3.42's installed & now leaking
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From: Laplace Louisiana
3.42's installed & now leaking
I had my 3.42's installed Friday, paid the mechanic, then next day looked under the car and saw leak. He was supposed to change all seals or o-rings to avoid this problem. Its leaking where it meets the transmission so I guess it a seal somewhere between the to, do anybody know for sure? I bought it used out of a low mileage C5, gears seems to be ok besides the leak and needing to be programed, This is
Burning Brakes
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From: St. Paul MN
I just replaced my 2.73 with a 3.42 unit...today as a matter of fact. Even if the mechanic didn't replace the seal and o-ring I wouldn't expect a leak...unless he damaged the seal prying the seal plate off. If you have a significant leak I might suspect the mechanic may have omited the install of the seal plate onto the new rearend. That's probably not it though...be interested to hear what it is.
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From: S.W. Ohio. . . . . . NRA Life Member
pic of seal plate installed:
pic of seal plate not installed:
One easy way to tell is - whether the seal plate is still on the removed carrier or not. Did you take the old carrier with you ?
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From: S.W. Ohio. . . . . . NRA Life Member
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From: Laplace Louisiana
I did get old differential back in about 100 pieces and the plate was missing, I talked to the guy a hour ago and he said that he would take everything back apart in the morning. He said that he changed all three seals but it was one big rubber o-ring that was one the plate that he did not change. Do anyone know that o-ring he,s talking about? He also wants to check to make sure that the seal off of a 6 speed is the same seal for my automatic. He ordered seals for my car not the six speed the 3.42 came out of. Any input on this one? 
Burning Brakes
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From: St. Paul MN
I did get old differential back in about 100 pieces and the plate was missing, I talked to the guy a hour ago and he said that he would take everything back apart in the morning. He said that he changed all three seals but it was one big rubber o-ring that was one the plate that he did not change. Do anyone know that o-ring he,s talking about? He also wants to check to make sure that the seal off of a 6 speed is the same seal for my automatic. He ordered seals for my car not the six speed the 3.42 came out of. Any input on this one?
I wonder why you received the old differential in about 100 pieces? The only thing you need to remove from it (asider from the mount and dampner) is the seal plate.
The six speed doesn't use the seal plate, just the automatics. So the six speed wouldn't have an output shaft seal nor the o-ring.
Does the thing just leak sitting there? Is it fluid come out the little slit between the diff and trans?
If the plate is in there I'm suspecting the o-ring was damaged on install. I lubed mine up with gear oil just to make sure I wouldn't do that.
Please keep us posted as to what the issue was.
Last edited by verano29; Jun 9, 2008 at 01:40 PM.
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From: Laplace Louisiana
Yes the oil is coming from that little slit between the trans and the diff. I asked him why did he have to break it down like that and he said that the plate does not just pop off, he said that part of the plate is in the inside and that he had to take apart to to free plate from diff. 
Burning Brakes
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From: St. Paul MN
I know you are a bit frustrated by this but if you don't mind my asking you what was you SOTP experience from the install? Did you have a new converter installed as well? I just installed a 3.42 and yank ss3600 an I'm expecting good things.
Burning Brakes
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From: St. Paul MN
Yes the oil is coming from that little slit between the trans and the diff. I asked him why did he have to break it down like that and he said that the plate does not just pop off, he said that part of the plate is in the inside and that he had to take apart to to free plate from diff.
Here's where my money is:
1)O-ring was damaged on install
- or-
2)Seal was put in backwards
Don't mean to make light of your situation. I'm concerned about my own install as well...just curious to know what happened so I can watch out for this as well.
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From: Laplace Louisiana
The car feels a lot better switching from a 2.73 to a 3.42 about like a small 50 shot of NOS. I hit the rev limit so after leak is fixed I'll be looking to have programed, best mod yet.
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WHAT ?????????????????
no need for that
Something doesnt sound right. The carrier fluid is not pressurized. So the only time it gets movement is when driving; and it just gets sloshed (is that a word ?) around. If you notice on my seal plate not installed carrier pic... there is a huge slot in the face of the carrier - towards the tranny. This slot is above the fluid fill line. And the A4 seal plate keeps any fluid entering this slot from going any further forward.
IMO either the seal plate center seal, or the outer O ring, or the seal plate itself - is missing.
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From: Laplace Louisiana
Hey Verano 29, did you do your change out yourself? if so how long did it take you? I started to do mine but don't have much time after work. I changed out my balancer about three or four weeks ago, it took me a week with the time I had to do the work .
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From: Laplace Louisiana
Hey Mike, is it something else besides the seal plate that would have needed to be removed from one car to another to swop these two differentials, maybe something towards the backside of the diff. that would've made him have to take my old one apart like that?
Burning Brakes
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From: St. Paul MN
Although Mike M. is the real expert here, I can answer that. No there is nothing else inside of the differential that needs to be swapped. You do, obviously need to use the mount off of the rear as well as the dampner...but those are external pieces.
Burning Brakes
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From: St. Paul MN
I haven't really kept track (and I've been taking my time) but I imagine if I had to do it again (working at a good pace) I could replace the converter and rear in around 6 hours...definitly less than 10.
Like you, however I don't have a whole lot of time to work on my car and I'm restricted to working on it Sat and Sunday morning. I was going to have it installed but why do I want to pay somebody else to have all the fun right?
I just finished up installing heads, cam, intake, exhaust (headers), and cold air intake....and the diff/tranny was a walk in the park compared to that. It looks very intimidating but it really wasn't that bad....of course I'm not completely done yet