4L80E, Is it a modification?

Hello all,

I have a puzzle for anyone that may have experience on 4L80E transmission modifications.
I have a 2003 4L80E behind a 1996 454 (carbureted) going in my build. I dont know a lot about the donor truck, or the transmission history, as the previous owner p***ed away before I bought it from his brother. The brother had driven it from Portland OR to Boise ID, and then stored if for a year.
When I bought it, I was able to drive it a couple miles to my shop. The shifting was not quite right, but I believe that was due to not having a computer connected.

I had been planning to rebuild the trans myself, but I think that because of my inexperience, I may be better off to have it done by someone that would be better equipped to know what's good and what's bad during teardown.

The question I have before I get too far into this particular transmission, is a possible modification, or repair, or ??? that has been done to the case, and what it might mean. I noticed it when I pulled the engine and transmission out and put them on stands.

On the front left side of the case in front of the shift lever, there is a hole with a fitting in it. It doesn't appear to be original, since I dont see it in other pictures of 4L80e's. The fitting that sits in the hole looks like it has been threaded into the hole from the inside of the transmission.

Does anyone recognize what this could have been for? could it be a modification for some reason, or ??

Mike

 

pull the pan and see what's inside. It's hard to tell what it is from the picture, which is kind of small and dark...

 

That's a Vacuum Modulator kit added to the 4L80E.

https://transgo.com/product-details/4l80e-vacuum-modulator-kit/

 

That's good info !

 

Just trying to learn here, what is advantage of a vacuum modulator kit on a 4L80E? Used instead of a throttle valve cable? Isn't it still an electronic valve body so you need a transmission computer. I'm confused as to why you need this, the link description isn't much help.

 

Wow, excellent info @Texas********
After researching that link and a couple other 4L80 pages, I'm thinking that may be the reason that the truck that it came in didn't have a TCM. According to a few posts from Bowler Transmissions in IL, if this modulator is used with a transgo stage III shift kit the transmission can be used as manual shift without a controller. I will try and reach out to Transgo to verify that sometime this week.
That would also correlate to what was in the truck. It had a ratchet shifter that would have worked well for manual shift, no TCM, and this Modulator. Now I will try to figure out if it has the shift kit inside. If it does, a lot of my questions may be answered.
Thank you for your help

 

Adding the modulator to the 4L80E allows you to regulate the line pressure, rather than having fixed line pressure. The modulator doesn't make the 4L80E shift without a computer. If you want the 4L80E to shift automatically, it needs a controller of some sort. It is simple to make the 4L80E full manual.