Harsh 1-2 shift

[johnmaster]

Just got the 80e swap done in my 99 5.3 Silverado 2wd 1500 and it has luckily been uneventful. Flash the new tune, add fluid, drive it... Haven't laid lots of throttle to it yet but so far light throttle 1-2 shifts are way to harsh. turbo, hd-2 transgo kit drilled to "average", 3400 stall Yank. I am not using torque management, I have shift times at 0, lock-up is maxed out so it will not engage. 2-3 and 3-4 so far feel good so should I change shift times even though I have a shift kit or should I start messing with the 1-2 pressure table? New to trans tuning but I understand most of the underlying theory.

Otherwise this 80 feels really stout and this stall converter was desperately needed, can't wait to really let er have it...

[Taz]

Take a look at the thread linked below ... from about post #91 onward. The gentleman was having a similar issue with the 2>3 shift on a "built" 4L80.

http://forum.efilive.com/showthread....l=1#post152756

Keep in mind that the shift "feel" is an interaction of the Shift Time, Shift Pressure, and TR (Torque Reduction). If you have "zeroed out" the Shift Time and TR - you have effectively negated 2 of the 3 tuning parameters regarding shift feel. Many novice tuners will set these to zero - for little more reason than bragging rights - but the transmission generally won't shift well for street / daily driving use.

Try Shift Times of 0.200 - 0.300, and at least 15% TR - in the problem areas. This should get you pointed in the right direction for taming the shift feel (at least a little).

I use TransGo kits in all 4L60 / 4L80 transmissions. The 4L80 kits seem very sensitive to the feed holes (orifices) being enlarged too much in the separator plate. Drilling too large a hole will cause issues with excessive shift firmness - that is often a challenge to tune out - I have had to replace a separator plate or two, when all else has failed to meet shift feel requirements.


Regards,
Taz

[johnmaster]

Thank you, will add some shift time to the 1-2 and see how it goes. Had it up to .200 but will try .300, read a bit about "zero out your table with a shift kit" so wasn't sure if there was something else I was missing. Is TR entirely timing based or does it pull fuel as well?

[johnmaster]

Messed around with it a bit more today, figured out from one of Joe's posts that when the pcs is at 0psi that is in addition to the base line pressure (he mentioned something like 130 psi). I had some 0's in my 1>2 base pressure table and was wondering if line pressure were too low but apparently not so.

Overall it is shifting great, 2-3 and 3-4 could be stiffer but at 90 psi pcs pressure the only thing to do would be to drill out the plate more. 1-2 feels great above~60% tps takeoffs but on very light acceleration it is still too harsh. Tried 20% tr with no noticeable improvement. Accidentally had desired shift at 2.5 seconds instead of .25 seconds so I know that isn't going to help.

These harsh 1-2 shifts are at light throttle when torque is reading about 100 ft lbs. I have 0 in the 1-2 pressure table all the way up to ~150 ft lbs torque, still harsh. Pcs is showing something like 40-50 psi

What factors drive the pcs figure when I scan?
Can I use a negative number in the base pressure table?

I think if I can get that number 10-15 psi lower at light throttle and leave it alone everywhere else it will be smooth as butter.

[joecar]

Try adding in some Torque Reduction on the 1->2 shift.

[johnmaster]

I think this is something I am going to have to live with until I get back inside the trans. TR doesnt seem to work with my carb set-up, it must be trying to pull fuel which is why it doesn't respond. If it's pulling timing then something else must be awry as I have it at 50% tr, .35 shift time and 0 pcs with no change in low throttle sunday driving 1-2.

pretty sure longer desired shift time adjusts pcs down, but since I'm already commanding 0 pcs at the shift point, nuthin from nuthin leaves nuthin...?

Going to try to firm up the full throttle 1>2 and part throttle 2>3 and 3>4 with the base pressure table. If I can't get it firm enough to chirp the tires I will have to open it up and drill them bigger anyway.

I will be calling Transgo back, they are going to help me figure out what springs were used in the accumulator to see if that could be a way to soften it up. Could do that all at once while I am in there. Helpful guys over there too.

Will post my results.

[slow67]

What size did you drill the 2nd feed hole to? If you drilled it to 1/8" nothing you do will get it soft, without making the feed hole smaller again (yes, its possible).

Transgo and B&M usually grossly oversize the holes they recommend.

[johnmaster]

Told the guy installing it to do the "average" .086 drill on all 3 holes. After some driving, the 1-2 wot feels really good, I may just have to sacrifice a bit of put put driving comfort.

[slow67]

.086 should be ok. How many amps does the PCS command during your harsh 1-2 low power shifts?

[johnmaster]

I will have to look at my logs again and see, they are in my crappy laptop I use for tuning. I made it much less noticeable by reducing my low throttle 1>2 shift mph. Now it shifts at such a low speed the clunk is not as harsh.