# 4l80 e trans problem



## Sharper Edge (Jan 26, 2005)

I went out to the garage today to take my 1991 gmc 3500 4x4 up to yhe car wash and no reverse??? checked the fluid it was fine. Decided I would take it up for the wash drive was still working. On the way there I notice no overdrive?? I have the 4L80 E trans Does this sound like a mechanical problem or electrical? THANKS


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## 26543 (Jan 28, 2008)

Sounds like its all over, time for a new trans


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## B&B (Nov 4, 2006)

If it lost reverse and forward _at the same time _it's not likely a hard parts failure.

Sounds like the "A" shift solenoid is stuck or defective. It's located in the valve body and can be changed without removing the trans.

Get a scanner on the truck first though before just replacing it. You can view the A solenoid activity on to see what you come up with. Could also be a wiring problem to the A solenoid.


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## Sharper Edge (Jan 26, 2005)

Just lost reverse. 1,2,3 still work and shift fine just no overdrive


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## Duncan90si (Feb 16, 2007)

The same exact thing happened to mine a few months ago, Except I lost 3rd too. Trans was junk. It had a cracked drum and a bad center support.


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## B&B (Nov 4, 2006)

Sharper Edge;517011 said:


> Just lost reverse. 1,2,3 still work and shift fine just no overdrive


Sorry Sharp, typed "forward" instead of "overdrive"...diagnosis is the same though.


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## KeeblerBP (Sep 4, 2005)

I had the exact same problem with my 4L80E in my last truck. It was a metal band that broke that runs reverse and overdrive. I heard a bang when mine went out. The dealer told me I could replace just the band for about $700 or rebuild the whole tranny for about $1500. I spent the $1500 thinking that with my luck something else would go out a few months later and I would have to spend it anyway.


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## B&B (Nov 4, 2006)

The rear band will definitely make it lose reverse, but isn't applied for overdrive. So I doubt thats the problem with Sharp's truck (if it sends debris though the trans it could clog a passage or solenoid though).

To lose reverse and OD at the same time almost has to be electrical or solenoid related.

Only way to help pinpoint it future is to get it on a scanner and check it.


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## bassfishn1 (Jan 14, 2008)

same thing happened to mine, lost reverse first, then all the others, except first, good thing my tranny guy was only 2 miles away

he told me the whole wiring harness and related solenoids were fried


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## Sharper Edge (Jan 26, 2005)

Thanks guys.. Getting it scanned this morning. I will let you know what it is.


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## Detroitdan (Aug 15, 2005)

I lost OD in mine, tranny shop told me tranny was junk. I replaced TCC solenoid, shift solenoids, ect switch, speed sensors, harness seal and finally rebuilt the valve body with a Sonnax kit. All it was is the afl valve (controls lockup) wears in it's bore, creating a hydraulic pressure leak so TCC won't work. With the kit you remove the valve, ream and sleeve the bore and reassemble. Tranny is working perfectly now, all told I spent less than $400 trying to fix it, it really only needed about $250 of that to fix with the kit. Far cheaper than the $2200 tranny shop wanted to replace my "junk" transmission.


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## Detroitdan (Aug 15, 2005)

BTW, keep us posted with your codes. If we can't help you here, I can hook you up with a guy who used to teach rebuilding 4L80Es to Motor T mechanics in the military. If he can't figure it out, then it isn't a 4L80E.


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## snowcan (Sep 28, 2006)

When the reverse band busts, you usually feel it, almost like sledge hammer hitting your rear bumper, very common for the reverse band to fail on the 4L80E. Before you rebuild, check for the price on brand new, I found there wasn't much difference and the new one had a 3 year/60 000 km warranty.....good luck.


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## Sharper Edge (Jan 26, 2005)

Had to get trans re built. on 2-18-08 it is now 12-2-2008 1345 miles on trans and I just lost 3rd and overdrive. any help? It is still under waaranty but would like to know what you might think it is before I take it up. 1345 miles not real sure about the rebuild being a good one..


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## dirtmandan2 (Nov 2, 2007)

my 4l80 also went out last winter, never made a dound just lost reverse... that and when i tried to go forward it fealt like i had a foot on the brake... 2250$ later I got it back... builder said no warranties on a plow truck... hope you have some luck with yours...


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## Sharper Edge (Jan 26, 2005)

Have the warrahty just want to know why it would go bad with 1345 miles on it..


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## dirtmandan2 (Nov 2, 2007)

Im by far not a tranny guy, but i would say that whoever rebuilt it missed something...


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## aeronutt (Sep 24, 2008)

Warranty = "not your problem". Let the rebuilder fix his mistake. If you want to understand the inner workings, not just get it fixed then I suggest buying the shop manual and reading it cover-to-cover. You'll learn far more than you will by sorting through an internet forum where clueless people (like myself) toss out a lot of "maybe this", and "maybe that" guesses. I'm not saying the forum isn't helpful, just that it's not a perfect data source.


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## Sharper Edge (Jan 26, 2005)

Pulled a code today off PCM of 81 says solenoid b short or open. going to change trans guy said not under warranty was not relaced with rebuild. Is this a easy job looks like just pull the pan and replace? Should I replace the filter with only 1345 miles on it or is that just a waste of money?


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## B&B (Nov 4, 2006)

If your replacing the B solenoid yes of course you will have to drop the pan....but you'll also have to drop the entire valve body assembly in order to remove the retaining pin that holds the solenoid in place. 

The B solenoid is likely the issue as to why you have no overdrive...and not uncommon, but wouldn't cause it to lose reverse. When they lose reverse its due to a broken hard component, such as the rear band or band anchor pin for example.

So basically you've got a bigger issue than just a non operating B solenoid. :crying:


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## Detroitdan (Aug 15, 2005)

I thought the a,b and tcc solenoids could be changed without dropping the valve body. It's been a year or so since I did mine, but I seem to remember doing them with the valve body in. I did pull the valve body to do the surecure, but that was a different time.


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## Sharper Edge (Jan 26, 2005)

The directions I found did not say you have to just drop the pan and remove 1 bolt and replace with torque head bolt supplied. Sorry for any confution I did not lose reverse this time that was from my first time around when I got the rebuild. This time I only lost 3 & 4


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## Sharper Edge (Jan 26, 2005)

Again THANK YOU for all the help you provide..


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## Sharper Edge (Jan 26, 2005)

Changed the B 3-4 selonoid workes great. For the test drive anyway. Simple to do drop pan remove 1 screw, un plug, replace. Also installed drain plug for pan.


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## mnic (Nov 27, 2008)

*4l80 trans probs*

The shift solenoids are a common occurence of problems the screen on the shift solenoid becomes clogged with metal shavings dirt etc hence no 1-2 or 3-4


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## Detroitdan (Aug 15, 2005)

I change all my shift solenoids every 150,000 miles.


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## mnic (Nov 27, 2008)

Yeh as long as you keep maintenance up that is really the only problems also blow out the trans lines keeping the trans cooler free is a good idea too


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## Detroitdan (Aug 15, 2005)

mnic;663676 said:


> Yeh as long as you keep maintenance up that is really the only problems also blow out the trans lines keeping the trans cooler free is a good idea too


Yes! Very important! I blew a tranny that way once. Original tranny was acting up, dropped the pan and it was full of metal shavings. Cleaned it out and fresh fluid and filter, but never gave the lines a thought. Burned the tranny up in about three hours, come to find up that metal sludge had plugged the cooler lines solid. Almost installed a new tranny with the same lines but my old man suggested I check the lines. Good thing, or I would have cooked the brand new tranny too. I just ran some solvent through with compressed air, until it came out clean.


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## BigLou80 (Feb 25, 2008)

Detroitdan;663674 said:


> I change all my shift solenoids every 150,000 miles.


I change my filter and fluid every fall and the fluid every spring. The truck plows and tows and hauls around all my tools all the time. So far its been 150,000 on the 4l80E and not even a hint of a problem. I see no need to replace any of the solenoids


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## Detroitdan (Aug 15, 2005)

BigLou80;664278 said:


> I change my filter and fluid every fall and the fluid every spring. The truck plows and tows and hauls around all my tools all the time. So far its been 150,000 on the 4l80E and not even a hint of a problem. I see no need to replace any of the solenoids


was just kidding. I changed them at 150k because I was having problems, so I said I do it every 150k. It remains to be seen if there is another 150k left in the truck. Somehow I doubt it. It's going strong but 300k is still a long ways off, and I don't exactly baby the old girl.
I wouldn't change them either until they act up.


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