4L80E failure

GT6Steve

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Not Vette related but there's so much knowledge on this site I thought I'd ask here first.

Yesterday afternoon the motorhome rolled up to a stop sign in Barstow California. No drama, no noise typical stop. Upon reapply the throttle there were no forward gears. Free spinning. Funny thing, I have reverse so I was able to get off the street.

Any chance this is electrical or purely mechanical?

53K miles on a P30 chassis that has always pulled the racecar trailer.

Thanx, Steve
 
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there are 2 sensors- inpout speed and output speed, if one gets some metal flakes on it or dies, it can cause the whole thing to go stupid. Not even hard to get to- external mount about 2 o'clock position looking from the front. 10mm head bolt holding it in IIRC. Just a shot, I'm pretty rusty on the "E" tranny stuff. But it's a quick place to look.
 
can you hear or feel anything when you shift from P to D or N to D ?? Just wondering if it is simply not shifting (staying in neutral) or shifting into gear and slipping...
 
Does your indicator show what gear your in? PRNDL switch/neutral switch was a common problem.
 
can you hear or feel anything when you shift from P to D or N to D ?? Just wondering if it is simply not shifting (staying in neutral) or shifting into gear and slipping...

Wow, Thanx for the inputs,

The shifter seems to be doing it's thing at the PRNDL and It goes into reverse just fine. Just the four forward gears are missing. I'll absolutely check those speed sensors. I must've seen it in the manual because I was suspicious of something like that.

No suspicious noises noted, no engine note change in any position but reverse. Fuse is good.

I'll do some pokin' about when the rain stops.

Thanx again, Steve
 
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Isn't the 4l80e like the 4l60e and the inputs only control shift points and lockup much like a old school TV cable? I had weird shifting issues with my 97 camaro but mine were not no forward gears just very weird shift points. Chevy did something with the cars pcm and the problems went away. Not sure what they did though.
 
Interesting development, Yesterday afternoon I backed it out of the way in the side yard. This morning I have no reverse gear either? Even though the dipstick looked good I added a quart of fluid just on the off chance, nothing.

I need to find out if I have any pump pressure.
 
Interesting development, Yesterday afternoon I backed it out of the way in the side yard. This morning I have no reverse gear either? Even though the dipstick looked good I added a quart of fluid just on the off chance, nothing.

I need to find out if I have any pump pressure.

You are going in the wrong direction. Your problem is most likely electrical.

It doesn't matter if you manually put the transmission in gear. If the computer doesn't know what gear your putting it in, you will only get neutral. With your problem being only forward gears and now being reverse, it's a good indicator that its electrical and that it's the PRNDL switch/Neutral safty switch. Combine that with all the problems that GM has had with them and I would say you can put money on this one. GM has tsb's (technical service bulletins) out on this switch for water intrusion problems. There is also a good possibility that you will need a new pigtail for it.

On a side note a good amount of your strange intermittent problems on electronically controled transmissions can be pin to this switch. A good example of this is Fords E4OD, I have seen this switch cause the trans to go to neutral at 60 on a WOT down shift only when its damp outside. When it was dry the trans would shift normaly.
 
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Thanx immensely for that. I do believe it's electrical because these things have a good reputation for strength and I'm only looking at 50K miles.

I'll focus on the electrical, that's my profession anyway so I should be equipped. ;-))

Really appreciate the thoughts guys, I have no experience with automatics.:drink::drink:

Oh, and reverse is back now???
 
FIRST off, I dunno jack diddly about the 4L80e, second off I am TOLD the computer commands are similar to the 4L60e.....

when doing a tranny for the Chebby van 30 class C motor home, I bought two tranny cores....a 700 and a 4L60e.....because the mechanicals are very similar, but the case and brain plates are totally different...it was the rotating mechanicals I was interested in....

and so....they both had similar burn up patterns...the 60e was totally burnt up, and had a sun shell failure...

the 700 was less so of a failure....

the 60e is not capable of taking a shift kit I know of...maybe a computer modification??

the TCC clutch solenoid is a famous failure enough that local parts houses stock them for 20 bux.....same unit in both...

when pulling the 60e down for examination last winter...that thing has more wires and solenoids and crazy valve body arrangements, and it all looked totally fried from high temps....

plastic and high temps do not get along well, and with being immersed in oil that can reach silly temps....it's a damn mistake to do that....

sorry folks, but I will stick to a hydraulically controlled tranny, none of that over done computer crap....

heard too many stories off the tranny supply shop selling me parts....

which means to me..WHY do this over use of electronics???


:crap::bomb::crutches:
 
Good thought about the shifts all being electric- on that note, does the indicator on the dash change? The shift lever does a switch, much like the old style neutral safety, that commands the PCM to change the indicator AND the solenoids in the trans. IIRC, there is still a mechanical linkage to the trans, but that's pretty much for park, and that is also the one that does the command thing to the PCM. After seeing that, I rememebr I had an indication problem on my pickup and it was that trans mounted switch. It's an Allison, but pretty much a HD version of the 4L80E.
 
FIRST off, I dunno jack diddly about the 4L80e, second off I am TOLD the computer commands are similar to the 4L60e.....

when doing a tranny for the Chebby van 30 class C motor home, I bought two tranny cores....a 700 and a 4L60e.....because the mechanicals are very similar, but the case and brain plates are totally different...it was the rotating mechanicals I was interested in....

and so....they both had similar burn up patterns...the 60e was totally burnt up, and had a sun shell failure...

the 700 was less so of a failure....

the 60e is not capable of taking a shift kit I know of...maybe a computer modification??

the TCC clutch solenoid is a famous failure enough that local parts houses stock them for 20 bux.....same unit in both...

when pulling the 60e down for examination last winter...that thing has more wires and solenoids and crazy valve body arrangements, and it all looked totally fried from high temps....

plastic and high temps do not get along well, and with being immersed in oil that can reach silly temps....it's a damn mistake to do that....

sorry folks, but I will stick to a hydraulically controlled tranny, none of that over done computer crap....

heard too many stories off the tranny supply shop selling me parts....

which means to me..WHY do this over use of electronics???


:crap::bomb::crutches:

Ok now you have this slightly wrong. You can get shift kits for the 4L60E. Electronics may control your shift points, but hydraulics still control shift characteristics. Those so called electronic shift kits that you can buy from companies like B&M that have like a three way switch to control how your transmission shifts are crap. Nothing more than resistors to trick the computer to shift a different point or change line pressure. To you it right you still need to do it hydraulically. Trans Go makes some nice kits both a shift correction kit and a shift recalibration kit.

Now with that I am really surprised to hear you talk this way Gene. You are one that seems to like moving forward and upgrading to efi, rack and pinion... Seems an electronically controlled trans would fit with your list of mods nicely.
 
Good thought about the shifts all being electric- on that note, does the indicator on the dash change? The shift lever does a switch, much like the old style neutral safety, that commands the PCM to change the indicator AND the solenoids in the trans. IIRC, there is still a mechanical linkage to the trans, but that's pretty much for park, and that is also the one that does the command thing to the PCM. After seeing that, I rememebr I had an indication problem on my pickup and it was that trans mounted switch. It's an Allison, but pretty much a HD version of the 4L80E.

That's right and normally if you loose a solenoid the trans can't shift or if it doesn't know what to do it will just default to 3rd as a limp home mode in fwd and you would also still have rev.
 
FIRST off, I dunno jack diddly about the 4L80e, second off I am TOLD the computer commands are similar to the 4L60e.....

when doing a tranny for the Chebby van 30 class C motor home, I bought two tranny cores....a 700 and a 4L60e.....because the mechanicals are very similar, but the case and brain plates are totally different...it was the rotating mechanicals I was interested in....

and so....they both had similar burn up patterns...the 60e was totally burnt up, and had a sun shell failure...

the 700 was less so of a failure....

the 60e is not capable of taking a shift kit I know of...maybe a computer modification??

the TCC clutch solenoid is a famous failure enough that local parts houses stock them for 20 bux.....same unit in both...

when pulling the 60e down for examination last winter...that thing has more wires and solenoids and crazy valve body arrangements, and it all looked totally fried from high temps....

plastic and high temps do not get along well, and with being immersed in oil that can reach silly temps....it's a damn mistake to do that....

sorry folks, but I will stick to a hydraulically controlled tranny, none of that over done computer crap....

heard too many stories off the tranny supply shop selling me parts....

which means to me..WHY do this over use of electronics???


:crap::bomb::crutches:

Ok now you have this slightly wrong. You can get shift kits for the 4L60E. Electronics may control your shift points, but hydraulics still control shift characteristics. Those so called electronic shift kits that you can buy from companies like B&M that have like a three way switch to control how your transmission shifts are crap. Nothing more than resistors to trick the computer to shift a different point or change line pressure. To you it right you still need to do it hydraulically. Trans Go makes some nice kits both a shift correction kit and a shift recalibration kit.

Now with that I am really surprised to hear you talk this way Gene. You are one that seems to like moving forward and upgrading to efi, rack and pinion... Seems an electronically controlled trans would fit with your list of mods nicely.

OH, ok, I didn't know that, on the TG kits....and I think there is a limit to electronics in cars, that most factories have FAR exceeded.....I can see EFI, obviously, I can see MAYBE ABS as helpful once in a while, my '87 vette had it, only activated it twice, once deliberately.....but when they go to 'body control computers'....sorry they lost me on the + side of that one, the amount of gimmicks in even my wife's '99 Escort is a bit much making the car more complicated than need be....
IF GM made a electronic 200 4r maybe it would be a better suit to the shark, I dunno, there is that controller expense, or maybe just junkyard a whole control system....:shocking:
but when I read of something like 6+ computers in the modern car, well, something is remiss....and then we get the mighty Toyota and the runaways....does anyone really trust DBW?? not me, gimme a simple cable and return springs...done deal...

:shocking::beer:
 
you can get a handheld programmer like the Predator for the 4l60 and 4l80, I bought one for my Z28 with a 4l60e - you can pretty much "tell" it when to shift and how .... nice toys these programmers :thumbs:
 
Studying the manual I see a forward clutch that has to be applied for any of the forward gears but not for reverse. Fits my symptoms except that it's purely hydraulic thru the manual shuttle valve.

I'll rent a scan tool on Saturday for a code check. Manual says I can count flashes using the ADL-something connector just as I do in the 81 C3. Just gotta find it...:huh:
 
Scan tool shows no codes so I'm looking at steel rather than copper. I'm wondering if I have a pressure problem, to be measured soon, that is not pushing the forward clutches. Reverse uses about double the oil pressure so could still work at a reduced pressure.

Finding out soon....:sweat:

a few minutes later:

Pressure seems perfect. 85 PSI at cold idle and going over 160 at raised RPMs. Pulsed every so often to high pressure and back to 85. Damn!

Anybody have experience rebuilding these things? Can a competent home mechanic do it? I can do manual transmissions with no sweat but there's a LOT more parts in this bugger...
 
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Scan tool shows no codes, but does it show the correct gear requested? You don't have to have a code to have an electrical problem.
 
Hmmm,

I saw no facility for checking that, just a code reader.

I very much expected at least a VSS mismatch but maybe the front VSS saw nothing turning.

To get this thing towed to a shop and repaired is going to be about what it's worth. I've got to fix it myself...
 
New question then...

Will all of the 4l80E's interchange but for the cooling lines? I can get a used one for $800 but it's a later model.
 
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