4L80E problems

lazysob · 04-21-2009, 07:42 PM

I have a 2001 1500HD crewcab 4x4 that is slow to shift from park to any other gear or from reverse to drive or vice versa. Once it is in gear it works fine. The shifts are firm and there is no slippage. It started doing this after a romp in some mud and water up to the doors a year or so ago. It didn't bother me much before because I'd rarely drive the truck but now I'm using it as a tow vehicle for a camper. There isn't any water or bad tranny fluid evident. I was told there is something on the side of the transmission that is prone to getting wet and muddy inside that may be causing this problem. Is there some sort of electronic shifter on the outside or something? I'm looking for any advice to find out what the problem is and how to go about getting it corrected before it leaves me stranded somewhere. Thanks in advance!

hotrodpc · 04-21-2009, 09:17 PM

I'd say you need to have diagnostics run on the trans. It sounds like it could be low pump pressure. Someone will need to check the pump pressure spec and hook a set of guages on the trans, then shift it from P to D, D to R etc. With low pump pressure it will take a bit to compress the clutch packs. When shifting gears in D, the fluid is usually already in its place and it is just hitting servos to apply and release bands etc. In a E trans the soloenoids do that work for you and not very dependant on the pressure once it is already built up. It just seems your pressure is low and taking some time to get where it needs to go. Also could be a clogged filter not drawing enough fluid from the pan. If this were NOT an E trans and this was your problem, it would be more evident. So it could be a # of things, but my first guess is low pressure for whatever reason that could be, clogged filter, damaged pump, stuck valve etc. It could even be a stuck bleed off valve not allowing pressure to build up rapidly. Auto trans are fascinating things. You may have great pressure one place, but not another. I just ASSUME it pump pressure because you said its all gear selections. Just thought of this too, how about your shift linkage? Could you have possibly have bent it? If the manual valve is not opening passage ways all the way then it can not get the fluid in quick enough through a bottleneck that is created by a misallinged manual valve? Sorry, I couldn't be any more specific but its a complicated trans. But I sure like it !!! I want to put one in my 86, but the computer kit to operate a 4L80-E is about $900. That kills that deal. So I may just make me one that is a full manual valve body. No need for the computer if you are going to shift it yourself.

lazysob · 04-22-2009, 04:11 PM

The linkage might be "tweaked" a little since I was bottomed out across a set of ruts when all this began. The transmission may have been resting in the mud.

Ok that jars my memory...while I was stuck and trying to rock back and forth my gear indicator stopped showing the right gears. For example when it showed reverse I was actually in neutral and in neutral it was in drive. Its like it was off a notch. Also I had no Park. After getting towed out of the mud I drove down the road a few hundred yards and it cleared up except for what I am still experiencing with the slow gear selection. It also got hung up in 4-low during all this but soon returned to normal as for as the transfer case is concerned after driving it a little ways down the road (dirt road). The transfer case has not acted up again. I know this sounds crazy but it happened.

batty1214 · 04-22-2009, 05:57 PM

There is a control module on the side of the transmission. I'm not sure that water or mud would hurt it, But, things do happen. I do know that you can replace them(Ive done a few) But, I don't know that It is what your problem is. If you take it to a shop with a Good scanner, It'll show any pre problem codes....... thats how I found the transfercase going bad In one of the trucks at work........ But I had to take it to a dealer to have it scanned......

lazysob · 04-23-2009, 07:00 PM

Thanks, I guess I'll just have to go have it checked.

Case 7230 · 04-24-2009, 06:39 AM

If it was mine I would drop the pan to see if the filter is off.

hotrodpc · 04-24-2009, 07:58 AM

BTW, I do know what you mean about the T case. I had a 2002 Avy 4x4. The transfer case did the same thing once. I could not get it out of 4Low. When I hit pavement and made turn, I heard the loudest bang I ever did hear. I just knew I broke a front axle as bad as it sounded. But nope, it came out of of 4Low, nothing broke. Took it to the dealer told them what happened, they found no damage, changed the T case fluid during inspection, and never had the problem again. You can bet I tried to recreate the problem 100 times while it was still under warranty. But was never an issue except the one time.

04-21-2009, 07:42 PM	#1
lazysob Junior Member Join Date: Apr 2009 Location: Louisiana Posts: 3	4L80E problems I have a 2001 1500HD crewcab 4x4 that is slow to shift from park to any other gear or from reverse to drive or vice versa. Once it is in gear it works fine. The shifts are firm and there is no slippage. It started doing this after a romp in some mud and water up to the doors a year or so ago. It didn't bother me much before because I'd rarely drive the truck but now I'm using it as a tow vehicle for a camper. There isn't any water or bad tranny fluid evident. I was told there is something on the side of the transmission that is prone to getting wet and muddy inside that may be causing this problem. Is there some sort of electronic shifter on the outside or something? I'm looking for any advice to find out what the problem is and how to go about getting it corrected before it leaves me stranded somewhere. Thanks in advance!

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04-21-2009, 09:17 PM	#2
hotrodpc Senior Member Join Date: Jul 2008 Location: OKC, OK Posts: 3,145	I'd say you need to have diagnostics run on the trans. It sounds like it could be low pump pressure. Someone will need to check the pump pressure spec and hook a set of guages on the trans, then shift it from P to D, D to R etc. With low pump pressure it will take a bit to compress the clutch packs. When shifting gears in D, the fluid is usually already in its place and it is just hitting servos to apply and release bands etc. In a E trans the soloenoids do that work for you and not very dependant on the pressure once it is already built up. It just seems your pressure is low and taking some time to get where it needs to go. Also could be a clogged filter not drawing enough fluid from the pan. If this were NOT an E trans and this was your problem, it would be more evident. So it could be a # of things, but my first guess is low pressure for whatever reason that could be, clogged filter, damaged pump, stuck valve etc. It could even be a stuck bleed off valve not allowing pressure to build up rapidly. Auto trans are fascinating things. You may have great pressure one place, but not another. I just ASSUME it pump pressure because you said its all gear selections. Just thought of this too, how about your shift linkage? Could you have possibly have bent it? If the manual valve is not opening passage ways all the way then it can not get the fluid in quick enough through a bottleneck that is created by a misallinged manual valve? Sorry, I couldn't be any more specific but its a complicated trans. But I sure like it !!! I want to put one in my 86, but the computer kit to operate a 4L80-E is about $900. That kills that deal. So I may just make me one that is a full manual valve body. No need for the computer if you are going to shift it yourself.

04-22-2009, 04:11 PM	#3
lazysob Junior Member Join Date: Apr 2009 Location: Louisiana Posts: 3	The linkage might be "tweaked" a little since I was bottomed out across a set of ruts when all this began. The transmission may have been resting in the mud. Ok that jars my memory...while I was stuck and trying to rock back and forth my gear indicator stopped showing the right gears. For example when it showed reverse I was actually in neutral and in neutral it was in drive. Its like it was off a notch. Also I had no Park. After getting towed out of the mud I drove down the road a few hundred yards and it cleared up except for what I am still experiencing with the slow gear selection. It also got hung up in 4-low during all this but soon returned to normal as for as the transfer case is concerned after driving it a little ways down the road (dirt road). The transfer case has not acted up again. I know this sounds crazy but it happened.

04-22-2009, 05:57 PM	#4
batty1214 Senior Member Join Date: Nov 2008 Location: Vernal Utah Posts: 1,135	There is a control module on the side of the transmission. I'm not sure that water or mud would hurt it, But, things do happen. I do know that you can replace them(Ive done a few) But, I don't know that It is what your problem is. If you take it to a shop with a Good scanner, It'll show any pre problem codes....... thats how I found the transfercase going bad In one of the trucks at work........ But I had to take it to a dealer to have it scanned......

04-23-2009, 07:00 PM	#5
lazysob Junior Member Join Date: Apr 2009 Location: Louisiana Posts: 3	Thanks, I guess I'll just have to go have it checked.

04-24-2009, 06:39 AM	#6
Case 7230 Senior Member Join Date: Dec 2007 Posts: 547	If it was mine I would drop the pan to see if the filter is off.

04-24-2009, 07:58 AM	#7
hotrodpc Senior Member Join Date: Jul 2008 Location: OKC, OK Posts: 3,145	BTW, I do know what you mean about the T case. I had a 2002 Avy 4x4. The transfer case did the same thing once. I could not get it out of 4Low. When I hit pavement and made turn, I heard the loudest bang I ever did hear. I just knew I broke a front axle as bad as it sounded. But nope, it came out of of 4Low, nothing broke. Took it to the dealer told them what happened, they found no damage, changed the T case fluid during inspection, and never had the problem again. You can bet I tried to recreate the problem 100 times while it was still under warranty. But was never an issue except the one time.