ALZ28

Fully rebuilt 4l60e with Alto race kit by a pro.
All shifts set at 6500, launch in D
testing ran mid 11.40's 3 runs. All ok. best times ever.
3 months later at race meet(nothing changed), in qualifiers won't go into 3rd. hitting rev limiter at 6800, lifted and floored it again and went into 3rd, ran 11.60.
It wasn't slipping as it was still pulling hard until it hit rev limiter.
2nd run same again.
dropped the shift point to 6200 for next run, same thing happened.
Out 1st round due to same problem.
unable to test since then. Track only car.


Checked ATF level, ok, drained it, no crap in it, fluid clean.
Any ideas???
2-3 shift solenoid?
I converted it from TCS to non TCS throttle cable a while ago, removed all TCS stuff etc. Can't be this, can it?
Log of run below, starts at about 3250 frames

mrvedit

This sounds exactly like a worn 3/4 clutch.
Sorry, but various pro builders have told me that the thin frictions and steels in the old Alto kits don't hold up long. IIRC they come with a thin backing plate; combined with high line pressure, the whole assembly "cones" ruining the frictions.
I suggest getting the trans rebuilt with BW HiEnergy (Green) 3/4 frictions. Use the thickest apply and backing plates, and 7 or 8 frictions. I document the details in post #2 here:
https://ls1tech.com/forums/automatic...some-info.html
Lots of members have successfully used those combos.

Obviously you also want either a complete shift kit installed or at least a .490/.500 boost valve from e.g. Transgo or Sonnax. The Sonnax is better as it has o-rings to prevent leaks and holds the pressure better.

ALZ28

Ouch!
That's not what I wanted to hear.
When you say "cones" do you mean they have gone concave/convex?
Any reason why it shifts ok once I back off and floor it again?

mrvedit

Yes, the friction/steel combo becomes concave due to the thin/weak backing plate, especially with high line pressure.
When you back off, the trans shifts under less power letting the frictions grab and then hold the full power later. Think of your tires - once they spin you have no traction until you lift a bit and let them grab again.

Sonnax makes a updated input drum that holds one more friction, but more importantly has a very solid bolt-on backing plate that eliminates any chance of coning.

Also, you should have your line pressure checked. WOT should be around 225psi. Some builders think "more is better" and tweak the Pressure Control Solenoid to exceed that value which increases the chance of coning.

While I answer many/most 4L60E questions here, I have limited experience with other people's transmissions and am certainly not a pro builder. I assume you have checked the obvious such as the fluid level and even tried overfilling by 1/2 quart.
I also always recommend connecting a pressure gauge to verify it is not too low or too high. The model "ATD 5550" is expensive and hopefully readily available in the UK. I suspect all trans shops and many auto shops have one.

Ohio Bird of Prey

I've experienced the same symptoms a time or two with my Performa Built 4L60E. This happened after I made some chassis improvements. Watching a video I noticed that my front end was much higher in the air at wot than it used to be. I overfilled my fluid by 1/2 qt. and the problem went away. Give that a shot next time you can test and tune.

ALZ28

The reason it was rebuilt was the band delaminated, so he only changed this and the clutch packs and new seals etc. It only had about 50 runs on it since I bought it off TCI, the pressure was left as TCI set it.
I have the fluid set at correct level when levelish(car sits nose down).
Thinking about what Bird of Prey is saying makes sense, having watched a vid of mine since I fitted a solid rear anti roll bar the nose is still way up(see avatar) by the time 2-3 shift happens.
Before I bin it and fit a 4l80e I will try the overfill trick.
Thanks

01ssreda4

iTrader: (96)

As for tcs, the module on the shock tower that controls tcs limits wot. Meaning it only allows you to go like 95% throttle, maybe less. Deleting it would cause some change. Enough to cause your issue? Not sure but something to consider.

ALZ28

I've taken it off completely, throws a code but that's just telling me its unplugged. Dash warning light comes on but that's better than forgetting to switch it off before every run
I have just fitted a new TPS sensor, done re-learn, logged it and its reading 0-100% and the voltage is correct too.
Cheers

buktooth

I just fixed mine that was doing the 2-3 shift flare. My combo is in a ls swapped vehicle and the engine and trans is installed with eng/trans tilted down a little lower than stock at the rear to prevent cutting the trans tunnel. I slightly overfilled the trans and all issues went away.

Brando5641

iTrader: (3)

I had a similar issue in my performabuilt. Upped my shift point from 6500 to 7K and it wouldn't go into 3rd under WOT. Pulled the trans to freshin it up and it had the Zpack. The friction material had started to flake off. Called performabuilt and they recommended the deep truck pan to help pump starvation. Replaced the 3/4 with BW HE 7 clutch setup and put a deep pan on and now I have crisp 2-3 shift at 7k.

Edit: The fluid looks fairly clean. Pulled the pan and it was super clean. Still was missing quite a bit of 3/4 material.