A few more updates and a bit of feedback on the Transgo Tugger kit.
I had to pull the valve body several more times to get things dialed in. One thing transgo gets right is their accumulator calibration plate, which makes SOME of the shift kit easily reversible. My only regret is not attempting to run the transmission with no shift kit at all. I suspect it would have worked fine, considering all the extra clutches. But once I drilled the factory separator plate, there was no fully going back. I tried running without the calibration plate, but light throttle harshness was excessive, even with the rest of the kit removed. I even tried reducing the EPC line pressure curve and I still had a light throttle harshness problem.
So the two main drivability problems were:
1. No engine braking in 2nd gear
2. Hard shifting/reverse engagement
Several of the threaded holes for the valve body bolts were stripped, so I had to get a TimeCert kit. Once this was fixed, it seemed to make no difference in performance. New valve body gaskets may have helped, but I made other changes at the same time so it's hard to be sure. So with the bolts able to hold proper torque again, I continued picking my way through the valve body.
I reversed several elements of the shift kit until it was able to engine brake again in manual "2", since that was the most serious problem. 1st gear engine braking worked perfectly through all of this. Currently, all the accumulator springs are back to stock, but the 4-3-2 timing valve (upper valve body) still has the added spring and spacer. This is supposed to reduce engine braking delay in manual "2". The calibration plate is also back in, which addressed the harshness issues.
One last mod reversal was to drill open the orifice plug on the low/reverse piston circuit to restore the original size. Reverse engagement is a little over one second once the calibration plate went back in, but it's a small price to pay. The transmission is consistently butter smooth at light throttle, while still firming up nicely at high throttle.
Aside from being much more enjoyable to drive a smooth shifting truck (I must be getting old..), I'm also trying to aim for longevity. The post mortem of the transmission showed wear marks from the clutch splines biting into many of the hard parts. High impact from bangy shifts can't be helping. And at the end of the day, clutch packs are the cheapest part of a rebuild. Hard parts are were $$$ start flying. Time will tell if I'm right.
Transgo Tugger Summary:
It's not a bad kit, but I don't like that it makes irreversible changes to the valve body separator plate (these are getting very hard to find). I also don't like their orifice plug solution for reverse engagement, especially considering that E4ODs have a problem with reverse engagement from factory. Richard at Precision Transmissions on YouTube made similar comments about adding the orifice to the reverse feed. Essentially, Transgo has dialed up the pressures across the board, then choked off the reverse apply to prevent harsh engagement. I may try and revisit some of the shift kit later on at the next fluid change but for now I'm happy with what feels like a stock transmission that shifts like a luxury car. I also have plenty of headroom left on the EPC pressure curve if I feel the need to firm things up. Maybe I'll program that as a tow/haul mode.
Transgo Tugger final score: 3.5/5
