Corvette C5 4L60e 2800 no 2nd gear upshift

[adamlewis82]

Hi everyone, I've recently swapped a 3.15 gear and 2800 stall and a transgo shift kit to my 2001 Vette....I've used the bluecat tool and other peoples experience for setting the trans up regarding shift points, pressures etc...i've also just put a trans cooler recently and for the last few weeks its been running around 170f.

Its been driving great, shifts 1-2 have been nice and punchy and much better than before the swap....but as of yesterday the 1-2 started to go mushy which I thought was weird, and then it would hit the limiter in 1st and not shift...so i've now lowered the WOT to 5900 but i've been out in it today and it will be barely shift in to 2nd at all even at low thottle it just slips loads and eventually goes in.

It will drive fine in all other gears and lock up fine, and also shift 3 to 2 fine....but its the 1-2 thats just left the room!

Is anyone free to have a look over my tune and quick log please and see if anythings wrong...or have any suggestions with what to try next, not looking forward to having to pull the trans again really, so hoping there's an easier option.

Thanks
3.15 and 2800 Stall.hpt22-06-07 13-57-36.hpl
Adam

[adamlewis82]

Anyone got any ideas? Thanks.

[blindsquirrel]

Something that gets progressively worse like that is not something you can cure by diddling the tune file. I am sorry.

[adamlewis82]

Thanks for getting back to me, was hoping I'd changed some settings that was causing it... Maybe that was wishful thinking. Have seen some mention about the 2nd and 4th apply pin being changed, it was fine before the shift kit and stall, wish I'd not changed it now.

[Alvin]

It may be low on fluid. most 4l6X applications will slip just a half a quart low especially if it's making decent power.

[adamlewis82]

I have recently installed a transcooler thinking about it but it's been driving with that for a few weeks, could possibly had an airlock as I've checked after install, and it took about 500ml.... Will check later, thanks for that... Ruled it out as been driving OK after the install.

[blindsquirrel]

now lowered the WOT to 5900

So where was it lowered from, and how long was it driven at the higher setting? 60Es have a weakness at the 2nd gear band and the reverse drum it wraps around - that reverse drum spins at way more than engine RPM while in 1st gear, then has to come to a complete stop when the band applies. Pushing the 1-2 shift point above 6K is not recommended.

[adamlewis82]

When I first pulled the file I think it was at 6150rpm and I lowered it to 6k and not done many full 6k shifts but a few, Ive now lowered it to 5900 but obv the damage is already been done, I'm just watching a video now at replacing the band, I think this may be my only course of action unfortunately... Esp if a long 2nd pin is only a bandaid. It is strange how me putting the shift kit and higher stall ans 3.15gears in has highlighted the previous issues with the trans, it's clearly been messed about with before I just didn't realise unfortunately.

[blindsquirrel]

6150 isn't instant-death territory; I was imagining more like 7500, lol. But 5900 is better than 6100, and 5600 is better than 5900...

If you can make it do the 1-2 at 5600, and it's got enough grunt to not fall on its face when dragged down to the bottom of 2nd gear, the trans will last longer and you probably won't be any slower than winding it out to 6000.

[adamlewis82]

Cheers dude, will try keep it a little lower next time and see how I get on, but I've now pulled the trans and tore into it and found the drum is screwed, warped, hot spotted and gouged, no beuno! I've just ordered the zpak level 3 full rebuild kit, beast sunshell, sonnax drum I think, and sonnax super hold 2 and 4 servo, hoping that will hold up now with the rest of the previous transgo shift kit. Maybe didn't help myself without checking band clearence before 🤷🏼

[msnookums]

As stated already low fluid will cause the issue, among other things like a leaky 1-2 accumulator, leaky servo seals, etc. The band won't take much of that before it leaves the chat itself. Band clearance with slightly short pin just delays the shift but it will complete, unless it's way out of spec. If you need or want help just ask. I build these things daily.