I've got my swap up and running. Trans is a 03 4l60e. 1 to 2 shift is very lazy. Not slipping just a very long drawn out shift. Rest of my shifts are quick and crisp. Converter locks and unlocks great.
Trans mods:
Sk4l60 kit, Plate drilled according to specs I got here, Clutch clearance and band clearance specs I got on here, Wide band, New drum, hardened shell, HD clutches, Sonnax painless 1-2 & 3-4,
sonnax hd 2-3 valve, Corvette servo , New stock pin..

I'm sure that I am forgetting a good bit of parts and mods done in the rebuild.

Why would only 1-2 shift so poorly?

 

What are all those specs? Did you replace the boost valve? What is the line pressure?

 

​​​​​​​https://ls1tech.com/forums/automatic...r-plate-2.html

 

That's the thread where I was having issues with clutch clearances and plate hole sizes for my setup. My band clearance I believe came out to .072

Can I look at shift pressures with hptuners when logging? Do I need to hook up a gauge to the Port on the side of the trans?

 

To get a true reading of line pressure you will need to hook up a Guage. A scanner will only show commanded pressure, as there is no line pressure sensor.

If you're up to it, you could pull the 2-4 servo and inspect the sealing rings and check the 2nd accumulator that it was assembled correctly. Did you plug the pin hole in the 2nd accumulator when installing the painless accumulator piston?

You could also open up the 1-2 shift feed orifice to.082 after confirming the 2-4 servo seals are good. If you decide the open up the 1-2 shift feed orifice, I would go back though the valve body to make sure everything is assembled correctly. It happens sometimes.

What is your 3-4 clutch clearance? Did you install a Sonnax Servo Release Check Valve? That check valve will cause shift issues is why I ask.

 

Thanks for the suggestions. I followed the instructions on the pinless accumulators, as far as putting the ball bearing into the pin bore and I think I used a stock spring in the 2nd since I had seen that recommended instead of ones from the shift kit. Since I didn't want harsh shifts.

I had a really hard time installing the 2-4 servo stuff, I need to pull it apart and check to make sure the seals didn't get messed up. I'm beginning to wonder if I put the wrong springs in the 2-4 setup.

.032 or .035 is what ended up with the 3-4 seven clutch stack. I put a new GM check ball assembly in the case. Not the sonnax.

I was so meticulous rebuilding this trans. Dble and triple checked almost everything. It goes right into gear and shifts perfect everywhere else.

Thanks again.

 

Your clearances look good, so that shouldn't be the problem.

I messed up the sealing rings on the 2-4 servo once myself, I remember that it felt a little funny going together, but I just kept going instead of taking it back apart.

On a F-Body if you unbolt the crossmember and let the back of the trans hang down you can get the 2-4 servo out, but only if you remove one piece at a time and remove the 2nd piston from the pin. It's not easy but can be done.

 

LS1/4l60e swap is in my 95 jeep. It's been 3 months since I started the swap. Shouldn't be a big deal taking off the pan. All I have to do is drop the skid plate.. Luckily the pan has a drain plug too. I will report back later this week after I get a chance to work on it.

Thanks again.

 

The 1-2 shift sometimes takes a little time to settle in. For one, the PCM will essentially relearn. Also, it takes a little bit for the band to settle into the drum.

Now, its hard to feel what you consider "lazy" but might consider the above

 

Well I drove it to and from work the last 2 days and it starting to shift normal. Thank for you help.