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2001 Silverado 2500hd 8.1
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22 Posts
Discussion Starter · #1 ·
I’ve noticed a leak around the pan gasket and where the bell housing meets with the motor from near the top was wandering if Lucas trans fix will affect the Allison? It’s a 2001 2500hd 8.1 with the Allison 167k miles
 

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‘01 Silverado 2500HD 8.1/Allison 5sp xcab long bed
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3,566 Posts
Not sure I’d recommend that. If it is truly the pan gasket leaking, that’s rather unusual since the factory one is a rubber over steel one. I just took my cover off this weekend and the pan gasket was not leaking. The drain plug leaked a little bit and the electrical connector O-ring was leaking, but not the transmission oil pan. The leak between the engine and transmission is most likely the engine rear main seal. Mine is doing the same thing.
 

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2001 Silverado 2500hd 8.1
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22 Posts
Discussion Starter · #3 ·
So I took closer look and looks my electrical connection is leaking like you said, is the o ring a pita to replace ? And what you recommend with the rear main seal ? Trans still shifts like butter
 

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‘01 Silverado 2500HD 8.1/Allison 5sp xcab long bed
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3,566 Posts
The recommended fix for the cable port is to replace the inside harness. You have to remove it anyway to get at the housing, so that is what I did.

Main seal: I’m going to try some transmission fluid to see if it will slow it down some before I tackle separating the pair. The transmission weighs over 300lbs.
 

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‘01 Silverado 2500HD 8.1/Allison 5sp xcab long bed
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3,566 Posts
Yes it does. Very wet, too. It continues to drip.
 

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2001 Silverado 2500hd 8.1
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22 Posts
Discussion Starter · #7 ·
Damn that sucks ....... I just sold my house so I don’t have my garage anymore fora while. I’m staying at my in-laws right now
 

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‘01 Silverado 2500HD 8.1/Allison 5sp xcab long bed
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For what it’s worth, my truck is sitting in my driveway and I did the pan with the front up on stands.
 

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2001 Silverado 2500hd 8.1
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22 Posts
Discussion Starter · #9 ·
Think I might I live with it for a bit until I buy my next house, I haven’t had to add oil yet been checking when it’s hot. I might disconnect that harness on the outside and try to pull the other end from the inside and get it seated better
 

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‘01 Silverado 2500HD 8.1/Allison 5sp xcab long bed
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3,566 Posts
I hear ya. Good luck on the bulkhead connector.
 

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If/when you do rear main, do the oil pan as well. Terrible design from the factory where the back of the pan has less surface area and can leak if you park on an incline. Speaking of, you ain’t parking on an incline are you? That can make it look like your rear main is leaking when it’s the oil pan. If it isn’t leaving pancakes on the ground, it’s either not the rear main or it ain’t time to worry about it yet.
 

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2001 Silverado 2500hd 8.1
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22 Posts
Discussion Starter · #14 ·
I’ve just got drips from rear of trans and from the front bell to the motor, I’ve been monitoring fluid level, and as mentioned above still shifts like dream so we’ll see I love this truck
 

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98 gmc k1500 5.7
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480 Posts
I agree stop leak just messes stuff up , don't wait too long on replacing harness in transmission , could short out computer system
 

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‘01 Silverado 2500HD 8.1/Allison 5sp xcab long bed
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3,566 Posts
Rostra 3500072

169627
 
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