Report: Shadetree Install of a 4L80E-HD2 TransGo Kit

[mikeyj350]

Hi guys, relatively new member here to the forum, been working on my 91 V3500 crew the last couple months since purchasing her at auction (Main project thread here). After completing the first round of repairs to get her on the road, which included replacing most of the fuel system, brakes, front end, driveshafts, and removal of no less than 1,000 mud dauber nests ; I wasn't really super happy with the shift quality of the 4L80E. It shifted through all the gears and lockup seemed to work fine, it just seemed sloppy and slow-shifting. Did some research, and decided to go with the TransGo 4L80E-HD2 shift reprogramming kit. I know this kit has been mentioned on here before, but I thought I'd share my experiences with it.

I should start by saying I'm pretty good with engines and electrical, not too shabby with brakes and suspension, and can hold my own with most everything else car-related. One thing I avoid like the plague though is transmissions-- they scare the crap out of me. All the little traces in the valve body are like black magic to me, and forgetting where all the seventy-five checkballs (that's how many there are, right?) go back into place seemed like a real possibility. This was my first transmission surgery that went beyond the standard fluid and filter service, or maybe the occasional one-off solenoid replacement or something.

I bought the HD2 kit from Summit, they had it the cheapest of anywhere I could find, and I also bought the Transgo 48ACTTL actuator valve kit from Amazon, figuring I could do both repairs at the same time. I watched this video to get a better understanding of the transmission (and for the recommendation on the actuator valve kit), and then I also watched this 90's-tacular TransGo video on installing the unit itself.

Starting on the actual repair, I immediately found it funny how the TransGo video linked above starts by saying something like "this video will give you confidence to do it yourself" but the actual paper TransGo instructions that come with it start with a huge bold disclaimer on the front that says "don't install this yourself unless you are a professional, full-time transmission mechanic who is already intimately familiar with the operation of a 4L80-E transmission." Lol... I'm guessing something happened lawsuit-wise between 1995 and the latest revision of these instructions. Anyway, undeterred by that disclaimer, I pulled the pan and the valve body and got to work. What's the worst that could happen?

I had laid out a small folding table next to my usual workbench, and lined it with floor protection paper that I had a roll of sitting around to perform the valve body mods. This setup ended up working out great. I kept any small parts like valve assemblies etc in ziplocs to keep them organized until it was time to go back together. Any time a hole had to be drilled or reamed, I'd take the valve body to the oil drip pan and rinse it out with carb cleaner, and then shoot it dry with some compressed air. Wear glasses when you use the carb cleaner! Those valve body passages have all been specially designed to fire that stuff straight into your eyeballs, and it burns badly.

So you basically drill a couple holes, replace some springs and plugs, and put things back together. I'm very glad to have watched the above videos before doing this, but really it wasn't too hard if you're just careful and follow the directions. The options I went with were as follows:

-Step 2: Used the outer blue spring by itself ("for slightly firmer shifts") on the pressure regulator valve
-Step 6, Drilling the separator plate holes:
-Hole "C" 1-2 shift: 0.081" (#46 drill)
-Hole "B" 2-3 shift: 0.110" (#35 drill)
-Hole "A" 3-4 shift: 0.098" (#40 drill)
(I chose these diameters after reading up on the operation of this kit, and the fact that the 2-3 shift needs the largest hole to feel similar to the other two shifts)

The only real issue I ran into was with Step 7 changing the boost valve, I missed that there is a new washer that the purple spring needs to pass through. I attempted to reinstall using the original washer, and it didn't seem to want to fit. After trying for probably half an hour I was like doh!!! And then it went together perfectly. Lesson learned, if it's not fitting then something probably isn't right!

Also, I needed a new EPC solenoid because being a 1991 mine had the early "non-vented" valve body. This isn't a well-documented discrepancy and is apparently uber-important to get correct... and I never realized it at all until stumbling into the note in the instructions. You have to drill an extra hole, and get the 93-03 version of the EPC. It was a real pain to look up, I struggled with numerous auto parts websites until I finally figured out the correct O'Reilly "PowerTorque" part number is TE137. Whew!

All back together, I was super nervous to try it out. Filled her up with fluid, fired her up on jack stands (as suggested in the TransGo video) and what do you know, IT WORKED!!

My thoughts on driving it... WOW, totally woke up the transmission. The 1-2 shift is definitely firm, but not violent. Since this isn't really a performance application I would say just 10% less firm would be my ideal sweet spot, but that's me being picky, it's great as-is. In contrast, the 2-3 shift is still actually just "meh" in my opinion, but it's definitely better than what was there before and it seems to hold just fine, but there's nowhere near any kind of "snap" that you'd expect from a shift kit. This seems to resonate with others' experience using this kit too. The 3-4 shift is perfect!

So, if you've got a 4L80E and want to firm up your shifts a bit, and you're comfortable trying something new (and risking blowing up a $1500 tranny lol) definitely give this kit a try!!! It really wasn't too bad, and the difference it made was huge!