vortec350s10

I figured I'd post this here as well as in my build thread to see if I could get some input. I've got an '88 700r4 that I built using Dana's pro street elite kit. It been great for the last 3 seasons. A month ago I accidentally made a 3-4 WOT shift or at least it tried to make the shift. I realized after a second or so that the rpms weren't dropping after I moved the shifter and let off. Immediately after that I noticed the 1-2 shift became very soft and then a few drives later it was slipping under boost in 2nd gear. I pulled the trans apart and this is what I have found so far:

There was nothing in the pan that indicated any issues, so I could rule out any catastrophic failure. Now last time I drove it, my issues were a soft 1-2 shift, slipping under boost in second gear, and intermittent TCC lockup. The TCC has been acting up for a long time which I've figured has been due to a partially broken wire (internal or external) or just a cheap (ebay purchased) or sticky solenoid.

Being that second gear was the main issue, I measured the clearance in the servo cover before taking it apart. I could move it about .200", where as when I first assembled it, it was at .075". So I could tell there was definitely some wear on the band. Nothing looked wrong in the servo assembly or the 1-2 accumulator housing that would cause a low pressure situation.

Next I pulled the pump and discovered something interesting. The snap ring and spring retainer that is normally in the reverse drum stayed in the trans while the drum came out! So the snap ring somehow came out of the reverse drum and the spring assembly and snap ring were just floating in there for who knows how long. I'm not sure what kind of symptoms this would cause. It could have been like this from the very beginning, 4 years ago. I would expect the clutches in the reverse drum to be worn out from the piston not being held back by the return springs, but they only have .020" more clearance than when I built it.

Then I pulled the band and it's definitely worn thin and has gotten hot. Most likely from slipping the last few times I drove it. The drum has some wear marks on it, but not heat marks since I didn't let it slip much once I noticed it wasn't the tires spinning. The band is wide Alto carbon band.

I'm trying to figure out why the band is already shot. I've got maybe 15,000 miles on it, although many of that is on the track and I'm not exactly easy on it. The 9 BW high energy 3-4 clutches show very little wear and are in great shape.

Pro Built Automatics

Give me a call and we can go through what needs to be addressed here. 909 795-1876 If you are up late give me a ring as I will be working all through the night until morning most likely.

willexoIX

Wow looks like that band was too tight for that 3-4 shift and it did the band in.

vortec350s10

I called Dana last night and we had a chat about my trans. He wasn't surprised the band was worn out and said that I got a decent amount of life out of it considering my driving habits and track use. He also said I could open up the 2nd gear feed hole a little in the separator plate from .096 to around .104 if I wanted. I might try the Borg Warner high energy band this go-round to see how it does. Dana said even in the highest hp apps he likes it the best. I'll be buying a new drum as well. He said a lot of drag race guys running 700r4's and 4L60e's simply re-shim the 3-4 clutches to get them back down to the .035-.055 range. He said it's not necessary to buy all new frictions if they are wearing evenly and in otherwise good shape. So I might just swap in a thicker steel or two (or go back to the thicker snap ring) to tighten them up a bit. The 2-3 shift was and still is awesome.

I'm going to enlarge the 4th apply hole a little as well as suggested by Dana. I also have a solid Sonnax 4th accumulator piston that I'm going to remove and block the feed with a 1/4" check ball to firm up the 3-4 a little more. I have no intentions of making 3-4 WOT shifts so I'll leave the stock 4th servo cover alone. It'll do at least 130mph in third with my gearing.