I just did a 4L80e conversion in my car about 4-5 months ago. It has all the upgraded parts, a 3500 stall and a transgo HD shift kit. I was not able to get it to work with my 98 PCM and until I can find someone willing to make the PCM conversion I have been using a pair of toggle switches to change gears.
Everything has been going just fine over the last 4,000 miles since I put the transmission in until about 2 days ago. I was on the HW and went to flip the switch into OD and the car stopped going forward and just slowed wayyyy down. The best description is kind of like when you pull up to a stop sign in a standard transmission car and use first gear to slow you down, no brakse, but still slowing way down. When I noticed I was slowing down I gave it some gas and heard a god awful noise. It was a cross between a grinding noise and the noise you get when a car bogs out when you try to drive from a standstill in 3rd gear in a standard transmission vehicle. All the other gears work perfectly fine, no noises, etc. But I have to have OD, I'm on the highway everyday and the OD is why I paid more for the 4L80e over the TH400.
Could this be the transmission ALREADY going out? Something else possible? The guy who installed it gave me a warranty on labor so I could fix it for the price of parts but I'd like to have an idea of what I'm looking at before I give him a call (He's about an hour and a half drive away). So, any help would be appreciated.

 

Wow... using toggle switches on an automatic, I'm guessing you blew the transmission up.

 

Toggle switches can work ok if you know what you're doing with them. But how were you controlling line pressure?
If it defaults to max line pressure it can blow stuff up, from pistons, to the case.

 

The toggle switches were what the guy installing the transmission reccomended until I had him manually plug and play all the wires to do the 98-99 PCM conversion.

On the way home yesterday, first-second gear shift started grinding horribly and it took about 20 seconds and feathering the gas for it to switch over. The second-first downshift also was grinding pretty badly.

I called the guy who installed it and described to him what was going on. Here's the kicker:
*He gave me a one year warranty on labor if anything happens to
the transmission based on his workmanship/install. He told me it sounds like it is one of the sprags that controls the 3-overdrive shift. He thinks it broke and fucked everything else up, he did not mention one thing about it being the toggle switches he installed or the control of line pressure*

He told me if it is a broken sprag it is not due to any error on his part and will not warranty the labor. He, as well as some other shops, quoted me $1500 to overhaul the transmission. This is a refreshed 4L80e with less than 4000 miles on it.

Is there anyway I can prove that this broke due to the toggle switches? I will pay the $1500 if it is indeed not his fault as I'm not out to rip anyone off, but, if it is his fault I want to be able to get the work done on his warranty. I am not a mechanic nor do I pretend to be one, I pay them to do the work, I trust what they say. So, I cannot really argue this point with him unless I have some technical information on how the toggle switches could have caused it to **** up. Please, if you have any info I could use I'm all ears. This $1500 repair and my tax return was supposed to be my 12bolt and suspension....Thank you all for any information you can send my way,
Mitchell

 

Since you have a 98 which cannot control the 4l80-e, why not just simply go with a manual valvebody?

 

The sprags in those are durable, it's very common to use a 4L80E direct drum with it's sprag/race to upgrade an old th400 for durability.
Some claim you need to upgrade the 4L80E sprag to a 34 element but every one I've seen already has it.

FWIW I've taken th400 roller drums out that were broken and hadn't messed anything else up. Put in a 4L80E drum/sprag/race and that was it.

Theoretically if you hit the switches wrong, and/or had the gear selector in the wrong position I guess you could have broken something.
The builder could also have not inspected the hardparts thoroughly.

It's anyones guess except for the guy who takes it apart and finds out whats making the noise.

 

Well I do plan on putting a manual valvebody shift kit in it this time around. When we originally did the install, we were going to do the PCM conversion but some time/money constraints prevented us from doing the conversion. I am going to go ahead and do it when this goes into the shop.

So, jxaxsxoxn, are you saying that chances are it was HIS fault due to the inability to control line pressure or that it was MY fault due to the 4L80e sprags? I am positive the switches were shifted corrrecly every time. There are only two of them, and only 4 possible combinations-I would have known if I flipped the wrong one and then it essentially blew up.

Should I just tell him that I have recieved some advice that it could be due to the toggle switches and line pressure and trust him to be honest in his inspection of it or should I take it to another shop and get their opinion on the cause?

The guy installing it has been an unbelievable help in my motor/trans build/install after the first shop screwed me over, however, I really do not want to get stuck with the bill because of the toggle switches he installed on his own accord (I did not know that is what we were going to do until I picked it up...).

Thanks alot, look forward to seeing what we can come up with.

 

If I understand you correctly the guy has nothing controlling line pressure?
I have had a gauge on a 4L80E that was putting out over 500 psi pressure, I have also seen drums broken, pistons broken, even worm tracks on the case blown out due to high line pressure. I wouldn't be suprised to see the direct drum blown up with the sprag intact and reusable.
There is not much of a chance you broke the sprag unless he used an old th400 direct drum with a roller clutch.

Who ever takes it apart will find the answer, if I were you I'd take it apart and post some pics here. What have you got to lose he's not going to warranty it anyways. If I understand correctly.
If you drop it off to him he probably has an old broken sprag laying around to say came out of yours. And who knows you may buy it and say damn this guy knows his stuff and let him fix it again.

It's guess work at this point.
See if he'll warranty anything, if not take it apart and post pics here.
If he will, thats a tough one, try to get pics of the old parts and new ones.

 

Well I talked with him a bit this evening and he sounded like he was just giving me the run around. He said a lot of things but it boiled down to me feeling like he was going to rebuild it and tell me it wasn't his fault. Like I said before, he is a long drive away, that is one expensive tow. So, I am going to cut my losses, save me the headache and the 3 week wait and just take it to a local shop.

I am wanting to build it up a bit with some beefier parts so I don't have to go through this again. I won't clutter this thread up with it, so, if you have any advice on what I should do as far as what full manual shift kit to go with and any aftermarket hard part replacements I should use, you can post it in my new thread:

https://ls1tech.com/forums/automatic-transmission/859973-performance-4l80e-rebuild.html

Thanks