheaper than the GM $300 bucks.
Unfortunately...The diff case if broke is toast..Time to find a donor 3.42 and and put your gears in it.
Phil
The mainshaft can be replaced in your tranny with a hardened mainshaft from LPE. You will also have to have the front and rear main bearings replaced also asa they will get detroyed on rebuild. If, it busted the rear housing on the case, thats replaceable too, but look at places like Karshop or local tranny rebuilder to get one way cheaper than the GM $300 bucks.
Unfortunately...The diff case if broke is toast..Time to find a donor 3.42 and and put your gears in it.
Phil
I'm going to rebuild this biatch like the 6 million dollar man!
Team Owner
Joined: Apr 2001
Posts: 54,204
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From: S.W. Ohio. . . . . . NRA Life Member
Sounds to me like events happened in reverse of what you were told. You probably broke the differential first, causing the casing to rotate in place and take out your tranny output shaft as a result.
cool tranny jack
looks exacytly like this one:
Transmission Jack from Harbor Freight: item 39178-0VGA
Race Director
Joined: May 2001
Posts: 16,106
Likes: 473
i can vouch for gene @ karshop. just got a tranny, gears and tc from him recently for install for my--ahem!--busted tranny, gears, and tc...(everything went great on install, a&a did the work).
Originally Posted by RoadRebel
I have broken enough of those parts to be amillionare just in scrap metal.
The mainshaft can be replaced in your tranny with a hardened mainshaft from LPE. You will also have to have the front and rear main bearings replaced also asa they will get detroyed on rebuild. If, it busted the rear housing on the case, thats replaceable too, but look at places like Karshop or local tranny rebuilder to get one way cheaper than the GM $300 bucks.
Unfortunately...The diff case if broke is toast..Time to find a donor 3.42 and and put your gears in it.
Phil
The mainshaft can be replaced in your tranny with a hardened mainshaft from LPE. You will also have to have the front and rear main bearings replaced also asa they will get detroyed on rebuild. If, it busted the rear housing on the case, thats replaceable too, but look at places like Karshop or local tranny rebuilder to get one way cheaper than the GM $300 bucks.
Unfortunately...The diff case if broke is toast..Time to find a donor 3.42 and and put your gears in it.
Phil
